Ecosystems

Ecosystems

1. Succession

   • Net Primary Productivity (NPP) = The total amount of energy transferred from sunlight to chemical potential energy (biomass) less any used in respiration.
   • Succession = When changes to the environment causes the plant and animal species to change.
   • Primary Succession: This is where life has to re-establish from bare rock.
   • Secondary Succession: Disturbance but the soil remains. This could be due to a forest fire. Pioneer species come in, then intermediate.
   • Climax stage: What happens after succession.

2. Population Sustainability

   • A limiting factor is an environmental resource or constraint that limits population growth. These are abiotic and biotic factors.
   • Population growth curve - This has three stages. Stage 1 - Lag phase where a small population is reproducing. Here the birth rate is higher than the death rate. This is a period of slow growth.
   • Log phase - A period of rapid growth. The population increases exponentially. Here there are no limiting factors.
   • Stationary phase - Population growth is prevented by external constraints. Here population size is generally stable but it can fluctuate.

3. Competition

   • Interspecific competition - competition between different species.
   • Intraspecific competition - competition between members of the same species.
   • Interspecific competition results in the decline in resources for both populations. Therefore less energy for growth and reproduction.
   • The less adapted species will be outcompeted.
   • Intraspecific variation - The availability of the resource determines the population size. Stage 1 - When a resource is plentiful , all organisms have enough of the resource to survive and reproduce. Stage 2 - Increased population means there are many more individuals sharing the same number of resources. So population decreases in size. Stage 3 - Less competition means less competition for the same resources. So population grows again.

4. Ecosystems

   • Ecology: The name given to the study of relationships between organisms and their environment.
   • An ecosystem is the area where living organisms and non-living conditions interact with each other.
   • Abiotic factors: Soil pH, temperature, light intensity, humidity, oxygen and edaphic (soil).
   • Biotic factors: Disease, invasive species and reproduction.

5. Energy Transfer

   • 1-3% of the sun's light is captured by the plants/algae.
   • 90% if the sun's energy is reflected by dust/clouds or absorbed by the atmosphere.
   • Light may not fall on a chlorophyll molecule.
   • A factor, such as low CO2 levels will inhibit photosynthesis, therefore the sun's energy isn't used for photosynthesis.