Lecture 7: Density Dispersion Demographics Flashcards
What is population ecology
Explores how biotic and abiotic factors influence the abundance dispersion and age structure of populations
ex. the number of turtle hatchlings that survive their first journey to the ocean is affected by both predation and light
Define population
a group of individuals of a single species living in the same general area
ex. Members of a population can be vague, people in a grocery store at a given time, students who attend UCR, people in southern California
What are the four emergent properties of population –
size, density, dispersion, and rate of change
What adds to the population size
births and immigration
What removes individuals from the population size
deaths and emigration
How do we measure density
A) Count
B) Count subsamples and extrapolate
C) Mark - recapture
D) Use proxy, nests, feeders, tracks
Why do scientists choose to use estimates or proxy measures or density instead of counting all individuals
Estimates and proxy takes less time, helps scientists to avoid disturbing fragile ecosystems
How are the individuals in the population distributed over the landscape or in the water column?
RANDOM dispersions
What are the causes of random dispersions which are very rare in nature
Caused by unequal distribution of resources, dispersal probabilities
ex. two toed sloths, some spiders
What is clumped dispersion
Individuals are more aggregated than in a random distribution
Causes: Resource availability, mating behavior, and group defense against predators
What is uniform dispersion
Individuals are more evenly spaced than in a random distribution and individuals are less likely to be found in close proximity to other individuals
Causes: (negative) social interactions, (territoriality - define of bounded space against other individuals), competition
What is demography
stdy of the vital statistics of a population and how they vary with age
What is a life table?
Age specific summary of the vital statistics of a population
What is a cohort
A group of individuals in a population born about the same time
What is survivorship (Ix)
Proportion of individuals born that survives to age x
