Interactions in Ecosystems
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Give four examples of biotic interactions that can influence an ecosystem
- Food suuply
Give four examples of abiotic factors that can influence an ecosystem
- Soil pH
- Light intensity
- Availability of water
Density dependent factors ______ as population size increases?
Give two examples of density dependent factors
- Food supply
Give two examples of density independent factors
- Forest fire
What is the difference between interspecific and intraspecific competition?
Interspecific competition is between members of different species whereas intraspecific is between members of the same species
Which is more intense and why?
Intraspecific is more intense as organisms are competing for exactly the same resources
What is predation?
Predation is a biotic interaction which causes death/injury of the prey organism for consumption. Predation is positive for the predator which gains energy and/or nutrients but negative for the prey species which suffers injury/death
In areas of low biodiversity a predator may be largely dependent on ____ prey species?
Give an example of a predator/prey relationship in which the predator relies on one prey species and when plotted their populations show an unstable chaotic cycle
Lynx and snoeshow hare
What role do predators have in maintaining biodiversity?
Predators control the numbers of more dominant competitors in an ecosystem, thus allowing weaker competitors to survive
Give an example of a predator maintaining biodiversity
- Starfish keeping numbers of acorn barnacles low
- Otters keeping numbers of sea urchins low
Name and describe the two types of camoflage? Give an example for each
- Crypsis - when the animals blend into the background/environment to avoid detection eg stick insects are brown and have a wood like texture which mirrors that of a tree
- Disruptive colouration - when the solid outline of an animal's body is broken up by patterns eg a sumatran tiger has stripes that help it hide among the tall grass
What is aposematic colouration?
When animals discourage predation by using yellow and red as warning signals to convey that they taste bitter or are poisonous or have painful bites and stings
Name and describe the two types of mimicry?
- Mullerian - when both animals have similar warning markings are dangerous/poisonous to a predator eg wasp and bee
- Batesian - when one animals is poisonous and the other is not eg wasp and hoverfly
When does competition occur?
When two or more organisms need the same resource and that resource is limited
Why is competition a negative interaction for both parties?
Both lose out as growth, reproduction and survival are affected
Name and describe the two types of competition
- Exploitation competition - Organisms use the same resource but do not directly interact with the other organism. Success depends on the superior abilit to find or exploit resources more efficiently
- Interference competition - Organisms interact directly (eg fight) when competing for the resource. One organism will restrict access of the resource to the other organism
What does the competitive exclusion principle state?
That if two species have completely overlapping niches they cannot continue to co-exist
What is resource partitioning?
The dividing up of each resource by species specialisation or adaptation eg different lengths of beaks in wading birds
What is the difference between a fundemental and realised niche?
A fundemental niche is the set of resources that an organism is capable of using if there is no competition whereas a realised niche is the set of resources actually used by an organism due to competition
What is an exotic species?
One that is not native to the ecosystem
Give two examples of exotic species that have been introduced to Britain
- New Zealand flatworm - eats earthworms which causes damage to argriculture
- Mink - eats many species of small birds
- Rhodedenron - never loses its leaves so blocks out all light for native annual plants
What is a grazer?
Any species that moves from one victim to another feeding on part of each victim but doesnt actually kill it
What is the effect of moderate grazing on biodiversity?
It increases biodiversity as the number of more dominant grasses will be reduced and other weaker competitors are given the chance to thrive
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