Populations in ecosystems Flashcards
(12 cards)
What is a community?
a community refers to populations of different species in a habitat.
What is an ecosystem?
An ecosystem is a community and the non-living components of its environment. An ecosystem may be small (pond) or large (sea).
What is a niche?
A niche is a species’ role within an ecosystem governed by its adaptation to both biotic and abiotic conditions. Only one species can occupy a niche at a given time. If 2 species try to occupy the same niche, they will compete with each other. If there is less competition, this results in broader niches.
What is the carrying capacity?
The carrying capacity is the maximum stable population size of a species that an ecosystem can support.
The carrying capacity depends on…
The effect of abiotic factors, interactions between organisms, and predation.
What abiotic factors affect the carrying capacity?
Light intensity, water availability, food availability, soil pH, and temperature.
How do interactions between organisms affect carrying capacity?
Interspecific competition is when organisms of different species compete for resources, resulting in less resources available to both species making the population size decrease as the chance of survival and reproduction decreases. If one is better adapted, it will have increased chance of survival and reproduction and may out compete the other.
Intraspecific competition is when organisms of the same species compete with each other for resources.
How does predation affect carrying capacity?
Predation is when one organism eats another. However, predator-prey relationships may be influenced by other factors (food availability) or be more complex if the predator feeds on more than 1 species.
What are two ways of estimating population sizes in non-motile or slow-moving organisms?
Randomly placed quadrats, and quadrats along a belt transect.
How can you use randomly placed quadrats to estimate population size of a non-motile or slow-moving organism?
1) Plot coordinates and use a random number generator to generate coordinates.
2) Place quadrat (1mx1m)
3) Count number of individuals
4) Repeat many times
5) Calculate mean
6) Multiply mean by total area
How can you use quadrats along a belt transect to estimate population size of a non-motile or slow-moving organism?
Quadrats along a belt transect can be used to measure gradual changes in population size across an area by taking samples at regular intervals along a transect.
How can we estimate population size of motile organisms?
Using mark-release-recapture:
1) Capture a sample of individuals from the population
2) Count number of individuals (S1) and mark them in a harmless way.
3) Release them and allow time to distribute evenly amongst the rest of the population.
4) Capture a second sample from the population
5) Count the number caught (S2) as well as those marked (R)
6) Calculate population estimate using (S1xS2)/R
