4.2.1 biodiversity Flashcards
what is biodiversity?
the variety of living organisms present in an area
what is habitat biodiversity?
the number of different habitats found within an area
what are the two components of species biodiversity?
- species evenness
- species richness
what is species richness?
the number of different species living in a particular area
what is species evenness?
a comparison of the numbers of individuals of each species living in a community
what is genetic biodiversity?
the variety of genes that make up a species
what is sampling?
taking measurements of a limited number of individual organisms present in a particular area
what is the purpose sampling?
- estimate the number of organisms in an area (the abundance of a species)
- measure a particular characteristic of an organism
what is random sampling?
each individual in the population has an equal likelihood of selection
what is non-random sampling?
where the sample is not chosen at random
what are some methods of non-random sampling?
- opportunistic sampling
- stratified sampling
- systematic sampling
what is opportunistic sampling?
sampling using the organisms that are conveniently available
the weakest form of sampling - may not be representative of the population
what is stratified sampling?
sampling where populations are divided into sub-groups based on a particular characteristic
a random sample is then taken from each of these strata proportional to its size
what is systematic sampling?
different areas of a habitat are identified and sampled separately
often carried out using a line or belt transect
how to carry out a random sample?
- mark a grid out of the area using two tape measures laid out at right angles
- use random numbers to determine the x coordinate and y coordinate on the grid
- use a quadrat to take a sample at each of the coordinate pairs generated
why is a sample not entirely representative?
- sampling bias - the selection process may be biased - deliberate or by accident
- chance - the organisms selected may not be representative of the whole population, effect minimised by large sample size
how can animals be sampled?
- pooter - catch small insects
- sweep nets - catch insects in areas of long grass
- pitfall traps - catch small crawling invertebrates , hole dug in ground which insects fall into
- tree beating - take samples of invertebrates that live in tree or bush, white cloth stretched under the tree, tree shaken or beaten to dislodge the invertebrates
- kick sampling - river bank and bed kicked to disturb the substrate, net held downstream to capture any organisms released into the flowing water
how can plants be sampled?
- point quadrat - consists of a frame containing a horizontal bar, pins pushed through bar to reach ground, species of plant that touches the pin is recorded
- frame quadrat - square frame divided into a grid, type and number of species in each section is recorded
how can frame quadrats be used?
- density - count number in 1m x 1m quadrat
- frequency - count number of small squares that a species is present in
- percentage cover - estimate of the percentage a species covers
how can animal population size be estimated?
capture-mark-release-recapture
compare number of marked individuals with the number of unmarked individuals in the second sample
the greater number of marked individuals recaptured, the smaller the population
Simpson’s Index of Diversity
D = 1 - Σ(n/N)² n = total number of organisms of a particular species N = total number of organisms of all species
what is the importance of genetic biodiversity?
more able to adapt to changes in the environment
factors that cause genetic biodiversity to increase
- mutations in the DNA of the organism
- gene flow - interbreeding between different populations
factors that cause genetic biodiversity to decrease
- selective breeding - only a few individuals within a population are selected for breeding for advantageous characteristics
- captive breeding programmes
- artificial cloning
- natural selection - alleles for less advantageous characteristics are lost from a population over time
- genetic bottleneck - only a few individuals in a population survive an event or change, reducing the gene pool
- founder effect - small number of individuals create a new colony, geographically isolated from the original. gene pool is small
- genetic drift - due to randomness of reproduction, the frequency of occurrence of an allele will vary