CH19 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

Question 3

Describe biotic factors

Answer 3

Living features of an ecosystem

Predators, disease

Question 4

Describe abiotic factors

Answer 4

Non-living features of an ecosystem

Light and temperature

Question 5

Define habitat

Answer 5

The place where an organism lives within an ecosystem

Question 6

Define niche

Answer 6

The role of a species within its habitat, consisting of both its biotic interactions and abiotic interactions

Question 7

What is carrying capacity

Answer 7

The maximum size of population an ecosystem can support

Question 8

Name 4 abiotic factors that affect population growth

Answer 8

Temperature
Light
pH
Water

Question 9

What is intraspecific competition

Answer 9

Competition between organisms of the same species

Question 10

What is interspecific competition

Answer 10

Competition between organisms of different species

Question 11

What resources might organisms compete for

Answer 11

Food
Water
Shelter
Minerals
Light
Mates

Question 12

Pattern of typical predator-prey relationship in terms of population change

Answer 12

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 survive, cycle begins again

Question 13

How are quadrats used to estimate population size

Answer 13

Can be placed on grid coordinates
Results reported as either % cover or frequency
For slow-moving or non-motile organisms

Question 14

How is mark-release-recapture used to estimate population size

Answer 14

Sample of species is captured, marked and released into the same area that are they were caught
After certain period of time another sample of species captured and number of marked organisms counted
Motile organisms

Question 15

Equation for mark-release-capture

Answer 15

Estimated pop. size =

(total num of individuals in sample 1 x total num of individuals in sample 2) / number of marked individuals recaptured

Question 16

What assumptions are made

Answer 16

Marked individuals distribute evenly
No migration in or out of the population
Few births or deaths
Method of marking does not affect survival
Mark does not come off

Question 17

Why are ecosystems described as being dynamic

Answer 17

Populations constantly rise and fall
Any small change can have a large effect
Biotic and abiotic factors may alter the conditions of the ecosystem

Question 18

What is meant by primary succession

Answer 18

Where an area previously devoid of life is colonised by a community of organisms

Question 19

Process of primary succession

Answer 19

Pioneer species can survive harsh conditions and colonise the area
They change abiotic factors of their environment
Over time, this allows more complex organisms to survive

Question 20

What is climax community and how is it reached

Answer 20

The final stage of succession where the ecosystem is balanced and stable
Reached when the soil is rich enough to support large trees and the environment is no longer changing

Question 21

How might a species alter the environment that develops during succession

Answer 21

A species may improve the environment to make it more suitable for other species
A species may worsen the environment by making it less suitable for other species

Question 22

Define conservation

Answer 22

The protection and management of species and habitats, in order to maintain biodiversity