3.7.4 Populations in ecosystems

Question 1

Define community

Answer 1

All the different species that live in one area and interact with eachother

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 and abiotic factors with examples

Answer 3

Biotic = living features of an ecosystem, predators, disease
Abiotic = non living features of an ecosystem, 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 eg what it eats, what time of day its active

Question 6

What is meant by carrying capacity

Answer 6

The maximum size of population an ecosystem can support

Question 7

4 abiotic factors that affect population growth

Answer 7

Temperature
Light
pH
Water/humidity

Question 8

What is meant by intraspecific and interspecific competition

Answer 8

Intraspecific = competition between organisms of 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 (intra spec only)

Question 10

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

Answer 10

Prey is eaten by predator, predator population increasing and prey population decreasing
Fewer prey means increased competition for food, so predator population decreases
Fewer predators means more prey survives so prey population increases and cycle repeats

Question 11

How is capture, release, recapture used for estimating population size

Answer 11

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

For motile organisms

Question 12

Equation for capture recapture

Answer 12

total individuals first sample x total in second sample / marked individuals recaptured

Question 13

What assumptions does capture recapture make

Answer 13

No births or deaths
Mark doesn’t come off
Method of marking doesn’t affect survival

Question 14

Why are ecosystems described as being dynamic

Answer 14

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

Question 15

What is meant by primary succession

Answer 15

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

Question 16

Summarise the process of primary succession

Answer 16

Pioneer species colonises area with harsh conditions
They change abiotic factors eg decomp adds nutrients to ground
Allows small plants and grasses to survive, as they decomp creates more nutritious deeper soil
Over time, this allows more complex organisms to survive, they outcompete pioneer species and they die out
Biodiversity increases as conditions improve and leads to a climax community with large trees

Question 17

What is the climax community and how is this reached

Answer 17

The final stage of succession, the ecosystem is balanced and stable
Soil is rich enough to support large trees or shrubs
Environment is no longer changing

Question 18

Define conservation

Answer 18

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

Question 19

How might succession be managed in order to aid conservation

Answer 19

Sometimes succession needs to be prevented in order to preserve an ecosystem at a certain point