Biology B6
- Created by: Mollie Derhun
- Created on: 01-05-13 17:07
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Microscopic life in Water
Advantages and disadvantages of living in water:
- No risk of water shortage/dehydration
- Water temp varies less than air temp
- Water helps provide support
- Waste products easily disposed of into water
- Water content of body can vary - needs to be controlled
- Water = denser than air - resists movement
- Freshwater - organisms take up too much water by osmosis
- Salt water - water lost to surroundings by osmosis
- Ameoba = contractile vacuole - stores excess water
- Vacuole - fuses with cell membrane, empty water to outside
Variations in number of Organisms
- Numbers of phytoplankton and zooplankton vary at different depths in different seasons
- Phytoplankton:
- Less light in winter, deeper in water
- Temp lower in winter, deeper in water
- Minerals used up near end of summer
- Food webs rely on different food sources:
- Most rely on green plants
- Those deeper in ocean feed on marine snow
- Some rely on bacteria
Water Pollution
- Sewage and fertiliser run-off = eutrophication = rapid growth of algae, which die and decay
- Uses up oxygen causing animal deaths (unable to respire)
- Some species are more sensitive to pollution - used as biological indicators
- Chemicals ( PBCs/DDT) kill animals:
- They are toxic
- Don't break down quickly, accumulate, become concentrated at higher end of food chain
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