chapter: animals

Chapter: Animals

Table of ContentsTable of Contents

Section 3: Vertebrate Animals

Section 1: What is an animal?

Section 2: Invertebrate Animals

• What makes an animal an animal?

• Animals are many-celled organisms that are made of different kinds of cells.

• Most animal cells have a nucleus and organelles. The nucleus and many organelles are surrounded by a membrane. This type of cell is called a eukaryotic (yew ker ee AH tihk) cell.

Animal Characteristics11What is an animal?What is an animal?

• Animals cannot make their own food.

• Animals digest their food.

• Most animals can move from place to place.

Animal Characteristics11What is an animal?What is an animal?

• Symmetry refers to the arrangement of the individual parts of an object that can be divided into similarhalves.

• Animals with body parts arranged in a circle around a central point have radial symmetry.

Symmetry11What is an animal?What is an animal?

• Animals with bilateral symmetry have parts that are nearly mirror images of each other.

• A line can be drawn down the center of their bodies to divide them into two similar parts.


• Some animals have an irregular shape.

• They are called asymmetrical (AY suh meh trih kul).


• They have bodies that cannot be divided into similar halves.

• Scientists place all animals into smaller, related groups.

• They can begin by separating animals into two distinct groups—vertebrates and invertebrates.

Animal Classification11What is an animal?What is an animal?

• Vertebrates (VUR tuh bruts) are animals that have a backbone.

• Invertebrates (ihn VUR tuh bruts) are animals that do not have a backbone.

• About 97 percent of all animals are invertebrates.


• Scientists classify the invertebrates into smaller groups, as shown.

• The animals within each group share similar characteristics.


Question 1

Answer

How do animals get food?

Animals can not make their own food. They must eat plants or other animals to supply their energy needs.

Section CheckSection Check

11

GLE 0707.Inq.5

11Section CheckSection Check

Question 2

Which has radial symmetry?

A. lobsterB. sea anemoneC. spongeD. none of them

GLE 0707.Inq.5


Answer

The sea anemone has radial symmetry. Symmetry refers to the arrangement of the parts of an animal. Animals with radial symmetry have body parts arranged in a circle around a central point.

GLE 0707.Inq.5


Question 3

Which describes most of the cells found in animals?

A. they have bilateral symmetry B. they have a nucleus and many organellesC. they help animals moveD. they help in reproduction

GLE 0707.1.1 SPI 0707.1.1


Answer

The correct answer is B. The cells found in animals are called eukaryotic cells. Animals are made of many different kinds of cells.

GLE 0707.1.1 SPI 0707.1.1

Sponges

• Adult sponges are sessile meaning they remain attached to one place.

• They are filter feeders, filtering food out of the water that flows through their bodies.

22Invertebrate AnimalsInvertebrate Animals

Sponges

• Sponge bodies are made of two layers of cells.

• The inner surface of the central cavity is lined with collar cells.


• Thin, whip-like structures called flagella extend from the collar cells and keep the water moving through the sponge.

Body Support and Defense

• The soft bodies of many sponges are supported by sharp, glass-like structures called spicules.

• Other sponges have a material called spongin. Spongin is similar to foam rubber because it makes sponges soft and elastic.


Sponge Reproduction

• Sponges care reproduce asexually and sexually. Asexual reproduction occurs when a bud on the side of the parent sponge develops into a small sponge.


Cnidarians• Cnidarians such as

jellies, sea anemones, hydra, and corals, have tentacles surrounding their mouth.


• Cnidarians are hollow-bodied animals with two cell layers that are organized into tissues. The inner layer forms a digestive cavity where food is broken down.

Cnidarians

• Cnidarians reproduce asexually and sexually. Some reproduce asexually by budding.

• Some can reproduce sexually by releasing eggs or sperm into the water.


Flatworms and Roundworms

• Flatworms are invertebrates with long, flattened bodies ant bilateral symmetry.

• Their soft bodies have three layers of tissue organized into organs and organ systems.


Flatworms and Roundworms

• A roundworm’s body is described as a tube within a tube, with a fluid-filled cavity in between the two tubes.

• Their digestive tract has two openings. Food enters through the mouth, is digested in a digestive tract, and wastes exit through the anus.


Mollusks• Mollusks are soft-

bodied invertebrates that usually have a shell. They also have a mantle and a large, muscular foot.

• If the mollusk has a shell, it is secreted by the mantle.


• The foot is used for moving or for anchoring the animal.

Mollusks

• Mollusks have a digestive system with two openings.

• Some mollusks have an open circulatory system, which means they do not have vessels to contain their blood.


• Others have a closed circulatory system, in which blood is carried through blood vessels instead of surrounding the organs.

Segmented Worms• Earthworms, leeches, and marine worms are

segmented worms, or annelids.• Each segment has nerve cells, blood vessels,

part of the digestive tract, and the coelom.


• The coelom, or internal body cavity, separates the internal organs from the body wall.

• Annelids have a closed circulatory system and a complete digestive system with two body openings.

Arthropods—Structure and Function

• Arthropods are animals that have jointed appendages.

• Appendages are structures such as claws, legs, and antennae that grow from the body.


Arthropods—Structure and Function


• Arthropods have a rigid body covering called an exoskeleton.

• They have an open circulatory system, and oxygen is brought directly to the tissues through spiracles.

Metamorphosis22

Invertebrate AnimalsInvertebrate Animals

• Many arthropods completely change their body form as they mature. This change in body form is called metamorphosis.

• Complete Metamorphosis has four stages—egg, larva, pupa, and adult.

Metamorphosis22


• Incomplete metamorphosis has only three stages—egg, nymph, and adult. A nymph looks similar to its parents, only smaller.

Echinoderms22


• Sea stars belong to a varied group of animals called echinoderms.

• Echinoderms have spines of various lengths that cover the outside of their bodies.

• All echinoderms have a water-vascular system.

Question 1

Answer

How do cnidarians use nematocysts?

Nematocysts, or stinging cells, are used to capture prey.


22

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22Question 2

This diagram of a sponge shows that sponges _______.

SPI 0707.4.1 GLE 0707.Inq.2


22

A. are hermaphroditesB. produce budsC. reproduce asexuallyD. use spicules for production

SPI 0707.4.1 GLE 0707.Inq.2


22Answer

The correct answer is A. Most sponges that reproduce sexually are hermaphrodites. Both sperm and eggs are produced from the same sponge.

SPI 0707.4.1 GLE 0707.Inq.2


22Question 3

Which of the following describes the body of a roundworm?

A. a medusa B. a polypC. a tube within a tubeD. has two cell layers

GLE 0707.1.2


22Answer

The correct answer is C. The two tubes are separated by a fluid-filled cavity. The inner tube is the digestive tract.

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What is a chordate?• Three characteristics of all chordates are a

notochord, a nerve cord, and pharyngeal pouches at some time during their development.

• The notochord is a flexible rod that extends along the length of the developing organism.

33Vertebrate AnimalsVertebrate Animals

• Pharyngeal pouches are slitlike openings between the body cavity and the outside of the body.

• They are present only during the early stages of the organism’s development.


What is a chordate?

Vertebrates

• Vertebrates have an internal system of bones called an endoskeleton.

• The vertebrae, skull, and other bones of the endoskeleton support and protect internal organs.


Body Temperature

• Most vertebrate body temperatures change as the surrounding temperature changes. These animals are ectotherms or cold-blooded animals.

• Humans and many other vertebrates are endotherms or warm-blooded animals. Their body temperature doesn’t change with the surrounding temperature.


Fish• There are three classes of fish: jawless, jawed

cartilaginous, and bony. Fish are ectotherms that can be found in warm desert pools and the subfreezing Artic Ocean.


Fish

• Fish have fleshy filaments called gills where carbon dioxide and oxygen are exchanged.


Fish• Most fish have pairs of fanlike fins. The top

and the bottom fins stabilize the fish. Those on the sides steer and move the fish.

• Most fish have scales.


• Scales are thin structures made of a bony material that overlap like shingles on a house to cover the skin.

Amphibians

• Amphibians are animals that spend part of their lives in water and part on land.

• Frogs, toads, newts, and salamanders are examples of amphibians.


Amphibian Characteristics

• Amphibians are vertebrates with a strong endoskeleton made of bones.

• Adult amphibians use lungs instead of gills to exchange oxygen and carbon dioxide.


Amphibian Characteristics

• Because amphibians have three-chambered hearts, the blood carrying oxygen mixes with the blood carrying carbon dioxide.

• Adult amphibians also exchange oxygen and carbon dioxide through their skin, which increases their oxygen supply.


Reptiles

• Reptiles are ectothermic vertebrates with dry, scaly skin.

• Because reptiles do not depend on water for reproduction, most are able to live their entire lives on land.


Reptile Adaptations

• All reptiles have lungs for exchanging oxygen and carbon dioxide.

• Reptiles also have a neck that allows them to scan the horizon.


Reptile Adaptations• Two adaptations enable reptiles to reproduce

successfully on land—internal fertilization and laying shell-covered, amniotic eggs.

• The embryo develops with the moist protective environment of the amniotic egg.


• When eggs hatch, young reptiles are fully developed.

Birds• Birds are endothermic vertebrates that have

two wings, two legs, and a bill or beak.

• Birds are covered mostly with feathers.


• They lay hard-shelled eggs and sit on these eggs to keep them warm until they hatch.

Adaptations for Flight

• The bodies of most birds are designed for flight.

• The inside of a bird’s bone is almost hollow. Internal crisscrossing structures strengthen the bones without making them as heavy as mammal bones are.


Adaptations for Flight

• Birds eat insects, nectar, fish, meats, or other high-energy foods.

• They also have a large, efficient heart and a specialized respiratory system. A bird’s lungs connect to air sacs that provide a constant supply of oxygen to the blood and make the bird more lightweight.


Functions of Feathers• Strong, lightweight contour feathers give

adult birds their stream-lined shape and coloring.

• Outer contour feathers help a bird move through the air or water.


• Birds have down feathers that trap and keep warm air next to their bodies. These fluffy feathers provide an insulating layer under the contour feathers of adult birds and cover the bodies of some young birds.

Mammals• Mammals are

endothermic vertebrates. They have mammary glands in their skin.


• A mammal’s skin usually is covered with hair that insulates its body from cold and heat.

• In females, mammary glands produce milk that nourishes the young.

Different Teeth• Plant-eating animals are called herbivores.

Animals that eat meat are called carnivores, and animals that eat plants and animals are called omnivores.

• Mountain lions are carnivores. They have sharp canines that are used to rip and tear flesh.


Different Teeth

• Humans are omnivores. They have incisors that cut vegetables, premolars that are sharp enough to chew meat, and molars that grind food.


Different Teeth

• Herbivores, like this beaver, have incisors that cut vegetation and large, flat molars that grind it.


Body Systems

• Mammals have well-developed lungs made of millions of microscopic sacs called alveoli, which enable the exchange of carbon dioxide and oxygen during breathing.

• They also have a complex nervous system and are able to learn and remember more than many other animals.


• All mammals have internal fertilization.

Mammal Types

• Monotremes make up the smallest group of mammals.

• They lay eggs with tough, leathery shells instead of having live births.


Mammal Types

• Marsupials live in Australia, Tasmania, and New Guinea. The opossum is the only marsupial that lives in North America.

• Most marsupials carry their young in a pouch.


Placentals

• Placentals are named for the placenta, which is a saclike organ that develops from tissues of the embryo and uterus.

• An umbilical cord connects the embryo to the placenta.


• Food and oxygen from the mother’s blood are carried to the developing young by the blood vessels in the umbilical cord.


33Question 1

_______ is the internal system of bones in vertebrates.

The answer is endoskeleton. The endoskeleton supports and protects the internal organs.

Answer

GLE 0707.1.3 SPI 0707.1.3 GLE 0707.1.2


33Question 2

Which is the largest group of vertebrates?

A. catsB. dogsC. fishD. humans


33Answer

The answer is C. Fish are ectotherms and live in water.


33Question 3

This illustration shows a typical body structure of what classification of fish?

A. bonyB. cartilaginousC. jawlessD. scale less

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33Answer

The answer is A. About 95 percent of all fish have skeletons made up of bone.

GLE 0707.1.2

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chapter: animals

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