Table of Contents – pages iv-v Unit 1: What is Biology? Unit 2: Ecology Unit 3: The Life of a Cell Unit 4: Genetics Unit 5: Change Through Time Unit 6: Viruses, Bacteria, Protists, and Fungi Unit 7: Plants Unit 8: InvertebratesInvertebrates Unit 9: Vertebrates Unit 10: The Human Body

Table of Contents – pages iv-v Unit 1: What is Biology? Chapter 1: Biology: The Study of Life Unit 2: Ecology Chapter 2: Principles of Ecology Chapter 3: Communities and Biomes Chapter 4: Population Biology Chapter 5: Biological Diversity and Conservation Unit 3: The Life of a Cell Chapter 6: The Chemistry of Life Chapter 7: A View of the Cell Chapter 8: Cellular Transport and the Cell Cycle Chapter 9: Energy in a Cell

Table of Contents – pages iv-v Unit 4: Genetics Chapter 10: Mendel and Meiosis Chapter 11: DNA and Genes Chapter 12: Patterns of Heredity and Human Genetics Chapter 13: Genetic Technology Unit 5: Change Through Time Chapter 14: The History of Life Chapter 15: The Theory of Evolution Chapter 16: Primate Evolution Chapter 17: Organizing Life’s Diversity

Table of Contents – pages iv-v Unit 6: Viruses, Bacteria, Protists, and Fungi Chapter 18: Viruses and Bacteria Chapter 19: Protists Chapter 20: Fungi Unit 7: Plants Chapter 21: What Is a Plant? Chapter 22: The Diversity of Plants Chapter 23: Plant Structure and Function Chapter 24: Reproduction in Plants

Table of Contents – pages iv-v Unit 8: InvertebratesInvertebrates Chapter 25: What Is an Animal?What Is an Animal? Chapter 26: Sponges, Cnidarians, Flatworms, and Roundworms Chapter 27: Mollusks and Segmented Worms Chapter 28: Arthropods Chapter 29: Echinoderms and Invertebrate Chordates

Table of Contents – pages iv-v Unit 9: Vertebrates Chapter 30: Fishes and Amphibians Chapter 31: Reptiles and Birds Chapter 32: Mammals Chapter 33: Animal Behavior Unit 10: The Human Body Chapter 34: Protection, Support, and Locomotion Chapter 35: The Digestive and Endocrine Systems Chapter 36: The Nervous System Chapter 37: Respiration, Circulation, and Excretion Chapter 38: Reproduction and Development Chapter 39: Immunity from Disease

Unit Overview – pages Invertebrates What is an animal? Sponges, Cnidarians, Flatworms and Roundworms Mollusks and Segmented Worms Arthropods Echinoderms and Invertebrate Chordates

Chapter Contents – page xi Chapter 25 What is an animal?What is an animal? 25.1: Typical Animal CharacteristicsTypical Animal Characteristics 25.1: Section CheckSection Check 25.2: Body Plans and AdaptationsBody Plans and Adaptations 25.2: Section CheckSection Check Chapter 25 SummarySummary Chapter 25 AssessmentAssessment

Chapter Intro-page 672 What You’ll Learn You will identify animal characteristics and distinguish them from those of other life forms. You will identify cell differentiation in the developmental stages of animals. You will identify and interpret body plans of animals.

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

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

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

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

Section 25.1 Summary – pages Scientists hypothesize that animals first evolved in water. Animals obtain food 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.

Section 25.1 Summary – pages Animals obtain food Organisms that are permanently attached to a surface are called sessile.

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

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

Section 25.1 Summary – pages 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. Animals digest food In some animals, digestion is carried out within individual cells; in other animals, digestion takes place in an internal cavity.

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

Section 25.1 Summary – pages 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. Animal cell adaptations Most animal cells are differentiated and carry out different functions.

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

Section 25.1 Summary – pages Male animals produce sperm cells and female animals produce egg cells. Fertilization Most animals reproduce sexually. 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.

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

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

Section 25.1 Summary – pages 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.

Section 25.1 Summary – pages 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.

Section 25.1 Summary – pages 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. Gastrulation

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

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

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

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

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

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

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

Section 25.1 Summary – pages 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. Formation of mesoderm

Section 25.1 Summary – pages 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.

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

Section 25.1 Summary – pages 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).

Section 25.1 Summary – pages Growth and development

Section 25.1 Summary – pages 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.

Section 25.1 Summary – pages 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.

Section 1 Check Question 1 Which of the following is NOT a characteristic of animals? (TX Obj 2; 8C, 10A, 10B) D. prokaryotic C. heterotrophic B. multicellular A. eukaryotic The answer is D.

Section 1 Check Sessile animals _______. (TX Obj 2; 8C, 10A, 10B) D. live only on land C. are permanently attached to a surface B. are autotrophs A. live only underground Question 2

Section 1 Check The answer is C. Sessile animals are permanently attached to a surface.

Section 1 Check Ingestion is another word for _______. (TX Obj 2; 8C, 10A, 10B) D. eating C. breathing B. physically responding to a light stimulus A. digestion Question 3

Section 1 Check The answer is D, eating.

Section 1 Check Question 4 Which of the following is NOT true of animal fertilization? (TX Obj 2; 8C, 10A, 10B) B. forms a haploid zygote A. occurs when a sperm cell penetrates an egg cell

Section 1 Check Question 4 Which of the following is NOT true of animal fertilization? (TX Obj 2; 8C, 10A, 10B) D. may be internal or external C. forms a diploid zygote The answer is B, forms a haploid zygote.

Section 1 Check Question 5 When a zygote divides by mitosis and cell division to form two cells, the process is called _______. (TX Obj 2; 8C, 10A, 10B) D. gastrulation C. ingestion B. fertilization A. cleavage

Section 1 Check The answer is A, cleavage. Cleavage

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

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

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

Section 25.2 Summary – pages 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.

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

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

Section 25.2 Summary – pages 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.

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

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

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

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. Section 25.2 Summary – pages

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.

Section 25.2 Summary – pages 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. Acoelomates

Section 25.2 Summary – pages Acoelomates 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. Acoelomate Flatworm Ectoderm Mesoderm Endoderm Body cavity Digestive tract

Section 25.2 Summary – pages 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. Acoelomate Flatworm Ectoderm Mesoderm Endoderm Body cavity Digestive tract Acoelomates

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

Section 25.2 Summary – pages It is called a pseudocoelom —a fluid-filled body cavity partly lined with mesoderm. Ectoderm Mesoderm Endoderm Body cavity Digestive tract Pseudocoelomate Roundworm Pseudocoelom Pseudocoelomates

Section 25.2 Summary – pages Pseudocoelomates can move quickly. Although the roundworm has no bones, it does have a rigid, fluid-filled space, the pseudocoelom. Its muscles attach to the mesoderm and brace against the pseudocoelom. Pseudocoelomates

Section 25.2 Summary – pages Pseudocoelomates Pseudocoelomates have a one-way digestive tract that has regions with specific functions. The mouth takes in food, the breakdown and absorption of food occurs in the middle section, and the anus expels waste. Mouth Intestine Round body shape Anus

Section 25.2 Summary – pages Coelomates The body cavity of an earthworm develops from a coelom, a fluid- filled space that is completely surrounded by mesoderm. The greatest diversity of animals is found among the coelomates. Ectoderm Mesoderm Endoderm Body cavity Digestive tract Coelomate Segmented Worm Coelom

Section 25.2 Summary – pages In coelomate animals, the digestive tract and other internal organs are attached by double layers of mesoderm and are suspended within the coelom. The coelom cushions and protects the internal organs. It provides room for them to grow and move independently within an animal’s body. Coelomates

Section 25.2 Summary – pages Over time, the development of body cavities resulted in a greater diversity of animal species. Some animals, such as mollusks, evolved hard shells that protected their soft bodies. Other animals, such as sponges, evolved hardened spicules between their cells that provided support. Animal Protection and Support

Section 25.2 Summary – pages Some animals developed exoskeletons. An exoskeleton is a hard covering on the outside of the body that provides a framework for support. Animal Protection and Support

Section 25.2 Summary – pages Exoskeletons also protect soft body tissues, prevent water loss, and provide protection from predators. Animal Protection and Support

Section 25.2 Summary – pages As an animal grows, it secretes a new exoskeleton and sheds the old one. Exoskeletons are often found in invertebrates. An invertebrate is an animal that does not have a backbone. Animal Protection and Support

Section 25.2 Summary – pages Invertebrates, such as sea urchins and sea stars, have an internal skeleton called an endoskeleton. It is covered by layers of cells and provides support for an animal’s body. Animal Protection and Support

Section 25.2 Summary – pages The endoskeleton protects internal organs and provides an internal brace for muscles to pull against. Animal Protection and Support

Section 25.2 Summary – pages Animal Protection and Support An endoskeleton may be made of calcium carbonate, as in sea stars; cartilage, as in sharks; or bone. Calcium carbonate cartilage

Section 25.2 Summary – pages Bony fishes, amphibians, reptiles, birds, and mammals all have endoskeletons made of bone. bone Animal Protection and Support

Section 25.2 Summary – pages A vertebrate is an animal with an endoskeleton and a backbone. All vertebrates are bilaterally symmetrical. Animal Protection and Support

Section 25.2 Summary – pages Origin of Animals Most biologists agree that animals probably evolved from aquatic, colonial protists. Scientists trace this evolution back in time to late in the Precambrian.

Section 25.2 Summary – pages Origin of Animals

Section 25.2 Summary – pages Origin of Animals Many scientists agree that all the major animal body plans that exist today were already in existence at the beginning of the Cambrian Period, 543 million years ago. All known species have variations of the animal body plans developed during the Cambrian Period.

Section 2 Check A sea star exhibits _______. (TX Obj 2; 8C, 10A, 10B) Question 1 D. bilateral – posterior C. bilateral – anterior B. asymmetry A. radial symmetry

Section 2 Check The answer is A, radial symmetry.

Section 2 Check Which of the following animals does NOT exhibit radial symmetry? (TX Obj 2; 8C, 10A, 10B) Question 2 D. sea urchin C. octopus B. starfish A. jellyfish

Section 2 Check The answer is C. An octopus exhibits bilateral symmetry.

Section 2 Check As you look at the cross sections of animals in the following figure, give the reason why animals with the basic cross section in the middle and on the far right will tend to be larger than animals with the far-left cross section. (TX Obj 2; 8C, 10A, 10B) Question 3

Section 2 Check Question 3 Ectoderm MesodermEndoderm Body cavity Digestive tract Acoelomate Flatworm Pseudocoelomate Roundworm Coelomate Segmented Worm Pseudocoelom Coelom

Section 2 Check The development of fluid-filled body cavities made it possible for animals to grow larger because it allowed for the efficient circulation and transport of fluids, and support for organs and organ systems.

Section 2 Check Which of the following pairs of terms is not related? (TX Obj 2; 8C, 10A, 10B) Question 4 D. coral – larvae C. flatworm – coelom B. mollusk – shell A. sponge – spicule The answer is C.

Section 2 Check Which of the following is NOT a vertebrate feature? (TX Obj 2; 8C, 10A, 10B) Question 5 D. pseudocoelom C. bilaterally symmetrical B. backbone A. endoskeleton The answer is D.

Chapter Summary – 25.1 Animals are multicellular eukaryotes whose cells lack cell walls. Their cells are specialized to perform different functions. Typical Animal Characteristics All animals are heterotrophs that obtain and digest food. At some point during its life an animal can move from place to place. Most animals retain this ability.

Chapter Summary – 25.1 Embryonic development of a fertilized egg cell by cell division and differentiation is similar among animal phyla. The sequence of developmental stages is: 1. formation of a blastula—a cell-covered, fluid-filled ball; Typical Animal Characteristics

Chapter Summary – gastrulation—the inward movement of cells to form two cell layers, the endoderm and ectoderm; 3. formation of the mesoderm—the development of a cell layer between the endoderm and ectoderm. Typical Animal Characteristics

Chapter Summary – 25.2 Animal adaptations include asymmetry, radial symmetry, or bilateral symmetry. Body Plans and Adaptations Flatworms and other acoelomates have flattened, solid bodies with no body cavities. Animals such as roundworms have a pseudocoelom, a body cavity that develops between the endoderm and mesoderm.

Chapter Summary – 25.2 A coelom is a fluid-filled body cavity that supports internal organs. Coelomate animals have internal organs suspended in a body cavity that is completely surrounded by mesoderm. Body Plans and Adaptations Exoskeletons provide a framework of support on the outside of the body. Endoskeletons provide internal support.

Chapter Assessment Question 1 What is the difference between a blastula and a gastrula? (TX Obj 2; 8C, 10A, 10B)

Gastrula A blastula is a cell- covered, fluid-filled ball. When the cells on one side of the blastula move inward, they form a gastrula, which is a structure made up of two layers of cells with an opening at one end. Chapter Assessment

Question 2 The layer of cells on the outer surface of the gastrula is called the _______. (TX Obj 2; 8C, 10A, 10B) D. blastula C. mesoderm B. ectoderm A. endoderm

The answer is B, ectoderm. Endoderm Ectoderm Mesoderm Chapter Assessment

Which of these organs develops from the endoderm? (TX Obj 2; 8C, 10A, 10B) D. circulatory system C. muscles B. skin A. digestive system The answer is A. Question 3

Chapter Assessment Question 4 Which of the following is NOT a deuterostome? (TX Obj 2; 8C, 10A, 10B) D. honey bee C. frog B. dolphin A. shark The answer is D.

Chapter Assessment List the following stages in the order of their occurrence. (TX Obj 2; 8C, 10A, 10B) D. blastula formation C. fertilization B. gastrulation A. embryo formation Question 5

Chapter Assessment D. blastula formation C. fertilization B. gastrulation A. embryo formation The answer is c,a,d,b.

Chapter Assessment Question 6 Why can an octopus squeeze through spaces much smaller than the width of its body? (TX Obj 2; 8C, 10A, 10B)

An octopus has no endoskeleton or exoskeleton to maintain a rigid shape for the animal. Therefore, it can modify its shape as necessity demands. Chapter Assessment

Question 7 Which of the following animals does NOT have an exoskeleton? (TX Obj 2; 8C, 10A, 10B) D. tarantula C. turtle B. ant A. horseshoe crab

The answer is C. A turtle is a vertebrate animal with an internal skeleton. Chapter Assessment

Question 8 Why are sessile animals more likely to live in water than on land? (TX Obj 2; 8C, 10A, 10B) Answer There is little suspended food in the air for these animals to eat.

Chapter Assessment Question 9 Why are sessile animals more likely to live in vigorously moving water than in still water? (TX Obj 2; 8C, 10A, 10B)

Vigorously moving water is much more likely to bring food particles past sessile animals where they can capture it than water that is standing still. Also, moving water has more oxygen suspended in it than still water. Chapter Assessment

Question 10 Describe the way somatic cell nuclear transfer produces stem cells. (TX Obj 2; 4B, 8C) Answer The nucleus is removed from a normal animal egg cell. A somatic cell is placed next to the egg cell without a nucleus and the two cells are made to fuse. The new cell undergoes many cell divisions and forms a blastocyst from which stem cells are taken.

Photo Credits Digital Stock NOAA PhotoDisc USDA- ARS Alton Biggs

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