3.2.3 Changing Ecosystems

Question 1

What is ecological succession?

Answer 1

The process of gradual evolution of an ecosystem.

Question 2

Describe primary succession in ecological succession.

Answer 2

Primary succession is the development of an ecosystem when new land is formed or bare rock is exposed. Thus a habitat is colonised for the first time.

E.g. volcanic eruption= new rock is formed (potential)

-weathering and other natural forces break down the volcanic rock so pioneer species can grow

Question 3

Describe secondary succession in ecological succession.

Answer 3

A previously occupied area is recolonised after a disturbance that destroys its community

E.g. forest cleared by wildfires

1. Fire destroys most vegetation and animals can’t flee
2. Nutrients return to the ground (through ash) so soil is rich
3. Recolonisation occurs quickly

Question 4

What are pioneer species

Answer 4

Pioneer species are species like plants and lichens which require minimal soil requirements to grow. Thes species break down the mineral (rock –> soil) so less hardy species can grow and eventually replace the pioneer species

• this is a cycle that repeats
• takes a long time

Question 5

What are the features of a pioneer species that make them effective colonisers

Answer 5

• able to tolerate extreme conditions
• fix nitrogen levels
• rapid spore and germination
• use wind to pollinate or/and speed dispersal
• photosynthesise
• opportunists (r- strategists, lots of babies) that disperse rapidly (large no. of offspring with short life cycles)

Question 6

What are lichens and their lifecycle?

Answer 6

an organism between fungi and algae that produce acid that assist in erosion

• the rocks expand and contract in temperatures causing them to crack (soil breaking down)
• decomposing bacteria break down lichens (add organic material to soil)
• gradual soil makes rock unhopsitable for lichens
• new species take over, making soil richer (its a cycle you get it lol until an ecosystem is formed)

Question 7

List and understand human impact on biodiversity

Answer 7

-fires (flushes out prey, maintains grass lands for grazing animals)

-domesticating animals (forest cleared, overgrazing, decreasing soil fertility= more erosion)

-deforestation (loss of plants and animals)

-land degradation (depletion of nutrients)

-building dams (erosion, decreased biodiveristy, water temperature change, increased soil salinity)