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Chapter 25 What is an animal? Sections 1 and 2 Typical Animal Characteristics Body Plans and Adaptations.

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Presentation on theme: "Chapter 25 What is an animal? Sections 1 and 2 Typical Animal Characteristics Body Plans and Adaptations."— Presentation transcript:

1 Chapter 25 What is an animal? Sections 1 and 2 Typical Animal Characteristics Body Plans and Adaptations

2 Characteristics of All Animals:  All eukaryotic.  All multicellular organisms.  All have cells without cell walls.  All are heterotrophic.

3 Characteristics of All Animals:  All animals must digest their food within individual cells or in an internal cavity.  Some of the digested food is stored as fat or glycogen to use as a source of energy at a later time.

4 Characteristics of Some Animals:  Most have ways of moving that help them reproduce, obtain food, and protect themselves.  Most have specialized cells that form tissues and organs.

5 Characteristics of Some Animals:  Some organisms are sessile:  Organisms that are permanently attached to a surface.  Do not expend much energy to obtain food.  Examples:  Adult forms of coral and sponges.

6 Development of Animals  Most animals reproduce sexually.

7 Development of Animals  A zygote is formed when female egg cells are fertilized by male sperm cells.  Fertilization may be internal or external.

8 Development of Animals  The zygote divides through mitosis to form two cells in a process called cleavage.  Once cell division has begun the zygote becomes an embryo.

9 Development of Animals  The two cells further divide by mitosis into four cells, and so on, until a cell- covered fluid-filled ball called a blastula is formed.

10 Development of Animals  After the formation of the blastula, cell division continues.  The cells on one side of the blastula move inward to form a structure made up of two layers of cells with an opening at one end called a gastrula.

11 Development of Animals  Gastrula  The layer of cells on the outer surface of the gastrula is called the ectoderm and eventually develops into skin and nervous tissue.

12 Development of Animals  Gastrula  The layer of cells on the inner surface of the gastrula is called the endoderm and eventually develops into the digestive tract and organs for digestion.

13 Development of Animals  Gastrula  In some animals the cells of the gastrula further divide into a third layer called the mesoderm, located between the ectoderm and the endoderm.  The mesoderm eventually forms the muscles, circulatory system, excretory system, and sometimes the respiratory system.

14 Development of Animals  Protostomes vs. Deuterostomes  When the opening of the gastrula develops into a mouth the animal is called a protostome.  Examples: snails, earthworms, and insects.

15 Development of Animals  Protostomes vs. Deuterostomes  When the mouth of the organism is not developed from the opening to the gastrula, the animal is called a deuterostome.  Examples: sea stars, fish, toads, snakes, birds, and humans.

16 Development of Animals  Cells in developing embryos continue to differentiate and become specialized to perform different functions.

17 Development of Animals  Some embryos develop into miniature forms of adults called juveniles.

18 Development of Animals  Some embryos develop inside an egg into an intermediate stage called a larva which has little resemblance to the adult.  Inside the egg, the larva is surrounded by a membrane formed right after fertilization.

19 Development of Animals  After the juvenile or larval stage the animal passes into the adult stage and cycle begins again.

20  ience-videos/2012/5/6/animals.html ience-videos/2012/5/6/animals.html

21 Symmetry  A term used to describe the arrangement of body structures:  Asymmetry  Radial Symmetry  Bilateral Symmetry

22 Asymmetry  An animal that is irregular in shape.  Asymmetrical animals are often sessile.  Example: Sponges

23 Radial Symmetry  Animals that can be divided along any plane through a central axis into roughly equal halves.  Radial symmetry enables an animal to detect and capture prey coming toward it from any direction.  Example: Hydra

24 Bilateral Symmetry  Animal can be divided down its length into similar right and left halves.

25 Bilateral Symmetry  Bilateral animals have four sides:  Anterior or head end (often with sensory organs)  Posterior or tail end  Dorsal or upper surface  Ventral or lower surface

26 Bilateral Symmetry  All animals with bilateral symmetry developed from three embryonic cell layers – ectoderm, endoderm, and mesoderm.

27 Bilateral Symmetry  Some animals with bilateral symmetry also have fluid-filled spaces inside their bodies in which internal organs are found called body cavities.  These cavities allow the animal to grow large because they provide efficient circulation and transportation of fluids and support for organs and organ systems.

28 Bilateral Symmetry  Animals with bilateral symmetry can be divided into:  Acoelomates  Psuedocoelomates  Coelomates

29 Bilateral Symmetry  Acoelomates:  Have no body cavities  Have digestive tracts that extend throughout the body.  May have been the first group of animals in which organs evolved.  The organs are embedded in the solid tissues of the body.  Example: Flatworm

30 Bilateral Symmetry  Psuedocoelomates:  Have a fluid-filled body cavity partly lined with mesoderm that develops between the endoderm and mesoderm  Have a one-way digestive tract that has regions with specific functions.  Can move quickly because muscles attach to the mesoderm and brace against the rigid, fluid-filled psuedocoelom.  Examples: Roundworm

31 Bilateral Symmetry  Coelomates:  Have a fluid-filled body cavity completely surrounded by mesoderm  Have the greatest diversity of all animals.  Specialized organs and organ systems develop in the coelom.  The digestive tract and other internal organs are attached by double layers of mesoderm and are suspended within the coelom, which cushions and protects them.

32 Animal Protection and Support  Exoskeleton  Hard covering on the outside of the body that:  Provides a framework for support  Protects soft body tissues  Prevents water loss  Provides protection from predators

33 Animal Protection and Support  Exoskeleton:  The exoskeleton is secreted by the epidermis and extends into the body where it provides a place for muscle attachment.  As an animal grows it secretes a new exoskeleton and sheds the old one.  Usually found in invertebrates which are animals that do not have a backbone.  Examples: Crabs, spiders, dragonflies, beetles

34 Animal Protection and Support  Endoskeleton:  Covered by layers of cells  Provides support for the body  Protects internal organs  Provides an internal brace for muscles to pull against  May be made of calcium carbonate, cartilage, or bone.

35 Animal Protection and Support  Endoskeleton:  May be found in invertebrates such as sea stars and sea urchins or in vertebrates, which are animals with both an endoskeleton and a backbone, such as fish, amphibians, reptiles, birds, and mammals.

36 Origin of Animals  Probably evolved from aquatic, colonial protists in the late Precambrian.  All the major body plans that exist today were thought to already be in existence by the beginning of the Cambrian Period 543 million years ago.


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