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Introduction to Vertebrates

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Introduction to Vertebrates

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1 Introduction to Vertebrates

2 fish list the major characteristics of these animals
Vertebrate Vocabulary Chapters Chordate vertebrate vertebra (712) agnathan (714) ectothermic (724) endothermic (724) primate (731) fish list the major characteristics of these animals amphibian list the major characteristics of these animals reptile list the major characteristics of these animals bird list the major characteristics of these animals Mammal list the major characteristics of these animals amniotic egg (775) mammary gland (806) placenta (810) gestation period (810) ungulate (814)

3 vertebrates Fishes Amphibians: Reptiles: Birds: Mammals:
3 types: jawless cartilaginous bony Amphibians: Reptiles: Birds: Mammals:

4 Vertebrates are chordates with a backbone
Vertebrates are chordates with a backbone. They take their name from the individual segments, called vertebrae, that make up the backbone.

5 The backbone provides support for and protects a dorsal nerve cord.
It also provides a site for muscle attachment.


7 Vertebrates share a number of other characteristics,
including segmentation, bilateral symmetry, and two pairs of jointed appendages, such as limbs or fins.

8 Cells make up tissues. The tissues of vertebrates compose organs.
In turn, the organs compose organ systems

9 Vertebrate organ systems tend to be more complex than the organ systems found in invertebrates.



12 The first vertebrates

13 The first vertebrates were
fishes Unlike most of the fishes you are familiar with, the earliest fishes, called agnathans, had neither jaws nor paired fins.

14 Today’s fishes belong to one of three major groups:
the jawless fish: agnathans, the cartilaginous fishes: Chondrichthyes, and the bony fishes: osteichthyes.

15 Jawless fishes - They are cylindrical, up to a meter long, with smooth, scaleless skin and no jaws or paired fins. There are two families of jawless fishes, e.g., the hagfishes are scavengers, feeding mainly on dead fishes, while some lampreys are parasitic.


17 About 400 million years ago, sharks and bony fishes appeared
About 400 million years ago, sharks and bony fishes appeared. Cartilaginous fishes - They are the sharks, the rays, and the skates, which have skeletons of cartilage instead of bone. Most sharks and bony fishes have streamlined bodies that are well adapted for rapid movement through the water.

18 Bony fishes Bony fishes have a skeleton made of bone, which is heavier and less flexible than cartilage. Bony fishes have a swim bladder, which compensates for this weight.

19 Examples


21 Fish traits 1. Gills. Fishes normally obtain oxygen from the oxygen gas dissolved in the water around them. They do this by pumping a great deal of water through their mouths and over their gills.


23 2. Single-loop blood circulation
. Blood is pumped from the heart to the capillaries in the gills. From the gills, blood passes to the rest of the body and then returns to the heart. (Lungfishes, which have a double-loop circulation, are an exception.)

24 3. Vertebral column (backbone).
All fishes have an internal skeleton made of either cartilage or bone, with a vertebral column surrounding the spinal cord. The brain is fully encased within a protective covering called the skull or cranium

25 Circulatory - The heart of a fish is a simple pump, and the blood flows through the chambers, including a non-divided atrium and ventricle, to the gills only. Oxygenated blood leaves the gills and goes to the body proper.


27 Digestive - The mouths shape is a good clue to what fish eat. The larger it is the bigger the prey it can consume. Fish have a sense of taste and may sample items before swallowing if they are not obvious prey items. The stomach and intestines break down (digest) food and absorb nutrients. Fish such as bass that are piscivorous (eat other fish) have fairly short intestines because such food is easy to chemically break down and digest. Fish such as tilapia that are herbivorous (eat plants) require longer intestines because plant matter is usually tough and fibrous and more difficult to break down into usable components.

28 The function of the pyloric caeca is not entirely understood, but it is known to secrete enzymes that aid in digestion, may function to absorb digested food, or do both. The liver has a number of functions. It assists in digestion by secreting enzymes that break down fats, and also serves as a storage area for fats and carbohydrates. The liver is also important in the destruction of old blood cells and in maintaining proper blood chemistry, as well as playing a role in nitrogen (waste) excretion.

29 Endocrine - All vertebrate animals (fish, amphibians, reptiles, birds and mammals, including humans) have the same endocrine glands and release similar hormones to control development, growth, reproduction and other responses. However, the pineal gland of fish and amphibians is located near the skin and functions to detect light. This is often referred to as the third eye.

30 Excretory - The kidney filters liquid waste materials from the blood; these wastes are then passed out of the body. The kidney is also extremely important in regulating water and salt concentrations within the fish’s body, allowing certain fish species to exist in freshwater or saltwater, and in some cases both.

31 The vent is the external opening to digestive urinary and reproductive tracts. In most fish it is immediately in front of the anal fin. Ammonia is formed immediately after the amino group is removed from protein. This process requires very little energy. Ammonia is highly soluble in water but very toxic. Aquatic animals such as bony fishes, aquatic invertebrates, and amphibians excrete ammonia because it is easily eliminated in the water.

32 Immune - The fish immune system comprises of the non-specific and specific immune defenses, having both humoral and cellular mechanisms to resist against infectious diseases. Studies in various species of fish have shown that the spleen and head kidney are major locations of immunological activity. The relative importance of these two organs varies among different species. Previous studies have demonstrated that the head kidney is a major source of lymphocytes (including B cells) in Bluegill.

33 Germs and bugs constantly probe and try to breach the fish’s immune system to gain a strong foothold. In general, for them to be successful there has to be an underlying predisposing factor such as poor environmental conditions, poor nutrition, overcrowding or poor water quality. In addition to causing stress, which will depress the fish’s immune system, such conditions will often encourage increased numbers of opportunistic pathogens.

34 Musculo-skeletal - Fish are covered by scales, which protect the body but do not prevent water loss. The spine is the primary structural framework upon which the fish’s body is built. It connects to the skull at the front of the fish and to the tail at the rear. The spine is made up of numerous vertebrae, which are hollow and house and protect the delicate spinal cord.

35 Nervous and Sensory - Fish see through their eyes and can detect color. Paired nostrils, or nares, in fish are used to detect odors in water and can be quite sensitive. The lateral line is a sensory organ consisting of fluid filled sacs with hair-like sensory apparatus that are open to the water through a series of pores (creating a line along the side of the fish). The lateral line primarily senses water currents and pressure, and movement in the water.

36 Reproductive - General speaking, reproduction in the fishes requires external water; sperm and eggs usually are shed into the water, where fertilization occurs. The zygote develops into a swimming larva that can fend for itself until it develops into the adult form.

37 Respiratory - Fishes breathe by means of gills, respiratory organs that are kept continuously moist by the passage of water through the mouth and out the gill slits. As the water passes over the gills, oxygen is absorbed by blood and carbon dioxide is given off.


39 Evolution of Amphibians “double life”
The first group of vertebrates to live on land were the amphibians, which appeared about 370 million years ago.


41 Adaptations for Life on Land
A number of major adaptations allowed some species to successfully invade land. 1. Legs. Legs support the body’s weight as well as allow movement from place to place. 2. Lungs. On land, lungs carry out gas exchange. 3. Heart. Land animals tend to have higher metabolic rates than aquatic animals. The structure of the vertebrate heart allows oxygen to be delivered to the body efficiently.


43 Frogs and toads make up the largest, and probably the most familiar, group of modern amphibians.

44 Fluid loss is a problem for all terrestrial animals, that is, animals that live on land. The adaptations that permitted amphibians to live on land further developed in reptiles. Two very important adaptations for terrestrial life evolved in reptiles. Reptiles were the first animals to have skin and eggs that are both almost watertight, and they differ from amphibians in this respect.



47 Circulatory - With the development of lungs, there is a change in the circulatory system. The amphibian heart has a divided atrium but a single ventricle. The right atrium receives impure blood with little oxygen from the body proper, and the left atrium receives purified blood from the lungs that has just been oxygenated, but these two types of blood are mixed partially in the single ventricle. Mixed blood is then sent, in part, to the skin, where further oxygenation can occur. The frog heart is the only organ contained within the coelom, which has its own protective covering. This is the pericardium.


49 Digestive - The frog's mouth is where digestion begins. It is equipped with feeble, practically useless teeth. These are present only in the upper jaw. The frog's tongue is highly specialized. Normally, the tip of its tongue is folded backward toward the throat. From this position the frog can flick it out rapidly to grasp any passing prey. To better hold this prey, the tongue is sticky. Food passes from the frog's mouth into the stomach by way of the esophagus. From the stomach, the food moves into the small intestine, where most of the digestion occurs. Large digestive glands, the liver and the pancreas, are attached to the digestive system by ducts. A gall bladder is also present.

50 Endocrine - Similar for all vertebrates.

51 Excretory - Liquid wastes from the kidneys travel by way of the ureters to the urinary bladder. Solid wastes from the large intestine pass into the cloaca. Both liquid and solid waste material leave the body by way of the cloaca and the cloacal vent. Terrestrial amphibians and mammals excrete nitrogenous wastes in the form of urea because it is less toxic than ammonia and can be moderately concentrated to conserve water. Urea is produced in the liver by a process that requires more energy to produce than ammonia does.

52 Immune - Studies of the ontogeny of immunity in a limited number of representative amphibians have shown that while the immune systems of the larval forms are competent to defend against potential pathogens in the temporary ponds they inhabit, they are not equivalent to the mature immune systems that develop after metamorphosis. Metamorphosis is a critical time of transition when increased concentrations of metamorphic hormones orchestrate the loss or reorganization of many tissues and organ systems, including the immune system. A working hypothesis suggests that common herbicide called atrazine somehow suppresses the amphibian immune system and leaves the animals more susceptible to parasite infection. The variation in occurrence is related to the year-to-year changes of water level that take place in the natural environment.

53 Musculo-skeletal - These animals have distinct walking legs, each with five or fewer toes. This represents an adaptation of land locomotion. The skull is flat, except for an expanded area that encases the small brain. Only nine vertebrae make up the frog's backbone, or vertebral column. The human backbone has 24 vertebrae. The frog has no ribs. The frog does not have a tail. Only a spike like bone, the urostyle, remains as evidence that primitive frogs probably had tails. The shoulders and front legs of the frog are somewhat similar to man's shoulders and arms. The frog has one "forearm" bone, the radio-ulna. Man has two forearm bones, the radius and the ulna. Both frog and man have one "upper arm" bone, the humerus. The hind legs of the frog are highly specialized for leaping. The single "shinbone" is the tibiofibula.


55 Man has two lower leg bones, the tibia and the fibula
Man has two lower leg bones, the tibia and the fibula. In man and in the frog, the femur is the single upper leg (thigh) bone. A third division of the frog's leg consists of two elongated anklebones, or tarsals. These are the astragalus and the calcaneus. The astragalus corresponds to the human talus (anklebone). The calcaneus in the human skeleton is the heel bone.

56 Nervous and Sensory - The important parts of the frog brain correspond to comparable parts in the human brain. The medulla regulates automatic functions such as digestion and respiration. Body posture and muscular co-ordination are controlled by the cerebellum. The cerebrum is very small in the frog. By comparison the human cerebrum is very large. In man the cerebrum is involved in many important life processes. Only 10 cranial nerves originate in the frog's brain. Man has 12

57 1. Olfactory lobes 2. Cerebral hemisphere 3. Optic lobes 4. Cerebellum 5. Medulla oblongata 6. Choroid plexus

58 Similarly, the frog has only 10 pairs of spinal nerves
. Similarly, the frog has only 10 pairs of spinal nerves. Man has 30 pairs. Two simple holes make up the nostrils for the frog. There are complex valves but no long nasal passages as there are in man. The frog's sense of smell is registered by olfactory lobes. These make up the forward portion of the brain.

59 The eye is crude. Its fixed lens cannot change its focus
The eye is crude. Its fixed lens cannot change its focus. Poorly developed eyelids do not move. To close its eye, the frog draws the organ into its socket. A third eyelid, or nictitating membrane, may be drawn over the pulled-in eyeball. There is no external ear. Both eardrums, or tympanic membranes, are exposed. There is only one bone in the frog's middle ear. The human middle ear contains three bones (malleus, incus, and stapes in the ossicles). As in man, semicircular canals help to maintain body balance.

60 Reproductive - Nearly all the members of this class lead an amphibious life, i.e., the larval stage lives in the water and the adult stage lives on the land. The adults must return to the water, however, for reproduction. Just as with the fishes, the sperm and the eggs are discharged into the water and fertilization results in a zygote that develops into the tadpole. The tadpole undergoes metamorphosis into the adult before taking up life on the land.

61 Respiratory - Respiration is accomplished by the use of small, relatively inefficient lungs, supplemented by gaseous exchange through the skin. Therefore, the skin is smooth, moist, and glandular. This is call cutaneous gas exchange, which occurs among many vertebrates in various degree. This is a distinct disadvantage in a dry environment; therefore, frogs spend most of their time in or near freshwater. All amphibians possess two nostrils that are connected directly with the mouth cavity.

62 Air enters the mouth by way of the nostrils, and when the floor of the mouth is raised, air is forced into the lungs. Lungless frogs have been found on the Borneo island in They have skin flaps coming off their arms and legs. The species is the first frog known to science without lungs and joins a short list of amphibians with this unusual trait, including a few species of salamanders and a wormlike creature known as a caecilian.

63 1. Legs. The evolution of legs was an important adaptation for living on land. Frogs, toads, salamanders, and newts have four legs. Caecilians lost their legs during the evolutionary course of adapting to a burrowing existence.

64 2. Lungs. Although larval amphibians have gills, most adult amphibians breathe with a pair of lungs. Lungless salamanders are an exception. 3. Double-loop circulation. Two large veins called pulmonary veins return oxygen-rich blood from the lungs to the heart. The blood is then pumped to the tissues at a much higher pressure than in the fish heart.

65 4. Partially divided heart
4. Partially divided heart. The atrium of the amphibian heart is divided into left and right sides, but the ventricle is not. A mixture of oxygen-rich and oxygen-poor blood is delivered to the amphibian’s body tissues.

66 5. Cutaneous respiration
5. Cutaneous respiration. Most amphibians supplement their oxygen intake by respiring directly through their moist skin. Cutaneous respiration (“skin breathing”) limits the maximum body size of amphibians because it is efficient only when there is a high ratio of skin surface area to body volume

67 1. Heart (ventricle)  2. Lung  3. Spleen  4. Liver  5. Stomach  6. Small intestine  7. Large intestine  8. Kidney  9. Urinary bladder 10. Oviduct 11. Fat bodies

68 reptiles The reptiles living today are turtles, alligators, snakes, and lizards. Reptiles with limbs, such as lizards, are able to lift their body off the ground, and the body is covered with hard, horny scales that protect the animal from desication and from predators. Both of these features are adaptations to life on land.


70 traits • Strong, bony skeleton and toes with claws • Ectothermic metabolism • Dry, scaly skin, almost watertight • Amniotic eggs, almost watertight • Respiration through well-developed lungs • Ventricle of heart partly divided by a septum • Internal fertilization

71 Circulatory - The atrium of the heart is always separated into right and left chambers, but division of the ventricle varies. There is always at least one interventricular septum, but it is incomplete in all but the crocodiles; therefore, exchange of oxygenated and deoxygenated blood between the ventricles occurs in all but the crocodile.


73 Reptiles do not regulate their body temperature.
Animals that cannot maintain a constant temperature, e.g., fishes, amphibians, and reptiles, are called cold blooded. They take on the temperature of the external environment. Thus, reptiles try to regulate body temperatures by exposing themselves to the sun if they need warmth or by hiding in the shadows if they want to cool off.

74 Digestive - Except for most snakes, reptiles have a cecum. The stomach of crocodilians has two compartments. The first is very muscular and frequently contains stones. The second is similar to the glandular stomach of mammals. All reptiles have a gall bladder. The liver of many reptiles contains melanin and can have black spots or streaks. Reptiles generally have little subcutaneous fat and store fat in discrete masses (fat bodies) in the caudal abdomen.

75 Endocrine - Similar for all vertebrates.

76 Excretory - The metanephric kidneys of reptiles are lobulated. One or more renal arteries can be present to receive blood from the renal portal system. The nitrogenous wastes of reptiles are in the form of ammonia, urea, uric acid or a combination of these. Crocodilians, snakes and some lizards do not have a urinary bladder. In chelonians and those lizards with a bladder, it is connected to the cloaca by a short urethra. Urine passes into the cloaca and then into the urinary bladder, if present, or into the distal colon where water resorption occurs. The cloaca typically consists of 3 chambers.

77 Immune - The reptile immune response is performed by a well-developed immune system whose leukocytes have been characterized as lymphocytes, monocytes and granulocytes.


79 A main characteristic of the reptile immune system is the effect of the seasonal cycle on its histology and function. A reptile's immune system is more efficient when the animals is warmer, however, since bacteria probably grow more slowly in lower temperatures, reptiles sometimes lower their body temperatures when they have an infection.

80 Musculo-skeletal - They have thick stratum corneum (top dead layer) with compacted layers of flat horny dead cells, filled with keratin. It is replaced by swelling/pressure from diffusion of lymph between new and old layers. The surface scales can be in varied form. In some lizards the scales are small and grainlike, while in others they are large and plate- like. The scales may be smooth or they may have little ridges called keels or they may even have developed into spines.


82 Nervous and Sensory - Most lizards see and hear well. They have external ear openings and their eyes have movable eyelids (unlike snakes). Some lizards have a "third eye," a tiny, light-sensitive, transparent structure on top of the head that helps them regulate how long they stay in the sun.

83 Reproductive - Reptiles have a means of reproduction suitable to a land existence. There is usually no need for external water to accomplish fertilization because the penis of the male passes sperm directly to the female. After internal fertilization has occurred, the egg is covered by a protective, leathery shell and is laid in an appropriate location.

84 The shelled egg made development on land possible and eliminated the need for a swimming-larva stage during development. It provides the developing embryo with oxygen, food, and water; it removes nitrogenous wastes; and it protects the embryo from drying out and from mechanical injury. This is accomplished by the presence of extraembryonic membranes.



87 Respiratory - Reptiles have well-developed lungs enclosed in a protective rib cage. The lungs expend together with the rib cage to let in air.


89 Evolution of Birds The earliest known bird is Archaeopteryx. Archaeopteryx was about the size of a crow and shared many features with small theropods. Archaeopteryx had a dinosaurlike skeleton, but birdlike wings and feathers.


91 Birds • Forelimbs modified into wings • Body covered with feathers • Lightweight bones • Endothermic metabolism • Super-efficient respiratory system • Heart with completely divided ventricle

92 Birds are characterized by the presence of feathers, which are actually modified reptilian scales. There are many orders of birds, including birds that are flightless (ostrich), web footed (penguin), divers (loons), fish eaters (pelicans), waders (flamingos), broad billed (ducks), birds of prey (hawks), vegetarians (fowl), shorebirds (sandpipers), nocturnal (owl), small (hummingbirds), and songbirds, the most familiar of the birds.

93 Circulatory - Birds have a four-chambered heart that completely separates oxygenated blood from deoxygenated blood.


95 endotherm Birds are warm blooded; like mammals, they are able to maintain a constant internal (core) temperature of 40 oC. Placental mammals maintain a temperature of 37 oC, for most marsupials it is 35 oC.


97 Digestive - Birds digest food quickly, they can't afford the extra weight. They have no teeth, the breakdown of food occurs in the gizzard - sometimes birds swallow rocks to assist the process. The crop stores food; mother birds regurgitate food stored in the crop to their babies. Waste exits through the cloaca - and so do eggs.


99 Endocrine - Similar for all vertebrates.

100 Excretory - Insects, reptiles, birds, and some dogs (Dalmatians) excrete uric acid. Reptiles and birds eliminate uric acid with their feces. The white material seen in bird droppings is uric acid. It is not very toxic and is not very soluble in water. Excretion of wastes in the form of uric acid conserves water because it can be produced in a concentrated form due to its low toxicity. There is no urinary bladder in birds.


102 Immune - The bird's immune system mainly consists of lymphatic vessels and lymphoid tissue. Primary tissues are the thymus. Secondary lymphatic organs and tissues would be the spleen, bone marrow, mural lymph nodules and lymph nodes. There is also a lymphatic circulatory system of vessels and capillaries that transport lymph fluid through the bird's body and communicate with the blood supply.

103 The lymphocyte is the most numerous white blood cell
The lymphocyte is the most numerous white blood cell.  Lymphocytes are either T-lymphocytes (formed in the thymus) or B-lymphocytes (formed in the bursa of Fabricius). B-lymphocytes produce antibodies; T-lymphocytes attack infected or abnormal cells.  The heterophil is the second most numerous WBC in most birds. Heterophils are phagocytic and use their enzyme-containing granules to lyse ingested materials. Heterophils are motile and can leave blood vessels to engulf foreign materials. 

104 Musculo-skeletal - The anterior pair of appendages (wings) is adapted for flight; the posterior is variously modified, depending on the type of bird. Some are adapted to swimming, some to running, and some to perching on limbs. The breastbone is enormous and has a ridge to which the flight muscles are attached.


106 Nervous and Sensory - Birds have well-developed brains, but the enlarged portion seems to be the area responsible for instinctive behavior. Therefore, birds, follow very definite patterns of migration and nesting.


108 Reproductive - Birds often engage in elaborate courtship behavior for mating purposes. These include: building nests, dancing and posturing, bringing gifts, bright colorful displays, and singing. Some birds mate for life, and often both parents raise young. Two types of reproduction occur in birds: some birds incubate eggs for a long time - chicks are born with feathers and can walk/swim (ducks); while others incubate eggs a short time - chicks are born featherless and helpless (robins).









117 Respiratory - Respiration is efficient since the lobular lungs are connected to air-sacs which fill with air during inhalation. The air then is released from the air sacs when the bird exhales - this means that the bird receives oxygen during inhalation and exhalation. Another benefit of air sacs is that the air-filled, hollow bones lighten the body and aid flying.

118 Mammals

119 mammals The chief characteristics of mammals are hair and mammary glands that produce milk to nourish the young. Human mammary glands are called breasts.

120 Mammals are classified according to their means of reproduction:
there are egg-laying mammals called Monotremes such as the duck-billed platypus;

121 mammals with pouches for immature embryos are the marsupials such as the kangaroos;

122 while the placental mammals are the majority of living mammals.

123 Circulatory - Mammal circulatory systems are divided into two circuits: pulmonary and systemic. The pulmonary circuit carries deoxygenated blood from the heart to the respiratory surface in the lungs, where it is re-oxygenated, and then back to the heart.

124 The systemic circuit carries oxygenated blood to all the body's cells via arteries, and deoxygenated blood back to the heart via veins. The mammalian double circulatory system is efficient because it uses a separate pump (the two ventricles) to power each circuit.


126 Digestive - The digestive tract is a tube, with coils and branches, which begins at the mouth and ends either at a cloaca or anus. The general pattern is to have an oral cavity, pharynx, esophagus, stomach and intestine.


128 Accessory organs are the pancreas, liver and gallbladder, which arise as envaginations from the embryonic digestive tract.

129 It processes food, which moves by peristalsis (waves of involuntary muscle contractions) through the process of digestion, absorption and elimination.

130 Endocrine - Similar for all vertebrates.

131 Excretory – In mammals, the two major excretory processes are the formation of urine in the kidneys and the formation of feces in the intestines. The waste products are eliminated by urination and defecation respectively. While urine and feces are both waste material of body processes, they are in completely different categories.


133 Urine is a waste product of the urinary system process while feces are waste products of the digestive system. Feces may contain harmful materials such as bacteria, viruses, and parasitic worms. Urine, on the other hand, contains excess water, salt, and protein waste in the form of urea, and seldom carries any pathogens.


135 Immune - In order to identify a foreign organism, the mammal immune system exploits the protein binding activity of antibodies. Depending on the invader, highly specialized antibodies are secreted by suitable cells, which are selected out of a large cell pool and induced to expand their population.


137 Musculo-skeletal - Mammals have an inner skeleton. It has developed muscles and generally has four limbs attached.

138 Nervous and Sensory - Mammal has a highly developed brain, nerves and sensory organs such as eyes, nose, mouth, ears and touch.

139 Reproductive - Monotremes - In the same manner as birds, the female monotreme incubates the eggs, but after hatching, the young are dependent upon the milk that seeps from glands on the abdomen of the female. Therefore, monotremes retained the reptilian mode of reproduction while evolving hair and mammary glands. The young are blind, helpless, and completely dependent on the parent for some months.


141 Marsupials - In marsupials, the young are born in a very immature state and finish their development in the mother's abdominal pouch, called the marsupium. Using clawed forelimbs, the newborn crawls toward the mother's fur-lined pouch. Once there, it attaches itself to a nipple. After 4 or 5 weeks in the pouch, some marsupials such as opossum spends an additional 8 or 9 weeks clinging to the mother's back.


143 Placental Mammals - In these mammals, the extraembryonic membranes have been modified for internal development within the uterus of the female. The chorion contributes to the fetal portion of the placenta, while a portion of the uterine wall contributes to the maternal portion. Here nutrients, oxygen, and waste are exchanged between fetal and maternal blood.

144 It also ensures that the mother's immune system does not attack the embryo by separating white blood cells and other immune system components (including blood) at the boundary. These mammals not only have a long embryonic period, they also are dependent on their parents until the nervous system is developed fully and they have learned to take care of themselves.

145 The embryonic disk had initially pressed to the wall of the uterus at implantation. It had moved around during the development for attaching the umbilical cord in the tummy button to the placenta.

146 Respiratory - The lungs of mammals have a spongy texture and are honeycombed with epithelium having a much larger surface area in total than the outer surface area of the lung itself. The lungs of humans are typical of this type of lung. The environment of the lung is very moist, which makes them a hospitable environment for bacteria.


148 Breathing is largely driven by the diaphragm below; a muscle that by contracting expands the cavity in which the lung is enclosed. The rib cage itself is also able to expand and contract to some degree.

149 . As a result, air is sucked into and pushed out of the lungs through the trachea and the bronchial tubes or bronchi; these branch out and end in alveoli which are tiny sacs surrounded by capillaries filled with blood. Here oxygen from the air diffuses into the blood, where it is carried by hemoglobin. The deoxygenated blood from the heart reaches the lungs via the pulmonary artery and, after having been oxygenated, returns via the pulmonary veins.



152 Humans are mammals in the order Primates
Humans are mammals in the order Primates. The first primates may have resembled today's tree shrews, rat-size animals with a snout, claws, and sharp front teeth. By 50 million years ago, however, primates had evolved characteristics suitable to move freely through the trees.

153 The first primates were prosimians (meaning "premonkeys")
The first primates were prosimians (meaning "premonkeys"). They are represented today by several types of animals, including the lemurs. Monkeys, along with apes and humans, are anthropoids. Monkeys evolved from the prosimians about 38 million years ago, when the weather was warm and vegetation was like that of a tropical rain forest. There are two types of monkeys: the New World (South America) monkeys such as the spider monkeys, which have long grasping tails and flat noses, and the Old World (Africa) monkeys such as the baboons, which are now ground dwellers and lack such tails. Ape (gibbon, gorilla, and chimpanzee) evolved later. The human lineage split from that of the apes occurred about million years ago in Africa.

154 Circulatory - Like the other mammals, primates have a four-chambered heart and a double-circuit circulatory system and are able to maintain a constant body temperature. The insulating covering is provided by hair, although in the humans nearly all the hair is lost, and insulation is now provided by clothing.

155 Digestive - Most primates are nearly or exclusively herbivores, but their digestive tract does not show the high degree of morphological specialization seen in many other herbivores. Even some of the smallest primates, which until recently were believed to be carnivorous, subsist on plant food. In humans the large intestine is relatively less voluminous than in apes (which are predominently plant eaters), but nevertheless, humans are surprisingly effective at digesting cellulose.

156 Endocrine - Similar for all vertebrates.

157 Excretory - The kidney is a major excretory organ of primates and other vertebrates. The principal responsibility of the organ is to separate urea, toxins, and other types of waste from the blood, while water, salt, and electrolytes are maintained at an appropriate level. Due to this important role, the kidney is also involved in blood pressure and acid-base regulation in the body. Nephrons are the basic filtering units of the kidney, more than a million of them being present in a normal adult human kidney. Working together, the nephrons are able to filter blood at an impressive rate, processing the entire five-quart water content of the human circulatory system about every 45 minutes. Only a minute portion of the material passing through the kidneys is actually excreted, however, the vast majority being reabsorbed by the nephrons.

158 Immune - A new study indicates that evolution of the immune system may be directly linked to the sexual activity of a species. A comparative analysis of 41 primate species demonstrates that the most promiscuous species have naturally higher white blood cell (WBC) counts -- the first line of defense against infectious disease -- than more monogamous species. The findings strongly suggest that the most sexually-active species of primates may have evolved elevated immune systems as a defense mechanism against disease.

159 Musculo-skeletal - The limbs of the primates became adapted to swinging and leaping from branch to branch. Their hands were especially dexterous and mobile because their thumbs were opposable; that is, they closed to meet the fingertips. Therefore, these animals easily could reach out and bring food to the mouth. Claws were replaced by nails, which allowed a tree limb to be grasped and released freely. The skeleton of most mammals including primates is simplified compared to that of most reptiles, in that it has fewer bones. For example, the lower jaw consists of a single bone, rather than several.

160 Nervous and Sensory - A snout is common in animals in which a sense of smell is of primary importance. In primates, the sense of sight is more important, and the snout has shortened considerably, allowing the eyes to move to the front of the head. This resulted in three-dimensional vision, permitting primates to make accurate judgments about the distance and the position of adjoining tree limbs. Primate sense of touch became also highly developed as a result of arboreal

161 living. It is useful as an effective feeling and grasping mechanism to grab their insect prey, and to prevent them from falling and tumbling while moving through the trees. By far the most outstanding characteristic of primate evolution has been the enlargement of the brain among members of the order. Primate brains tend to be large, heavy in proportion to body weight, and very complex.

162 Reproductive - One birth at a time became the norm with primates; it would have been difficult to care for several offspring as large as primates in trees. The period of postnatal maturation was prolonged, giving immature young an adequate length of time to learn complex behavior patterns.

163 Respiratory - Similar to all mammals, primates have a constant body temperature, an efficient respiratory system featuring a separation between the nasal and mouth cavities, an efficient four-chambered heart that prevents mixing of oxygenated and deoxygenated blood, among other characteristics.



166 Evolution of Mammals The first mammals appeared about 220 million years ago, just as the dinosaurs were evolving from thecodonts. It is most likely that mammals were descendants of the therapsids, an extinct order of reptiles that were probably endotherms. Mammals are the only vertebrates that have fur and mammary glands.


168 Modern Mammals Modern mammals other than monotremes show one of two patterns of development.

169 Marsupials. Marsupial young are born at a very
Marsupials. Marsupial young are born at a very immature stage and complete their development in their mother’s pouch (called a marsupium).

170 2. Placentals . Placental mammals develop within their mother’s body and are nourished by an organ called the placenta.

171 A primate A primate is a member of the mammalian order Primates, which includes prosimians, monkeys, apes, and humans. The first primates had: 1. Grasping hands and feet 2. Forward orientation of the eyes

172 An opposable thumb—such as your own—stands out at an angle from the other fingers and can be bent inward toward them to hold an object. This gives the hand a greatly increased level of ability to manipulate objects.

173 Apes, which share a common ancestor with monkeys, first appeared about 30 million years ago.
Modern apes include gibbons, orangutans, gorillas, and chimpanzees. Apes have larger brains with respect to their body size than monkeys, and none of the apes have tails.



176 Hominds Hominds are primates that walk upright on two legs.
Hominids are members of the group that led to the evolution of humans. According to the fossil record, hominids first appeared on Earth about 5 million to 7 million years ago.

177 Homo sapiens is the only surviving species of the genus Homo. The name Homo sapiens is from the Latin homo, meaning “man,” and sapiens, meaning “wise.” Homo sapiens is a newcomer to the hominid family. Early Homo sapiens left behind many fossils and artifacts, including the first known paintings

178 Review questions 1. Where does the name vertebrate come from?
2. What is the purpose of the vertebral column?

179 3. What are the levels of organization in vertebrates
3. What are the levels of organization in vertebrates? Start with cell and end with organism. 4. Name the organ systems: briefly explain what each does 1. ___________________________ 2. ___________________________ 3. _____________________________ 4. ______________________________ 5. _____________________________ 6. ______________________________ 7. _______________________________ 8. _______________________________ 9. _______________________________ 10. _________________________________ 11. _________________________________ 12. _______________________________

180 5. What kind of organisms were the first vertebrates?
6. What is the name for the jawless fish? 7. What is the difference between boney fish and cartilaginous fish? 8. What is the next group of vertebrates to move on to land ? 9. What is the word that means double life ? 10. What are the two adaptations reptiles have and amphibians do not have to help them live on land?

181 11. Birds evolved from reptiles but have what, that makes them different?
12. Mammals have ____________________and _________________that are unique to them. 13. List the vertebrate groups in order from the most primitive to the most advanced. 1. ______________________ 2. ______________________ 3. ______________________ 4. ______________________ 5. ______________________

182 14. What does Ectotherm mean?
15. List the vertebrates that are ectotherms. 1. ____________________ 2. ____________________ 3. ____________________ 16. What does endotherm mean? 17. List the endotherms. 1. _____________________ 2. _____________________

183 18. What does external fertilization mean? What does internal mean?
19. Which vertebrates have external fertilization? Internal? External internal _____________ __________________ 20. Which organisms need water to lay eggs? 21. What is the purpose of a shell for the egg

184 Mind Map Vertebrates

185 Vertebrates Fish Reptiles amphibians Ectotherm,external fert. jawless
boney Reptiles cartilaginous


187 1. Where does the name vertebrate come from?
2. What is the purpose of the vertebral column? 3. What are the levels of organization in vertebrates? 4. What kind of organisms were the first vertebrates?

188 5. An example of a cartilaginous fish is
6. What is the name of a jawless fish? 7. What is the first group of vertebrates to move on to land? 8. What does the word amphibian mean?

189 9. What are the two adaptations reptiles have and amphibians do not have to help them live on land?
10. Why do birds need hollow bones? 11. Birds evolved from reptiles but have what, that makes them different? _____________ 12. Mammals have ________________and _________________that are unique to them. 13. List the vertebrate groups in order from the most primitive to the most advanced.

190 14. What does Ectotherm mean?
15. List the vertebrates that are ectotherms. 16. What does endotherm mean? 17. List the endotherms. 18. Which vertebrates use internal fertilization? 19. Which vertebrates have external fertilization? 20. Which organisms need water to lay eggs?

191 20. Which organisms need water to lay eggs?
21. What is the purpose of a shell for the egg? 22. The type of respiration found in an amphibian is ____.

192 What is the number of chambers in the heart?
23. Birds 24. Reptiles 25. Amphibian 26. Mammal 27. Fish

193 Which vertebrate am I describing?
28. Wet skin, lays eggs in the water cold blooded, external fertilization, respiration with skin and lungs and a 3 chambered heart. 29. Has hair, mammary glands, is an Endotherm with a 4 chambered heart and uses internal fertilization. 30. These mammals have a pouch that the young develop in. 31. What structure in the fish helped the fish detect vibrations in the water? What type of fish? 32. Skeleton made of cartilage, gills, no jaw 33. Pair of fins, scales, bony skeleton, Swim bladder 34. Skeleton made of cartilage, gills, paired fins Jaws, rows of teeth 35. What in the chordate becomes the backbone?

194 30. These mammals have a pouch that the young develop in.
31. What structure in the fish helped the fish detect vibrations in the water? What type of fish? 32. Skeleton made of cartilage, gills, no jaw 33. Pair of fins, scales, bony skeleton, Swim bladder 34. Skeleton made of cartilage, gills, paired fins Jaws, rows of teeth 35. What in the chordate becomes the backbone?

195 32. Skeleton made of cartilage, gills, no jaw
33. Pair of fins, scales, bony skeleton, Swim bladder 34. Skeleton made of cartilage, gills, paired fins Jaws, rows of teeth 35. What in the chordate becomes the backbone?


197 1. Where does the name vertebrate come from?
the name of the bones in the back 2. What is the purpose of the vertebral column? protect the spinal cord 3. What are the levels of organization in vertebrates? cell, tissue, organ, organ system, organism 4. What kind of organisms were the first vertebrates? jawless fish, hag fish

198 5. An example of a cartilaginous fish is
. a ray 6. What is the name of a jawless fish? . lamprey 7. What is the first group of vertebrates to move on to land? agnathans --- jawless fish 8. What does the word amphibian mean? double life

199 9. What are the two adaptations reptiles have and amphibians do not have to help them live on land?
hard skin, eggs with shells 10. Why do birds need hollow bones? to allow for less weight during flight 11. Birds evolved from reptiles but have what, that makes them different? feathers

200 12. Mammals have hair and mammary glands that are unique to them.
13. List the vertebrate groups in order from the most primitive to the most advanced. fish, amphibian, reptile, bird, mammal

201 14. What does Ectotherm mean?
cold blooded internal temperature is like that of the external environment 15. List the vertebrates that are ectotherms. fish, amphibians, reptiles 16. What does endotherm mean? able to maintain a constant internal body temperature warm blooded

202 17. List the endotherms. birds and mammals 18. Which vertebrates use internal fertilization? cartilaginous fish, reptiles, birds and mammals 19. Which vertebrates have external fertilization? jawless fish 20. Which organisms need water to lay eggs? amphibians

203 21. What is the purpose of a shell for the egg?
to protect the egg from drying out 22. The type of respiration found in an amphibian is ____. both lungs and skin

204 Match the vertebrate with the correct number of chambers in the heart.
23. Birds 4 24. Reptiles 3 25. Amphibian 3 26. Mammal 4 27. Fish 2

205 29. Has hair, mammary glands, is an Endotherm with a 4 chambered heart and uses internal fertilization. mammal 30. These mammals have a pouch that the young develop in. marsupial 31. What structure in the fish helped the fish detect vibrations in the water? lateral line

206 Match the description to the type of fish
32. Skeleton made of cartilage, gills, no jaw Lamprey, hag fish/Agnathes 33. Pair of fins, scales, bony skeleton, Swim bladder Bony/ Osteictheyes 34. Skeleton made of cartilage, gills, paired fins Jaws, rows of teeth cartilaginous/Chondrichthyes 35. What in the chordate becomes the backbone? notochord

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