BIO 115 Lecture Notes - Lecture 9: Ecdysis, Neural Crest, Acanthodii
9. Animal Diversity
What is an animal?
oHeterotrophs (ingest their food)
oMulticellular eukaryotes
oCells lack cell walls
oBodies are held together by proteins like collagen
oNervous tissue and muscle tissue are unique to animals
oReproduce sexually with the diploid stage dominating
After sperm fertilizes egg, the zygote ➝ cleavage ➝ formation of blastula
Cleavage- a sharp division; split
Blastula- hollow ball of cells
blastula ➝ gastrulation ➝ formation of embryonic tissue layers & gastrula
Gastrula- hollow cup shaped having 3 layers
oAll animals have HOX genes: regulate the development of body form; where part
is located
Eras
oNeoproterozoic (1 billion- 524 mya)
Early members of the animal fossil record appeared
Fossils may be formed by
Permineralization
Molds, casts & impressions
Whole organism preservation
Ediacaran fauna
oPaleozoic (542-251 mya)
Cambrian explosion
Marks earliest fossil appearance of many major groups of living animals
Described by several current hypotheses
Why/How
Predator-prey relationships
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Rise atmospheric oxygen
Evolution of Hox genes (developmental flexibility)
oMesozoic (251-65.5 mya)
Dinosaurs!
Coral reefs emerged, becoming important marine ecological niches for
other organisms
oCenozoic (65.5 mya- present)
Beginning of this era followed mass extinctions of both terrestrial and
marine animals
Modern mammal orders & insects diversified
Supergroup Opisthokonta
oCommon ancestor of living animals may have lived 1.2billion -800 mya
oResembled modern choanoflagellates
Hypotheses of animal phylogeny
oMorphological and developmental comparisons
oMolecular Data
Animals can be characterized by Body Plans: how zoologists categorize the diversity of
animals
1. Levels of organization
1. Cellular
2. Tissue: collections of specialized cells
3. Organ Systems
2. Symmetry
1. Radial Symmetry: radiate from the center; slice through the central axis into
mirror images
2. Bilateral Symmetry: has a left side and right side; mirror image halves
1.1. Dorsal (top) and ventral (bottom) side
1.2. Right and left side
1.3. Anterior (head) and posterior (tail) ends
1.4. Cephalization, development of a head
2. Cephalization
3. Type of Gut
1. Incomplete: one opening
2. Complete: two openings; anus and mouth
2. Body Cavities
1. Animal embryos form germ layers and embryonic tissues
1.1. Diploblastic: 2 germ layers
1.2. Triploblastic: 3 germ layers
1.2.1. Body cavity could be present or absent
2. True/Coelom: derived from mesoderm: presence is advantageous bc it allows
room for the development and movement of internal organs
1.1. Ectoderm space mesoderm space endoderm
2. Pseudocoelom: derived from blastocoel
1.1. Ectoderm mesoderm space endoderm
2. Acoelomates: no body cavity
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Document Summary
After sperm fertilizes egg, the zygote cleavage formation of blastula. Blastula- hollow ball of cells blastula gastrulation formation of embryonic tissue layers & gastrula. Gastrula- hollow cup shaped having 3 layers: all animals have hox genes: regulate the development of body form; where part is located. Eras: neoproterozoic (1 billion- 524 mya) Early members of the animal fossil record appeared. Marks earliest fossil appearance of many major groups of living animals. Evolution of hox genes (developmental flexibility: mesozoic (251-65. 5 mya) Coral reefs emerged, becoming important marine ecological niches for other organisms: cenozoic (65. 5 mya- present) Beginning of this era followed mass extinctions of both terrestrial and marine animals. Supergroup opisthokonta: common ancestor of living animals may have lived 1. 2billion -800 mya, resembled modern choanoflagellates. Hypotheses of animal phylogeny: morphological and developmental comparisons, molecular data. Animals can be characterized by body plans: how zoologists categorize the diversity of animals. Levels of organization: cellular, tissue: collections of specialized cells, organ systems.
