Test 2.2 Adaptations

Question 1

Are rivers and lakes more or less diverse than oceans?

Answer 1

Rivers and lakes are less diverse than oceans

Surface area of oceans > freshwater

Question 2

What is the meaning of primary colonisation?

Answer 2

Freshwater organisms coming/evolving from oceans e.g. bacteria, prokaryotes, primitive plants, molluscs, fish

Question 3

What is the meaning of secondary colonisation?

Answer 3

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

Question 4

What are the challenges of living in freshwaters coming from marine systems?

Answer 4

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

Question 5

Is the range of types of organisms found in freshwater greater or lesser in comparison to the ocean?

Answer 5

Smaller range of organisms in freshwater systems than oceans

13 orders of insects found in freshwaters, 5 of which only found in freshwaters

Question 6

List 4 adaptations for respiration in flowing water

Answer 6

Air breathing
Plastron (tiny hairs)
Pigments
Tracheal gills

Question 7

List 6 adaptations for coping with / exploiting flow in flowing water

Answer 7

Streamlines bodies 'hydrofoils'
Suckers
Modified gills
Modified feeding appendages
Hooks
Silk

Question 8

What are the adaptations of water Crowfoot (plant) to flowing water?

Answer 8

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

Question 9

What are the adaptations of water Nuphar ‘brandy bottle’ to flowing water?

Answer 9

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

Question 10

Adaptations of mayfly larvae and freshwater muscles to flowing water

Answer 10

Both: streamlines bodies

Mayflies: modified gills create suction

Question 11

Adaptations of cased caddisfly larvae to flowing water

Answer 11

Hydrofoil legs
Streamlines cases
Weighted cases

Question 12

Adaptations of net-wing midges & mountain midges

Answer 12

Suckers to cling to substrates

Question 13

What is the boundary layer effect?

Answer 13

The lower you get to the substrate the lower the velocity experienced. Layer of almost static water

Question 14

Adaptations of Blackfly or Buffalo Gnat?

Answer 14

Streamlined cocoon

Filtering fan silk glands- spin onto stones- filter down to bacteria size

Rear abdominal hooks to anchor

Question 15

Adaptations of Freeliving Caddis

Answer 15

Spin net to live within to protect from flow and predators

Collect food particles from flow

Question 16

How do freshwater shrimp disperse and colonise new areas?

Answer 16

Active swimming movement upstream

Question 17

How do flying adult stage organisms disperse and colonise new areas?

Answer 17

Adults fly upstream, lay eggs, larvae move downstream
Some species scatter eggs on surface, some beneath surface on stones
e.g. mayflies

Question 18

What is macroinvertebrate drift and why is it important?

Answer 18

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

Question 19

What are the three types of macroinvertebrate drift?

Answer 19

1. Catastrophic drift:
   Due to unfavourable conditions
2. Constant (background)
   Occurring all the time at low levels
3. 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

Question 20

How does instar stage affect pattern of drift?

Answer 20

Larger instars become only nocturnal

Peak at midnight and before sunrise

Question 21

What are the advantages of drifting?

Answer 21

1. Colonisation of downstream areas of disturbed patches
2. When food is scarce
3. Avoid unfavourable conditions- pollutants, temp, ice, floods, drought, low DO
4. avoid predation

Question 22

What are the four dimensions of stream and river ecosystems?

Answer 22

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

Question 23

What is the hyporheic zone

Answer 23

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

Question 24

Importance of hyporheic zone

Answer 24

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

Question 25

Characteristics of hyporheic zone

Answer 25

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

Question 26

Advantages to living in hyporheic zone

Answer 26

Lack of predators

Plentiful food

More steady environment e.g. temp

Survival during adverse conditions e.g. floods

Question 27

Disadvantages to living in hyporheic zone

Answer 27

Limited space
Reduced current velocities
Low DO, high CO2
Lack of light
Accumulation of waste