7.4 Populations in ecosystems Flashcards
Define ecosystem:
A community and all the non living factors of it’s environment
Define Population:
A group of organisms, of the same species, that occupy the same habitat at the same time and which potentially can interbreed.
Define Community:
All the populations of different species living and interacting in a particular place at the same time.
Define Habitat:
The place where an organisms usually lives
Define biotic factor:
A living factor in an ecosystem.
Define abiotic factor:
A non living factor in an ecosystem
Define abiotic factor:
A non living factor in an ecosystem
What is an ecological niche:
How an organism fits into an ecosystem. It includes where the organism lives and what it does there. It also includes the biotic and abiotic conditions to which it is adapted. In an ecosystem no two organisms can occupy exactly the same niche.
What is carrying capacity?
The largest population a particular environment can sustain
What is carrying capacity?
The largest population a particular environment can sustain
What is meant by limiting factor:
Any factor that stops the population increasing in size. Can be abiotic/biotic
How does population size vary as a result of interactions between organisms?
Interspecific competition = competition between species
- Reduces resources available to both -> limits both populations
If one species is better adapted, it will out-compete the others
Intraspecific competition = competition within species
- Smaller population = less competition -> better for growth and reproduction -> larger population = more competition -> less growth and reproduction -> smaller population.
Predation
- Population sizes of predators and prey are interlinked
Increased predator population size -> more prey eaten -> prey population falls -> less food for predators -> predator population size falls -> prey population rises -> predator population rises again
What are specialists?
- Narrow niche
- Less adaptable because of specialised needs
- More likely to become extinct
- Use of specific set of resources
- Easily affected by changing conditions
- Have an advantage when conditions are more constant
What are generalists?
- Broad niche
- Adaptable to many environments
- Less likely to become extinct
- Use a variety of resources
- High range of tolerance
- Have an advantage when conditions change
When does competition occur?
Happens when resources are not present in adequate amounts ot satisfy all the individuals that depend upon them
Describe how you would use frame quadrats to compare the number of daisies in two different fields?
Use a grid / split area into squares
Obtain random coordinates using a random number generator / calculator – place quadrats here
Deciding the number of quadrats to use to collect representative data:
- Calculate running mean
- When enough quadrats, this shows little change
- Count frequency of species in quadrat
Calculate mean per quadrat
Calculate population size by multiplying the mean by the number of quadrats that would cover the habitat
Describe how you would use frame quadrates to investigate how the percentage cover serrated wrack (a seaweed) changes with distance from the shore-line?
- Used to look at changes in distribution
- Lay tape measure from one place to another
- Place quadrats at regular intervals along the line
- Count frequency / percentage cover in quadrats
How would you go about estimating the size of a population of motile (moving) organisms?
Mark-release recapture:
- Capture sample (harmlessly)
- Count and mark the sample
- Release sample back into the environment - and allow time for organisms to re-integrate
- Capture a second sample
- Count marked individuals in the second sample
What is the formula for mark-release-recapture?
Estimated population size = no. of individuals in first sample x no. of individuals in second sample / number of marked individuals recaptured
Assumptions made when using the mark-release-recapture method:
- Sufficient time for marked individuals to mix within the population
- Marking not removed and doesn’t affect chances of survival e.g. more visible to predators
- No immigration/emigration
- No births/deaths/breeding
What is succession?
The changes that happen over time in the species that occupy a particular area. In an uncolonised piece of land the first organisms to grow would be the pioneer species. Succession will then take place, and the ecosystem will change, until the climax community is reached.
Define pioneer species:
First species to colonise a previously un-colonised habitat.
Define climax community:
Final, stable community – Usually mixed woodland in the UK.
Describe the process of succession:
- Colonisation by pioneer species
- Pioneer species (or generally just certain species at each stage in succession) change the abiotic conditions and make the environment less hostile e.g. die and decompose, forming soil which retains water
- Environment becomes more suitable for other species with different adaptations, and may be less suitable for the previous species – better adapted species outcompetes previous species
- As succession goes on, biodiversity increases
- Climax community: final, complex, stable community
Explain the characteristics of a pioneer species?
- Survive in tough/harsh conditions
- Photosynthetic
- Asexual production
- Nitrogen fixation
- Rapid germination
What is the difference between primary and secondary succession? Give an example of each.
Primary succession: development of community on an area previously never colonised eg/ volcanic islands, sand dunes
Secondary succession: takes place on previously colonised habitats that have been disrupted eg/ after a forest fire
Define conservation:
The management of habitats and ecosystems in a way that ensures they can continued to be used in the future
What are the reasons for conservation?
- Conservation sometimes involves preventing succession in order to preserve an ecosystem in its current stage of succession
- Food eg/ hunting and fishing
- Resources - eg/ medicinal plants
- Aesthetics (tourism, ethics)
What are the reasons for conservation?
- Conservation sometimes involves preventing succession in order to preserve an ecosystem in its current stage of succession
- Food eg/ hunting and fishing
- Resources - eg/ medicinal plants
- Aesthetics (tourism, ethics)
