Populations in ecosystems Flashcards
What is a community
all populations of different species in the same area at a given time
What is an ecosystem
a community and the non living components of an environment
What is a niche
an organisms role within the ecosystem, each species has its own niche
What are biotic factors
impact of interactions between organisms
What are abiotic factors
non-living factors in an ecosystem
what is carrying capacity
the maximum population size an ecosystem can support
Examples of abiotic factors
pH, temperature, light intensity, oxygen levels, carbon dioxide levels
How do plants + animals become adapted to abiotic factors
natural selection
how is diversity and population size affected by abiotic factors
extreme abiotic conditions leads to less species diversity and smaller population sizes as less species are likely to survive and reproduce in extreme conditions
What is interspecific competition
Biotic factor
members of different species compete for the same resource that is in limited supply
the better adapted individual is less likely to survive and reproduce
What is intraspecific competition
Biotic factor
members of the same species compete for resources or a mate
more well adapted individuals will perform more impressive courtship behaviour or have features in better conditions so more likely to attract a mate and reproduce
How can predation influence population size
Predator population increases as prey population increase as there are more food sources, so increasing survival for predators but decreasing survival for prey
However as prey population decreases due to increasing predators, this will cause predator population to decrease as there are less food sources
this decrease in predator population causes an increase in prey population and this cycle repeats itself
3 ways of estimating population size
quadrats
belt transects
mark release recapture
How are quadrats used to estimate population size
used to sample slow or non-motile organisms
place 2 tape measures at right angles to take a gridded area to take samples from
use a random number generator to generate co-ordinates to take samples from, this avoids bias
place quadrat on co-ordinate and count the number of species or calculate percentage cover
repeat this at least 30 times to obtain a representative sample of mean abundance or percentage cover for one quadrat
multiply this value by how many quadrats fit in the total area of field or area you’re investigating
How to use a belt transect to estimate population size
Tape measure is placed in a non uniform ecosystem
quadrat placed at intervals along the transect to measure the impact of changes in the environment
count the number of squares the species is present in, the total number of individuals in the quadrat or the percentage cover of the quadrat of the species
How is mark release recapture used to estimate population size
what is the equation to estimate
used for motile organisms
animals are trapped and marked with a non toxic, weather resistant substance, also does not influence predation or reproduction
they are released and left to distribute themselves in the population
recaptured a few days later and a 2nd sample is taken, this is repeated at least 10 times to give a representative result
POPULATION SIZE = (SIZE OF 1ST SAMPLE X SIZE OF SECOND SAMPLE)/NUMBER OF MARKED IN 2ND SAMPLE
Assumptions made for mark release recapture estimations
Enough time for organisms to distribute themselves
no migration
no births or deaths
marking of the organisms hasn’t made them susceptible to predation
What is succesion
a change in an ecological community over time
Steps of primary succession
- a pioneer species colonises bare rock or sand
- these are adapted to survive harsh abiotic conditions and change abiotic factors to be less harsh through death and decomposition
- moss and smaller plants can now survive, and they further increase depth and nutrient density of the soil when they die
- this process continues, and larger plants can survive, which furthers change in the environment
- each new species can change the environment in a way that the previous species can no longer survive in as they become out competed
- these changes result in a less hostile environment and increases biodiversity
- primary succession results in a climax community which is mainly made up of trees
How are habitats conserved and what is an example
succession can be manages
this prevents a climax community, so a wider variety of habitats and therefore a higher species diversity
this can provide conflict between human needs and conservation
coppice trees, so timber can be harvested but the tree can still survive
