7. Genetics Populations and Ecosystems Flashcards
what is a population?
a group of organisms of the same species occupying a particular space at a particular time that can potentially interbreed
what is a habitat?
the part of an ecosystem where an organism lives
what is a community?
all the populations of different species living in the same habitat at the same time
what is an ecosystem?
a community of all living and non living components of an environment (the biotic and abiotic factors)
what is a niche?
the role of a species within an ecosystem and their habitat, including their position in the food web and what they eat. governed by adaptation to abiotic and biotic factors. no two species have the same niche.
what is the carrying capacity?
the maximum population size an ecosystem can support
what are the abiotic factors?
the non living features of an ecosystem eg the temperature and the water availability
what are the biotic factors?
the living factors eg. the presence of predators and food
the niche a species occupies within a population includes what?
its biotic interactions - what it eats and what its eaten by
its abiotic interactions - eg the oxygen it breaths in and the co2 it breaths out
what is a species?
organisms that can interbreed to produce fertile offspring (can exist as one or more populations)
give 6 examples of abiotic factors
- temperature
- oxygen
- carbon dioxide concentration
- light intensity
- pH
-soil conditions
what is evolution?
the change in the allele frequencies in a population
what are the three types of selection?
directional
stabillising
disruptive
what is directional selection?
when the extreme trait has the selective advantage, so organisms with alleles that code for an extreme trait are more likely to survive and reproduce. this is in response to an environmental change.
what is stabilising selection?
when the modal trait (organisms with alleles that code for characteristics towards the middle of the range) are more likely to survive and reproduce. occurs when there is no environmental change.
what is disruptive selection?
when extreme traits on both ends of the range have the selective advantage
what is an adaptation?
a feature that increases an organisms chance of survival and reproduction
state and describe the three types of adaptation
behavioural = the way the organism acts, such as migrating to find food
physiological = internal biological functions helping the organism survive
structural = features of an organisms body that help it survive
by what process do adaptations develop?
natural selection
explain how natural selection increases an organisms chances of survival
- organisms better adapted to the environment are more likely to survive and reproduce
- by doing this, they will pass on their alleles
- thus, the frequency of this allele will become increase within the population
give two examples of biotic factors that can affect population size
competition and predation
what is interspecific competition?
when members of different species compete for the same resources that are in limited supply.
(the individual better adapted to the environment is more likely to succeed in the competition)
what is intraspecific competition?
when members of the same species compete for resources and a mate. (individuals that are fitter, have more energy or are in better condition are more likely to attract the mate)
state 4 things that species may compete for
- space
- food
- water
- a mate
what is the general strategy for taking a random sample?
- chose a random area to sample to avoid bias by dividing the field into a grid, and then using a random number generator to select coordinates
- chose an appropriate technique to take a sample (eg. quadrats or transects)
- repeat the process, taking as many samples as possible (reducing the likelyhood results are down to chance)
- number of individuals in the whole area can be estimated by taking a mean of the data in each sample and then multiplying it by the size of the whole area
describe the population relationship between predators and prey
- as the prey population increases, theres more food for the predators, so the predator population increases.
- however, as the predator population increases, more prey is eaten, so the prey population begins to fall.
- this means theres less food for the predators, so their population decreases too.
how to ensure samples accuratley represent the population?
random sampling in uniform areas to eliminate bias
- line transects to examine a change over distance
- a large number of samples (30+) to ensure your accuratley representing the population
when is it appropriate to use a quadrat?
- when the sample contains slow/non moving organisms
- when the organisms are uniformly distributed in the area
when do we use a line transect?
- when there is uneven distribution of organisms in the area (populations that change over distance)
- when the sample contains slow/non moving organisms
with moving organisms, what sampling technique do we use?
mark-release-recapture method
describe how the mark-release-recapture method works
include the equation
- an initial sample of the population is captured
- these individuals are marked and then released back into the wild, and the number of marked individuals is recorded (mark must be weather resistant)
- marked individuals are then left for a period of time to allow them to randomly disperse throughout the habitat
- the second sample is then captured
- the total number captured in the second sample is recorded, and the number recaptured is also recorded
- the process is repeated multiple times, and a mean is then calculated for more reliable results
population size = (number initially captured x number in second sample) / number marked in second sample
what are the ethics to consider when doing the capture-recapture method?
- how organisms are captured and marked must not cause permanent harm
- the mark must be non toxic
- mark must not increase chances of predation or reduce chances of reproduction
what are the assumptions associated with the capture recapture method?
- that the population size is constant (no birth/death or migration)
- that the animals always distribute evenly (they may all huddle near food in reality)
how would a student use a quadrat to estimate a sample population on a uniformly distributed field of daisies? (6)
- lie two tape measures at a right angle to create a gridded area
- use a random number generator to generate two coordinates
- place the quadrat and collect the data (calculate the percentage cover or the frequency of the daisies)
- repeat this process at least 30 times and then calculate a mean, before multiplying by the size of the field.
what are the two different types of line transect?
the belt transect and the interrupted belt transect
how does a belt transect work?
the quadrats are placed next to eachother along the transect
how does an interrupted belt transect work?
the quadrat is placed at uniform intervals along the tape measure with spaces in between them eg. every five metres (to cover a larger distance OR if not much distance will be observed using a belt transect)
describe a method as to how a student would set up and conduct a sampling experiment using a line transect (4-6)
- place a tape measure at a right angle to the shore line
- take a 1m quadrat divided into 100 squares and place it next to the tape measure every 5 meters/ next to eachother
- count the squares containing organism and calculate the percentage cover, then record this in a table
- repeat by placing another 30 transects at right angles to the shore line along your sampling area
state and describe the different methods that can be used to estimate the abundance of a species
- local frequency = the % of squares in the quadrat with the species present
- density = count how many of one species you have within the quadrat (eg how many daisies) and then apply this to the area of the field
- percentage cover = the % of full squares occupied within the quadrat
what are the advantages and disadvantages of using the local frequency method?
advantages = quick method to sample a large area, and useful if its too difficult to identify individual organism or too many to count
disadvantages = poor accuracy as it doesnt consider overlapping plants or the size of the plant
what are the advantages and disadvantages of using the density method?
more accurate if you can easily distinguish an individual plant, and there are not too many to count. can be used to estimate species richness
more time consuming
what are the advantages and disadvantages of using the percentage cover method
advantages = quicker method than density, and useful if its too difficult to identify the individual organism or if theres too many to count
disadvantages = subjective, which limits accuracy. and doesnt consider overlapping plants or the size of the plant