Ch14: Populations Flashcards
Define population
A group of individuals of the same species that occupy the same spatial area, interacting with each other and being affected by (or using) the same resources
What are the 4 properties of a population? Describe them
1) Boundary: the spatial area for inclusion
- Natural, arbitrary or match study requirements
2) Size: dynamic/changing = affected by
- births, deaths, emigration and immigration
3) Distribution: arrangement of species:
- Clumped: if there is clumping of resources or social structure (these can be uniform or random)
- Uniform: equally spaced because of high competition
- Random: no regard for other species (high resources) = little competition
4) Structure: different ages + sex ratio (can influence dynamics of population)
What are 4 reasons why we may need to manage populations?
1) Endangered species
2) Pest control
3) Harvested species
4) Disease dynamics
Describe the sampling method: full census, and why it may be hard to complete
Where we count every individual in a population
- there could be too many organisms or too hard to see them
Describe sampling estimate;
sections plots of a boundary; count all individuals within some lots
- estimate population density
- extrapolate to entire boundary
What is the difference between accuracy and precision?
Accuracy: How close our data is to the true or actual value
Precision: How close our replicates are to each other
what would be the reason for low accuracy and high precision, and high accuracy with low precision:
low accuracy and high precision: another factor is acting (sampling error)
high accuracy with low precision: okay its just the estimate of true value is less reliable
Equation for abundance of individuals (N)?
N = n/P
where n = number of individuals we see
P = probability of detection
Define mark recapture:
capture individuals, mark them, release them and allow time for them to mix into the population, and then recapture and see how many marked individuals you capture.
If we capture 12 (n) individuals and mark them, let assimilate, and catch 10 more, but only 6 are marked, what is the probability of detection (P) and thus what is the estimated abundance (N)?
P= 6/10 = 0.6
N = n/P = 12/0.6 = 20 individuals
What are the assumptions of mark recapture? (Hint: there are 4)
1) Closed population: no immigration, emigration, births or deaths + individuals need time to re-enter and spread in populace
2) Mark do NOT affect mortality rate: they do NOT increase or decrease mortality
- increase = overestimate abundance
i decrease = underestimate abundance
3) Marks remain for entire study: distinction between captured and uncaptured is importance
- if fall off = overestimate population
4) Probability of recapture remains consistent: the baits are NOT associated with positive (“trap happy”) or negative (“trap shy”) connotations
What happens if you break the assumptions of mark recapture?
You introduce bias: leading to over/under estimation of abundance
- modify analysis: open-population methods = requires deeper understanding of populace demography
Define artificial marks:
placed on animal by ecologists + cannot impact behaviour of individuals, otherwise bias is introduced
Define natural marks:
patterns or pigmentation or other natural identifying features: MUST persist entirety of study (NOT change) (relatively consistent)
What are signs that act as indices of animal presence? What is the benefit of using this?
Signs become an index for relative abundance (ie~ burrowing, scat, footprints (trails))
This method is LESS intrusive, and less likely to influence survival + behaviour of individuals = better estimate of abundance + more ethical
