populations in ecosystems

Question 1

Define community.

Answer 1

All the different species that live in one area and interact with each other.

Question 2

Define ecosystem.

Answer 2

All the living organisms found in one area, combined with non-living aspects of their environment. Can vary from very large to very small.

Question 3

Describe biotic and abiotic factors, giving examples.

Answer 3

Biotic = living features of an ecosystem e.g. predators, disease.
Abiotic = non-living features of an ecosystem e.g. light, temperature.

Question 4

Define habitat.

Answer 4

The place where an organism lives within an ecosystem.

Question 5

Define a niche.

Answer 5

The role of a species within its habitat, consisting of both its biotic interactions e.g. what it eats, and abiotic interactions e.g. time of day it is active.

Question 6

What is meant by carrying capacity?

Answer 6

The maximum size of a population an ecosystem can support.

Question 7

Name four abiotic factors that affect population growth.

Answer 7

1. Temperature.
2. Light.
3. pH
4. Water/humidity.

Question 8

What is meant by intraspecific and interspecific competition?

Answer 8

Intraspecific = competition between organisms of the same species.
Interspecific = competition between organisms of different species.

Question 9

What resources might organisms compete for?

Answer 9

Food, water, shelter, minerals, light, mates (intraspecific only).

Question 10

Describe the pattern of a typical predator-prey relationship in terms of population change.

Answer 10

Prey is eaten by predator, resulting in predator population increasing and prey population decreasing.
Fewer prey means increased competition for food, so predator population decreases.
Fewer predators means more prey survives, and the cycle begins again.

Question 11

How are quadrats used for estimating population size?

Answer 11

Can be placed on grid coordinates, or at intervals along a belt transect. Results reported as either percentage cover or frequency. For slow-moving or non-motile organisms.

Question 12

How is mark-release-capture used for estimating population size?

Answer 12

A sample of a species is captured, marked, and then released back into the same area they were caught.
After a certain period of time another sample of the species is captured, and the number of marked organisms are counted.
For motile organisms.