Animal Form and Function

Chapter 32

What you need to know!

The characteristics of animals. The stages of animal development How to sort the animal phyla based

on symmetry, development of a body cavity, and the fate of the blastopore

The traits used to divide animals into groups

All animals

1. Multicellular2. Heterotrophic

Obtain nutrients by ingestion (eating)3. Extracellular matrices hold the cells

together (tight junctions) No cell walls

4. Mobility (at some point in their life)5. Diploid dominant6. Nervous and muscular tissue (most)7. Sexual Reproduction

Gametes fuse to form zygotes

Embryonic Stages

a) Morula: mitosis forms cell ball through cleavage of zygote

b) Blastula: hollow cell ball

c) Gastrula: infolding of cellular layers

Embryonic Germ Layers Endoderm

Internal sac that becomes the digestive system

Ectoderm Outermost layer

that becomes the skin and nerves

Mesoderm Cells between the

endo- and ectoderm that become muscles and other organs

Embryonic Development

Coelom Fluid filled body cavity

for cushioning organs or to form a hydrostatic skeleton

Animals with 3 germ layers may develop this

Coelomates: organisms with coelom

Acoelomates: organisms w/out coelom

Coelom

True coelom: body cavity is completely lined by mesoderm cells (segmented worms and vertebrates)

Pseudocoelom: mesoderm and other tissue cells form body cavity (roundworms)

Animal Evolutionary Trends Tissue Complexity

Cells grouped into tissues according to similar function

Tissues develop from germ layers during embryogenesis

Organisms are said to be diploblastic when they have 2 layers, triploblastic when they have 3 layers

Body symmetry Either radial (circular) symmetry with top

and bottom or Bilateral symmetry with front (anterior),

behind (posterior), backside (dorsal), and stomach (ventral)

Animal Evolutionary Trends

Cephalization In animals with bilateral symmetry progressive

accumulation of nerve tissue anterior as animals gain complexity: accessory organs for seeing, feeling, tasting evolve

Gastrovascular cavity Digestion of foods can have one opening: saclike gut, or 2

openings: digestive tract Coelom

fluid filled cavity cushioning internal organs Segmentation

Body is divided into segments sometimes repeating (worms, insects) or are modified into body parts

Protostomes and Deuterostomes Forms different cleavage patterns of early morula – spiral

cleavage or radial cleavage

Protostome vs. Deuterostome

Characteristic Proto DeuteroEarly cleavages spiral(angle)

Radial(straight)

Infolding of Forms mouth Forms anus

archenteron

Coelom develops split of archenteronOutpouching of

from sides archenteron