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CXB Ecological Systems > Test 2.2 Biotic & Abiotic Interactions > Flashcards

Test 2.2 Biotic & Abiotic Interactions Flashcards

1
Q

What filters in order of size affect regional pools of species in terms of multiple species traits?

A
  1. (Biggest) Watershed/basin filters
  2. Valley/reach filters
  3. Channel unit filters
  4. (Smallest) Microhabitat filters
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2
Q

What is the idea of Trophic Structure

A

The relationships of different feeding groups and how the types of food and energy availability affects what’s present

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3
Q

Definition of particular organic carbon

A

Coarse particular organic matter (CPOM) + fine particular organic matter (FPOM)

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4
Q

What size is coarse particular organic matter

A

> 1mm

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5
Q

What size is fine particular organic matter

A

<1mm

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6
Q

What proportion of trophic groups are found in sand and mud mesohabitats of a river

A

Mesohabitat: middle of river

Dominated by collector gatherers and
In mud: >25% predators
In sand: <25% predators

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7
Q

What do food webs illustrate?

A

Trophic links and energy transfer

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8
Q

When does competition occur and in what forms?

What is the difference between interspecific and intraspecific

A

When resources are limited in supply.

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9
Q

What are the two forms of competition?

How can competition be reduced?

A

Exploitation: food or space is limited

Interference: aggression between competing species or individuals

Competition can be reduced through resource partitioning

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10
Q

Competition case study between reduced Glossosma (Caddisfly) and Baetis

A

Baetis: good coloniser but poor competitor. Fugitive species. Multivoltine. Quickly drifts into new areas.

Reduced Glossosma = increased Baetis

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11
Q

Meaning of uni, bi & multivoltine

A

Organisms with x number of generations per year

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12
Q

2 different types of partitioning?

A

Time (temporal):
Cyprinid fish feeding at different times of day

Space (spatial):
Case less caddis larvae feeding at different sites e.g.
Exposed boulder surface
Crevices between boulders
Gravel bed sites
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13
Q

What do predators consider when selecting prey

A

Size & activity
-Diurnal patterns, prey size, presence of fish predators

Contrast
-Visibility

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14
Q

What are prey vulnerability and avoidance tactics

A

Avoid encounter

  • Spatial segregation, use of refuge
  • Temporal segregation
  • Low movement rates
  • Reduced detectiveness (visual, mechanical & chemical)

Avoid capture

  • Detect and flee
  • Warning/ startling behaviour
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15
Q

Definition of instars

A

Development stages of arthropods

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16
Q

Examples of prey tactics to avoid capture

A

Morphological: Daphnia tail/ helmet spines

Fast swimming: Baetis

Thanotaxis: playing dead

Hide in vegetation if fish present: Gerridae (Water striders)

Adaptation of lifecycle in presence of predators: Baetis emerge as adults in smaller sizes faster. Although fewer eggs

Camouflage:
Body colouration
Use of materials to hide in e.g. cased caddisfly

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17
Q

What is aposematism?

A

The use of bright colours to warn predators not to eat the organism e.g. red water mites ‘distastefulness’

18
Q

What is predation training bias?

A

Predators preferentially seek out a familiar food type

May switch prey type

19
Q

What is top down or bottom up control

A

Classic assumption of bottom up trophic pyramid

But predators may exert top down control

20
Q

What is the influence of grazing on periphyton growing on stones? (Diatoms)

A

Reduces standing crop of periphyton

Influences community composition of periphyton by selective feeding

21
Q

Definition of disturbance

A

Events that remove existing organisms to open up for colonisation by new organisms

e.g. flooding, pollution events

22
Q

What does the ‘harsh-benign’ concept of Peckarsky (1980) state?

A

A gradient from harsh to benign

Harsh- few competition/ predation effects

Benign- environment allows for well developed competition/ predation effects

23
Q

What is the intermediate Disturbance Hypothesis (IDH)

A

Suggests the maximum species diversity tends to find an intermediate level of disturbance. Colonisers keep recolonising.

24
Q

What is the Patch Dynamics Concept (PDC)

A

Disturbance continually opens up patches that can be colonised.

Fugitive species have recurrent opportunities for recolonisation

25
Q

Meaning of fugitive species

A

Species that are quick to colonise a habitat but are poor competitors.

26
Q

What are Patch Dynamics?

A

Patches can be made available at any scale:

  • Reach after a major flood
  • New gravel bar
  • Small patch on a stone

Biological activity may create new patches ‘ecosystem engineers’
e.g. salmon & trout redds turn over gravel to lay eggs; removing diatoms

27
Q

What is the impact of crayfish on freshwater systems?

A

Burrowing helps remove silt to create clean gravel patches

Create a lot of suspended sediment due to burrowing

28
Q

What is the impact of beavers on freshwater systems?

A

Create dams in slow flowing areas; provides refuge for juvenile fish

29
Q

What is the impact of blackly larvae on freshwater systems?

A

60m downstream of larvae current velocity reduced by 75%

30
Q

Impact of Hydropsyche (net spinning caddis)

A

Increase stability of gravel by silk spinning. Making gravel adhesive to each other.

Increasing substrate stability; reduce flow/provide retreats for mayfly nymphs

31
Q

What are Reciprocal Subsidies?

A

Subsidies between environments e.g.
Terrestrial <> freshwater
Marine > freshwater > terrestrial

32
Q

What is a subsidy in ecology?

A

Payment in terms of energy, food and materials

33
Q

What is the impact of movement of salmon?

A

Migratory fish: adults spend most time at sea. Lay eggs in freshwater.

All adults die when they spawn eggs (especially NA species).
Brings nutrients up glacial stream systems (nutrient poor) when salmon decay. Inputs C,N & P into the system

34
Q

How does the terrestrial environment benefit from salmon movement?

A

Dead salmon dragged up into riparian zone by bears.

Left behind carcass decays-enriches soil

35
Q

Why has no marine derived nitrogen been found in Wolf Creek food webs despite >10,000 pink salmon spawning?
How is this detected?

A

Stable isotope analysis of marine derived N not present in aquatic insects, juvenile fish or in leaves of willow or alder.

Due to low retention of carcasses

36
Q

How much do terrestrial invertebrate prey subsidies contribute to stream fish?

A

As much as 250 mg/m^2

Terrestrial input may equal the production of benthic macro invertebrates within the stream

37
Q

What are the temporal differences in subsidy through terrestrial invertebrates

A

Seasonally- peaks in summer

Year to year- lower in cooler wetter summers

Diurnal changes- highest during the afternoon

Quantity also varies according to type of riparian vegetation growing alongside the stream- higher in deciduous (alder) than coniferous

38
Q

What is Allen’s Paradox?

A

Trout eating 30x more prey invertebrates than present.

Mainly eating terrestrial invertebrates entering the system. Can eat up to 80% benthic production of invertebrates

39
Q

Meaning of allochthonous and autochthonous food source?

A

Autochthonous: food source from within system

Allochthonous food source from outside system

40
Q

How does availability of allochthonous food source affect predators?

A

May lead to increase in predators or predator switching

41
Q

How do terrestrial invertebrates affect aquatic insects?

A

Aquatic insects make up around 50% diet of spiders and 80% of beetles on braided river floodplain

Fewer of adult stonefly surviving

42
Q

How can humans affect allochthonous inputs of terrestrial invertebrates?

A

Removal of riparian vegetation: forestry activity or channel modification

Balance can be redressed by importing salmon carcasses

CXB Ecological Systems (11 decks)

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