Biology 2nd period McFall

1. Biology 2nd periodMcFall

2. Chapter Contents – page xi Chapter 25What is an animal? 25.1:Typical Animal Characteristics 25.2:Body Plans and Adaptations

3. 25.1 Section Objectives – page 673 Section Objectives: • Identify the characteristics of animals. • Identify cell differentiation in the development of a typical animal. • Sequence the development of a typical animal.

4. Section 25.1 Summary – pages 673 - 679 Characteristics of Animals • Animals are eukaryotic, multicellular organisms with ways of moving that help them reproduce, obtain food, and protect themselves.

5. Section 25.1 Summary – pages 673 - 679 Characteristics of Animals • Most animals have specialized cells that form tissues and organs—such as nerves and muscles. • Animals are composed of cells that do not have cell walls.

6. Section 25.1 Summary – pages 673 - 679 Animals obtain food • One characteristic common to all animals is that they are heterotrophic, meaning they must consume food to obtain energy and nutrients. • All animals depend either directly or indirectly on autotrophs for food.

7. Section 25.1 Summary – pages 673 - 679 Animals obtain food • Scientists hypothesize that animals first evolved in water. • In water, some animals, such as barnacles and oysters, do not move from place to place and have adaptations that allow them to capture food from their water environment.

8. Section 25.1 Summary – pages 673 - 679 Animals obtain food • Organisms that are permanently attached to a surface are called sessile.

9. Section 25.1 Summary – pages 673 - 679 Animals obtain food • Some aquatic animals, such as corals and sponges move about only during the early stages of their lives. • Most adults are sessile and attach themselves to rocks or other objects.

10. Section 25.1 Summary – pages 673 - 679 Animals obtain food • There is little suspended food in the air. • Land animals use more oxygen and expend more energy to find food.

11. Section 25.1 Summary – pages 673 - 679 Animals digest food • In some animals, digestion is carried out within individual cells; in other animals, digestion takes place in an internal cavity. • Some of the food that an animal consumes and digests is stored as fat or glycogen, a polysaccharide, and used when other food is not available.

12. Section 25.1 Summary – pages 673 - 679 Animals digest food • In animals such as planarians and earthworms, food is digested in a digestive tract. Mouth Digestive tract Digestive tract Extended pharynx Anus

13. Section 25.1 Summary – pages 673 - 679 Animal cell adaptations • Most animal cells are differentiated and carry out different functions. • Animals have specialized cells that enable them to sense and seek out food and mates, and allow them to identify and protect themselves from predators.

14. Section 25.1 Summary – pages 673 - 679 Development of Animals • Most animals develop from a fertilized egg cell called a zygote. • After fertilization, the zygote of different animal species all have similar, genetically determined stages of development.

15. Section 25.1 Summary – pages 673 - 679 Fertilization • Most animals reproduce sexually. • Male animals produce sperm cells and female animals produce egg cells. • Fertilization occurs when a sperm cell penetrates the egg cell, forming a new cell called a zygote. • In animals, fertilization may be internal or external.

16. Section 25.1 Summary – pages 673 - 679 Cell division • The zygote divides by mitosis and cell division to form two cells in a process called cleavage. cleavage

17. Section 25.1 Summary – pages 673 - 679 Cell division • Once cell division has begun, the organism is known as an embryo.

18. Section 25.1 Summary – pages 673 - 679 Cell division • The two cells that result from cleavage then divide to form four cells and so on, until a cell-covered, fluid-filled ball called a blastula is formed. • The blastula is formed early in the development of an animal embryo.

19. Section 25.1 Summary – pages 673 - 679 Gastrulation • After blastula formation, cell division continues. • The cells on one side of the blastula then move inward to form a gastrula—a structure made up of two layers of cells with an opening at one end.

20. Section 25.1 Summary – pages 673 - 679 Gastrulation • The cells at one end of the blastula move inward, forming a cavity lined with a second layer of cells. • The layer of cells on the outer surface of the gastrula is called the ectoderm. • The layer of cells lining the inner surface is called the endoderm.

21. Section 25.1 Summary – pages 673 - 679 Gastrulation Ectoderm • The ectoderm cells of the gastrula continue to grow and divide, and eventually they develop into the skin and nervous tissue of the animal.

22. Section 25.1 Summary – pages 673 - 679 Gastrulation • The endoderm cells develop into the lining of the animal’s digestive tract and into organs associated with digestion. Endoderm

23. Section 25.1 Summary – pages 673 - 679 Formation of mesoderm • Mesoderm is found in the middle of the embryo; the term meso means “middle.” Mesoderm • The mesoderm is the third cell layer found in the developing embryo between the ectoderm and the endoderm.

24. Section 25.1 Summary – pages 673 - 679 Formation of mesoderm • The mesoderm cells develop into the muscles, circulatory system, excretory system, and, in some animals, the respiratory system.

25. Section 25.1 Summary – pages 673 - 679 Formation of mesoderm • When the opening in the gastrula develops into the mouth, the animal is called a protostome. • Snails, earthworms, and insects are examples of protostomes.

26. Section 25.1 Summary – pages 673 - 679 Formation of mesoderm • In other animals, such as sea stars, fishes, toads, snakes, birds, and humans, the mouth does not develop from the gastrula’s opening.

27. Section 25.1 Summary – pages 673 - 679 Formation of mesoderm • An animal whose mouth developed not from the opening, but from cells elsewhere on the gastrula is called a deuterostome.

28. Section 25.1 Summary – pages 673 - 679 Formation of mesoderm • Scientists hypothesize that protostome animals were the first to appear in evolutionary history, and that deuterostomes followed at a later time. • Determining whether an animal is a protostome or deuterostome can help biologists identify its group.

29. Section 25.1 Summary – pages 673 - 679 Cell differentiation in Animal Development • The fertilized eggs of most animals follow a similar pattern of development. From one fertilized egg cell, many divisions occur until a fluid-filled ball of cells forms. • The ball folds inward and continues to develop.

30. Section 25.1 Summary – pages 673 - 679 Sperm cells Cell Differentiation in Animal Development Fertilization Egg cell Formation of mesoderm First cell division Endoderm Mesoderm Ectoderm Gastrulation Additional cell divisions Formation of a blastula

31. Section 25.1 Summary – pages 673 - 679 Growth and development • Most animal embryos continue to develop over time, becoming juveniles that look like smaller versions of the adult animal. • In some animals, such as insects and echinoderms, the embryo develops inside an egg into an intermediate stage called a larva (plural larvae).

32. Section 25.1 Summary – pages 673 - 679 Growth and development

33. Section 25.1 Summary – pages 673 - 679 Growth and development • A larva often bears little resemblance to the adult animal. • Inside the egg, the larva is surrounded by a membrane formed right after fertilization. • When the egg hatches, the larva breaks through this fertilization membrane.

34. Section 25.1 Summary – pages 673 - 679 Adult animals • Once the juvenile or larval stage has passed, most animals continue to grow and develop into adults. • This growth and development may take just a few days in some insects, or up to fourteen years in some mammals. • Eventually the adult animals reach sexual maturity, mate, and the cycle begins again.

35. 25.2 Section Objectives – page 680 Section Objectives: • Compare and contrast radial and bilateral symmetry with asymmetry. • Trace the phylogeny of animal body plans. • Distinguish among the body plans of acoelomate, pseudocoelomate, and coelomate animals.

36. Section 25.2 Summary – pages 680 - 685 What is symmetry • Symmetry isa term that describes the arrangement of body structures. • Different kinds of symmetry enable animals to move about in different ways.

37. Section 25.2 Summary – pages 680 - 685 Asymmetry • An animal that is irregular in shape has no symmetry or an asymmetrical body plan. • Animals with no symmetry often are sessile organisms that do not move from place to place. • Most adult sponges do not move about.

38. Section 25.2 Summary – pages 680 - 685 Asymmetry • The bodies of most sponges consist of two layers of cells. • Unlike all other animals, a sponge’s embryonic development does not include the formation of an endoderm and mesoderm, or a gastrula stage.

39. Section 25.2 Summary – pages 680 - 685 Radial symmetry • Animals with radial symmetry can be divided along any plane, through a central axis, into roughly equal halves.

40. Section 25.2 Summary – pages 680 - 685 Radial symmetry • Radial symmetry is an adaptation that enables an animal to detect and capture prey coming toward it from any direction.

41. Section 25.2 Summary – pages 680 - 685 Radial symmetry • The body plan of a hydra can be compared to a sack within a sack. • These sacks are cell layers organized into tissues with distinct functions.

42. Section 25.2 Summary – pages 680 - 685 Radial symmetry • A hydra develops from just two embryonic cell layers—ectoderm and endoderm. Inner cell layer Outer cell layer

43. Section 25.2 Summary – pages 680 - 685 Bilateral symmetry • An organism with bilateral symmetry can be divided down its length into similar right and left halves.

44. Section 25.2 Summary – pages 680 - 685 Bilateral symmetry • Bilaterally symmetrical animals can be divided in half only along one plane. • In bilateral animals, the anterior, or head end, often has sensory organs. • The posterior of these animals is the tail end.

45. Section 25.2 Summary – pages 680 - 685 Bilateral symmetry • The dorsal, or upper surface, also looks different from the ventral, or lower surface. • Animals with bilateral symmetry can find food and mates and avoid predators because they have sensory organs and good muscular control.

46. Section 25.2 Summary – pages 680 - 685 Bilateral Symmetry and Body Plans • All bilaterally symmetrical animals developed from three embryonic cell layers—ectoderm, endoderm, and mesoderm. • Some bilaterally symmetrical animals also have fluid-filled spaces inside their bodies called body cavities in which internal organs are found.

47. Section 25.2 Summary – pages 680 - 685 Acoelomates • Animals that develop from three cell layers—ectoderm, endoderm, and mesoderm—but have no body cavities are called acoelomate animals. • They have a digestive tract that extends throughout the body.

48. Section 25.2 Summary – pages 680 - 685 Acoelomates Acoelomate Flatworm • Flatworms are bilaterally symmetrical animals with solid, compact bodies. Like other acoelomate animals, the organs of flatworms are embedded in the solid tissues of their bodies. Ectoderm Mesoderm Endoderm Body cavity Digestive tract

49. Section 25.2 Summary – pages 680 - 685 Acoelomates Acoelomate Flatworm • A flattened body and branched digestive tract allow for the diffusion of nutrients, water, and oxygen to supply all body cells and to eliminate wastes. Ectoderm Mesoderm Endoderm Body cavity Digestive tract

50. Section 25.2 Summary – pages 680 - 685 Pseudocoelomates Pseudocoelomate Roundworm • A roundworm is an animal with bilateral symmetry. Ectoderm Mesoderm Endoderm • The body of a roundworm has a space that develops between the endoderm and mesoderm. Body cavity Digestive tract