Chapter 32 Notes

Introduction to Animal Evolution

Concept 32.1

General characteristics of animals:- multicellular, heterotrophic eukaryotes

- take in food by ingestion- lack cell walls; have cell junctions made of structural proteins that hold cells and tissues together

Concept 32.1

- tissues of impulse conduction and movement: nervous and muscle tissue- reproduce sexually; zygote that undergoes cleavage

-divides into smaller cells after fertilization creating a multicellular structure called a blastula

Concept 32.1

- following the blastula stage is gastrulation

- rearrange the cells to form a 3 layered structure called a gastrula

Concept 32.1

Concept 32.1

Concept 32.1

Concept 32.1

- some develop directly into adults; others develop into a larva stage (sexually immature). Will undergo metamorphosis.

- animals most likely developed from a colonial, flat protist

Concept 32.1

Concept 32.1

Concept 32.3

Animals can be classified by their body structure

Subkingdom Parazoa:- ex. Sponges- have only 2 layers of cells; lack true organs

Concept 32.3

Subkingdom Eumetazoa:- possess true tissues- divided into 2 branches based on symmetry: radial and bilateral

Concept 32.3

Concept 32.3

Radial Symmetry:- phylum Cnidaria and Ctenophora- has a top and a bottom- adapted for sessile (not motile) lifestyle- develop two tissue layers: ectoderm (outer covering) and endoderm (digestive tube lining)

Concept 32.3

Bilateral Symmetry:- phylum platyhelminthes through chordata - have a top (dorsal), bottom (ventral), head (anterior), and tail (posterior)

Concept 32.3

- have three germ (tissue) layers: triploblastic

- ectoderm: forms epidermis of skin and nervous system

- endoderm: lining of digestive tract, liver, pancreas- mesoderm: skeletal, muscle, circulatory, and lymphatic

systems

Concept 32.3

Animals can also be grouped by the development of a body cavity or coelom- separates the digestive tract from the outer body wall- triploblastic animals can be grouped by the coelom development

Concept 32.3

Acoelomates: - phylum platyhelminthes- no body cavity between the digestive tract and the outer wall- have only one opening; only a gastrovascular cavity- no blood vascular system

Concept 32.3

Psuedocoelomates:- phylum rotifera and nematoda- have a fluid filled cavity that is incompletely or partially lined with mesoderm-cavity develops between the mesoderm and endoderm

Concept 32.3

Coelomates:- everything else- fluid filled cavity that is completely lined with mesoderm- the digestive tract is suspended in the cavity and held in place with connective tissue called mesentery

Concept 32.3

Concept 32.3

Coelomates are further divided according to the pattern of development that their zygote goes through- divided into protosome and deuterosome coelomates

Concept 32.3

Protosome coelomates:- spiral cleavage: during early cell divisions, the divisions are diagonal to the vertical axis of the embryo- cells end up lying between rather than on top of other cells- first opening becomes the mouth, second becomes the anus

Concept 32.3

- determinate cleavage: casts the developmental fate of each cell very early

Concept 32.3

Deuterosome coelomates:- radial cleavage: cells divide at right angles so the cells are above or below each other- first opening becomes the anus, second becomes the mouth- indeterminate cleavage: cells retain ability to develop into complete embryo

Concept 32.3