Population ecology Flashcards
Requirements for this method to be valid (marked recapture method)
Markings cannot harm the organism
Marks clearly visible for the duration of the process
Marks should not change the animals behaviour
Enough time should be allowed for sufficient population mixing
A closed population for the duration of the sampling
Short duration between samples so few births or deaths affect the results
Requirements for this method to be reliable
Exact number in quads needs to be counted
Repeats are necessary
The size of the quad needs to be known
The area of the population being measured must be known
The quad needs to be placed randomly
Is not reliable for clumped populations
Ecology
The study of how living things interact with each other and their physical environment.
Species
A group of organisms with similar characteristics, breeding freely, which produce fertile offspring.
Population
A group of organisms of the same species found in a particular area at the same time, and hence able to interbreed freely
Community
A collection of different populations in a particular area
Ecosystem
Units of communities (biotic) interacting with each other and the abiotic factors of a particular area. Can be very large areas or very small areas
Factors causing environmental resistance
Density-dependent factors are factors causing environmental resistance that are directly related to the density of the population. Generally these are biological in nature / biotic factors:
Access to nutrients/food & water
Competition for mates & breeding habitats
Diseases spread by microbes
Parasitism
Predation
Accumulation of metabolic wastes (e.g. CO2 levels)
Density-independent factors are factors that cause environmental resistance but that are not directly related to population density.
Human activities (e.g. habitat destruction, pollution of air, land and water)
Environmental disasters (e.g. earthquakes, volcanoes, tsunamis, floods, droughts, fires, hurricanes)
Equilibrium
The stability of ecosystems makes the competition for resources inevitable.If that were not so, populations would explode, which they rarely do. Ecologists use the term equilibrium to describe the point at which a population’s size stabilizes in relation to its available resources; and they use the term carrying capacity to refer to the number of individuals in a species that a habitat can support at equilibrium.
In many ecosystems, each trophic level has one-tenth the biomass and energy of the level below it. This forms a food pyramid. Its base is made up of primary producers, plants that carry out photosynthesis. This is the first trophic level, the one with the most biomass and energy.
Unstable populations
When a population far exceeds the carrying capacity the environment will be damaged. This results in a decrease in the carrying capacity and population numbers will decrease. Extinction is a possibility.
predators
Too much predatory activity at the top of the food pyramid can destroy the levels below it, leading to ecological collapse. This is the reason large, fierce animals are so rare as their numbers are limited by the ability of the trophic levels below to support them. Similarly, if a disease or a severe frost destroys plants at the first trophic level, the effects are quickly at the second and then third and fourth levels. So ecosystem equilibrium is constantly changing and populations tend to shrink and grow with some regularity.
Population control
Conservation managers sometimes need to manage natural populations in a way that is logistically and economically feasible so that biodiversity is maintained. Population control is the practice of artificially altering the size of any population. It typically refers to the act of limiting the size of an animal population so that it remains manageable or stays within the carrying capacity of a habitat
methods of population control
Culling
Manipulation of the reproductive capability
Translocation
Creating corridors of migration to mimic nature
