Test 2.2 Adaptations Flashcards
Are rivers and lakes more or less diverse than oceans?
Rivers and lakes are less diverse than oceans
Surface area of oceans > freshwater
What is the meaning of primary colonisation?
Freshwater organisms coming/evolving from oceans e.g. bacteria, prokaryotes, primitive plants, molluscs, fish
What is the meaning of secondary colonisation?
Colonisation of freshwaters from land ancestors e.g. insects, higher plants, birds, insect groups and mammals. Some molluscs e.g. snails evolved from land ancestors
What are the challenges of living in freshwaters coming from marine systems?
Very dilute environment in comparison to body fluid concentration
-osmoregulation of body fluids
e.g. Swan muscle (mollusc) has low body fluid concentration and cannot tolerate change
Mitten crab however can move between fresh and salt water- more concentrated body fluids. Can osmoconform to match surroundings. Has limits
Is the range of types of organisms found in freshwater greater or lesser in comparison to the ocean?
Smaller range of organisms in freshwater systems than oceans
13 orders of insects found in freshwaters, 5 of which only found in freshwaters
List 4 adaptations for respiration in flowing water
Air breathing
Plastron (tiny hairs)
Pigments
Tracheal gills
List 6 adaptations for coping with / exploiting flow in flowing water
Streamlines bodies 'hydrofoils' Suckers Modified gills Modified feeding appendages Hooks Silk
What are the adaptations of water Crowfoot (plant) to flowing water?
Very fine leaves presenting little resistance to flow
Grows in patches
Forms large clumps to trap sediments around roots
Fragments break off and colony further downstream
What are the adaptations of water Nuphar ‘brandy bottle’ to flowing water?
2 types of leaves; ecosystem engineering?
Surface water lily big flat leaves
Thinner leaves that deform in increase in flow velocity- present less resistance.
Not much photosynthesis function:
Possibly trap silt brought down by the flow, creating silty conditions around the roots allowing the plant to spread
Adaptations of mayfly larvae and freshwater muscles to flowing water
Both: streamlines bodies
Mayflies: modified gills create suction
Adaptations of cased caddisfly larvae to flowing water
Hydrofoil legs
Streamlines cases
Weighted cases
Adaptations of net-wing midges & mountain midges
Suckers to cling to substrates
What is the boundary layer effect?
The lower you get to the substrate the lower the velocity experienced. Layer of almost static water
Adaptations of Blackfly or Buffalo Gnat?
Streamlined cocoon
Filtering fan silk glands- spin onto stones- filter down to bacteria size
Rear abdominal hooks to anchor
Adaptations of Freeliving Caddis
Spin net to live within to protect from flow and predators
Collect food particles from flow
How do freshwater shrimp disperse and colonise new areas?
Active swimming movement upstream
How do flying adult stage organisms disperse and colonise new areas?
Adults fly upstream, lay eggs, larvae move downstream
Some species scatter eggs on surface, some beneath surface on stones
e.g. mayflies
What is macroinvertebrate drift and why is it important?
The movement downstream of invertebrates either involuntarily due to disturbance or voluntarily
Important mechanisms for decolonizing new areas
Fish feed partly or almost exclusively on invertebrates that move downstream with the flow
What are the three types of macroinvertebrate drift?
- Catastrophic drift:
Due to unfavourable conditions - Constant (background)
Occurring all the time at low levels - Behavioural drift:
Chose to enter drift. Some form of diurnal periodicity involved.
Peak at time of maximum darkness. Light levels will change behaviour and amount of organisms
- due to predation by fish
Distance travelled max 50 to 60m, varies with species, current velocity, type of substrate and life stage
Varies with season (low in winter), day to day and insect life stage
How does instar stage affect pattern of drift?
Larger instars become only nocturnal
Peak at midnight and before sunrise
What are the advantages of drifting?
- Colonisation of downstream areas of disturbed patches
- When food is scarce
- Avoid unfavourable conditions- pollutants, temp, ice, floods, drought, low DO
- avoid predation
What are the four dimensions of stream and river ecosystems?
Lateral dimension
-importance of links between stream and catchment e.g. riparian zone, leaf and energy inputs into channel
Longitudinal dimension
Vertical dimension
-Hyporheic zone
Temporal dimension
-evolutionary change, behavioural response
What is the hyporheic zone
Spaces beneath the stream that contains portion of channel water
Middle zone bordered by surface water above and groundwater below
Hyporheos: Community that lives there. Wide variety of taxa
Can extend up to 2km
Importance of hyporheic zone
Permanent hyporheous:
Below 40cm organisms are specialised to live there e.g. copepods
Meiofauna <1mm
Occasional hyporheous:
Spend part of life in this zone but not permanent e.g. chironomids, careless caddis
Refuge from flooding/drying out
Characteristics of hyporheic zone
Temperature: less diurnal and seasonal variation
Light: does not penetrate greater than 4-5 x grain size of sediment
Current velocity: reduced when water infiltrates down to 1/1000 of that surface
Dissolved oxygen: declines with decreasing depth.
At 30cm can be 5% of that at surface
CO2: Linked to respiration and flow.
Up to 1 unit less pH
Nitrate: acts as a buffer zone between terrestrial and aquatic environments
Advantages to living in hyporheic zone
Lack of predators
Plentiful food
More steady environment e.g. temp
Survival during adverse conditions e.g. floods
Disadvantages to living in hyporheic zone
Limited space Reduced current velocities Low DO, high CO2 Lack of light Accumulation of waste
