Topic 10.3 Changes in ecosystems

Question 1

What is meant by primary succession?

Answer 1

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

Question 2

Summarise the process of primary succession

Answer 2

• Pioneer species, able to survive harsh conditions, colonise the area
• They die, decompose, and add nutrients to the ground
• Over time, this allows more complex organisms to survive

Question 3

What is the climax community and how is it reached?

Answer 3

The final stage of succession, where the ecosystem is balanced and stable. It is reached when the soil is rich enough to support large trees or shrubs, and the enviroment is no longer changing.

Question 4

What is meant by plagioclimax?

Answer 4

Where human intervention prevents the expected climax from forming. This may be done in the interest of conservation.

Question 5

Define biotic factors and give an example

Answer 5

Living feature of an ecosystem e.g. predators, disease.

Question 6

How can biotic factors affect population size?

Answer 6

• Predator/ prey populations oscillate
• Disease reduces population size
• Availability of mates can either increase or reduce population size

Question 7

Define abiotic factors and give an example

Answer 7

Non-living features of an ecosystem e.g. light, temperature.

Question 8

How can abiotic factors affect population size?

Answer 8

• Light effect circadian rhythms, influences plant growth
• Temperature affects enzyme activity
• Adverse weather conditions require certain adaptations
• Availability of water an oxygen

Question 9

What is meant by intraspecific and interspecific competition?

Answer 9

Intraspecific = competition between organisms of the same species

Interspecific = competition between organisms of different species