Population

What defines a population in ecology?

A group of organisms of the same species living in an area at one time who can interbreed.

What happens to two populations of the same species that are geographically isolated for a long period of time?

They may develop differences in their characteristics and eventually become different species.

What is the method to estimate total population size using samples from a small area?

Count a sample from a small area and multiply this by the total area of the habitat.

What is Quadrat sampling used for in ecology?

A method to measure the population size of stationary organisms without bias.

• line or belt transects

What types of organisms is Quadrat sampling suitable for?

Sessile organisms like plants or very small moving animals.

What is the procedure for Random Quadrat Sampling?

1. Use a measuring tape to create a baseline

2. Generate random numbers to determine the distance along the tape

3. Quadrat is placed precisely at those locations determined by two random numbers

What formula is used to calculate Percentage Error?

Percentage Error = [(estimated value - actual number)/actual number] x 100.

What is the Capture-Recapture method used for?

To estimate the size of motile organisms (organisms that move around)

What are common methods used in Capture-Recapture?

Pitfall traps, pouters (aspirators), mammal traps, and nets.

Captrue-Recapture Procedure

1. Capture as many individuals as possible in the area occupied by the animal population using different methods

2. Mark each individual, without making them more visible to predators

3. Release all the marked individuals and allow them to settle back into their habitat

4. Recapture as many individuals as possible and count how many are marked and how many are unmarked

5. Calculate the estimated population size by using the Lincoln Index

What assumptions are made during the Capture-Recapture process?

• No migration

• No deaths or births

• Marked individuals mix back

• Marks remain visible

• Marks do not increase predation risk.

What is the Lincoln index formula for estimating population size?

Population size = (M x N)/R

M is marked individuals

N is total recaptured

R is marked recaptured.