Populations in ecosystems

Question 1

What is an ecosystem?

Answer 1

All the organisms living in a community and their interaction with the abiotic conditions.

Question 2

What are the biotic conditions?

Answer 2

The living features of an ecosystem.

Question 3

What are the abiotic conditions?

Answer 3

The non-living features of an ecosystem.

Question 4

What is a community?

Answer 4

All the populations of all the species living in a particular area at a particular time.

Question 5

What is a population?

Answer 5

All the organisms of one species in a habitat.

Question 6

What is a habitat?

Answer 6

The place where an organism lives.

Question 7

What is a niche?

Answer 7

The role of a species within a habitat.

Question 8

What happens if two species occupy the same niche?

Answer 8

They will compete with each other. One species will be more successful than the other until only that species is left.

Question 9

What is an adaptation?

Answer 9

A characteristic an organism has that makes them more likely to survive breed and reproduce.

Question 10

What is natural selection?

Answer 10

If an organism has an allele that codes for an advantageous characteristic they are more likely to survive, reproduce and pass on that allele to their offspring. This means the offspring is more likely to survive reproduce and pass on those genes as well. Over time the frequency of that allele increases and this leads to evolution.

Question 11

What is the population size?

Answer 11

The total number of organisms of a species in a habitat.

Question 12

What is the carrying capacity?

Answer 12

The maximum population size of a species that an ecosystem can support.

Question 13

What happens to the population size if the abiotic conditions are ideal?

Answer 13

The organisms grow quickly and reproduce successfully. This means the population size increases.

Question 14

What biotic conditions affect population size?

Answer 14

1. Interspecific competition.
2. intraspecific competition.
3. Predation-prey relationships.

Question 15

How does intraspecific competition affect population size?

Answer 15

Organisms of the same species will compete for the same resources. This will lead to there being a shortage of those resources. This means the organisms of that species won’t be able to grow and reproduce successfully. This decreases the population size. This decrease can then lead to an increase in population size as more resources will be available for the other members of the population.

Question 16

How does interspecific competition affect population size?

Answer 16

If organisms of different species compete for the same resources the resources available to both populations will reduce. This means both populations will have less food and energy for growth and
reproduction so the population sizes will be lower for both species. One species will be better adapted to the environment meaning it will outcompete the other species.

Question 17

How does predation affect population size?

Question 18

Why should samples be random?

Answer 18

To avoid bias

Question 19

Why must you do repeats when investigating a population of a species?

Answer 19

1. To make sure that any patterns are not due to chance.
2. So you get sufficient data.
3. So you can calculate a mean and use it to make comparisons with other data.

Question 20

How do you use a quadrat?

Answer 20

1. Place it in an area.
2. Measure the species frequency, which is how many times a species is present in the quadrant.
3. You can also measure the percentage cover.

Question 21

What is a transect used for?

Answer 21

To find out how organisms are distributed across an area.

Question 22

Describe the mark release-recapture method.

Answer 22

P= (number caught in first sample x number caught in the second sample)/ number marked in the second sample

Question 23

What is succession?

Answer 23

The process by which an ecosystem changes over time.

Question 24

Where does primary succession take place?

Answer 24

On land that is newly formed or exposed.

Question 25

Describe primary succession.

Answer 25

1. A pioneer species colonises a hostile environment.
2. The pioneer species dies and the dead organic matter is broken down by decomposition which adds nutrients to the soil.
3. This change in abiotic conditions makes the environment less hostile so new, larger organisms can grow there.
4. The new species also changes the abiotic conditions when it dies and this allows even bigger organisms to grow in that environment.
5. Some species can change the environment so it becomes less suitable for the previous species.
6. Those species that are better adapted outcompete the organisms that are already there and become the dominant species.
7. As time goes on the ecosystem becomes more complex.
8. This continues until you reach a climax community which won’t change much.

Question 26

What is a climax community?

Answer 26

The ecosystem is supporting the largest and most complex community of organisms it can.

Question 27

Where does secondary succession occur?

Answer 27

On land that’s been cleared of all plants but still has its soil.

Question 28

What is conservation?

Answer 28

The protection and management of species and habitats in a sustainable way.

Question 29

What does sustainable mean?

Answer 29

That there are enough resources to support the people today without reducing the ability of people in the future to meet their own needs.

Question 30

Why is succession sometimes interrupted by humans?

Answer 30

To conserve the ecosystem in its current stage of succession.