populations in ecosystems Flashcards
what is a community
all populations of different species in the same area at the same time
what is an ecosystem
a community and the non-living components of an environment
e.g. tropical rainforests, deserts e.t.c
Ecosystems are dynamic and can be of different sizes
when we say that an ecosystem is dynamic we mean that its characteristics can vary over time
what is a niche
A niche is an organism’s role within the ecosystem. Each species occupies its own niche this is influenced by abiotic and biotic factors
what are biotic factors
impact of interactions between organisms e.g. competition, predation e.tc.
what are abiotic factors
non-living factors in an ecosystem
what is the definition of carrying capacity
the maximum population size an ecosystem can support
what are some abiotic factors that affect population size
- Ph
- soil quality
- temperature
- oxygen levels
- CO2 levels
- light intensity
plants and animals are adapted to abiotic factors, which develop through the process of natural selection
when are species diversity and population size at their largest
species diversity and population size is larger when abiotic conditions are less extreme because there is a higher chance that species survive and reproduce and therefore pass their allele to the next generation
what are some of the biotic factors that influence population size
interspecific competition
intraspecific competition
predation
what is INTERspecific competition
it is when members of DIFFERENT SPECIES compete for the SAME RESOURCES that are in LIMITED SUPPLY e.g. light, water, food e.t.c
The BETTER ADAPTED INDIVIDUAL is more likely to survive and reproduce
what is INTRAspecific competition
it is when members of the SAME species compete for RESOURCES and a mate
these resources can be light, water food e.t.c
when competing for mates, who is more likely to “win”
when they are competing for mates, the more well-adapted individuals will be able to perform more “impressive” courtship display pr may have features in better conditions e.g. neater feathers
so they will be more likely to attract a mate and reproduce to produce fertile offspring possessing the advantageous alleles that make them more advantageous in getting a mate
this is another factor that affects population size
what is predation
predation is another factor that affects population size
It is the interaction between predator and prey
how does predation work
predation has a cyclic fluctuation
the predator population increases as the prey increases because there are more food resources, increasing survival
the prey population increases as predator population decreases as they’re less likely to be predated on so survive
what are the different ways that we can estimate population size
- quadrants
- belt transects
- mark- release recapture technique
how do quadrats work
- place 2 tape measures at right angles to create a gridded area to take samples from
- use a random number generator to generate coordinates to take samples (avoid bias)
- Place quadrat on the coordinate and either count the abundance of the species or calculate species cover
- Repeat at least 30 times ( to get a representative sample of the whole population)
how do belt transects work
- tape measures are placed through a NON-UNIFORM ECOSYSTEM e.g. a rocky beach (belt transects are a crucial environment as it would be difficult to place a quadrant here)
- quadrats placed at intersects along the transect to measure the impact of changes in the environment (in an environment that is non-uniform, the abiotic factors are likely to be different) on different populations of species
when do we use mark release recapture
this is used for motile organisms e.g. insects
If we used a quadrant for motile organisms, they may move out of the quadrant when sampling leading to inaccuracies
how does mark release recapture works
- animals are trapped and marked with a substance that must be non-toxic ( so it does not kill them),
weather resistant (so it does not wash off)
and not impacted by predation or reproduction (as this would lead to fluctuation in population size which is not what we want in our experiment)
- released and left to distribute themselves in the populations
- They’re recaptured a few days later and a 2nd sample is taken. This is repeated 10 times * this is done to get a represented and reliable result
how do we work out population size after mark release and recapture
population size = size of 1st sample x size of 2nd sample/ number of marked recaptured
what are the assumptions of mark and release
- enough time must pass in order for organisms to distribute themselves
- no migration (they don’t leave the boundary of the investigation)
- no births or deaths (so it does not affect the population size)
what is succession
succession changes in an ecological community overtime
what are the first steps of primary succession
- A pioneer species colonises bare rock or sand
- Pioneer species are adapted to survive harsh abiotic conditions and change abiotic factors to become less harsh through their death and decomposition
- moss and smaller plants can now survive, and they further increase the depth and nutrient density of the soil as they die
- this process continues and continues and larger plants can survive because the abiotic conditions are less harsh and change the environment
- each new species may change the environment in a way that the previous species can no longer survive as they become outcompeted e.g. larger plants block the sunlight for smaller plants
- these changes result in a less hostile environment and increase biodiversity
- Final stage of succession is a climax community
what is a climax community
it is a community made of mainly one species (usually trees)
what is secondary succession
secondary succession happens on land that’s been cleared or all the plants, but where the soil remains e.g. after a forest fire
The established community of species is usually destroyed, but without too much disturbance to the soul
It can occur during any stage (including the climax stage) after the pioneer stage
The process is similar to primary succession, but because there’s already a soil layer, secondary succession starts at a later stage and the pioneer species are larger plants e.g. shrubs
what are conservation techniques
to conserve habitats, succession is often managed
e.g. grazing of cows in the field prevents the grass from releasing nutrients into the soil.
By doing this, a climax community is prevented, so there is a wider variety of habitats and therefore higher species diversity
what are some issues with conservations
conservation creates a conflict with human needs
To balance this need, we can e.g. coppice trees, which allows the furniture to be made and allows trees to survive
what are the different conservation techniques
- management of succession
- seed banks
- captive breeding programmes
- fishing quotas
- protected areas
what are the assumptions of Hardy Weinberg equation
five conditions must be met:
- no mutation arise
- the population is isolated that is, there is no flow of alleles or our of the population
- there is no selection, that is all alleles are equally likely to be passed to the next generation
- the population is large
- mating within the population is random
