B6f: Microscopic life in water Flashcards
Explain the advantages of life in water (4)
no problem of water shortage and dehydration
less variation in temperature; aquatic organisms need not cope w/ rapid temp changes
water provides support to organisms w/o skeletal systems
easy disposal of waste products; washed away, easily dispersed, does not accumulate, greatly diluted in water and broken down
Explain the disadvantages of life in water (2)
regulating water content - water content of the body can vary and needs to be controlled
resistance to movement; water denser than air, harder to move through so more energy needed
Explain the problems of water balance caused by osmosis (2)
fresh water, animal cells have +solute conc, water enters by osmosis, swell/burst; not problem for plants; cell walls stop cells bursting, prevent excess water getting in; animals must remove excess water from body
salt-water, animal cells have lower solute concentration, water leaves body via osmosis, shrivel and die; many invertebrates have bodies at same salt concentration so no problem
How do amoeba and other microscopic animals get rid of excess water?
microscopic animals (amoeba) have contractile vacuole; fills with excess water from osmosis, moves to cell membrane, fuses with cell membrane, and contracts to release water outside cell
Describe how light varies at different depths and in different seasons in water, and how this affects phytoplankton (2)
+day length (summer, spring), +light available for photosynthesis, +rate of photosynthesis, +energy for growth/reproduction, +phytoplankton
light only penetrates surface waters, phytoplankton limited to those waters
Describe how temperature varies at different depths and in different seasons in water, and how this affects phytoplankton (2)
+surface water temperature (spring, summer), +rate of photosynthesis, +energy for growth/reproduction, +phytoplankton
deep water temp is constant 4 degrees celcius, too cold for phytoplankton to grow, so they live near surface
Describe how minerals vary at different depths and in different seasons in water, and how this affects phytoplankton (2)
+depth, +mineral concentration, but phytoplankton limited there by light and temperature
in summer near the water’s surface mineral concentration is low and limits the rate of photosynthesis
How do seasonal changes in phytoplankton numbers influence numbers of zooplankton?
spring/summer, +phytoplankton/algal bloom, +food for zooplankton, +zooplankton (vice versa for winter/autumn)
What are phytoplankton?
photosynthetic microorganisms; producers in aquatic food chains and webs
What are zooplankton?
animallike microorganisms; consumers in aquatic food chains and webs
Grazing food webs (2)
begin w/ photosynthetic producers
most common in the surface layers of the oceans because more light for photosynthesis
What do other aquatic food chains rely on? (2)
detrital food chains (deep water, no light, no photosynthesis, no phytoplankton;) rely on ‘marine snow’ - dead food falling from above as source of nutrients
bacteria, deep in ocean, act as producers that get their energy from chemical reactions (via chemosynthesis)
Eutrophication stages (5)
- sewage/fertiliser runoff into rivers/lakes
- +conc of nitrates/phosphates in the water; algae use these minerals to grow rapidly, produce thick green layer above (algal bloom)
- blocks sunlight to plants in water, die + decay
- aerobic decay bacteria use up oxygen
- animals in water unable to respire and die
How can biologists determine pH and oxygen levels in water?
by looking for the presence/numbers of indicator species species sensitive to diff pHs and oxygen levels
Explain the effect of PCBs and DDT on animals such as whales (4)
chemicals absorbed by organisms at bottom of food chain
doesn’t break down/egested so when organism eaten, they are passed on
+concentration in organisms at each trophic level up the food chain as each organism eats many organisms in lower trophic levels
in higher trophic level, whales accumulate toxic levels of chemical in body; suppresses immune system, -population
