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Definitions:
Habitat: Place where an organism lives e.g. field
Population: All of the organisms of one species in a habitat living together at the same time.
Community: Populations of different species in a habitat living at the same time.
Ecosystem: A community plus all the non-living factors (abiotic) in the area in which it resides.
Abiotic: Non-living factors e.g. temperature/pH/light intensity/wind speed.
Biotic: Living factors e.g. predation/competition/food availability.
Niche: The role of an organism within its habitat (where it goes/what it eats).
Species: Individuals with similar characteristics which can breed successfully to produce fertile offspring.
NPP: Net Primary Production (NPP) which is the energy available from producers after respiratory losses have been taken into account.
Random sampling:
-Grid out an area of habitat e.g. field/woodland and map out the grid into a series of coordinates.
-Use a random number generator to generate sets of coordinates.
-Place quadrat at coordinate corner and measure number of individuals or percentage cover of quadrat.
-Use a large sample size (number of samples) to make results more representative, as well as calculate a mean.
-Repeat the process multiple times, reducing the likelihood of the results arising due to chance.
-Number of individuals for the whole area/habitat calculated by multiplying quadrat mean with size of the area.
Biotic factors: Competition
Intraspecfic competition:
This describes the competition between individuals of the same species for resources (light/food etc)
Those individuals better adapted to compete for the resources will survive and reproduce and out compete others.
Interspecific competition:
This describes the competition between individuals of different species for certain resources. This usually means there are less resources to share between the two species, so one may out compete the other. This would cause the number of individuals of each species to change.
Predator-prey population relationship:
As the population size of the prey increases, there is more food available for the predator population. This means the predator population is more able to survive and reproduce, and therefore predator population numbers rise.
The increased population of predators means that more prey is eaten. It also means there is typically more intraspecific and interspecific competition between predators. This makes it less likely for the predators to survive and reproduce and therefore predator population decreases. Predator and prey populations are therefore in a dynamic state of flux.
Distribution along a line:
-Taking samples using quadrats along a tape measure is known as a belt transect. Leaving intervals between samples is a method of systematic sampling.
-The disadvantage of this is that some areas are not sampled (missed).
Mark-release-recapture technique:
-Capture number of organisms using an appropriate technique.
-Mark the individuals with a tag that won't be lost and is non-toxic to the organism.
-Release them back into their habitat and allow a sufficient time for them to mix to give rise to a uniform distribution.
-Capture second sample of organisms and count how many of the second capture are marked individuals from the first capture.
-Estimate total population size using:
Number caught 1st x Number caught 2nd
Number marked in the 2nd sample
MRR Assumptions:
-Marking has no effect on organism (physiologically or socially)
-Enough time has been given for organisms to mix.
-No births/deaths/migration events (no change in pop. size)
Succession explained:
-Pioneer species (e.g. moss) colonise new surface where abiotic factors may be harsh. Pioneer species adapted to harsh abiotic factors.
-Pioneer species change abiotic factors and make them less hostile (decomposition/soil formation)
-New species with different adaptations can grow on surface. These also die and are broken down, making the abiotic factors less hostile again. Water retention begins to increase.
-Some species change the habitat and its abiotic factors to make it less suitable for other species to survive (competition).
Quadrat or MRR?:
-Quadrats and transects are used for non-motile organisms such as plants or slow moving insects, for example.
-Mark-release-recapture is used for motile organisms e.g. deer. This is because they move around too much to try and estimate population size through using quadrats.
-Also due to size! Quadrats used for smaller organisms.
Understanding biodiversity:
-Range of alleles (in a given area at a given time)
-Variety of alleles (in a given area at a given time)
-Variety of ecosystems and habitats (at the same time)
*More species = More diversity
*More habitats = More diversity
The importance of conservation:
-Without conservation there is an impact on food chains.
-Animals have a 'right to exist'
-Aesthetic reasonings (pretty flowers/landscapes)
-Economic reasonings (attraction of tourism etc)
Advantage of conserving seeds:
-Small (easy to store).
-Collected with minimal damage to seed and environment.
-Last a long time (viability).
-Can store an increased diversity of seeds (as there are more seeds).
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