Feeding and Digestion• All animals are heterotrophic.

• The structure or form of an animal’s mouth parts determines how its mouth functions.

• After obtaining food, all animals must digest it, either in specialized cells or organs.

Animal CharacteristicsCopyright © McGraw-Hill Education

Support• Between 95-99 percent of animals are invertebrates – animals

without backbones.

• Many invertebrates are covered by exoskeletons, which are hard or tough outer coverings.

• Some invertebrates have an internal support structure called an endoskeleton.

• If an animal has an endoskeleton and a backbone, it is called a vertebrate.

Animal CharacteristicsCopyright © McGraw-Hill Education

Habitats• Animal adaptations around feeding, digestion, and support allow

them to live in a variety of habitats.

• Invertebrates and vertebrates are found in terrestrial, marine, and freshwater ecosystems.

Animal CharacteristicsCopyright © McGraw-Hill Education

Animal Cell Structure• Animal cells do not have cell walls.

• The cells of all animals except sponges are organized into tissues, which have specialized functions.

Animal CharacteristicsCopyright © McGraw-Hill Education

Movement• Evolution of nerve and muscle tissue allows animals to move in

unique ways.

• Some animals are stationary as adults, but most have a body form that can move during some stage of development.

Animal CharacteristicsCopyright © McGraw-Hill Education

Reproduction• Most animals reproduce sexually.

• Some animals are hermaphrodites, meaning the produce both sperm and eggs in the same body.

• Fertilization occurs when the sperm penetrates the egg to form a fertilized egg called the zygote.

• Internal fertilization occurs when sperm and egg meet inside an animal’s body.

• External fertilization occurs when sperm and egg meet outside an animal’s body.

Animal CharacteristicsCopyright © McGraw-Hill Education

Reproduction• Asexual can occur through:

• Budding – offspring develops as a growth on the parent body

• Fragmentation – parent breaks into pieces that develop into adults

• Regeneration – a new organism can grow from a lost body part

• Parthenogenesis – egg develops in a female without fertilization

Animal CharacteristicsCopyright © McGraw-Hill Education

Reproduction

Early development• The zygote undergoes mitosis and a series of cell divisions to form

new cells.

• The cells continue to divide, forming a fluid-filled ball of cells called the blastula.

• The blastula continues to undergo cell division, and some cells form a gastrula, a two-cell-layer sac with an opening at one end.

Animal CharacteristicsCopyright © McGraw-Hill Education

Development of a Zygote

Animation

FPOAdd link to concepts in motion animation from page 696 (Figure 5) here.

Animal CharacteristicsCopyright © McGraw-Hill Education

Reproduction

Tissue development• The inner layer of the gastrula develops into the endoderm, which

forms the digestive organs.

• The outer layer of the gastrula develops into the ectoderm, which becomes the nervous system and skin.

• The mesoderm forms between the ecto- and endoderm, and forms the muscle, circulatory, excretory, and respiratory system in some animals.

Animal CharacteristicsCopyright © McGraw-Hill Education

Animal CharacteristicsCopyright © McGraw-Hill Education

Review

Essential Questions• How do adaptations enable animals to live in different habitats?• How is structure and function related in animals?• What are the stages of embryonic development in animals?

Vocabulary

• invertebrate • exoskeleton • endoskeleton • vertebrate • hermaphrodite

• zygote • internal

fertilization• external

fertilization• blastula• gastrula

• endoderm• ectoderm• mesoderm