1. 34-1 The Nature of Animals

2. Vertebrate An animal with a backbone Invertebrate An animal without a backbone

3.  Animals are: Multicellular Heterotrophic Lack cell walls Most reproduce sexually Most have movement

4.  Body of adult human contains 50 trillion cells.  Cells of multicellular organisms do not live independently. Each cell depends on the presence and functioning of other cells. They cooperate and work together…  Cells – tissues – organs – organ systems – organism  Specialization is the adaptation of a cell for a particular function.  Cell junctions are connections between cells. The formation of tissue from many individual cells occurs because of cell junctions. Cell junctions hold the cells together as a unit.

5.  Ingestion is the taking in of organic material.  Digestion then takes place: Carbohydrates, lipids, amino acids, and other organic molecules are extracted from the material or cells the animal eats.

6.  Sexual: Most animals reproduce sexually. This allows for more genetic variability, since with male and female contributions, there are more genes introduced into the gene pool.

7.  Asexual: Hydra – budding Sponges – internal budding (gemmules) Planaria – fragmentation (head / tail), although most reproduce sexually Echinoderms (starfish) – regeneration  zygote: 1 st cell of a new individual (diploid) Will undergo repeated mitotic divisions  Differentiation: cells become different from each other, i.e.: Blood cells Bone cells The process of differentiation is the path to cell specialization.

8.  Attachment: Barnacles attach to a surface, aka substrate. Life Cycle: Egg – larva – then leaves parent's shells, spends youth swimming, sticks to rocks for all adulthood.

9.  Neurons are cells of nervous tissue.  Nervous tissue… through electrical signals (impulses), allows animals to detect stimuli.  Muscle tissue allows animals to respond to the stimuli. LINK

10.  Page 669  The 1 st animals probably originated in the sea.  The structural characteristics of invertebrates suggest they were the first multicellular animals.  It also suggests that they evolved from protists.  Protists are both heterotrophic and eukaryotic.  Because of this, scientists have inferred that multicellular invertebrates may have developed from colonies of loosely connected, flagellated protists.

11. Cell specialization during early period of evolution…  Colonial protists may have lost their flagella as individual cells in the colony became more specialized.  They may have been similar to modern colonial protists that do show some degree of cell specialization. In these species, the gametes are distinct from non-reproductive cells.

12.  A similar division of labor in early protists may have been the 1 st step toward multicellularity.  Many taxonomists recognize 30+ animal phyla.  Some phyla contain a very small # of species.