Unit 6 - Population and Sustainability Flashcards
Stages on population graph
Slow growth
Rapid growth - resources plentiful, reproductive rate > mortality rate
Stable state (no growth) - mortality = reproduction
Cannot support a larger pop. due to carrying capacity, small fluctuations
Populations can
Remain stable
Rise or fall suddenly
Oscillate up and down w. the reg. pattern
Predator prey interactions
When predator pop increases, more prey eaten
Prey pop decreases, less food available for predator s
W/ less food, fewer predators survive so their pop. decreases
W/ fewer predators, fewer prey are eaten so their pop. increases
More prey = more food, predator pop. increases
Two populations are in eqm and stable due to -ve feedback
When does competition occur
When there are not enough resources to satisfy all of the organisms that depend on them
Examples of interspp comp. affecting population
Red and grey squirrels - Invasive species
May leads to extinction of one species
Greater specialisation to avoid competition
Change in distribution of the species
Competitive exclusion principle
2 competitive species cannot coexist at the same population level esp if ones staring population is higher than the other
Scramble competition
Relies on all individuals finding food and nest sites by chance this allows natural selection as some may be better adapted than others
Dominance hierarchy
Strongest, most dominant individuals breed and pass on their alleles - if there’s only 1 dominant individual there is likely to be less variation in the next gen.
Measuring distribution
Line or belt transects (systematic sampling)
Measuring plant abundance
Randomly placed quadrats
No. of individuals in sample / Area of sample
Measuring animal abundance
Capture, mark, release, recapture (all occurs in orig. sample area)
(no. in first sample * no in 2nd sample) / no. of recaptured marked individuals
