Changing population Flashcards
What Limits A Population?
Density-Dependent and Density-Independent Factors
What is Density-Dependent?
factors that affect population size In Relation to population density
what is Density-Independent
factor that affect population size Regardless of population density
What are the Density Independent Factors?
- natural disasters
- pollutants
- extreme temperatures
- events in which the population size doesn’t matter
What are the Negative Density dependence Factors?
mostly happens in Big population
- Disease
- Competition (food, shelter, space)
- more individuals = not enough resources
What is Law of Constant Final Yield?
No matter how many seeds were sown, the final amount of biomass was the same because
- resources are limited
- increasing amount of seeds doesn’t increase the biomass of plants because they are overcrowded causing their biomass to level off instead
What are the Positive Density Dependence
happens in tiny population
Causes Allele effect
What is Allele effect?
increase ease of finding a mate, sex rations, reduced inbreeding
- lacks genetic diversity
- when the allele effect ease, rapid growth is seen
In graph, Positive Density Dependence would
Increase Breeding pairs = Increase in Population Growth
In graph, Negative Density Dependence would
Increase resource competition = Decrease population growth
What do methods depend on to quantify population size?
- type of organism
- density of organism
- their environment
What is Sub-sampling?
To estimate abundance over large areas
- uses Quadrats and transects
- typically used for sessile (doesn’t move) organism
What is Mark-Recapture?
Organism is captured -> mark -> releases in habitat -> repeat and look how many are marked
M/N = R/C
What is carrying capacity (K)
- result of Negative density-dependent factors
- no set of numbers which means it depends on the quality of the environment which would eventually level off
This equation (1 - (N/K)) in Logistic Growth Model mean
- decline in growth rate as population approaches K
This equation (1 - (N/K)): when population is Small
- N/K ~ 0, term in bracket ~ 1
- would grow rapidly as its exponential, not near the carrying capacity
This equation (1 - (N/K)): when population is Large
- N/K ~ 1, term in brackets ~ 0
- growth rate approaches 0 so population is slowing down
What is Inflection point in Carrying Capacity?
The point of fastest growth after which growth begins to slow
What is Overshoot?
population grows beyond carrying capacity
- may occur if habitat carrying capacity decreases
What happens when a population overshoot?
when population is still growing but carrying capacity is depleting then it would overshoot
followed by Die-Off (when a massive crash in pop’n)
What is Population Cycle?
population would go up and down, repeat overshoot and die-off (due to availability to resources and carrying capacity)
What is Delayed Density Dependence?
Delayed b/w environmental change and the time population reproduces
- population is not as responsive so population growth delays
- uses population in THE PAST instead of using the population in the present
Size of Oscillations depends on what factors?
- magnitude of time delay [ increase time, decrease in responsiveness which means more likely to overshoot]
- growth rate [ grow rapidly, capacity drops (leads to overshoot as they can’t control pop’n growth) ]
What is No Oscillations?
population size is easily reached
What is Dampened Oscillation?
population size is mid range, delay, grows quickly and eventually find carrying capacity (level off)
What is Stable Limit Cycle?
population size is continuous cycle
Energy reserves can cause oscillations because?
they can cushion themselves against carrying capacity
High-Energy stores means?
- energy stores keep growing
- overshot and no more reserves
Low-Energy stores means?
population grows quickly, overshot (a little bit) and stay near carrying capacity
Small population also have high risk of extinction because?
of Demographic stochasticity: random variation in birth and death rates
and of Environmental stochasticity; such as changing in weather
Positive Density Dependent factors cause small population to grow quickly only when?
all individuals have equal birth rate and likelihood of dying based on Deterministic model
- so small population have higher extinction probability in Short Term
