2. 34-1 The Nature of Animals Vertebrate  Animal with backbone. Invertebrate *Animal without backbone. These make up more than 95% of all animal species.

3. Characteristics of Animals   Multicellular organization  Heterotrophs  Sexual reproduction Have movement

4. 1. Multicellular Organization   dults have 50 trillion cells  Specialization: adaptation of cells for a particular function Cell junctions: the formation of tissue from many individual cells which are held together by these connections.

5. 2. Heterotrophy  I ngestion, take in organic matter then digestion.

6. 3. Sexual Reproduction and Development   ygote: first cell of new individual Differentiation: an enlarging mass of dividing cells become different from each other

7. 4. Movement   R esults from interrelationship of two tissues, nervous and muscle. Neurons transmit the information and muscles contract and respond.

8. Origin and Classification   First animals arose in the sea Invertebrates were first multicellular animal and evolved from protists