Intro to Animals

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06/10/11
Intro to animals
Characteristics of animals:
Eukarya:
1) Eukaryotic true nucleus
2) Heterotrophic (different feeding):
- using pre-formed organic materials as energy and carbon source
- predators (tiger), herbivores (cow), filter feeders (fan worm), parasites
(tape worm), detritovores (earth worm), omnivores
- Most have internal digestion:
- Most use internal processes to break down food (unlike fungi)
- Most have a gut continuous with the outside environment =
internal digestion
3) Multicellularity:
- specialized cells for specific functions
- allows organisms to grow larger small cells = bigger SA Volume ratio
-facilitate diffusion, increases efficiency of transport across the cell
membrane and within the cell
4) No cell walls
Support? = Skeletons
- hydostatic skeleton: muscle contract against fluid-filled cavity
- exoskeleton (external): non living cover that doesn’t grow, must molt.
hardening of new shell leaves animals vulnerable
-Ecdysozoans = molting animals
-Endoskeleton (internal): living tissue in vertebrates, non-living tissue
(calcium
carbonate) in invertebrates
5) Motility at some life stage:
- movement reduces competition for resources and enhances genetic
diversity (move away from parents to mate with more separate organisms)
6) Somatic body cells are diploid (2N)
-Germ cells are haploid and come together to make a diploid zygote
7) Animals are diplontic
-as opposed to alternation of generation and haplontic life cycle
(8) Most animals have tissues = groups of similar cells organized into a functional
unit
(muscular, nervous, connective, epithelial)
-Tissues come together = organs for more complex tasks
Animal diversity and origins:
-35 phyla
-1 million classified species
- 97% are invertebrates
- monophyletic (one common ancestor)
Evidence:
- similar gene sequences unique to animals (hox genes act in
development and control specialization of stem cells)
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