Bio 184 Animals Notes
Cambrian Explosion
505 mya
Lots of new species – mostly bilaterians
Fossil evidence in Burgess Shale, BC
65 million years later – mass extinction of earlier life due to natural selection
1. Rise in atmospheric oxygen
Would help some species and hurt some
2. Homeotic genes evolved
Homeotic gene – regulate body plan
3. New predator prey relationships
New adaptations to attack or defend
Avg life span of species = 1 million years
Humans been around 100,000-200,000 years
99% of all life extinct
Animal features
1) Multicellular
2) No cell walls
3) Collagen – structural support
4) Nutrition – ingest all food
Different from plants (ps) and fungi (absorption)
5) Homeotic genes – regulate development and position of body parts
6) Diploid dominant lifecycle
Zygote – cleavage (mitosis) to 8 cells then to form blastula
Blastula – hollow ball of cells (cavity called blastocoel)
Gastrulation – one end of embryo folds inwards, expands and fills blastocoel
Archenteron – pouch formed from gastrulation
Pouch opens to outside via blastopore
Endoderm – walls of archenteron
Ectoderm – outside layer
7) Body plan
1. Symmetry
Radial Bilateral
Sides Oral, aboral Dorsal, ventral, anterior,
posterior, left, right
Blastic Diploblastic(no mesoderm) Triploblastic
Movement Sessile or drifting Move actively
Cephalization No Yes
e.g. Cniderians and comb jellies Everyone else
Cambrian Explosion
505 mya
Lots of new species – mostly bilaterians
Fossil evidence in Burgess Shale, BC
65 million years later – mass extinction of earlier life due to natural selection
1. Rise in atmospheric oxygen
Would help some species and hurt some
2. Homeotic genes evolved
Homeotic gene – regulate body plan
3. New predator prey relationships
New adaptations to attack or defend
Avg life span of species = 1 million years
Humans been around 100,000-200,000 years
99% of all life extinct
Animal features
1) Multicellular
2) No cell walls
3) Collagen – structural support
4) Nutrition – ingest all food
Different from plants (ps) and fungi (absorption)
5) Homeotic genes – regulate development and position of body parts
6) Diploid dominant lifecycle
Zygote – cleavage (mitosis) to 8 cells then to form blastula
Blastula – hollow ball of cells (cavity called blastocoel)
Gastrulation – one end of embryo folds inwards, expands and fills blastocoel
Archenteron – pouch formed from gastrulation
Pouch opens to outside via blastopore
Endoderm – walls of archenteron
Ectoderm – outside layer
7) Body plan
1. Symmetry
Radial Bilateral
Sides Oral, aboral Dorsal, ventral, anterior,
posterior, left, right
Blastic Diploblastic(no mesoderm) Triploblastic
Movement Sessile or drifting Move actively
Cephalization No Yes
e.g. Cniderians and comb jellies Everyone else
