Populations in Ecosystems

Question 1

What is an ecosystem?

Answer 1

A community and the non-living components of its environment.

Question 2

What is a community?

Answer 2

All the populations of different species living in the same place at the same time.

Question 3

What is a niche?

Answer 3

1. The specific role of a species within its habitat.
2. Governed by its adaptation to both abiotic and biotic conditions.

Question 4

What is the advantage of species occupying different niches?

Answer 4

1. Less competition for food and resources.
2. If two species tried to compete for the same niche, one would outcompete the other.

Question 5

Define the term abiotic conditions.

Answer 5

The non-living components of an environment.

Question 6

POPULATION SIZE

Question 7

Define the term carrying capacity.

Answer 7

The maximum stable population size that an ecosystem can support.

Question 8

What factors affect carrying capacity?

Answer 8

Abiotic: Light intensity, temperature, soil pH, humidity and mineral content.
Biotic: 1. Interspecific competition.
2. Intraspecific competition.
3. Predation.

Question 9

Define the term interspecific competition? Give an example of the things they compete for.

Answer 9

1. Competition between members of different species.
2. Light, Water, Oxygen, Nutrients.

Question 10

Define the term intraspecific competition? Give example of the things they compete for.

Answer 10

1. Competition between organisms of the same species.
2. Territory, Mates, Food.

Question 11

Define the term predation.

Answer 11

Predators kill and eat prey.

Question 12

Explain how abiotic factors may affect the population size.

Answer 12

1. If the conditions are favourable, organisms are more likely to survive to reproduce.
2. Increasing abiotic factors like light intensity increases the rate of photosynthesis. Increasing nitrates increases protein production. Increasing phosphates increases phospholipid production in plants.
3. This increases the population size of the variety of plant species.
4. This increases the number and variety of habitats, niches and food sources for animals.
5. This increases the population size of a variety of animal species.

Question 13

Explain how interspecific competition may affect the population size.

Answer 13

1. It reduces the resources available for both species, meaning both species are less likely to survive and reproduce.
2. This causes the population size of both species to decrease.
3. If one species is better adapted to its environment, it will outcompete the other.
4. This causes the population size of the less well-adapted species to decrease.

Question 14

Explain how intraspecific competition may affect the population size.

Answer 14

1. As the population size increases, the resource availability for each organism decreases and competition increases.
2. This means the organisms are less likely to survive and reproduce, and the population size decreases.
3. As the population size decreases, the resource availability per organism increases, and competition decreases.
4. This means organisms are more likely to survive and reproduce, meaning the population size decreases.

Question 15

Explain how predation may affect the population size.

Answer 15

1. The prey population increases, so the predators have more food.
2. This means they are more likely to survive and reproduce.
3. The predator population size increases, so more prey are being eaten.
4. This means fewer prey survive and reproduce.
5. The prey population decreases, so the predators have less food.
6. This means they are less likely to survive and reproduce.
7. The predator population size decreases, so fewer prey are being eaten.
8. This means more of the prey survive and reproduce. This causes the prey population size to increase.

Question 16

SUCESSION

Question 17

Define the term succession.

Answer 17

On newly formed land with hostile abiotic conditions.

Question 18

Describe the process of primary sucession?

Answer 18

1. A pioneer species colonises the newly formed land with hostile abiotic conditions. They can do this as they have adapted to survive in those hostile environmental conditions.
2. The pioneer species changes the abiotic conditions and makes them less hostile.
3. Other species can now live in the environment.
4. These species then change the biotic conditions. This happens when they die and are broken down by saprobiotes to release nutrients into the soil.
5. The pioneer species is outcompeted as the new species could be better adapted to live in the environment.
6. New species continue to grow, change the environment and make it less suitable for the previous species to live there.
7. A climax community is eventually reacheded.

Question 19

What is a climax community?

Answer 19

The largest and most complex community that an ecosystem can support. There will be no major changes to this community.

Question 20

Where does secondary succession occur?

Answer 20

In an environment where there is already a layer of soil.

Question 21

CONSERVATION

Question 22

Define the term conservation.

Answer 22

Meeting the needs of the current population while protecting valuable resources so they are available for future generations.

Question 23

What are some methods of conservation?

Answer 23

1. Disrupting succession to maintain a habitat in its current state.
2. In situ conservation: Making a protected area in the natural habitat of a species. This benefits both the species and the habitat.
3. Ex-situ conservation: Removing a species from its natural habitat. This protects the species from harm but reduces genetic diversity and biodiversity in the habitat.