1. Chapter 32 Introduction to Animals
Section 1
The nature of animals

2. Characteristics Animals lack cell walls Vertebrates- have a backbone
Invertebrates- do not have a backbone
95% of all animals are invertebrates

3. Multicellular Organization
Adult humans have trillion cells
Specialization- evolutionary adaptation of a cell for a particular function
Digesting food, removing wastes, or reproducing
Cells  tissues  organs  organ systems  organism

4. Heterotrophy Animals cannot make their own food
Ingestion- animal takes in organic material
Animals cannot make their own food
Ingestion- animal takes in organic material

5. Sexual Reproduction & Development
Asexual and sexual reproduction
Zygote- diploid cell that results from the fusion of the gametes, then undergoes mitotic divisions
Differentiation- cells become specialized and become different from each other

6. Movement Most animals move in some way throughout their environment
Nervous and muscle tissue are responsible for allowing animals to move
Neurons conduct electrical signals that initiate a response.

7. Origin & Classification
Animals are theorized to have come from the sea
Unicellular  multicellular  specialized functions
Phylogenetic diagram shows how animals are related through evolution
Separated by phylum

10. Invertebrates Do not have a backbone
Make up the greatest number of animal species

11. Chordates
Chordate- refers to animals with a notochord- a firm flexible rod of tissue located in the dorsal part of the body

12. Chordates
During development, all chordates have a notochord, a dorsal nerve cord, pharygeal pouches, and a postanal tail
Pharygeal pouches- small outpockets of digestion tract
Dorsal nerve cord- hollow tube above notochord

13. Chordates
In vertebrates, the dorsal nerve cord becomes the brain & spinal cord, and the notochord is replaced by the backbone
In aquatic vertebrates, the pharyngeal pouches have evolved into gills

14. Body Structure
Some animals lack true tissues and body symmetry, while others have organized tissues and consistent body shape

15. Patterns of Symmetry
Body plans- describe animal’s shape, symmetry, & internal organization
Symmetry- body arrangement in which parts that lie on opposite sides of an axis are identical
Radial symmetry- body plan organized in a circle around axis

16. Radial Symmetry

17. Patterns of Symmetry Dorsal- back Ventral- abdomen side (front)
Anterior- toward the head
Posterior- toward the tail
Bilateral symmetry- two similar halves on either side

19. Patterns of Symmetry
Bilaterally symmetrical animals tend to exhibit cephalization- concentration of sensory and brain structures in the anterior end of an animal

20. Germ Layers
Germ layers- tissue layers in the embryos of all animals except sponges, which have no true tissues
Organs and tissues arise from germ layers
Ctenophores & cnidarians have two germ layers, and all other animals have three

22. Body Cavities
Most animals have a fluid-filled cavity between their digestive tract and outer wall of the body during development.
Roundworms have a fluid-filled body cavity that helps them move

23. Body Cavities

24. REVIEW!!!
Explain how the first animals may have evolved from unicellular organisms.
Identify four features only found in chordates.
What are the two types of tissue for allowing animals to move?