Animal Kingdom

Animals… Animal life cycles include a period of embryonic development. Three germ tissue layers called ectoderm, endoderm, and mesoderm (present in most species) give rise to adult organs.embryonic development. Animals with backbones are vertebrates. Animals without a backbone are invertebrates. Body symmetry, degree of cephalization, type of gut, type of body cavity, and presence or absence of segmentation are key characteristics in invertebrate evolution and in distinguishing the different groups.Animals

Vertebrates vs Invertebrates Humans have characteristics that can be traced back millions of years to the invertebrates. Invertebrate animals are not primitive and evolutionarily stunted, but rather display adaptations to an amazing variety of environments. Most animals have the following characteristics: multicellular, heterotrophic, aerobic, reproduce sexually (and perhaps asexually), develop from embryos, and are motile at some point in their life cycle.

Levels of organization in multicellular organisms Cell- least inclusive Tissue Organ Organ system Organism- most inclusive

Body Symmetry Body Symmetry and Cephalization Animals show either radial (round) or bilateral (left and right sides) symmetry. Bilateral animals also show anterior (head end), posterior (tail end), dorsal (back), and ventral (belly) orientations. As illustrated in this evolutionary lineage, radial and bilateral symmetry led to two major lineages of invertebrates.evolutionary lineage, Cephalization means having a definite head end, usually with feeding and sensory features.

4 Directions Anterior Posterior Dorsal Ventral

Type of Gut The gut is the region where food is digested and then absorbed. Some guts are saclike with one opening for taking in food and expelling waste. "Complete" digestive tracts have two openings (mouth and anus) for continuous food processing, often through specialized regions.

Body Cavities A coelom (lined with peritoneum) is a space between the gut and body wall that allows internal organs to expand and operate freely. A peritoneum is a smooth transparent membrane that lines the abdomen and doubles back over the surfaces of the internal organs to form a continuous sac.coelom Some animals (flatworms or Platyhelminthes) are acoelomate. They do not have a coelom but are packed solidly with tissue. acoelomate. Others, such as roundworms (Nematoda), have a "false" coelom or pseudocoel, not lined with peritoneum.pseudocoel, This animation (no audio) reviews the types of body cavities.body cavities.

Coeloms Acoelomate: Animals without a body cavity. Coelomate: Animals with a body cavity lying between the digestive tract and body wall that is completely lined with mesoderm (True body cavity). Pseudocoelomate: Animals with a body cavity lying between the digestive tract and body wall that is incompletely lined with mesoderm (False body cavity).

Segmentation A segmented animal is composed of repeating body units. The units may or may not be similar to one another. Earthworms would be a familiar example in which the segments appear similar. The segments may also be grouped and modified for specialized tasks, as they are in insects.

1 opening or 2 Deuterostomes: Group of coelomate animals in which the blastopore is associated with the anus, a second opening is associated with the mouth. Proterostomes: Group of coelomate animals in which the blastopore is associated with the mouth

3 skins!! def. Ectoderm: In animal embryos, the outermost primary tissue layer that gives rise to the nervous system and the outer layer of the integument. def. Endoderm: In animal embryos, the innermost primary tissue layer that gives rise to the linings of the digestive tract and associated structures. def. Mesoderm: In animal embryos, the middle primary tissue layer that gives rise to muscles, connective tissue layers (e.g., lining the body cavity), and several internal organs.