Populations and Ecosystems - B11 Flashcards
Define habitat.
the place where an organism lives within an ecosystem
Define community.
all the different populations of different species in a habitat.
Define environment/ecosystem.
the set of conditions that surround an organism, consisting of biotic factors and biotic factors
What is a biotic factor?
living features if the ecosystem
What is an abiotic factor?
non-living features of the environment
What factors reduce population size?
predation, human activity(hunting, pesticides), disease/parasites, intraspecific competition, interspecific competition
Define niche.
the role of an organism within it’s ecosystem including it’s biotic and abiotic interactions e.g. what it eats, where and when it feeds
What is included in the niche a species occupies?
-it’s biotic interactions
-it’s abiotic interactions, e.g. the temp range an organism can live in, the time of day it’s active
What are the implications of no two species having the same niche?
if species don’t have the same niche, there is no/less interspecific competition for resources such as food
What is the competitive exclusion principle?
if two species have the same niche, one will outcompete the other.
What is an adaptation?
An adaptation is a feature of a species that increases their chances of survival and reproduction. It can be physiological, physical or behavioural.
What is population size?
The total no. of organisms of one species in a habitat.
What is the carrying capacity?
The maximum population size of a species that an ecosystem can support. It varies as a result of biotic and abiotic factors.
How do abiotic factors effect population size?
-the pop. size of any species varies due to abiotic factors
-e.g. the amount of light, water or space availability, temperature, chemical composition of surroundings
-when abiotic conditions are favourable, organisms grow and reproduce successfully
What intraspecific competition?
competition between individuals of the same species
Why is intraspecific competition a cyclical change?
-population grows and changes continuously
-population grows when resources are plentiful
-resources become limited so population decreases
-smaller population means less competition so more growth and reproduction occurs
What is interspecific competition?
competition between organisms of different species for the same resources
-the resource to the populations could be limited to both populations
-or if two organisms are competing but one is better adapted, the less adapted species is likely to be out-competed
How do the populations of prey and predator change due to predation?
-their populations interlinked, as the population of one changes, so does the other.
-as prey population increases, there’s more food for predators, so predator population grows
-as the predator population increases, more prey are eaten so the prey population then begins to fall
-less food for predators, so predator population decreases
Why do we use a log graph?
the range between the smallest and largest number is too big, so allows for a large range to be plotted.
What are the mark points for quadrat questions?
-grid the area you want to sample
-take random samples to remove bias
-use a random no. generator to generate coordinates to take samples at
-place quadrat at that coordinate and count the number
-take a large sample by repeating many times(which makes the sample representative)
-running mean can be calculated and when the running mean stabilises, enough samples have been taken
-calculate mean per quadrat
-multiply per quadrat by number of quadrats that fit into the area(other methods are available)
define population
a group of the same species in a particular space at a time, that can interbreed.
Why do we take samples?
to estimate numbers of plants and animal species in a particular habitat, to estimate the numbers of each organisms
What are the different methods for investigating populations?
-quadrats
-used for studying non-motile organisms
-always a known size e.g. 1m^2 or 0.25m^2
-a square frame divided into a grid of 100 smaller squares
define abundance
the number of individuals of one species in a particular area(i.e. population size)
-can be estimated by counting the number of individuals in samples.
define frequency
the number if samples a species is recorded in - e.g. 70% of samples
define percentage cover
how much of an area you’re investigating is covered by a species
how is percentage cover estimated?
-visual estimate
-if over half the square is covered, count it
define distribution
where particular species is within the area you’re investigating
Why do we use random sampling?
too time consuming to count every organism so instead we take samples
What are the mark points for random sampling?
1)choose a small area within the area being investigated
2)some samples should be random to avoid bias. Use a random number generator
3)use appropriate technique to sample
4)take a large sample so that data is representative
5)take mean of data and multiply by size of the whole area
How is the running mean calculated?
-the running mean is calculated each time a new sample is collected
-once the mean no longer changes by a large amount, stop sampling, as you have a representative estimate for that area
What is a transect?
lines across an area if interest can help you to find out how organisms are distributed across an area
What is a belt transect?
Quadrats are placed next to each other along the transect to sample species along the transect
What is an interrupted belt transect?
Quadrats placed at regular intervals - makes it easier to sample over large distances
What are the mark points for a transect question?
-randomly place transect down across sampling area using random coordinates using a random number generator
-place quadrat down at regular intervals along transect
-record abiotic factor
-repeat many times at other randomly placed lines across the area
-until the running mean does not vary much
What is mark-release-recapture?
a method used to measure the abundance of more mobile species
What are the mark points for mark-release-recapture questions?
1)capture a sample of species and count
2)mark in a harmless way e.g. spot of paint or tag
3)release back into habitat
4)wait a set amount of time and take a second sample from the same population
5)count how many of the sample are marked
6)calculate total population using equation:
total population= no. caught in 1st sample x no. caught in second sample / no. marked in second sample
What ways do we evaluate the accuracy of MRR?
1)the marked sample has had enough time and opportunity to mix back into the population
2)marking is not toxic so doesn’t effect survival
3)marking doesn’t make more visible to predators
4)marking doesn’t was off so recaptured organisms can be identified
5)there are no changes in population size sue to births, deaths or migration during the period of study
What are some of the ethical issues with MRR?
-could cause the animals unnecessary stress - could reduce their chances of survival on release
-animals may learn not to be trapped the next time - skewing the results
-to minimise stress, investigations should be planned so that organisms are treated carefully and kept and handled as little as possible
