BIO2231 - Sponges Flashcards
Definition
Metazoa
- Multicellularity with differentiation of cells
- Blastula stage in development
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Definition
Synapomorphies
Characters shared within a group
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Definition
Autapomorphies
Characters that define different groups
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Key points
Metazoa?
2 points.
Animals
- Multicellular
- Blastula stage in development
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Key points
Porifera
3 points.
- Cell aggregates
- No germ layers
- No true tissues, organs or gut
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Key points
Eumetazoa
4 points.
- True tissues
- Gastrula stage
- Germ layers
- Digestive cavity (gut)
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Cnidaria
3 points.
- Two germ layers (diploblastic)
- Radial symmetry
- No anus
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What is diploblastic?
Having a body derived from only two embryonic cell layers
(ectoderm and endoderm, but no mesoderm), as in sponges and coelenterates.
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What is the advantages of Multicellularity?
2 points.
- Size
- Complexity
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Multicellularity
Why not become one big cell?
- SA/V ratio
- structural integrity of cell membrane and cell division machinery
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What is the impact of Increasing complexity?
2 points.
Compartmentalisation
- Specialised cells for certain tasks = greater efficiency
- BUT loss of independence for cells = greater vulnerability to injury
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What are the advantages of increased body size?
6 points.
- Efficiencies of scale (bigger is better)
- Buffers against environmental fluctuations
- Easier to retain heat for metabolism
- Development of specialised body compartments
- Better in attack (as predators)
- Better for defence against predators
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What are the Consequences of body size?
3 points.
Changes in surface to volume ratios limit exchange of oxygen and nutrients
Necessitates specific body shapes:
- Sponge like
- Flat sheets (bell/cup shape)
- Tubes
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How can an animal be a shape other than flat/long/spongy?
4 points.
Need to develop delivery systems
Diffusion no longer adequate → evolution of:
- fluid filled body cavities
- circulatory systems
- respiratory systems
- excretory systems
Note: Has Metabolic costs (e.g. pumping)
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What will you not find in sponges?
3 points.
- Gastrula stage with two germ layers
- A digestive cavity (gut)
- True tissues
General rule is above are absent in sponges … but that could be wrong
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