1. communities

2. A BIOTIC FACTOR is An abiotic factor is
the living part of an ecosystem
e.g. competitors, parasites, pathogens, predators, symbionts
An abiotic factor is
the non-living part of an ecosystem
e.g. wind, humidity, air temp, light intensity, pH, dissolved O2 nutrients

3. i.e. all of the different species ….
A population is
all organisms of the same species living in the same place at the same time
A community is
the biotic component of an ecosystem AND involves interactions between autotrophic and heterotrophic populations
i.e. all of the different species ….

4. An ecosystem is the environment is
A community of different species which are interdependent and interact with each other AND their abiotic environment, involving energy flow, nutrient and gas exchanges
i.e. the biotic and abiotic interactions
the environment is
The biotic and abiotic factors that surround an organism

5. The place where an organism lives
A habitat is
The place where an organism lives
A niche is
The way in which an organism carries out its life cycle and the factors in its habitat

6. community
development

7. The species composition in a community changes over time and is known as
succession

8. An area of bare ground is a harsh environment in which the abiotic factors are dominant.
With time the area will go through a series of stages (called seres)
The changes that occur are summarised below:

9. Initially pioneer plant species that are able to tolerate harsh conditions grow
changing the environment by
adding humus, nutrients such as nitrates or making the soil more water retentive.
This allows different plant species to colonise the area
creating more habitats and
bringing more animals into the area, increasing species diversity.

10. As there are more food chains, food webs become more complex and the community becomes more stable
eventually forming a stable climax community.

11. In the early stages of succession,
populations rapidly replace one another.
The climax community is stable and
dominated by long-lived plants such as trees.

14. The beach

15. Rocky Shore Web

16. Types of climax climatic climax
The climate determines the dominant species e.g.
deciduous woodland in lowland UK
tundra in northern Canada
rainforest in central south America

17. biotic climax
Other organisms (usually humans) determine the dominant species and hence the species in the climax community e.g.
Burning heather and grazing sheep prevents the development of young trees and so halts the natural succession into woodland

18. primary succession secondary succession
This is a relatively slow process of community development in a previously unoccupied area
secondary succession
This is a predictable, repeatable and faster process of community development in an area where the climax community was destroyed by fire, flooding, wind damage or human interference.

19. Primary and Secondary Succession - YouTube
Volcano! Surtsey and Heimaey