investigating populations Flashcards
what is an ecosystem
a community and non-living components of its environment together form ecosystem, can range from very small to very large.
what is a species
is a group of closely related individuals which are capable of interbreeding and producing fertile offspring
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 carrying capacity
is the maximum population size that can be sustained in a given area, at a given time with the available resources
what is a community
is all the individuals of all the different species living together in the same area at the same time.
what is a habitat
the place where an organism lives within an ecosystem
what is a niche
describes where an organism lives and what it does. This includes what it feeds on and how it interacts with other organisms and the environement.
Abiotic factor
is a non living factor which affects the distribution of an organsim e.g. temperature, light intensity and water pH
what is a biotic factor
a living factor which affects the distribution of an organism e.g. competition, predation and disease.
what is the abundance of a species
the estimation of a population size within a species
what is important to remember when estimating population sizes
- to ensure data collected is not biased, the samples must be selected at random
- to ensure data collected is both reliable and suitable for statistcial analysis a large enough number of samples must be taken
- the method of collection of samples must also be appropriate to the species
what is a quadrat
a frame of known area which is placed on the ground and an estimate of the population sizes within the quadrat are made
there are 3
how can you measure abundance
- actual count of individuals present (population density )
however this can be difficult to do and can be very time consuming - percentage cover - the area of the quadrat covered by one species is recorded as a percentage of the total area
- frequency - the proportion of quadrats that contain a particular species
why is random quadrat sampling done
to find out what species are present and their relative abundance. This data can then be used to :
compare the species abundance in 2 different areas
compare the species abundance at one site at different times
what is the method of random samplign using a frame quadrat
-two measuring tapes arranged at right angles to each other to form the axes of a grid of co ordinates
- random co ordinates are generated in a random number generator
- a quadrat is placed at the intersection of these co ordinates
- abundance can then be estimated using quadrat by one of the following methods :
population density, frequency, percentage cover
- repeat many times to calculate a running mean
- a statistical test should then be used to check results
what are the methods of estimating
- measuring the population density- count the number of individuals in quadrat area and calculate density per metre sqaured
- frequency - count number of hits in quadrat area average per metre squared
- percentage cover - measure % cover of species in quadrat area and calculate average % per metre squared of field
what does sampling consists of
- recording what species are touching the line at each sampling point
- placing two parallel lines across, a metre apart and recording what species are found between two lines ( belt transect )
- interupted belt transecters can be done using onen line and placing a quadrat down at equally spaced sampling points and recording abundance of species within the quadrat
a transect is a line across the area and sampling is done at set predete
what is the method of mark - release- recapture
- capture animals of particular species and count them
- mark the animals in some way that is not harmful or makes them more visible to predators
- release the animals and allow time for them to disperse and reintergrate into the population
- capture a second time and count the number caught, as well as how many of them have been marked
- calculate population size
how do you calculate population size
(N1 x N2 ) / Nm
N1= number caught in 1st sample
N2= number caught in 2cnd sample
Nm = number caught second time which were marked
what are the assumptions made in mark- release- recapture
- population size does not change between the 2 capture times
- birth rate and death rate should be equal
- no emigration or immigration into the population
- marking does not affect survival
- sufficient time should be left after the release so marked individuals fully disperse through population
what are the ethics of sampling
- species should not be removed from their postion
- if removal is necessary individuals should be returned to the same spot
- as few individuals as possible should be removed
- minimal damage to organisms or habitats
how does temperature impact abundance of species
extreme temperatures affect enzymes
if temperature is too cold, the enzymes will not have enough kinetic energy to catalyse reactions quickly enough.
if temp is too high, enzymes may start to denature and activity will fall
in hot environments some animals would suffer dehydration
how does light intensity impact abundance of species
needed for photosynthesis, more light intensity would result in more light intensity and therefore growth.
more plants = more growth
also affects plant flowering
how does humidity impact species abundance
organisms can loose water through evaporation
lower humidity = more water loss
how does pH impact species abundance
pH can affect extracellular enzymes and surface protiens
can also affect the availability of mineral salts in the soil and therefore can affect growth of plants
what is intraspecific competition
competition between members of the same species
could be for mates
what is interspecific competition
competition between members of different species
could be for territory, food etc
what are the reasons we conserve habitats
to maintain niches
to maintain diversity
