Animal Diversity I
Bio lecture March 22
Animals are diverse, but share similar body plans and development
First animals are closely related to protists (Choanoflagellates)
Characteristics of Kingdom Animalia
• Multicellular eukaryotes
• Complex cells, many organelles
• Muscular movement* and nervous systems*
• {mostly} sexual reproduction
• Chem[organo]heterptrophs
• Common body development
– Embryonic development
– Hox genes
• Variable life cycles
– Sexual, asexual, both
– Metamorphosis
Animal Cell
• Golgi apparatus
• Plasma membrane
• Mitochondrion
• Centrioles
• Ribosomes
• Nuclear envelope
• Nucleus
The Cambrian Explosion
• 535-525Ma- Diversification of animals during the Cambrian Period
– Most living invertebrate phyla started here
Sponges are primitive animals, descended from choanoflagellate protists
Characteristics that define the major animal phyla include:
1. Body symmetry
2. Tissues (# layers)
3. Internal body cavity
4. Orientation of mouth
5. Skeleton
6. Motility
7. Reproduction
8. Habitat, ecological role, feeding strategy
1. Body symmetry
– Radical symmetry: body sections are distributed evenly around a central point
– Bilateral symmetry: only two sides are mirror images of each other
– Asymmetry: body is not symmetrical around any point
2. Embryonic Development and formation of tissue (germ) layers
– Ectoderm= outer layer
– Endoderm= inner layer
– Mesoderm= middle layer
Zygote –> (cleavage) –> Eight-cell stage (cleavage) –> Blastula –> cross section of
blastula –> Gastrulation–> Blastocoel, Endoderm, Ectoderm, Blastopore = cross section
of Gastrula
