Ch 6: Changes in Ecosystems

Question 1

What is ecological succession?

Answer 1

changes in the population of species present in a habitat. These changes impact the abiotic and biotic interactions in the community which in turn influence further changes in the species present and their population size

ALSO- communities change progressively over time, with one community being replaced by the next in the process of succession

Question 2

What are the main differences between primary and secondary succession?

Answer 2

Question 3

What is a climax community?

Answer 3

the end point in a community succession where the community has become relatively stable

• not all successions reach a climax community. A combination of factors such as fire or selective grazing herbivores can contribute to this
• deflected succession:* when a community is prevented from reaching a stable successional end point because of some sort of interference i.e. fire regimes

Question 4

What does natural disturbance lead to?

Answer 4

succession. The type of succession that will follow depends on the severity, type and extent of the disturbances

Question 5

What are the biotic effects of fire?

Answer 5

immediate

• loss of vegetation
• reduction of leaf litter
• decrease in animal numbers

subsequent effects

• heat of fire leads to some plant species regeneration from released seeds
• smoke particles and fire damage can stimulate regrowth
• these attract many mobile organisms

Question 6

What are the abiotic effects of fire?

Answer 6

• ash creates nutrient rich soil
• new open spaces offer max light availability but also remain vulnerable to effects of harsh sun or perlting rain

Question 7

What are fire regimes and what are they and example of?

Answer 7

a sequence of fires in an ecosystem

• in Australia, human intervntion disrupted regular succession to maintain a grassland state- example of deflected succession

Question 8

What is the process of eutrophication?

Answer 8

Process

1. fertilisers close to bodies of water, due to rain and run off, end up in the body of water
2. This increases the nutrient level (phosphorous/nitrogen) of the water body
3. The algae grows and can cover the top layer of the water body
4. Bacteria starts to decompose the algae which uses up a lot of oxygen, causing hypoxia
5. Other oxygen dependent organisms perish

Question 9

What is the impact of eutrophication?

Answer 9

Impact

1. algae starts to increase because of increased nutrients
2. increased cover of algae will decrease sunlight to producers under the surface, decreasing their productivity to photosynthesise
3. animals such as fish no longer have enough oxygen to perform respiration
4. many animals will perish (loss of biodiversity)

Question 10

What are some solutions to eutrophication?

Answer 10

Solutions

1. change fertiliser type (decrease nitrogen adn phosphorous)

+ decrease nutrient run off into body of water

• may decrease productivity for farmers
  2. remove algae

+ allow producers underneath to photosynthesise

• expensive
• when it rains, more nutrients will enter water bodies and algae will regrow