Edexcel Biology Gcse - Biodiversity and the Effect of Human Interaction on Ecosystems Part 2

1) Nutrient load up: excessive nutrients from fertilisers are flushed from the land into rivers or lakes by rainwater.

2) Plants flourish: these pollutants cause aquatic growth of algae, duckweed and other plants.

3) Algae blooms, oxygen is depleted: algae blooms, preventing sunlight reaching other plants. The plants die and oxygen in the water is depleted

4) Decomposition further depletes oxygen: dead plants are broken down by bacteria decomposers, using up even more oxygen in the water.

5) Death of the ecosystem: oxygen levels reach a point where no life is possible. Fish and other organisms die.

Combustion of fossil fuels and other fuels releases carbon dioxide. This contributes to the greenhouse effect and leads to global warming. It also releases sulfur dioxide and nitrogen oxides which can cause acid rain. Air pollution can also be caused by tiny particulates from smoke which can cause smog. Some of the world's major cities like Delhi in India and Karachi in Pakistan have dangerously high levels of air pollution.

The rubbish we throw out that is not recycled goes into a land fill. These are huge holes in the ground into which our rubbish is dumped. Some things like batteries cannot be put into landfill sites because of the toxic chemicals they contain. They must be recycled. Other land pollution comes when some people dump rubbish in public or other private places, often to avoid paying for it to be disposed of. This is caused fly tipping and is illegal.

The larger the human population gets, the more land we require. More houses must be built, more resources found, more food must be grown and more waste is produced. This often means less space and fewer resources for other animals and plants.

Often biodiversity is significantly reduced when land is cleared for human uses, such as building, quarrying, farming and waste disposal. Think about the reduction in biodiversity, which occurs when an area of rainforest is cut down to grow crops.

For thousands of years humans have been deforesting small areas of woodland to build their own houses or grow crops to feed their families. However, in recent years the increase in the human population and development of industrial machinery has meant that much larger areas have been cleared. This is often by large companies who deforest to provide land for cattle, rice fields and growing crops for biofuels.

Conservation is the preservation of ecosystems and the organisms that live within them.

The increase in the human population and waste it produces, deforestation, peat bog destruction and global warming are all reducing biodiversity. Conservation helps reverse this. Conservation is the preservation of ecosystems and the organisms that live within them.

breeding programs to help preserve endangered species, like the panda

protection and development of new endangered habitats, often by making National Parks

replanting hedgerows because there is higher biodiversity in them than the fields they surround

reducing deforestation and the release of greenhouse gases

reforestation planting trees to replace those cut down

recycling rather than dumping waste in landfill sites

Human interactions within the ecosystem may have a positive impact on biodiversity such as conservation or a negative affect such as eutrophication. Negative effects include reduced populations, reduced biodiversity or extinction.

Conservation

reduced populations

reduced biodiversity

extinction

As the human population increases, we need more food and increased use of fertilisers has impacted on the biodiversity of aquatic environments through eutrophication. Nitrates in the fertilisers run off from fields into rivers and lakes causing the overgrowth of algae. The light is blocked so plants cannot photosynthesise so they die. This causes bacteria to decompose the plants and use up most of the oxygen in the water. Without oxygen, animals such as fish will die. This is a negative impact as the biodiversity of the river or lake will decrease.

Fish are farmed in large nets or tanks within lakes or in the sea.

Farm waste, chemicals, pathogens and parasites are released into the surrounding water, harming other marine life.

Carnivorous species of farmed fish, such as salmon, need high amounts of protein in their diet. They are often fed on wild fish, reducing their populations.

Sometimes fish can escape and compete with indigenous wild species and compete for resources, resulting in reduced biodiversity. Predators of the fish such as sea lions can become trapped in the nets and die.

A non-indigenous species does not live in an area and may be introduced by humans for a particular purpose such as removal of pest species or for hunting. However, the new species may out-compete or kill indigenous or naturally occurring species. These may be reduced in number, resulting in reduced biodiversity or maybe extinction.

Cane toads are native to South and Middle America but were introduced into Australia in the 1930s to control pests that ate sugar cane, an important crop.

the cane toads are poisonous to animals that eat it, reducing the number of predators

the toad eat insects, reducing their population

it competes with native species for food

Biodiversity

Extinction is when a species is wiped out forever.

Deforestation is cutting trees down to provide land for other uses.

Reduced number of habitats and decreased biodiversity

The human population is growing because there are more births than deaths.

Oxygen levels in the river or lake will decrease due to the bacteria using it up.

Carbon dioxide