LIFE ON THE EARTH (Part 1)

 LIFE ON THE EARTH

Biodiversity and the Distribution of Life 

An ecosystem is a natural biological area made up of all living things (community) and their non-living environment. 

The variety of things which can live in an ecosystem (biodiversity), and how they are spread out (distributed) can be affected by both biotic and antibiotic factors.

Biotic factors involve living organisms e.g.

1.Space

2. Food supply

3. Water supply 

4.Disease

5. Predators 

6.Build up of toxic waste in the environment

Anbiotic factors are non-living variables in the environment that affects the organisms living there e.g.

• Light intensity
•  Soil/water pH 
• Temperature
•  Soil moisture
•  Flow rate 
• Slope 
• Weather 
• Climate 
• Depth of Soil
•  Underlying rock 

Human activities which can affect biodiversity in an ecosystem. 

Over-fishing

o This can lead to destruction of stocks and local extinction.

o This is usually controlled by restricting the numbers of fish that can be caught (quotas) 

o Public are encouraged to eat less well known fish to preserve stocks of cod and herring. 

Untreated sewage is a source of fresh water pollution

o Micro-organisms in the sewage use the sewage as an energy source (food) 

o They multiply rapidly 

o They use up the oxygen in the water for their respiration 

o Organisms that require oxygen cannot survive.

o Organisms that don’t require oxygen increase in number. 

o Further downstream the food in the sewage is used up and gradually the river returns to normal. 

o In highly polluted conditions, there is a reduction in the number of species that can survive. 

Acid rain

o Coal and oil produce oxides of sulphur and nitrogen when burned. 

o The oxides of sulphur and nitrogen dissolve in the moisture in clouds 

o This produces acid which falls as rain 

o Fish and trees are killed.

Climate change can be caused by two pollutants:

o Domestic (household) e.g. sewage, litter, car exhaust fumes and smoke. 

o Industrial e.g. smoke, carbon dioxide and poisonous chemicals. 

1. Fossil fuels (coal, oil & gas)cause pollution when burned 
2. Coal is the worst, gas is the least damaging 
3. All fossil fuels release carbon dioxide when burned. 
4. This prevents heat escaping and results in the greenhouse effect 
5. Heat is trapped in the atmosphere instead of passing out to space overnight. 
6.  The world warms up. 
7. Ice caps melt, sea levels rise and weather patterns are disrupted. 
8. Alternative energy sources such as wind, wave, hydroelectric, and solar (sunlight) can reduce the volume of CO2 produced.

Intensive agriculture (farming) e.g. fertilisers, pesticides and slurry (see subtopic 5 for more information).

Over-Grazing 

1. too many cattle on poor land 
2. Plants are killed right down to the roots 
3. The soil isn’t held together 
4. Erosion of the soil occurs 
5. Leading to desertification

Deforestation

1. Rainforests are destroyed to grow cash crops, e.g. coffee or tobacco. 
2. This results in loss of species through habitat destruction
3.  May disturb the climate 
4. To improve the situation farmers may be given money to prevent growth of cash crops 
5. Native hardwood trees, e.g. teak and mahogany, can be replanted Rainforest can be protected by law. 

Oil and Chemical spills

1.  Can destroy habitats and damage wildlife on land and sea.

Organisms and the role they play in their ecosystem

• The natural world is filled with plants and animals, each with their own special job or niche. A niche is the role played by an organism in the natural world. 
• Animals and plants all have a special role in making natural communities work and stay healthy. Some animals, like the pileated woodpecker, are insect eaters. 
• They control insect populations in a community. 
• The pileated woodpecker eats carpenter ants. It chisels them out of trees with its beak. 
• Without animals like the woodpecker, insect populations could grow out of control. 

Biomes 

There are large areas (often in different parts of the world), which have similar animal (fauna) and plant life (flora) living there. These geographical areas will experience similar temperatures and rainfall, and are referred to as Biomes.