1. Chapter 18 الباب الثامن عشر
The Evolution of Invertebrate Diversity
تطور تنوع اللافقاريات
Lecture by Joan Sharp

2. ANIMAL EVOLUTION AND DIVERSITY تطور الحيوانات وتنوعها
ANIMAL EVOLUTION AND DIVERSITY
تطور الحيوانات وتنوعها
Copyright © 2009 Pearson Education, Inc.

3. 18.1 What is an animal? ما هو الحيوان ؟
Animals are eukaryotic, multicellular heterotrophs that ingest their food
الحيوانات هي كائنات حقيقية النواة، عديدة الخلايا ، عضوية التغذية تبتلع غذائها
Animal cells lack cell walls
تفتقر الخلايا الحيوانية للجدار الخلوي
Most adult animals are diploid, producing short-lived gametes by meiosis
معظم الحيوانات البالغة ثنائية العدد الكروموزومي، تنتج أمشاجاً قصيرة الحياة بالانقسام الاختزالي
Two gametes fuse to produce a diploid zygote, which grows to maturity by mitosis
يندمج مشيجان ليكونا لاقحة ثنائية العدد الكروموزومات والتي تنمو حتى البلوغ بالانقسام الفتيلي
Life cycle of most animals includes a blastula, gastrula, and larval stage
تشتمل دورة حياة معظم الحيوانات على مرحلة المفلجة والبطينة والمرحلة اليرقية
Hox genes control transformation of the zygote into an adult animal
تتحكم جينات الهوكس في تحول اللاقحات إلى حيوان بالغ
Student Misconceptions and Concerns
1. When considering animals in general, students are typically biased towards vertebrate examples. As a thought exercise, start your first lecture on animal diversity by asking students to write down the name of the very first type of animal that comes to their minds, without giving it any thought. Depending upon your class size, either tabulate their responses quickly or have students raise their hands to indicate the type of animal they chose. In general, fewer than 5% (often fewer than 1%) of my students have pictured an invertebrate. This exercise makes the point that what we tend to think of, when we think of animals, is vertebrates. Many of us have had a dog, cat, or other vertebrate for a pet. Yet, more than 95% of all known species of animals are invertebrates. Students must expand their understanding of what it means to be an animal. The content in Chapter 18 should facilitate that understanding.
2. Students often struggle to conceptualize the basic needs of invertebrates, and may find it challenging to think of the similarities between, for example, an earthworm and a dog, or a tick and a cat. The common features of animals addressed at the start of Chapter 18 can be expanded to include the needs for oxygen, nourishing food, a tolerable environment, and a suitable habitat to reproduce, which apply to animals representing all of the major phyla. Illustrating these common demands can help students build the intellectual foundations that can be so difficult to fully establish.
Teaching Tips
1. Depending upon what chapters you have covered in your course up to this point, you might begin your lectures on animals by asking your class to compare the features of plants, fungi, and animals. You may want to present a table listing the following characteristics, and ask the class to identify the condition for each kingdom: eukaryotic or prokaryotic cells, single or multicellular organisms, presence of cell walls, and use of photosynthesis.
2. You might wish to share the now somewhat-famous quote of Lewis Wolpert, who in 1986 said, “It is not birth, marriage, or death, but gastrulation, which is truly the most important time in your life.” The development and arrangement of the basic embryonic layers (ectoderm → skin and nervous system, mesoderm → muscle and bone, and endoderm → digestive tract) establishes the basic body plan.
3. Your students might enjoy discussing whether or not they are larvae and if they can be said to go through metamorphosis. (The answer to both questions is, of course, no.)
Copyright © 2009 Pearson Education, Inc.

4. Zygote (fertilized egg)1 8 7 6 5 4 3 2
Zygote (fertilized egg)
لاقحة (بيضة مخصبة)
Eight-cell stage
مرحلة الثماني خلايا
Metamorphosisتحول شكلي
Blastula
(cross section)
المفلجة (قطاع عرضي)
Digestive tract
قناة هضمية
Larvaيرقة
Ectoderm
طبقة داخلية
Endoderm
طبقة خارجية
Internal sac
كيس داخلي
Later gastrula
Future mesodermطبقة وسطى مستقبلية
Early gastrula
Haploid (n)
Diploid (2n)
Key
عدد كروموزومات أحادي
عدد لكروموزومات ثنائي
Spermحيوان منوي
Meiosisانقسام اختزالي
Eggبيضة
Adultحيوان بالغ
بطينة مبكرة
(قطاع عرضي)
بطينة متأخرة
The life cycle
of a sea star
دورة حياة نجم البحر
Figure 18.1B The life cycle of a sea star.

5. 18.3 Animals can be characterized by basic features of their “body plan” يمكن أن تتصف الحيوانات بمظاهر أساسية في ”تصميم أجسادها“
Animal body plans vary in symmetry, body cavity, and number of germ layers
تختلف تصاميم أجساد الحيوانات في التماثل ، والتجويف الجسدي ، وعدد الطبقات الجرثومية
Body symmetry
Radial symmetry, any slice through the central axis divides the animal into mirror image halves. The animal has a top and bottom but lacks back and front or right and left sides
بالتماثل الشعاعي ، فإن أي قطاع خلال المحور المركزي يقسم الحيوان إلى نصفين كل منهما شكل مرآتي للآخرتملك الحيوانات المتماثلة شعاعياً قمة وقاعدة ولكنها تفتقر إلى خلف ومقدمة أو إلى جانب أيمن أو أيسر
Bilateral symmetry have mirror-image right and left sides, a distinct head and tail, and a back (dorsal) and belly (ventral) surface
تملك الحيوانات ذات التماثل الجانبي صورةً مرآتيةً للجانبين الأيمن والأيسر ، ورأساً وذيلاً مميزان ، وظهرا (ظهرياً) وبطناً (بطني)
Explain to your students that the symmetry of animals fits their lifestyle.
Radial animals are sedentary or passively drifting.
Bilaterally symmetrical animals have a brain, sense organs and mouth located in the head. This arrangement facilitates mobility, as the animal meets the environment head-first.
Student Misconceptions and Concerns
1. When considering animals in general, students are typically biased towards vertebrate examples. As a thought exercise, start your first lecture on animal diversity by asking students to write down the name of the very first type of animal that comes to their minds, without giving it any thought. Depending upon your class size, either tabulate their responses quickly or have students raise their hands to indicate the type of animal they chose. In general, fewer than 5% (often fewer than 1%) of my students have pictured an invertebrate. This exercise makes the point that what we tend to think of, when we think of animals, is vertebrates. Many of us have had a dog, cat, or other vertebrate for a pet. Yet, more than 95% of all known species of animals are invertebrates. Students must expand their understanding of what it means to be an animal. The content in Chapter 18 should facilitate that understanding.
2. Students often struggle to conceptualize the basic needs of invertebrates, and may find it challenging to think of the similarities between, for example, an earthworm and a dog, or a tick and a cat. The common features of animals addressed at the start of Chapter 18 can be expanded to include the needs for oxygen, nourishing food, a tolerable environment, and a suitable habitat to reproduce, which apply to animals representing all of the major phyla. Illustrating these common demands can help students build the intellectual foundations that can be so difficult to fully establish.
Teaching Tips
1. You might wish to share the now somewhat-famous quote of Lewis Wolpert, who in 1986 said, “It is not birth, marriage, or death, but gastrulation, which is truly the most important time in your life.” The development and arrangement of the basic embryonic layers (ectoderm → skin and nervous system, mesoderm → muscle and bone, and endoderm → digestive tract) establishes the basic body plan.
2. Your students might enjoy discussing whether or not they are larvae and if they can be said to go through metamorphosis. (The answer to both questions is, of course, no.)
3. Before addressing the subject of animal symmetry, you might wish to have your students speculate about the adaptive advantages of radial or bilateral symmetry found in animals. This sort of comparison raises an opportunity to make some larger points about biology. There is no “one” best animal. Each form, each adaptation, and each body plan has advantages and disadvantages. The value of adaptations is relative to the organism’s environment and most adaptations represent a compromise.
Copyright © 2009 Pearson Education, Inc.

6. Radial (left) and bilateral (right) symmetry
Dorsal surface
السطح الظهري
Topقمة
Anterior
end
الطرف الأمامي
Posterior
end
الطرف الخلفي
Figure 18.3A Radial (left) and bilateral (right) symmetry.
Ventral surface
السطح البطني
Bottomالقعر
Radial (left) and bilateral (right) symmetry
تماثل شعاعي (لليسار) وجانبي (لليمين)

7. تفتقر الإسفنجيات للأنسجة الحقيقية
18.3 Animals can be characterized by basic features of their “body plan” يمكن توصيف الحيوانات بمظاهر أساسية في ”الخطة التصميمية لأجسادها“
Animal body plans vary in organization of tissues
تختلف الخطط التصميمية لجسد الحيوان في تنظيم الأنسجة
Sponges lack true tissues
تفتقر الإسفنجيات للأنسجة الحقيقية
In other animals, cell layers formed during gastrulation give rise to tissues and organs
في حيوانات أخرى ، الخلايا المتكونة أثناء التبطن (في التكوين الجنيني) تنتج الأنسجة والأعضاء
Some animals have only ectoderm and endoderm, but most animals also have mesoderm
تمتلك بعض الحيوانات طبقة خارجية وداخلية فقط ، ولكن معظم الحيوانات لديها أيضاً طبقة وسطى
Student Misconceptions and Concerns
1. When considering animals in general, students are typically biased towards vertebrate examples. As a thought exercise, start your first lecture on animal diversity by asking students to write down the name of the very first type of animal that comes to their minds, without giving it any thought. Depending upon your class size, either tabulate their responses quickly or have students raise their hands to indicate the type of animal they chose. In general, fewer than 5% (often fewer than 1%) of my students have pictured an invertebrate. This exercise makes the point that what we tend to think of, when we think of animals, is vertebrates. Many of us have had a dog, cat, or other vertebrate for a pet. Yet, more than 95% of all known species of animals are invertebrates. Students must expand their understanding of what it means to be an animal. The content in Chapter 18 should facilitate that understanding.
2. Students often struggle to conceptualize the basic needs of invertebrates, and may find it challenging to think of the similarities between, for example, an earthworm and a dog, or a tick and a cat. The common features of animals addressed at the start of Chapter 18 can be expanded to include the needs for oxygen, nourishing food, a tolerable environment, and a suitable habitat to reproduce, which apply to animals representing all of the major phyla. Illustrating these common demands can help students build the intellectual foundations that can be so difficult to fully establish.
Teaching Tips
1. You might wish to share the now somewhat-famous quote of Lewis Wolpert, who in 1986 said, “It is not birth, marriage, or death, but gastrulation, which is truly the most important time in your life.” The development and arrangement of the basic embryonic layers (ectoderm → skin and nervous system, mesoderm → muscle and bone, and endoderm → digestive tract) establishes the basic body plan.
2. Your students might enjoy discussing whether or not they are larvae and if they can be said to go through metamorphosis. (The answer to both questions is, of course, no.)
3. Before addressing the subject of animal symmetry, you might wish to have your students speculate about the adaptive advantages of radial or bilateral symmetry found in animals. This sort of comparison raises an opportunity to make some larger points about biology. There is no “one” best animal. Each form, each adaptation, and each body plan has advantages and disadvantages. The value of adaptations is relative to the organism’s environment and most adaptations represent a compromise.
Copyright © 2009 Pearson Education, Inc.

8. The body cavities of animals vary تختلف التجاويف الجسدية للحيوانات
18.3 Animals can be characterized by basic features of their “body plan” يمكن توصيف الحيوانات بمظاهر أساسية في ”الخطة التصميمية لأجسادها“
The body cavities of animals vary
تختلف التجاويف الجسدية للحيوانات
Flatworms have a solid body and lack a coelom
تمتلك الديدان المفلطحة أجساداً مصمتة وتفتقر للتجويف السيلومي
A pseudocoelom is partially lined by tissue derived from mesoderm
يُبطن التجويف السيلومي الكاذب جزئياً بنسيج مشتق من الطبقة الوسطى
A true coelom is completely lined by tissue derived from mesoderm
يُبطن التجويف السيلومي الحقيقي بالكامل بنسيج مشتق من الطبقة الوسطي
Distinguish between a body cavity (a fluid-filled space between the digestive tract and outer body wall) and a digestive tract.
Explain that in soft-bodied animals, the fluid in the body cavity forms a hydrostatic skeleton against which muscles can contract.
Student Misconceptions and Concerns
1. When considering animals in general, students are typically biased towards vertebrate examples. As a thought exercise, start your first lecture on animal diversity by asking students to write down the name of the very first type of animal that comes to their minds, without giving it any thought. Depending upon your class size, either tabulate their responses quickly or have students raise their hands to indicate the type of animal they chose. In general, fewer than 5% (often fewer than 1%) of my students have pictured an invertebrate. This exercise makes the point that what we tend to think of, when we think of animals, is vertebrates. Many of us have had a dog, cat, or other vertebrate for a pet. Yet, more than 95% of all known species of animals are invertebrates. Students must expand their understanding of what it means to be an animal. The content in Chapter 18 should facilitate that understanding.
2. Students often struggle to conceptualize the basic needs of invertebrates, and may find it challenging to think of the similarities between, for example, an earthworm and a dog, or a tick and a cat. The common features of animals addressed at the start of Chapter 18 can be expanded to include the needs for oxygen, nourishing food, a tolerable environment, and a suitable habitat to reproduce, which apply to animals representing all of the major phyla. Illustrating these common demands can help students build the intellectual foundations that can be so difficult to fully establish.
Teaching Tips
1. You might wish to share the now somewhat-famous quote of Lewis Wolpert, who in 1986 said, “It is not birth, marriage, or death, but gastrulation, which is truly the most important time in your life.” The development and arrangement of the basic embryonic layers (ectoderm → skin and nervous system, mesoderm → muscle and bone, and endoderm → digestive tract) establishes the basic body plan.
2. Your students might enjoy discussing whether or not they are larvae and if they can be said to go through metamorphosis. (The answer to both questions is, of course, no.)
3. Before addressing the subject of animal symmetry, you might wish to have your students speculate about the adaptive advantages of radial or bilateral symmetry found in animals. This sort of comparison raises an opportunity to make some larger points about biology. There is no “one” best animal. Each form, each adaptation, and each body plan has advantages and disadvantages. The value of adaptations is relative to the organism’s environment and most adaptations represent a compromise.
Copyright © 2009 Pearson Education, Inc.

9. No body cavity (a flatworm)لا وجود للتجويف الجسدي (دودة مفلطحة)
Tissue-filled region
(from mesoderm)
منطقة مليئة بالأنسجة (من الطبقة الوسطى)
Body covering
(from ectoderm)
غطاء الجسد (من الطبقة الخارجية)
Figure 18.3D No body cavity (a flatworm).
Digestive sac
(from endoderm)
كيس هضمي (من الطبقة الداخلية)
No body cavity (a flatworm)لا وجود للتجويف الجسدي (دودة مفلطحة)

10. Pseudocoelom (a roundworm)تجويف سيلومي كاذب (دودة مستديرة)
Body covering
(from ectoderm)
غطاء الجسد (من الطبقة الخارجية)
Muscle layer
(from mesoderm)
طبقة عضلية
(من الطبقة الوسطى)
Digestive tract
(from endoderm)
قناة هضمية
(من الطبقة الوسطى)
Figure 18.3C Pseudocoelom (a roundworm).
Pseudocoelom
سيلوم كاذب
Pseudocoelom (a roundworm)تجويف سيلومي كاذب (دودة مستديرة)

11. True coelom (a segmented worm)تجويف سيلومي حقيقي (دودة حلقية)
Body covering
(from ectoderm)
غطاء الجسد
(من الطبقة الداخلية)
Coelom
تجويف السيلوم
Tissue layer
lining coelom
and suspending
internal organs
(from mesoderm)
طبقة نسيجية تبطن تجويف
السيلوم ويعلق بها الأعضاء
الداخلية (من الطبقة الوسطى)
Figure 18.3B True coelom (a segmented worm).
Digestive tract
(from endoderm)
القناة الهضمية ( من الطبقة الداخلية)
True coelom (a segmented worm)تجويف سيلومي حقيقي (دودة حلقية)

12. شجرة التشعب هي افتراض للتاريخ التطوري للمجاميع التي تشملها هذه الشجرة
18.4 The body plans of animals can be used to build phylogenetic trees يمكن استخدام الخطط التصميمية لجسد الحيوانات لإنشاء شجرة التشعب
A phylogenetic tree is a hypothesis for the evolutionary history of the groups involved
شجرة التشعب هي افتراض للتاريخ التطوري للمجاميع التي تشملها هذه الشجرة
This phylogenetic tree is based on comparative morphology of animal taxa
تعتمد شجرة التشعب على الشكل الخارجي المقارن لأصناف الحيوانات
Student Misconceptions and Concerns
1. When considering animals in general, students are typically biased towards vertebrate examples. As a thought exercise, start your first lecture on animal diversity by asking students to write down the name of the very first type of animal that comes to their minds, without giving it any thought. Depending upon your class size, either tabulate their responses quickly or have students raise their hands to indicate the type of animal they chose. In general, fewer than 5% (often fewer than 1%) of my students have pictured an invertebrate. This exercise makes the point that what we tend to think of, when we think of animals, is vertebrates. Many of us have had a dog, cat, or other vertebrate for a pet. Yet, more than 95% of all known species of animals are invertebrates. Students must expand their understanding of what it means to be an animal. The content in Chapter 18 should facilitate that understanding.
2. Students often struggle to conceptualize the basic needs of invertebrates, and may find it challenging to think of the similarities between, for example, an earthworm and a dog, or a tick and a cat. The common features of animals addressed at the start of Chapter 18 can be expanded to include the needs for oxygen, nourishing food, a tolerable environment, and a suitable habitat to reproduce, which apply to animals representing all of the major phyla. Illustrating these common demands can help students build the intellectual foundations that can be so difficult to fully establish.
Teaching Tips
1. Your students might enjoy discussing whether or not they are larvae and if they can be said to go through metamorphosis. (The answer to both questions is, of course, no.)
2. Before addressing the subject of animal symmetry, you might wish to have your students speculate about the adaptive advantages of radial or bilateral symmetry found in animals. This sort of comparison raises an opportunity to make some larger points about biology. There is no “one” best animal. Each form, each adaptation, and each body plan has advantages and disadvantages. The value of adaptations is relative to the organism’s environment and most adaptations represent a compromise.
For the Discovery Video Invertebrates, go to Animation and Video Files.
Copyright © 2009 Pearson Education, Inc.

13. One hypothesis of animal phylogeny based on morphological comparisons
No true
tissues
لا وجود لأنسجة حقيقية
Sponges
الاسفنجيات
Radial
symmetry
تماثل شعاعي
Cnidarians
الجوفمعويات
Ancestral colonial
protist
سلف أولي استعماري
Echinoderms
شوكيات الجلد
Deuterostomes
ثانويات الفم
Chordates
الحبليات
البعديات القيقيةEumetazoans
أنسجة حقيقية
True
tissues
Flatworms
الديدان المفلطحة
Bilateriansمتماثلة الجانبين
تماثل جانبي
Bilateral
symmetry
Molluscs
الرخويات
Protostomes
أوليات الفم
Annelids
الديدان الحلقية
Figure 18.4 One hypothesis of animal phylogeny based on morphological comparisons.
Go through the tree with your students:
On the far left is the ancestral colonial protist.
The first branch point splits sponges from eumetazoans with true tissues.
The second branch point separates animals with radial symmetry from those with bilateral symmetry (bilaterians).
The third branch point splits bilaterians into two clades based on embryology: deuterostomes and protostomes.
Arthropods
مفصليات الأرجل
Nematodes
الديدان المستديرة
One hypothesis of animal phylogeny based on morphological comparisons
أحد فرضيات تشعب الحيوان المعتمد على مقارنة الشكل الخارجي

14. INVERTEBRATE DIVERSITY
INVERTEBRATE DIVERSITY
تنوع اللافقاريات
Students may use the word animal to mean mammal or vertebrate. Point out to your students that over 95% of all known species of animals are invertebrates.
Copyright © 2009 Pearson Education, Inc.

15. 18.5 Sponges have a relatively simple, porous body تمتلك الاسفنجيات اجساماً مثقبة بسيطة نسبياً
Sponges (phylum Porifera) are simple, sessile (sedentary) animals
الاسفنجيات (شعبة المساميات) حيوانات بسيطة جالسة (ثابتة)
They cannot escape from predators, thus produce defensive toxins and antibiotics that deter pathogens, parasites, and predators
الأسفنج لا يستطيع الهروب من مفترسيه لذا ينتج سموم دفاعية ومضادات حيوية تردع بها الممرضات والطفيليات والمفترسات
The body of a sponge without true tissues and consists of two layers of cells separated by a gelatinous region
لا تحتوي جسد الاسفنج على أنسجة حقيقية لكن يتألف من طبقتين من الخلايا تفصل بينهما منطقة هلامية
The inner layer of flagellated choanocytes filters food and engulfs it by phagocytosis
ترشح الطبقة الداخلية من الخلايا السوطية الطعام وتبتلعه بواسطة الالتهام الخلوي
Amoebocytes wander through the middle body region and produce skeletal fibers
تتجول الخلايا الأميبية في منطقة وسط الجسد وتنتج أليافاً هيكلية
Student Misconceptions and Concerns
1. Students typically expect that an animal will have a head. The subject of a head might have already been introduced when discussing body plans. As you proceed through the animal phyla, have students consider how sponges and cnidarians meet their basic needs without the benefit of a well-defined head.
2. As students survey the major animal phyla, they might perceive the diversity of animals as spread somewhat evenly across the nine major phyla of invertebrates. Yet, two-thirds of all known species of life (and at least 80% all described animal species) are arthropods. Although sources disagree on the number of living species that have been described, there is widespread agreement that the number of undescribed species is many times more than the number of described species. By examining the number of described species, some amazing proportions emerge. You might consider this exercise to make the point. Determine how many students represent 1% of the class. Then have the entire class stand. Tell the students that collectively, they represent all of the animal species known to exist today. Have 5% of the class sit, representing the proportion of known animal species that are vertebrates. Next, have 15% of the class sit, representing all of the remaining types of animals except arthropods. At this point, everyone standing (80% of the class) represents the proportion of known animal species that are arthropods (a conservative fraction). Finally, have 50% of the entire class sit, leaving 30% standing. Have the class guess what group of animals is represented now (clearly some subgroup of arthropods). This final 30% represents the known number of species of beetles! (The numbers used are rounded. Even high percentages for beetles and invertebrates may be more accurate. The point of this exercise is the relative proportions rather than precise percentages.)
Teaching Tips
1. Imagine a country cabin with a roaring fire in a fireplace. The windows are partially opened to permit air to rush into the house to feed the fire. This flow of air through the windows, through the home, to the fireplace, and then out the chimney is analogous to the flow of water through a sponge. Side note: Many sponges, especially commercial bath sponges, have outer body walls that are highly folded. Simpler vase sponges, with straighter walls, are good examples to show students when discussing this basic water flow pattern.
2. Students may find it challenging to understand why sponges are animals. It might be helpful to return to the distinctions between animals, plants, and fungi when introducing sponges.
Copyright © 2009 Pearson Education, Inc.

16. A purple tube sponge اسفنج بنفسجي الأنبوب Scypha اسفنج السيفا
Sponges are suspension feeders, filtering food particles from water passed through food-trapping equipment
الاسفنجيات متغذيات بالعوالق (تتغذي على العوالق المائية ”البلانكتون“) ، حيث ترشح جزيئات الغذاء من الماء الذي يمر خلال أجهزة حجز الغذاء
Water is drawn in through pores in the body wall into a central cavity, and then flows out through a larger opening
يتغلغل الماء خلال ثقوب جدار الجسم إلى التجويف المركزي، ويتدفق للخارج خلال فتحات أكبر
To grow by 100 g, a sponge must filter 1,000 kg of water
ليبلغ الاسفنج وزن الـ 100 جرام ، فلابد له من ترشيح 1000 جرام من الماء
An azure vase sponge
اسفنج مزهري الشكل
Figure 18.5A Scypha.
A purple tube sponge
اسفنج بنفسجي الأنبوب
Scypha
اسفنج السيفا

17. Structure of a simple sponge تركيب الاسفنج البسيط
Pores
ثقوب
Choanocyte
خلايا سوطية
Amoebocyte
خلايا أميبية
Water flow
تدفق الماء
Skeletal
fiber
ألياف هيكلية
Central cavity
تجويف وسطي
Flagella
أسواط
Figure 18.5D Structure of a simple sponge.
Choanocyte in contact
with an amoebocyte
خلايا سوطية متصلة
بالخلايا الأميبية
Structure of
a simple sponge
تركيب الاسفنج البسيط

18. 18.6 Cnidarians are radial animals with tentacles and stinging cells الجوفمعويات حيوانات شعاعية ذات لوامساً وخلايا لاسعة
Cnidarians (phylum Cnidaria) have two tissue layers: an outer epidermis and an inner cell layer lining the digestive cavity
تملك الجوفمعويات (شعبة الجوفمعويات) طبقتين نسيجيتين : بشرة خارجية وطبقة خلوية داخلية تبطن التجويف الهضمي
A jelly-filled middle region may have scattered amoeboid cells
قد تحتوي المنطقة الوسطى المليئة بالهلام على خلايا أميبية متفرقة
Cnidarians use tentacles to capture prey and push them into their mouths
تستخدم الجوفمعويات اللوامس لإمساك ودفع الفريسة إلى أفواهها
The mouth leads to the gastrovascular cavity, which functions in digestion and circulation and as a hydrostatic skeleton
يؤدي الفم إلى التجويف الوعائي المعدي والذي يقوم بالهضم والدوران وكهيكل اتزان مائي
Cnidocytes on tentacles sting prey and function in defense
الخلايا اللاسعة الموجودة على اللوامس تلسع الفريسة كما تقوم بالوظيفة الدفاعية
Explain that the gastrovascular cavity of cnidarians (and flatworms) is the functional equivalent of two systems in our bodies, serving as the site of digestion and the method of nutrient delivery.
Student Misconceptions and Concerns
1. Students typically expect that an animal will have a head. The subject of a head might have already been introduced when discussing body plans. As you proceed through the animal phyla, have students consider how sponges and cnidarians meet their basic needs without the benefit of a well-defined head.
2. As students survey the major animal phyla, they might perceive the diversity of animals as spread somewhat evenly across the nine major phyla of invertebrates. Yet, two-thirds of all known species of life (and at least 80% all described animal species) are arthropods. Although sources disagree on the number of living species that have been described, there is widespread agreement that the number of undescribed species is many times more than the number of described species. By examining the number of described species, some amazing proportions emerge. You might consider this exercise to make the point. Determine how many students represent 1% of the class. Then have the entire class stand. Tell the students that collectively, they represent all of the animal species known to exist today. Have 5% of the class sit, representing the proportion of known animal species that are vertebrates. Next, have 15% of the class sit, representing all of the remaining types of animals except arthropods. At this point, everyone standing (80% of the class) represents the proportion of known animal species that are arthropods (a conservative fraction). Finally, have 50% of the entire class sit, leaving 30% standing. Have the class guess what group of animals is represented now (clearly some subgroup of arthropods). This final 30% represents the known number of species of beetles! (The numbers used are rounded. Even high percentages for beetles and invertebrates may be more accurate. The point of this exercise is the relative proportions rather than precise percentages.)
Teaching Tips
1. Just about any glass bottle with a narrow neck makes a good model of the cnidarian body plan. The narrowed neck of the body represents the constricted region of a cnidarian that regulates what enters and leaves the gastrovascular cavity. Additional note: The name “gastrovascular” represents the dual function of the cavity. It must serve as the site of digestion and the method of delivery of the nutrients. The cavity extends, like a primitive circulatory system, throughout the body, and is thus vascular in nature.
2. If students have been stung by a jellyfish, it was a toxin on the cnidocytes that caused a reaction. (Nematocysts are the firing part of a cnidocyte cell. The toxin is delivered by the firing of the nematocysts. A new cnidocyte must take the place of one that has fired its nematocyst, since cnidocytes cannot “reload.”) (18.6)
3. The gastrovascular cavity of cnidarians and flatworms is the functional equivalent of two systems in our bodies. Ask students to explain how nutrients consumed at a meal nourish the cells in our toes. Nutrients absorbed by our gut are transported throughout our body by the circulatory system. Extensions of the gastrovascular cavity permit nutrient distribution in these cnidarians and flatworms.
Copyright © 2009 Pearson Education, Inc.

19. 18.6 Cnidarians are radial animals with tentacles and stinging cells الجوفمعويات حيوانات شعاعية التماثل ذات لوامس وخلايا لاسعة
Cnidarians have two kinds of radially symmetrical body forms: polyp and medusa
تمتلك الجوفمعويات نوعان من التماثل الشعاعي للأشكال الجسدية البوليبية (اللحمية) والهلامية
Some cnidarians have alternating polyp and medusa forms in their life cycle, while others exist only as polyp or medusa forms
تمتلك بعض الجوفمعويات تعاقب شكلي بين البوليب والهلام في دورة حياتها بينما يوجد بعضها كشكل بوليبي أو هلامي
Student Misconceptions and Concerns
1. Students typically expect that an animal will have a head. The subject of a head might have already been introduced when discussing body plans. As you proceed through the animal phyla, have students consider how sponges and cnidarians meet their basic needs without the benefit of a well-defined head.
2. As students survey the major animal phyla, they might perceive the diversity of animals as spread somewhat evenly across the nine major phyla of invertebrates. Yet, two-thirds of all known species of life (and at least 80% all described animal species) are arthropods. Although sources disagree on the number of living species that have been described, there is widespread agreement that the number of undescribed species is many times more than the number of described species. By examining the number of described species, some amazing proportions emerge. You might consider this exercise to make the point. Determine how many students represent 1% of the class. Then have the entire class stand. Tell the students that collectively, they represent all of the animal species known to exist today. Have 5% of the class sit, representing the proportion of known animal species that are vertebrates. Next, have 15% of the class sit, representing all of the remaining types of animals except arthropods. At this point, everyone standing (80% of the class) represents the proportion of known animal species that are arthropods (a conservative fraction). Finally, have 50% of the entire class sit, leaving 30% standing. Have the class guess what group of animals is represented now (clearly some subgroup of arthropods). This final 30% represents the known number of species of beetles! (The numbers used are rounded. Even high percentages for beetles and invertebrates may be more accurate. The point of this exercise is the relative proportions rather than precise percentages.)
Teaching Tips
1. Just about any glass bottle with a narrow neck makes a good model of the cnidarian body plan. The narrowed neck of the body represents the constricted region of a cnidarian that regulates what enters and leaves the gastrovascular cavity. Additional note: The name “gastrovascular” represents the dual function of the cavity. It must serve as the site of digestion and the method of delivery of the nutrients. The cavity extends, like a primitive circulatory system, throughout the body, and is thus vascular in nature.
2. If students have been stung by a jellyfish, it was a toxin on the cnidocytes that caused a reaction. (Nematocysts are the firing part of a cnidocyte cell. The toxin is delivered by the firing of the nematocysts. A new cnidocyte must take the place of one that has fired its nematocyst, since cnidocytes cannot “reload.”) (18.6)
3. The gastrovascular cavity of cnidarians and flatworms is the functional equivalent of two systems in our bodies. Ask students to explain how nutrients consumed at a meal nourish the cells in our toes. Nutrients absorbed by our gut are transported throughout our body by the circulatory system. Extensions of the gastrovascular cavity permit nutrient distribution in these cnidarians and flatworms.
Sea anemones (Anthopleura)
(about 6 cm in diameter), exist only as polyps
شقائق النعمان ( الأنثوبليورا) (حوالي 6 سم قطراً) يوجد كبوليبات فقط
Medusa form: a marine jelly sea nettle (5 cm in diameter)
الشكل الهلامي: قنديل بحري لاسع البحر (حوالي 5 سم قطرا(
Polyp body form: a hydra
الشكل الجسدي البوليبي : هيدرا
Copyright © 2009 Pearson Education, Inc.

20. 18.7 Flatworms are the simplest bilateral animals الديدان المفلطحة هي أبسط الحيوانات ذات التماثل الجانبي
Flatworms (phylum Platyhelminthes) are the simplest bilateral animals
الديدان المفلطحة (شعبة الديدان المفلطحة) هي أبسط الحيوانات المتماثلة جانبياً
There are three major groups of flatworms
هناك ثلاث مجاميع رئيسية للديدان المفلطحة
Free-living flatworms (planarians) have heads with light-sensitive eyespots and flaps to detect chemicals
الديدان المفلطحة حرة المعيشة (البلاناريات) لديها رؤوس بها بقع عينية مرهفة الحس وأغطية تكتشف بها المواد الكيمائية
Dense clusters of nerve cells form a simple brain, and a pair of nerve cords runs the length of the body
تشكل التجمعات الكثيفة من الخلايا العصبية الدماغ البسيط، وزوجين من الحبال العصبية والتي تمتد بطول الجسم
Planarians have a branched gastrovascular cavity with a single opening
تمتلك البلاناريات تجويف وعائي معدي متفرع ذا فتحة واحدة
Student Misconceptions and Concerns
1. As students survey the major animal phyla, they might perceive the diversity of animals as spread somewhat evenly across the nine major phyla of invertebrates. Yet, two-thirds of all known species of life (and at least 80% all described animal species) are arthropods. Although sources disagree on the number of living species that have been described, there is widespread agreement that the number of undescribed species is many times more than the number of described species. By examining the number of described species, some amazing proportions emerge. You might consider this exercise to make the point. Determine how many students represent 1% of the class. Then have the entire class stand. Tell the students that collectively, they represent all of the animal species known to exist today. Have 5% of the class sit, representing the proportion of known animal species that are vertebrates. Next, have 15% of the class sit, representing all of the remaining types of animals except arthropods. At this point, everyone standing (80% of the class) represents the proportion of known animal species that are arthropods (a conservative fraction). Finally, have 50% of the entire class sit, leaving 30% standing. Have the class guess what group of animals is represented now (clearly some subgroup of arthropods). This final 30% represents the known number of species of beetles! (The numbers used are rounded. Even high percentages for beetles and invertebrates may be more accurate. The point of this exercise is the relative proportions rather than precise percentages.)
Teaching Tips
1. The gastrovascular cavity of cnidarians and flatworms is the functional equivalent of two systems in our bodies. Ask students to explain how nutrients consumed at a meal nourish the cells in our toes. Nutrients absorbed by our gut are transported throughout our body by the circulatory system. Extensions of the gastrovascular cavity permit nutrient distribution in these cnidarians and flatworms.
2. A planarian, indicated in Figure 18.7A, ingests food in the middle of its body. Challenge students to think of other animals that have a mouth located far from the head. The discussion that will follow this challenge is likely to touch on the defining features of a head, invoking a critical analysis of animal body plans and providing an important exercise for this chapter.
Copyright © 2009 Pearson Education, Inc.

21. A free-living flatworm, the planarian
Gastrovascular cavity
التجويف الوعائي المعدي
Nerve cords
أحبال عصبية
Mouthفم
Eyespotsبقع عينية
Figure 18.7A A free-living flatworm, the planarian (most are about 5–10 mm long).
Nervous tissue clusters
تجمعات من أنسجة عصبية
A free-living flatworm, the planarian
دودة مفلطحة حرة المعيشة ، البلاناريا
(most are about 5–10 mm longمعظمها يبلغ حوالي 5-10 ملم طولاً )
Bilateral symmetry
تماثل جانبي

22. 18.7 Flatworms are the simplest bilateral animals الديدان المفلطحة هي أبسط الحيوانات ذات التماثل الجانبي
Flukes and tapeworms are parasitic flatworms with complex life cycles
الديدان الورقية و الديدان الشريطية ديدان مفلطحة طفيلية ولها دورات حياة معقدة
Flukes live as parasites, with suckers to attach to their hosts
تعيش الديدان الورقية كطفيليات ذات ممصات تلصقها بعوائلها
Tapeworms inhabit the digestive tracts of vertebrates
تسكن الديدان الشريطية في القنوات الهضمية للفقاريات
They consist of a ribbon-like body with repeated units
وتتألف من جسد يشبه الشريط متكرر الوحدات
The anterior scolex is armed with hooks and suckers for attachment, while posterior units are full of eggs and sperm
الرأس الأمامي بمُزود بخطاطيف وممصات للالتصاق، بينما تكون الوحدات الخلفية مليئة بالبويضات والحيوانات المنوية
Tapeworms lack a digestive tract and absorb nutrients from the intestines of their hosts
تفتقر الديدان الشريطية لقناة هضمية وتمتص المواد المغذية من أمعاء عوائله
Point out that tapeworms are unusual animals in that they do not ingest food.
Student Misconceptions and Concerns
1. As students survey the major animal phyla, they might perceive the diversity of animals as spread somewhat evenly across the nine major phyla of invertebrates. Yet, two-thirds of all known species of life (and at least 80% all described animal species) are arthropods. Although sources disagree on the number of living species that have been described, there is widespread agreement that the number of undescribed species is many times more than the number of described species. By examining the number of described species, some amazing proportions emerge. You might consider this exercise to make the point. Determine how many students represent 1% of the class. Then have the entire class stand. Tell the students that collectively, they represent all of the animal species known to exist today. Have 5% of the class sit, representing the proportion of known animal species that are vertebrates. Next, have 15% of the class sit, representing all of the remaining types of animals except arthropods. At this point, everyone standing (80% of the class) represents the proportion of known animal species that are arthropods (a conservative fraction). Finally, have 50% of the entire class sit, leaving 30% standing. Have the class guess what group of animals is represented now (clearly some subgroup of arthropods). This final 30% represents the known number of species of beetles! (The numbers used are rounded. Even high percentages for beetles and invertebrates may be more accurate. The point of this exercise is the relative proportions rather than precise percentages.)
Teaching Tips
1. The gastrovascular cavity of cnidarians and flatworms is the functional equivalent of two systems in our bodies. Ask students to explain how nutrients consumed at a meal nourish the cells in our toes. Nutrients absorbed by our gut are transported throughout our body by the circulatory system. Extensions of the gastrovascular cavity permit nutrient distribution in these cnidarians and flatworms.
2. A planarian, indicated in Figure 18.7A, ingests food in the middle of its body. Challenge students to think of other animals that have a mouth located far from the head. The discussion that will follow this challenge is likely to touch on the defining features of a head, invoking a critical analysis of animal body plans and providing an important exercise for this chapter.
Copyright © 2009 Pearson Education, Inc.

23. A tapeworm, a parasitic flatworm دودة شريطية ، دودة مفلطحة طفيلية
Units with
reproductive
structures
وحدات ذات تراكيب تكاثرية
Scolex
(anterior end)
رأس (طرف أمامي)
Figure 18.7B A tapeworm, a parasitic flatworm.
Hooksخطاطيف
Sucker
ممصات

24. 18.8 Nematodes have a pseudocoelom and a complete digestive tract تمتلك الديدان المستديرة تجويفاً سيلومياً كاذباً وقناة هضمية متكاملة
Roundworms (phylum Nematoda) have bilateral symmetry and three tissue layers
الديدان المستديرة (شعبة النيماتودا) ذات تماثلاً جانبياً كما وتمتلك طبقات نسيجية ثلاثية
They are abundant and diverse, with an estimated 500,000 species
هذه الديدان كثيرة ومتنوعة حيث قدرت بـ 500,000 نوع
The body cavity is a pseudocoelom, which functions to distribute nutrients and as a hydroskeleton
تجويف جسد عبارة عن سيلوم كاذب يقوم بتوزيع الغذاء والاتزان المائي الهيكلي
The complete digestive tract has a mouth and anus
يحتوي الجهاز الهضمي المتكامل على فم وشرج
Humans host at least 50 species of nematodes
يعول الإنسان حوالي 50 نوعاً من النيماتودا
A one-way digestive tract functions as a sort of “disassembly line.” Roundworms (and all animals with a mouth separate from the anus) “disassemble” food as it moves through the digestive tract.
Student Misconceptions and Concerns
1. As students survey the major animal phyla, they might perceive the diversity of animals as spread somewhat evenly across the nine major phyla of invertebrates. Yet, two-thirds of all known species of life (and at least 80% all described animal species) are arthropods. Although sources disagree on the number of living species that have been described, there is widespread agreement that the number of undescribed species is many times more than the number of described species. By examining the number of described species, some amazing proportions emerge. You might consider this exercise to make the point. Determine how many students represent 1% of the class. Then have the entire class stand. Tell the students that collectively, they represent all of the animal species known to exist today. Have 5% of the class sit, representing the proportion of known animal species that are vertebrates. Next, have 15% of the class sit, representing all of the remaining types of animals except arthropods. At this point, everyone standing (80% of the class) represents the proportion of known animal species that are arthropods (a conservative fraction). Finally, have 50% of the entire class sit, leaving 30% standing. Have the class guess what group of animals is represented now (clearly some subgroup of arthropods). This final 30% represents the known number of species of beetles! (The numbers used are rounded. Even high percentages for beetles and invertebrates may be more accurate. The point of this exercise is the relative proportions rather than precise percentages.)
Teaching Tips
1. The undercooking of meat contributes to the spread of parasitic diseases. If you addressed the denaturation of proteins in Chapter 3, here is a chance to reinforce the points about the effects of heat. Proteins denature and discolor when heated (pink meat turns brown). This same process denatures proteins in parasites and kills them (although some parasites can survive relatively high temperatures). If any portion of a steak is still pink, the meat has not been cooked enough to denature the meat or parasitic proteins. Trichinosis is acquired by eating pork that has not been cooked enough to denature all the proteins (and kill the parasites). The details of just about any parasitic infection of humans will get the attention of your students…and likely cause them to start scratching!
2. Annelids (and nematodes, Module 18.8) have the advantage of a digestive tract with openings at both ends. This permits the efficiency of a digestive tract specialized for a one-way flow of ingested materials and enjoying the same advantages as an assembly line, but in reverse, serving in fact as a sort of “disassembly” line. These worms (and all animals with a mouth separate from the anus) “disassemble” food as it moves through the digestive tract.
Video: C. elegans Crawling
Video: C. elegans Embryo Development (time lapse)
Copyright © 2009 Pearson Education, Inc.

25. A free-living nematode نيماتودا حرة المعيشة
Dog heart infected by heartworm, a parasitic nematode
قلب كلب مصاب بالدودة القلبية ، نيماتودا طفيلية
Figure 18.8A A free-living nematode.
Mouth
الفم
A free-living nematode
نيماتودا حرة المعيشة

26. 18.9 Diverse molluscs are variations on a common body plan الرخويات المتنوعة عبارة عن تنوعات لخطة تصميم جسد مشتركة
Molluscs (phylum Mollusca) have a true coelom and a circulatory system
تملك الرخويات (شعبة الرخويات) تجويفاً سيلومياً حقيقياً وجهازاً دورياً
Many molluscs feed with a rasping radula, used to scrape up food
تتنغذي الرخويات بواسطة مبرد قاشط يعمل على تقشير الغذاء
All molluscs have
تحتوي كل الرخويات على:
A muscular foot that functions in locomotion
قدم عضلي يستخدم في الحركة
A visceral mass containing most of the internal organs
كتلة حشوية تحتوي على أغلب الأعضاء الداخلية
A mantle, which may secrete a shell that encloses the visceral mass
برنس (عباءة) والتي قد تفرز صدفة تغلف الكتلة الحشوية
Student Misconceptions and Concerns
1. As students survey the major animal phyla, they might perceive the diversity of animals as spread somewhat evenly across the nine major phyla of invertebrates. Yet, two-thirds of all known species of life (and at least 80% all described animal species) are arthropods. Although sources disagree on the number of living species that have been described, there is widespread agreement that the number of undescribed species is many times more than the number of described species. By examining the number of described species, some amazing proportions emerge. You might consider this exercise to make the point. Determine how many students represent 1% of the class. Then have the entire class stand. Tell the students that collectively, they represent all of the animal species known to exist today. Have 5% of the class sit, representing the proportion of known animal species that are vertebrates. Next, have 15% of the class sit, representing all of the remaining types of animals except arthropods. At this point, everyone standing (80% of the class) represents the proportion of known animal species that are arthropods (a conservative fraction). Finally, have 50% of the entire class sit, leaving 30% standing. Have the class guess what group of animals is represented now (clearly some subgroup of arthropods). This final 30% represents the known number of species of beetles! (The numbers used are rounded. Even high percentages for beetles and invertebrates may be more accurate. The point of this exercise is the relative proportions rather than precise percentages.)
Teaching Tips
1. When we eat clams, we usually eat strips of the muscular foot. If the clams are mushy and/or contain sand, the serving may also include portions of the intestines.
2. A simple demonstration of the bivalve body plan can be obtained by purchasing smoked oysters in a grocery store. Each smoked oyster (ready to be consumed) is the soft body removed from the paired shells. For an enjoyable demonstration, discuss the anatomy of a specimen and then enjoy it for lunch.
Copyright © 2009 Pearson Education, Inc.

27. The general body plan of a mollusca خطة تصميم الجسم العامة لكائن رخو
كتلة حشوية
Visceral mass
Mouthفم
Anusشرج
Coelomتجويف سيلومي
Reproductive organs
أعضاء تناسلية
Kidneyكلية
Heartقلب
Trochophore larva
يرقة سابحة
Digestive tractقناة هضمية
برنس Mantle
Shellصدفة
Digestive tract
قناة هضمية
Mantle
cavity
تجويف البرنس
Radula
مبرد
Radula مبرد
Anus
شرج
Figure 18.9A The general body plan of a mollusc.
Mouthفم
Gill
خيشوم
Mouth فم
Foot
قدم
Nerve
cords

28. 18.9 Diverse molluscs are variations on a common body plan الرخويات المتنوعة عبارة عن تنوعات لخطة تصميم جسد مشتركة
Gastropods are the largest group of molluscs and include the snails and slugs
بطنية القدم هي أكبر مجاميع الرخويات وتشمل الحلزونيات (القواقع) والبزاقات
Most snails are protected by a single, spiral shell
أغلب الحلزونيات محمية بواسطة صدفة حلزونية مفردة
In land snails, the lining of the mantle cavity functions as a lung
تقوم بطانة التجويف البرنسي في الحلزونيات البرية بوظيفة الرئة
Slugs have lost their mantle and shell and have long colorful projections that function as gills
فقدت البزاقات برنسها وصدفتها وامتلكت نتوءات ملونة تعمل كخياشيم
Student Misconceptions and Concerns
1. As students survey the major animal phyla, they might perceive the diversity of animals as spread somewhat evenly across the nine major phyla of invertebrates. Yet, two-thirds of all known species of life (and at least 80% all described animal species) are arthropods. Although sources disagree on the number of living species that have been described, there is widespread agreement that the number of undescribed species is many times more than the number of described species. By examining the number of described species, some amazing proportions emerge. You might consider this exercise to make the point. Determine how many students represent 1% of the class. Then have the entire class stand. Tell the students that collectively, they represent all of the animal species known to exist today. Have 5% of the class sit, representing the proportion of known animal species that are vertebrates. Next, have 15% of the class sit, representing all of the remaining types of animals except arthropods. At this point, everyone standing (80% of the class) represents the proportion of known animal species that are arthropods (a conservative fraction). Finally, have 50% of the entire class sit, leaving 30% standing. Have the class guess what group of animals is represented now (clearly some subgroup of arthropods). This final 30% represents the known number of species of beetles! (The numbers used are rounded. Even high percentages for beetles and invertebrates may be more accurate. The point of this exercise is the relative proportions rather than precise percentages.)
Teaching Tips
1. When we eat clams, we usually eat strips of the muscular foot. If the clams are mushy and/or contain sand, the serving may also include portions of the intestines.
2. A simple demonstration of the bivalve body plan can be obtained by purchasing smoked oysters in a grocery store. Each smoked oyster (ready to be consumed) is the soft body removed from the paired shells. For an enjoyable demonstration, discuss the anatomy of a specimen and then enjoy it for lunch.
Video: Nudibranchs
Copyright © 2009 Pearson Education, Inc.

29. A marine gastropod: a sea slug بطن قدمي بحري : بزاقة بحرية
Figure 18.9c A terrestrial gastropod: a land snail.
A terrestrial gastropod: a land snail
بطن قدمي أرضي : القوقع البري

30. Bivalves have shells divided into two halves that are hinged together
18.9 Diverse molluscs are variations on a common body plan الرخويات المتنوعة عبارة عن تنوعات لخطة تصميم جسد مشتركة
Bivalves have shells divided into two halves that are hinged together
تملك ذوات المصرعين أصدافاً مقسمة إلى نصفين مرتبطين ببعضهما البعض
Bivalves include clams, oysters, mussels, and scallops
تشمل ذوات المصرعين الأصداف والمحارات وذوات المصرعين والمحارات السكلوبية
Most bivalves are sedentary suspension feeders, attached to the substrate by strong threads
معظم ذوات المصراعين متغذيات على العوالق ثابتة، وتلتصق بالأشياء بواسطة خيوط قوية
Student Misconceptions and Concerns
1. As students survey the major animal phyla, they might perceive the diversity of animals as spread somewhat evenly across the nine major phyla of invertebrates. Yet, two-thirds of all known species of life (and at least 80% all described animal species) are arthropods. Although sources disagree on the number of living species that have been described, there is widespread agreement that the number of undescribed species is many times more than the number of described species. By examining the number of described species, some amazing proportions emerge. You might consider this exercise to make the point. Determine how many students represent 1% of the class. Then have the entire class stand. Tell the students that collectively, they represent all of the animal species known to exist today. Have 5% of the class sit, representing the proportion of known animal species that are vertebrates. Next, have 15% of the class sit, representing all of the remaining types of animals except arthropods. At this point, everyone standing (80% of the class) represents the proportion of known animal species that are arthropods (a conservative fraction). Finally, have 50% of the entire class sit, leaving 30% standing. Have the class guess what group of animals is represented now (clearly some subgroup of arthropods). This final 30% represents the known number of species of beetles! (The numbers used are rounded. Even high percentages for beetles and invertebrates may be more accurate. The point of this exercise is the relative proportions rather than precise percentages.)
Teaching Tips
1. When we eat clams, we usually eat strips of the muscular foot. If the clams are mushy and/or contain sand, the serving may also include portions of the intestines.
2. A simple demonstration of the bivalve body plan can be obtained by purchasing smoked oysters in a grocery store. Each smoked oyster (ready to be consumed) is the soft body removed from the paired shells. For an enjoyable demonstration, discuss the anatomy of a specimen and then enjoy it for lunch.
Copyright © 2009 Pearson Education, Inc.

31. Eyesعيون A bivalve: a scallopذو مصراعين : محار السكلوب
A cephalopod with an internal shell: a squid
رأس قدمي ذو صدفة داخلية : حبار
Eyesعيون
Figure 18.9F A cephalopod with an internal shell: a squid.
A bivalve: a scallopذو مصراعين : محار السكلوب

32. 18.9 Diverse molluscs are variations on a common body plan الرخويات المتنوعة عبارة عن تنوعات لخطة تصميم جسد مشتركة
Cephalopods are fast, agile predators and include squids and octopuses
الرأسيات القدم هي مفترسات رشيقة سريعة وتشمل الحبارات والإخطبوطات
Cephalopods have large brains and sophisticated sense organs, including complex image-focusing eyes
تمتلك الرأس قدميات أدمغة كبيرة وأعضاء حسية معقدة تشمل أعين معقدة مركزة للصور
In most cephalopods, the shell is small and internal (squid) or missing (octopuses)
في معظم الرأس قدميات تكون الصدفة صغيرة وداخلية (الحبار) أو غير موجودة (الإخطبوطات)
Squid are fast, streamlined predators that use a muscular siphon for jet propulsion
الحبار عبارة عن مفترس انسيابي سريع ويستخدم ممصاً عضلياً للدفع النفاث
Octopuses live on the seafloor, where they creep about in search of food
تعيش الإخطبوطات على قاع البحر حيث تزحف بحثاً عن الطعام
Student Misconceptions and Concerns
1. As students survey the major animal phyla, they might perceive the diversity of animals as spread somewhat evenly across the nine major phyla of invertebrates. Yet, two-thirds of all known species of life (and at least 80% all described animal species) are arthropods. Although sources disagree on the number of living species that have been described, there is widespread agreement that the number of undescribed species is many times more than the number of described species. By examining the number of described species, some amazing proportions emerge. You might consider this exercise to make the point. Determine how many students represent 1% of the class. Then have the entire class stand. Tell the students that collectively, they represent all of the animal species known to exist today. Have 5% of the class sit, representing the proportion of known animal species that are vertebrates. Next, have 15% of the class sit, representing all of the remaining types of animals except arthropods. At this point, everyone standing (80% of the class) represents the proportion of known animal species that are arthropods (a conservative fraction). Finally, have 50% of the entire class sit, leaving 30% standing. Have the class guess what group of animals is represented now (clearly some subgroup of arthropods). This final 30% represents the known number of species of beetles! (The numbers used are rounded. Even high percentages for beetles and invertebrates may be more accurate. The point of this exercise is the relative proportions rather than precise percentages.)
Teaching Tips
1. When we eat clams, we usually eat strips of the muscular foot. If the clams are mushy and/or contain sand, the serving may also include portions of the intestines.
2. A simple demonstration of the bivalve body plan can be obtained by purchasing smoked oysters in a grocery store. Each smoked oyster (ready to be consumed) is the soft body removed from the paired shells. For an enjoyable demonstration, discuss the anatomy of a specimen and then enjoy it for lunch.
Copyright © 2009 Pearson Education, Inc.

33. رأس قدمي بدون صدفة : إخطبوط
Figure 18.9G A cephalopod without a shell: an octopus.
A cephalopod without
a shell: an octopus
رأس قدمي بدون صدفة : إخطبوط

34. 18.10 Annelids are segmented worms الحلقيات هي ديدان عُقلية (ذات عُقل)
Annelids (phylum Annelida) have a closed circulatory system in which blood is enclosed in vessels
تمتلك الحلقيات (شعبة الديدان الحلقية) جهازاً دورياً مغلقاً حيث يجري الدم في أوعية
Their nervous system includes a simple brain and ventral nerve cord with cluster of nerve cells in each segment
يشمل الجهاز العصبي دماغاً بسيطاً وحبلاً عصبياً ظهرياً وتجمُعاً من الخلايا العصبية في كل عُقلة (حلقة)
The true coelom functions as hydrostatic skeleton
يعمل تجويف السيلوم الحقيقي كهيكل اتزان مائي
Earthworms ingest soil and extract nutrients, aerating soil and improving its texture
تبتلع دودة الأرض التربة وتستخلص منها المواد المغذية، مما يؤدي إلى تهوية التربة وتحسين قوامها
Student Misconceptions and Concerns
1. As students survey the major animal phyla, they might perceive the diversity of animals as spread somewhat evenly across the nine major phyla of invertebrates. Yet, two-thirds of all known species of life (and at least 80% all described animal species) are arthropods. Although sources disagree on the number of living species that have been described, there is widespread agreement that the number of undescribed species is many times more than the number of described species. By examining the number of described species, some amazing proportions emerge. You might consider this exercise to make the point. Determine how many students represent 1% of the class. Then have the entire class stand. Tell the students that collectively, they represent all of the animal species known to exist today. Have 5% of the class sit, representing the proportion of known animal species that are vertebrates. Next, have 15% of the class sit, representing all of the remaining types of animals except arthropods. At this point, everyone standing (80% of the class) represents the proportion of known animal species that are arthropods (a conservative fraction). Finally, have 50% of the entire class sit, leaving 30% standing. Have the class guess what group of animals is represented now (clearly some subgroup of arthropods). This final 30% represents the known number of species of beetles! (The numbers used are rounded. Even high percentages for beetles and invertebrates may be more accurate. The point of this exercise is the relative proportions rather than precise percentages.)
Teaching Tips
1. When discussing cephalopods, the subject of animal intelligence may be noted. Defining and identifying animal intelligence is not a simple task. Consider discussing the correlation of intelligence and predation. Why might these two traits be linked? What other characteristics, such as sophistication of communication, correlate with intelligence?
2. Annelids (and nematodes, Module 18.8) have the advantage of a digestive tract with openings at both ends. This permits the efficiency of a digestive tract specialized for a one-way flow of ingested materials and enjoying the same advantages as an assembly line, but in reverse, serving in fact as a sort of “disassembly” line. These worms (and all animals with a mouth separate from the anus) “disassemble” food as it moves through the digestive tract.
3. As noted in Module 18.10, leeches remain an important tool in modern medicine. Consider presenting some examples of the latest use of leeches in medicine to the class, or having students research and discuss them. Such short asides will often liven up your class.
Video: Tubeworms
Video: Earthworm Locomotion
Copyright © 2009 Pearson Education, Inc.

35. Segmentation and internal anatomy of an earthworm
Epidermis
بشرة خارجية
Segment wall
(partition
between
segments)
جدار العُقلة
(الحاجز بين العُقلي)
Anusشرج
Circular
Muscle
عضلة دائرية
Segment
wall
جدار العُقلة
Longitudinal
muscle
Mucus-secreting organ
عضو إفراز المخاط
Dorsal
blood
vessel
Excretory
organ
عضو افرازي
Intestine
أمعاء
Bristles
شعر خشن
Bristles
شعر خشن
Dorsal blood
vessel
وعاء دموي ظهري
Nerve cord
حبل عصبي
Ventral blood vessel
أوعية دموية بطنية
Excretory
organ
عضو افرازي
Digestive tract
قناة هضمية
Coelom
سيلوم
Segment wall
جدار العُقلة
Brainدماغ
Figure 18.10A Segmentation and internal anatomy of an earthworm.
Ventral blood vessel
شعيرة دموية بطنية
Nerve cord
حبل عصبي
Mouthفم
Pumping segmental vessels
أوعية ضخ عُقلية
Giant
Australian
earthworm
دودة الأرض
الأسترالية العملاقة
Segmentation and internal anatomy of an earthworm
تشريح العُقل والأجزاء الداخلية لدودة أرض

36. 18.10 Annelids are segmented worms الحلقيات هي ديدان عُقلية
Polychaetes are the largest group of annelids
عديدات الأشواك هي المجموعة الأكبر بين الحلقيات
Each polychaete segment has a pair of fleshy appendages with stiff bristles or chaetae
تحتوي كل عُقلة من عُقل عديدة الأشواك على زوج من الزوائد اللحمية ذات شعر خشن صلب أو تراكيب إبرية
Polychaetes search for prey on the seafloor or live in tubes and filter food particles
تبحث عديدة الأشواك عن الطريدة في قاع البحر ، أو قد تعيش في أنابيب وترشح جزيئات الغذاء
Most leeches are free-living carnivores, but some suck blood
يعيش أغلب العلق كآكلات لحوم حرة، ولكن بعضه يمتص الدم
Blood-sucking leeches use razor-like jaws, secrete an anesthetic and an anticoagulant, and suck up to 10 times their own weight in blood
يستخدم العلق الماص للدم فكوك شبيهة بالشفرة ، ويفرز مواد مخدرة وأخرى مضادة للتخثر، ويمتص من الدم ما يصل إلى10 أضعاف وزنه
Student Misconceptions and Concerns
1. As students survey the major animal phyla, they might perceive the diversity of animals as spread somewhat evenly across the nine major phyla of invertebrates. Yet, two-thirds of all known species of life (and at least 80% all described animal species) are arthropods. Although sources disagree on the number of living species that have been described, there is widespread agreement that the number of undescribed species is many times more than the number of described species. By examining the number of described species, some amazing proportions emerge. You might consider this exercise to make the point. Determine how many students represent 1% of the class. Then have the entire class stand. Tell the students that collectively, they represent all of the animal species known to exist today. Have 5% of the class sit, representing the proportion of known animal species that are vertebrates. Next, have 15% of the class sit, representing all of the remaining types of animals except arthropods. At this point, everyone standing (80% of the class) represents the proportion of known animal species that are arthropods (a conservative fraction). Finally, have 50% of the entire class sit, leaving 30% standing. Have the class guess what group of animals is represented now (clearly some subgroup of arthropods). This final 30% represents the known number of species of beetles! (The numbers used are rounded. Even high percentages for beetles and invertebrates may be more accurate. The point of this exercise is the relative proportions rather than precise percentages.)
Teaching Tips
1. When discussing cephalopods, the subject of animal intelligence may be noted. Defining and identifying animal intelligence is not a simple task. Consider discussing the correlation of intelligence and predation. Why might these two traits be linked? What other characteristics, such as sophistication of communication, correlate with intelligence?
2. Annelids (and nematodes, Module 18.8) have the advantage of a digestive tract with openings at both ends. This permits the efficiency of a digestive tract specialized for a one-way flow of ingested materials and enjoying the same advantages as an assembly line, but in reverse, serving in fact as a sort of “disassembly” line. These worms (and all animals with a mouth separate from the anus) “disassemble” food as it moves through the digestive tract.
3. As noted in Module 18.10, leeches remain an important tool in modern medicine. Consider presenting some examples of the latest use of leeches in medicine to the class, or having students research and discuss them. Such short asides will often liven up your class.
Copyright © 2009 Pearson Education, Inc.

37. A tube-building polychaete عديدة أشواك بانية للأنابيب
Figure 18.10B A free-swimming marine polychaete.
A medicinal leech applied to drain blood from a patient
علق طبي يُستخدم لامتصاص الدم من مريض
A free-swimming marine polychaete
عديدة أشواك بحرية سابحة حرة المعيشة

38. Video: Lobster Mouth Parts
18.11 Arthropods are segmented animals with jointed appendages and an exoskeleton مفصليات الأرجل هي حيوانات عُقلية ذات زوائد مفصلية وهيكل خارجي
Arthropods (phylum Arthropoda) include over a million species of including crayfish, lobsters, crabs, barnacles, spiders, ticks, and insects
هناك ما يزيد عن المليون نوع من مفصليات الأرجل (شعبة مفصليات الأرجل) ، ومنها جراد البحر والكركندات (أمهات الربان) والسرطنات والقشريات الصدفية والعناكب والقراد والحشرات
- The diversity and success of arthropods are due to segmentation, a hard exoskeleton, and jointed appendages
- يُعزى تنوع ونجاح مفصليات الأرجل للتعقيل والهيكل الخارجي الصلب والزوائد المفصلية
- Arthropods have an open circulatory system
- تمتلك مفصليات الأرجل جهازاً دورياً مفتوحاً
- The body of most arthropods includes a head, thorax, and abdomen
- تشمل معظم أجساد مفصليات الأرجل رأساً وصدراً وبطناً
Remind your students that the arthropod population of the world includes about a billion, billion individuals.
Student Misconceptions and Concerns
1. As students survey the major animal phyla, they might perceive the diversity of animals as spread somewhat evenly across the nine major phyla of invertebrates. Yet, two-thirds of all known species of life (and at least 80% all described animal species) are arthropods. Although sources disagree on the number of living species that have been described, there is widespread agreement that the number of undescribed species is many times more than the number of described species. By examining the number of described species, some amazing proportions emerge. You might consider this exercise to make the point. Determine how many students represent 1% of the class. Then have the entire class stand. Tell the students that collectively, they represent all of the animal species known to exist today. Have 5% of the class sit, representing the proportion of known animal species that are vertebrates. Next, have 15% of the class sit, representing all of the remaining types of animals except arthropods. At this point, everyone standing (80% of the class) represents the proportion of known animal species that are arthropods (a conservative fraction). Finally, have 50% of the entire class sit, leaving 30% standing. Have the class guess what group of animals is represented now (clearly some subgroup of arthropods). This final 30% represents the known number of species of beetles! (The numbers used are rounded. Even high percentages for beetles and invertebrates may be more accurate. The point of this exercise is the relative proportions rather than precise percentages.)
Teaching Tips
1. Conceptually, and very generally speaking, the exoskeleton of an arthropod is like the hard outside of an M&M. The exoskeleton prevents physical damage to the internal organs and protects them against desiccation. The outside of an M&M prevents damage to the chocolate and keeps the chocolate from melting or drying out.
Video: Lobster Mouth Parts
Copyright © 2009 Pearson Education, Inc.

39. Cephalothoraxالرأسصدر
Abdomenالبطن
Head
رأس
Thorax
صدر
Antennae
(sensory
reception)
الزباني
(الاستقبال الحسي)
Swimming
appendages
زوائد السباحة
Figure 18.11A The structure of a lobster, an arthropod.
Walking legsأرجل المشي
Mouthparts (feeding)أجزاء الفم (للتغذية)
Pincer (defense)كلاب (دفاعي)
The structure of a lobster, an arthropod
تركيب الكركند ، مفصلي الأرجل

40. Living arthropods represent four major lineages:
18.11 Arthropods are segmented animals with jointed appendages and an exoskeleton مفصليات الأرجل هي حيوانات عُقلية ذات زوائد مفصلية وهيكل خارجي
Living arthropods represent four major lineages:
تتمثل مفصليات الأرجل التي تعيش حالياً في أربعة مسارات انحدارية رئيسية
Chelicerates include horseshoe crabs and arachnids, such as spiders, scorpions, mites, and ticks
تشمل المخلبيات سرطانات حدوة الفرس والعنكبيات كالعناكب والعقارب والحلم والقراد
- Most are terrestrial معظمها أرضية
- Scorpions are nocturnal hunters, while spiders hunt prey during the day تقوم العقارب بالصيد ليلاً بينما تصيد العناكب نهاراً
Student Misconceptions and Concerns
1. As students survey the major animal phyla, they might perceive the diversity of animals as spread somewhat evenly across the nine major phyla of invertebrates. Yet, two-thirds of all known species of life (and at least 80% all described animal species) are arthropods. Although sources disagree on the number of living species that have been described, there is widespread agreement that the number of undescribed species is many times more than the number of described species. By examining the number of described species, some amazing proportions emerge. You might consider this exercise to make the point. Determine how many students represent 1% of the class. Then have the entire class stand. Tell the students that collectively, they represent all of the animal species known to exist today. Have 5% of the class sit, representing the proportion of known animal species that are vertebrates. Next, have 15% of the class sit, representing all of the remaining types of animals except arthropods. At this point, everyone standing (80% of the class) represents the proportion of known animal species that are arthropods (a conservative fraction). Finally, have 50% of the entire class sit, leaving 30% standing. Have the class guess what group of animals is represented now (clearly some subgroup of arthropods). This final 30% represents the known number of species of beetles! (The numbers used are rounded. Even high percentages for beetles and invertebrates may be more accurate. The point of this exercise is the relative proportions rather than precise percentages.)
Teaching Tips
1. Conceptually, and very generally speaking, the exoskeleton of an arthropod is like the hard outside of an M&M. The exoskeleton prevents physical damage to the internal organs and protects them against desiccation. The outside of an M&M prevents damage to the chocolate and keeps the chocolate from melting or drying out.
Copyright © 2009 Pearson Education, Inc.

41. عنكبوت الأرملة السوداء (يبلغ طوله 420 ميكرومتراً)
A black widow spider
(about 1 cm wide)
عنكبوت الأرملة السوداء
(يبلغ عرضه ا سم)
Figure 18.11C Arachnids.
A scorpion
(about 8 cm long)
عقرب (يبلغ طوله 8 سم)
A dust mite
(about 420  m long)
حلم الغبار
(يبلغ طوله 420 ميكرومتراً)
Arachnidsالعنكبيات

42. A millipede (about 7 cm long) ذات ألف قدم (يبلغ طولها حوالي 7 سم)
18.11 Arthropods are segmented animals with jointed appendages and an exoskeleton مفصليات الأرجل هي حيوانات عقلية ذات زوائد مفصلية وهيكل خارجي
Millipedes and centipedes are identified by the number of jointed legs per body segment: 2 in herbivorous millipedes, 1 in carnivorous centipedes
تُعَرف ذوات الألف قدم و ذوات المائة قدم بعدد الأرجل المفصلية لكل عُقلة حيث تمتلك ذوات الألف قدم آكلة النبات قدمان مفصليتان في كل عُقلة بينما تمتلك ذوات المائة قدم آكلة اللحوم قدماً مفصلية واحدة في كل عُقلة
Student Misconceptions and Concerns
1. As students survey the major animal phyla, they might perceive the diversity of animals as spread somewhat evenly across the nine major phyla of invertebrates. Yet, two-thirds of all known species of life (and at least 80% all described animal species) are arthropods. Although sources disagree on the number of living species that have been described, there is widespread agreement that the number of undescribed species is many times more than the number of described species. By examining the number of described species, some amazing proportions emerge. You might consider this exercise to make the point. Determine how many students represent 1% of the class. Then have the entire class stand. Tell the students that collectively, they represent all of the animal species known to exist today. Have 5% of the class sit, representing the proportion of known animal species that are vertebrates. Next, have 15% of the class sit, representing all of the remaining types of animals except arthropods. At this point, everyone standing (80% of the class) represents the proportion of known animal species that are arthropods (a conservative fraction). Finally, have 50% of the entire class sit, leaving 30% standing. Have the class guess what group of animals is represented now (clearly some subgroup of arthropods). This final 30% represents the known number of species of beetles! (The numbers used are rounded. Even high percentages for beetles and invertebrates may be more accurate. The point of this exercise is the relative proportions rather than precise percentages.)
Teaching Tips
1. Conceptually, and very generally speaking, the exoskeleton of an arthropod is like the hard outside of an M&M. The exoskeleton prevents physical damage to the internal organs and protects them against desiccation. The outside of an M&M prevents damage to the chocolate and keeps the chocolate from melting or drying out.
Giant Peruvian centipede (30 cm in length)
أم أربعة وأربعون العملاقة (30 سم)
A millipede (about 7 cm long)
ذات ألف قدم (يبلغ طولها حوالي 7 سم)
Copyright © 2009 Pearson Education, Inc.

43. 18.11 Arthropods are segmented animals with jointed appendages and an exoskeleton مفصليات الأرجل هي حيوانات عُقلية ذات زوائد مفصلية وهيكل خارجي
Crustaceans are nearly all aquatic including crabs, shrimps, and barnacles, which feed with jointed appendages
القشريات أغلبها كائنات مائية تشمل السلطعونات والروبيان والقشريات الصدفية والتي تتغذي بواسطة زوائدها المفصلية
Crustaceans: goose barnacles (about 2 cm high)
القشريات : القشريات الصدفية الأوزية (يبلغ ارتفاعها حوالي 2 سم )
Student Misconceptions and Concerns
1. As students survey the major animal phyla, they might perceive the diversity of animals as spread somewhat evenly across the nine major phyla of invertebrates. Yet, two-thirds of all known species of life (and at least 80% all described animal species) are arthropods. Although sources disagree on the number of living species that have been described, there is widespread agreement that the number of undescribed species is many times more than the number of described species. By examining the number of described species, some amazing proportions emerge. You might consider this exercise to make the point. Determine how many students represent 1% of the class. Then have the entire class stand. Tell the students that collectively, they represent all of the animal species known to exist today. Have 5% of the class sit, representing the proportion of known animal species that are vertebrates. Next, have 15% of the class sit, representing all of the remaining types of animals except arthropods. At this point, everyone standing (80% of the class) represents the proportion of known animal species that are arthropods (a conservative fraction). Finally, have 50% of the entire class sit, leaving 30% standing. Have the class guess what group of animals is represented now (clearly some subgroup of arthropods). This final 30% represents the known number of species of beetles! (The numbers used are rounded. Even high percentages for beetles and invertebrates may be more accurate. The point of this exercise is the relative proportions rather than precise percentages.)
Teaching Tips
1. Conceptually, and very generally speaking, the exoskeleton of an arthropod is like the hard outside of an M&M. The exoskeleton prevents physical damage to the internal organs and protects them against desiccation. The outside of an M&M prevents damage to the chocolate and keeps the chocolate from melting or drying out.
Copyright © 2009 Pearson Education, Inc.

44. 70% of all animal species are insects
18.12 EVOLUTION CONNECTION: Insects are the most successful group of animals رابطة تطويرية : الحشرات هي اكثر المجاميع الحيوانية نجاحاً
70% of all animal species are insects
تشكل الحشرات نسبة70% من مجمل الأنواع الحيوانية
There may be as many as 30 million insect species
قد يبلغ عدد الأنواع الحشرية 30 مليون نوعاً
The body of an insect includes a head, thorax, and abdomen; three sets of legs; and (in most insects) wings
يتكون جسم الحشرة من رأس وصدر وبطن وثلاث مجاميع من الأرجل و أجنحة (في أغلب الحشرات)
Student Misconceptions and Concerns
1. As students survey the major animal phyla, they might perceive the diversity of animals as spread somewhat evenly across the nine major phyla of invertebrates. Yet, two-thirds of all known species of life (and at least 80% all described animal species) are arthropods. Although sources disagree on the number of living species that have been described, there is widespread agreement that the number of undescribed species is many times more than the number of described species. By examining the number of described species, some amazing proportions emerge. You might consider this exercise to make the point. Determine how many students represent 1% of the class. Then have the entire class stand. Tell the students that collectively, they represent all of the animal species known to exist today. Have 5% of the class sit, representing the proportion of known animal species that are vertebrates. Next, have 15% of the class sit, representing all of the remaining types of animals except arthropods. At this point, everyone standing (80% of the class) represents the proportion of known animal species that are arthropods (a conservative fraction). Finally, have 50% of the entire class sit, leaving 30% standing. Have the class guess what group of animals is represented now (clearly some subgroup of arthropods). This final 30% represents the known number of species of beetles! (The numbers used are rounded. Even high percentages for beetles and invertebrates may be more accurate. The point of this exercise is the relative proportions rather than precise percentages.)
Teaching Tips
1. Conceptually, and very generally speaking, the exoskeleton of an arthropod is like the hard outside of an M&M. The exoskeleton prevents physical damage to the internal organs and protects them against desiccation. The outside of an M&M prevents damage to the chocolate and keeps the chocolate from melting or drying out.
2. Many students assume that all insects possess six legs and two pairs of wings. As common examples of variation on this theme, challenge students to consider beetles (in which the outer wings, called elytra, are hardened) and flies (in which one pair of wings is reduced to a pair of structures called halteres).
3. Beetles have a long history in human culture, where they have been used in textiles, ornamentation, and jewelry. A quick image search of the Internet will reveal many examples. In particular, note the significance for scarab beetles in ancient Egypt.
4. The life history of dung beetles is a fun and amusing insect story for lecture, revealing the important role of these animals in recycling animal waste. Details of their interesting life cycle can be obtained from many resources, including those resulting from an Internet search for “dung beetle life history.”
Copyright © 2009 Pearson Education, Inc.

45. Insect anatomy, as seen in a grasshopper
Head
رأس
Thorax
صدر
Abdomen
بطن
Antenna
الزباني
(قرن استشعار)
Forewing
جناح أمامي
Eyeعين
Figure B Insect anatomy, as seen in a grasshopper.
Mouthpartsأجزاء الفم
Hindwingجناح خلفي
Insect anatomy, as seen in a grasshopper
تشريح الحشرة, كما يشاهد في نطاط الحشائش

46. 18.13 Echinoderms have spiny skin, an endoskeleton, and a water vascular system for movement الجلدشوكيات لها جلداً شوكياً وهيكلاً داخلياً وجهازاً وعائياً مائياً للحركة
Echinoderms (phylum Echinodermata) include slow-moving or sessile radially symmetrical organisms such as sea stars and sea urchins
تشمل الجلد شوكيات (شعبة الجلدشوكيات) كائنات بطيئة الحركة أو متماثلة شعاعياً ثابتة (مثبتة) كنجم البحر وقنافذ البحر
The water vascular system has water-filled canals branching into tube feet, which are used for respiration, feeding, and locomotion
الجهاز الوعائي المائي به قنوات مليئة بالماء تتشعب في الأقدام أنبوبية حيث تستخدم في التنفس والتغذية والحركة
Echinoderms have an endoskeleton of hard calcareous plates under a thin skin
تملك الجلد شوكيات هيكلاً داخلياً مكون من صفائح كلسية مصمتة تحت جلدها الرقيق
Echinoderms and chordates belong to a clade of bilateral animals called deuterostomes
تنتمي الجلدشوكيات والحبليات إلى فرع تشعبي واحد من الحيوانات المتماثلة جانبياً ويُعرف هذا الفرع بثانويات الفم
Student Misconceptions and Concerns
1. As students survey the major animal phyla, they might perceive the diversity of animals as spread somewhat evenly across the nine major phyla of invertebrates. Yet, two-thirds of all known species of life (and at least 80% all described animal species) are arthropods. Although sources disagree on the number of living species that have been described, there is widespread agreement that the number of undescribed species is many times more than the number of described species. By examining the number of described species, some amazing proportions emerge. You might consider this exercise to make the point. Determine how many students represent 1% of the class. Then have the entire class stand. Tell the students that collectively, they represent all of the animal species known to exist today. Have 5% of the class sit, representing the proportion of known animal species that are vertebrates. Next, have 15% of the class sit, representing all of the remaining types of animals except arthropods. At this point, everyone standing (80% of the class) represents the proportion of known animal species that are arthropods (a conservative fraction). Finally, have 50% of the entire class sit, leaving 30% standing. Have the class guess what group of animals is represented now (clearly some subgroup of arthropods). This final 30% represents the known number of species of beetles! (The numbers used are rounded. Even high percentages for beetles and invertebrates may be more accurate. The point of this exercise is the relative proportions rather than precise percentages.)
Teaching Tips
1. The bodies of adult echinoderms reveal degrees of radial symmetry, which may cause students to wonder why echinoderms are not grouped with cnidarians. As discussed in Module 18.13, the bilateral symmetry of embryonic echinoderms demonstrates the acquisition of radial symmetry from a bilaterally symmetrical ancestor. Thus, echinoderms are more closely associated with other bilaterally symmetrical organisms.
2. Radial symmetry, such as that seen in many adult echinoderms, permits an organism to respond well in any direction. You can’t sneak up “behind their back.” This ability is especially adaptive in sedentary or relatively sedentary organisms, such as sea urchins, sea stars, and cnidarians. Ask your students if these same advantages also occur in radially symmetrical plants.
Copyright © 2009 Pearson Education, Inc.

47. 18.13 Echinoderms have spiny skin, an endoskeleton, and a water vascular system for movement الجلدشوكيات لها جلداً شوكياً وهيكلاً داخلياً وجهازاً وعائياً مائياً للحركة
Anusشرج
Spinesأشواك
The water vascular system (canals and tube feet) of a sea star
الجهاز الوعائي المائي (القنوات والأقدام الأنبوبية) لنجم البحر
Stomach
معدة
Student Misconceptions and Concerns
1. As students survey the major animal phyla, they might perceive the diversity of animals as spread somewhat evenly across the nine major phyla of invertebrates. Yet, two-thirds of all known species of life (and at least 80% all described animal species) are arthropods. Although sources disagree on the number of living species that have been described, there is widespread agreement that the number of undescribed species is many times more than the number of described species. By examining the number of described species, some amazing proportions emerge. You might consider this exercise to make the point. Determine how many students represent 1% of the class. Then have the entire class stand. Tell the students that collectively, they represent all of the animal species known to exist today. Have 5% of the class sit, representing the proportion of known animal species that are vertebrates. Next, have 15% of the class sit, representing all of the remaining types of animals except arthropods. At this point, everyone standing (80% of the class) represents the proportion of known animal species that are arthropods (a conservative fraction). Finally, have 50% of the entire class sit, leaving 30% standing. Have the class guess what group of animals is represented now (clearly some subgroup of arthropods). This final 30% represents the known number of species of beetles! (The numbers used are rounded. Even high percentages for beetles and invertebrates may be more accurate. The point of this exercise is the relative proportions rather than precise percentages.)
Teaching Tips
1. The bodies of adult echinoderms reveal degrees of radial symmetry, which may cause students to wonder why echinoderms are not grouped with cnidarians. As discussed in Module 18.13, the bilateral symmetry of embryonic echinoderms demonstrates the acquisition of radial symmetry from a bilaterally symmetrical ancestor. Thus, echinoderms are more closely associated with other bilaterally symmetrical organisms.
2. Radial symmetry, such as that seen in many adult echinoderms, permits an organism to respond well in any direction. You can’t sneak up “behind their back.” This ability is especially adaptive in sedentary or relatively sedentary organisms, such as sea urchins, sea stars, and cnidarians. Ask your students if these same advantages also occur in radially symmetrical plants.
Tube feet
أقدام أنبوبية
Canalsقنوات
Video: Echinoderm Tube Feet
Copyright © 2009 Pearson Education, Inc.

48. A sea star feeding on a clam
A sea urchinقنفذ بحري
Spines
أشواك
Tube
feet
أقدام انبوبية
Tube foot
قدم أنبوبي
Figure 18.13B A sea star feeding on a clam.
A sea star feeding on a clam
نجمة بحر تتغذى على صدفة

49. Chordates (phylum Chordata) have تمتلك الحبليات (شعبة الحبليات)
18.14 Our own phylum, Chordata, is distinguished by four features تتميز شعبة الحبليات بأربعة سمات
Chordates (phylum Chordata) have
تمتلك الحبليات (شعبة الحبليات)
A dorsal hollow nerve cord حبلاً عصبياً أجوفاً ظهرياً
A flexible, supportive notochord حبلاً ظهرياً مرناً وداعماً
Pharyngeal slits فتحات بلعومية
A muscular post-anal tailذيلاً ما بعد شرجي عضلي
Student Misconceptions and Concerns
1. As students survey the major animal phyla, they might perceive the diversity of animals as spread somewhat evenly across the nine major phyla of invertebrates. Yet, two-thirds of all known species of life (and at least 80% all described animal species) are arthropods. Although sources disagree on the number of living species that have been described, there is widespread agreement that the number of undescribed species is many times more than the number of described species. By examining the number of described species, some amazing proportions emerge. You might consider this exercise to make the point. Determine how many students represent 1% of the class. Then have the entire class stand. Tell the students that collectively, they represent all of the animal species known to exist today. Have 5% of the class sit, representing the proportion of known animal species that are vertebrates. Next, have 15% of the class sit, representing all of the remaining types of animals except arthropods. At this point, everyone standing (80% of the class) represents the proportion of known animal species that are arthropods (a conservative fraction). Finally, have 50% of the entire class sit, leaving 30% standing. Have the class guess what group of animals is represented now (clearly some subgroup of arthropods). This final 30% represents the known number of species of beetles! (The numbers used are rounded. Even high percentages for beetles and invertebrates may be more accurate. The point of this exercise is the relative proportions rather than precise percentages.)
Teaching Tips
1. If you can obtain a model or image of a one-month-old human embryo, you can demonstrate our four main chordate characteristics. A figure of a human embryo, comparing human and dog embryos of similar stages, was prepared by Charles Darwin and included in the first chapter of his book The Descent of Man. This image can be viewed at _Descent_F937/1871_Descent_F937.1_fig02.jpg.
Copyright © 2009 Pearson Education, Inc.

50. 18.14 Our own phylum, Chordata, is distinguished by four features تتميز شعبة الحبليات بأربعة سمات
The simplest chordates are tunicates and lancelets, which use their pharyngeal slits for suspension feeding
أبسط الحبليات هي الزقيات و السهيميات والتي تستخدم فتحاتها البلعومية للتغذية على العوالق
Adult tunicates are stationary and attached, while the tunicate larva is a tadpole-like organism
الزقيات البالغة مستقرة ومثبتة بينما يرقاتها شبيهة بكائنات أبو ذنيبة
Tunicates represent the deepest branch of the chordate lineage
تمثل الزقيات الفرع الأعمق ”الأقدام“ في المسار الانحداري للحبليات
Lancelets are small, bladelike chordates that live in marine sands
السهيميات كائنات صغيرة شبيهة بالشفرة وتعيش في رمال البحر
Lancelets are the closest living relatives of vertebrates
السهيميات هي أقرب الأقرباء الحية للفقاريات
Student Misconceptions and Concerns
1. As students survey the major animal phyla, they might perceive the diversity of animals as spread somewhat evenly across the nine major phyla of invertebrates. Yet, two-thirds of all known species of life (and at least 80% all described animal species) are arthropods. Although sources disagree on the number of living species that have been described, there is widespread agreement that the number of undescribed species is many times more than the number of described species. By examining the number of described species, some amazing proportions emerge. You might consider this exercise to make the point. Determine how many students represent 1% of the class. Then have the entire class stand. Tell the students that collectively, they represent all of the animal species known to exist today. Have 5% of the class sit, representing the proportion of known animal species that are vertebrates. Next, have 15% of the class sit, representing all of the remaining types of animals except arthropods. At this point, everyone standing (80% of the class) represents the proportion of known animal species that are arthropods (a conservative fraction). Finally, have 50% of the entire class sit, leaving 30% standing. Have the class guess what group of animals is represented now (clearly some subgroup of arthropods). This final 30% represents the known number of species of beetles! (The numbers used are rounded. Even high percentages for beetles and invertebrates may be more accurate. The point of this exercise is the relative proportions rather than precise percentages.)
Teaching Tips
1. If you can obtain a model or image of a one-month-old human embryo, you can demonstrate our four main chordate characteristics. A figure of a human embryo, comparing human and dog embryos of similar stages, was prepared by Charles Darwin and included in the first chapter of his book The Descent of Man. This image can be viewed at _Descent_F937/1871_Descent_F937.1_fig02.jpg.
Copyright © 2009 Pearson Education, Inc.

51. A tunicateحيوان زقي Post-anal tailذيل ما بعد شرجي Dorsal, hollow
Excurrent
Siphon
ممص طارد للتيار
Post-anal tailذيل ما بعد شرجي
Dorsal, hollow
nerve cord
حبل عصبي ظهري أجوف
Pharyngeal slits
فتحات خيشومية
Mouth
الفم
Muscle segments
عُقل عضلية
Figure 18.14A A tunicate.
Notochordحبل ظهري
Adultالحيوان البالغ
(about 3 cm high)
(حوالي 3 سم طولاً)
Larvaاليرقة
A tunicateحيوان زقي

52. عضلات عُقلية A lancelet (5–15 cm long) السهيم (من 5-15 سم طولاً)
Headرأس
Notochord
حبل ظهري
Mouthفم
Pharynxبلعوم
Dorsal, hollow
nerve cord
حبل عصبي ظهري أجوف
Pharyngeal slits
فتحات بلعومية
Figure 18.14B A lancelet (5–15 cm long).
Digestive tract
قناة هضمية
Water exitمخرج مائي
Post-anal tail
ذيل ما بعد شرجي
Segmental muscles
عضلات عُقلية
Anusشرج

53. You should now be able to ما ينبغي عليك معرفته بعد الانتهاء من هذا الباب
1. Describe the defining characteristics of animals صف الصفات التي نُعرف بها الحيوانات
2. Describe the general animal life cycle and the basic body plan صف دورة حياة الحيوان العامة وخطة التصميم الأساسية للجسد
3. Explain how a hydrostatic skeleton helps an animal move and keep its shape
اشرح كيف يساعد هيكل الاتزان المائي على حركة الحيوان والحفاظ على شكله
4. Compare the nine animal phyla discussed in this chapter with respect to the following traits: (a) presence of true tissues; (b) no symmetry, radial symmetry, or bilateral symmetry; (c) no coelom, a pseudocoelom, or a true coelom; and (d) protostome or deuterostome
قارن بين الشعب الحيوانية الثمان التي تم مناقشتها في هذا الباب مع وضع الصفات التالية في الاعتبار : أ) وجود نسيج حقيقي ، ب) عدم وجود تماثل ، التماثل الشعاعي ، التماثل الجانبي ، جـ) عدم وجود تجويف سيلومي ، السيلوم الكاذب ، السيلوم الحقيقي ، د) الفم الأولي، الفم الثانوي
5. Define segmentation, explain its functions, and note the animal phyla where it occurs
عرف التعقيل واشرح وظائفه واذكر في أي شعبة حيوانية تحدث العُقل
7. Compare the characteristics of the four major arthropod lineages; note examples of each
قارن صفات أربع مسارات انحدارية رئيسية لمفصلية الأرجل، مع ذكر أمثلة لكل منها
8. Describe the common characteristics of insects
صف الصفات المشتركة للحشرات
9. Describe the process and significance of complete metamorphosis
صف عملية وأهمية التحول الشكلي الكامل
10. Compare the phylogenetic relationships shown in Figures 18.4 and 18.15, noting similarities and differences
قارن بين علاقات صلات التشعب الموضحة في الأشكال 18.4 و 18.5 ، مع ذكر أوجه الشبه والاختلافات بينها
Copyright © 2009 Pearson Education, Inc.