Populations Flashcards
What is a population
A group of interbreeding individuals of the same species inhabiting the same area
Population distribution vs dispersion
Distribution concerns a populations geographic and ecological ranges
Dispersion describes the spacing of individuals in a pop. (clumped, uniform, random)
Population density and absolute density
- Number per unit area, unit volume, or unit of habitat
- Absolute density is the total count
What are the two ways quadrats or transects can be dispersed?
- Random - least biased (every member has equal chance of being selected)
- Systematic (Sample are chosen in a regular way - evenly/regularly distributed in a spatial context)
3 requirements for a reliable quadrat
1) The number of individuals in each quadrat must be determined exactly
2) Area of each quadrat must be known
3) Quadrats counted must be representative of the whole area (randomly sampled)
What is the capture-recapture method?
Capture animals, mark and release them. In subsequent capture, the proportion marked should be representative of the proportion marked in the entire population
What are important features of a tag on an animal?
- Longevity
- Visibility
- Effect on animal (can’t influence animal life)
What is capture recapture formula?
(Marked on 1st capture/Total population) = (Marked on recapture)/(total on recapture)
What are three main assumptions of the capture-recapture method?
- Marked and unmarked animals are captured randomly
- Marked animals are subject to the same mortality rate as unmarked animals
- Marks are not lost or overlooked
What is age structure?
The proportion of individuals in each age group is called the age structure of the population
What three population characteristics determine the rate at which females produce offsping?
- Clutch size
- Time between reproductive events
- Age at first reproduction
Potential longevity vs realized longevity
- Potential longevity is the maximum life span attainable by individuals of a particular species
- Realized longevity is the average longevity of individuals in a population under real environmental conditions
What is alpha diversity?
Number of species found within a small homogeneous area
What is beta diversity?
Rate of change in species composition across habitats or among communities
- quantitative measure of diversity of communities that experience changing environments
What is gamma diversity?
Changes in richness across larger landscape units