Session 3: Population Ecology Flashcards
Define population.
group of organisms of the same species
Define Community
all populations of different species living in an area
Define ecosystem
all of the biotic and abiotic factors in an area
What are the 3 main ways to quantify and describe populations?
density: number of organisms per area, etc.
distribution: the location of organisms in an area
size/abundance: total number of individuals
Define high-density and low-density.
Low: only a few individuals per unit area, e.g. with highly territorial organisms, or solitary mammalian species like tigers.
High: individuals are crowded together, many individuals per unit area, e.g. colonial organisms such as corals or insects.
What are the three types of distribution?
random, clumped, and uniform.
Define random distribution.
When the spacing between individuals is irregular, the presence of one individual does not directly affect the location of any other individual. Commonly seen in plants.
Define clumped distribution.
individuals are grouped together in certain areas, often around a resource (e.g. a waterhole) or when living in large groups is beneficial (safety in numbers).
Define uniform distribution.
individuals are evenly and regularly spaced in an area.
How do you calculate population growth? (define the terms.)
PG = (births - deaths) + (immigration - emigration)
birth rate = births per 1000 per year
death rate = deaths per 1000 per year
immigration = movement of individuals into the population
emigration = movement of individuals out of the population
Explain Malthus’s Theory of Population Growth.
Populations increase exponentially while food production increases arithmetically (population growth easily outstrips resource production). Meaning, populations increase quickly until competition for resources occur and the carrying capacity is reached.
Explain J and S shaped curves.
They are the main ways that population growth is represented and is said to occur. J-shaped goes up in a J shape then is said to go straight back down (population reaches its limit and declines back to the start). S-shaped is similar to J except it flattens at the carrying capacity (population reaches a limit and is maintained)
Define carrying capacity.
The maximum number of individuals an area can support on a sustained basis given the prevailing resources. The top of an S curve represents a population size which is supportable by the resource base (at this point resources become a limited factor and competition starts)
Explain the four main parts of an S-curve.
1 - the start: slow growth due to low numbers of reproducing individuals
2 - steeper gradient: exponential growth due to birth rate exceeding death rate.
3 - starts to plateau: growth rate slows due to death rate increasing and birth rate decreasing
4 - plateau: equilibrium at carrying capacity due to similarities in birth and death rates.
What is r and K selection?
There are two main types of “strategists” in populations. r strategists often follow J-shaped curves. K strategists often follow S-shaped curve.
