1. E6 COMMUNITIES ARE CONTINUALLY UNDERGOING CHANGE
Chapter 22
E6 COMMUNITIES ARE CONTINUALLY UNDERGOING CHANGE

2. Resources and energy available influence productivity of a community
E6.1 Illustrate how community change may involve succession over time which leads to changes in the mixture of species
Resources and energy available influence productivity of a community
Type of conditions also has influence on the community and habitats
Organisms occupy specific habitats because their needs are met and have adaptations that enable them to survive there
Succession is the gradual process by which the species composition of a community changes-brought about by modification of the habitat caused by the organisms living there

3. As a result of living in an environment, organisms may change their habitat in a variety of ways:
They may provide food or shelter for others. Trees trap the sun’s energy and provide food and shelter for various bird species
They may change the soil structure by causing the breakdown of rock or increasing the organic matter in the soil
They may decompose dead material and make nutrients available for others to use.

4. succession
If an area is devoid of all life and colonisation begins from scratch- succession can be studied
New sand dunes
Lava flow as in the Hawaiian Islands
Hardy species that have special adaptations to enable them to survive harsh environments move in first- lichens
these break down rock/bacteria break down the lichen and new soil is formed
This is the first stage of succession-soil formation

5. Lichen and succession communities

6. Primary /secondary succession
Primary succession is where there is nothing and life forms after creation of new soil as stated-
mosses survive these new conditions- from the lichen forming soil- then as more decomposition occurs, new grasslands, then plants and shrubs, then birds move in and insects
seeds are dispersed, more species grow, havens and habitats develop for more and more species as do the food resources

7. Secondary Succession
Changes occur in an environment that has been exposed to a disaster like fire, logging etc
There is some basis to support life remaining and maybe some life itself….so a community and environment are rebuilt on the foundations remaining…small animals move in and then larger and so , new plants grow from seed dispersal by the new organisms coming in.
Succession and biodiversity-bozoneman

8. Ecologists view succession as the result of competition between organisms
In new or disturbed habitats those species with higher reproductive effort tend to have the advantage
As an ecosystem develops those organisms with low reproductive effort and longer lifespans proliferate and take over
Sometimes established ecosystems still undergo succession if damaged in some way like fire, flood or extreme weather conditions
Secondary succession is quicker than primary as a greater mix of organisms is available

9. Characteristics of succession communities
As ecosystem matures there is more Biomass, but productivity decreases
There are usually more species in mature ecosystems
As the ecosystems matures the number of heterotrophic species tends to increase more than the number of autotrophic species
Mature ecosystems are more efficient at recycling nutrients
Mature ecosystems have organisms that tend to be more specialised

10. Biodiversity can be considered at three levels:
E6.2 Explain why biodiversity is essential for the perpetuation of communities
Biodiversity can be considered at three levels:
Genetic diversity
Species diversity
Ecosystem diversity
Biodiversity refers to the variety of life forms that are found in the biosphere, the different sets of genes they contain and the variety of ecosystems found in different habitats.

11. Australia Geographically isolated
Highly endemic fauna and flora- found no where else in the world
High level of species richness
Arid climate/ poor soils- unique adaptations have arisen with various species
Thick leaves/waxy cuticles
Urine concentration in hopping mice etc
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12. ECOSYSTEM RELATIONSHIPS:
Species diversity must be maintained for the growth and productivity of communities
Communities-several trophic levels
Producers trap suns energy-herbivores feed on them-and so on- each organisms having its place in the food chain or web
Organisms then interact with each other in various ways-predator/prey relationships

13. Mutualism/predator/prey relationships etc
In an ecosystem some organisms offer benefits to one another
No organisms are in isolation they work together/interact for survival
Bacteria and fungi recycle
Nitrogen fixing bacteria and some plants have a crucial relationship in terms of survival

14. Co-evolution
Australian plants and animals living in the same area often have unique interactions resulting on co-evolution
This means the evolution of two species occurs in tandem- they depend on each other
Many insects evolved side by side with plants to develop pollination techniques??? (mm)
Some orchids are shaped like the wasps that pollinate them
Some fungi form symbiotic relationships with plants and when destroyed the plants are adversely affected

15. Ecosystems are not static
Constantly changing
Populations and communities shaped by forces of evolution
Disturbed areas- faster reproducing species have the advantage, colonise first causing changes to the ecosystem and allow other organisms to colonise
Biodiversity and genetic variability within a species as stated is essential for species survival
When organisms are selcted to survive for their differences which may be better adapted to a particular habitat- NATURAL SELECTION