B18 Biodiversity and Ecosystems

Pollution

• Pollution kills plants and animals which can reduce biodiversity

Water Pollution

• Caused by the discharge of harmful substances into rivers, lakes and seas.
• Fertilisers are used by farmers to increase their crop yield, supplying extra minerals to their plants so they can grow better. However, these minerals can run off into waterways and lead to a process called eutrophication.
• Toxic chemicals from industries and mining can pollute waterways. These chemicals may be highly toxic and might accumulate in food chains to toxic levels.
• ppm - parts per million ppb - parts per billion
• Sewage and fertilisers entering waterways and toxic chemicals (pesticides and herbicides) entering waterways are examples

Eutrophication

• Fertilisers are washed off the land by the rainwater into rivers and lakes. The resulting increase in minerals in the water encourages the growth of algae, which forms a bloom over the water surface. This prevents sunlight reaching other water plants such as pondweed, which then die. Bacteria break down the dead plants and use up the oxygen in the water, resulting in the death of invertebrates and fish.
• Sewage may also pollute waterways. Sewage contains high mineral levels and can lead to eutrophication.

Land Pollution

• Herbicides increase crop yields by killing or inhibiting the growth of weeds, reducing the competition for resources such as minerals, space, and sunlight. Pesticides increase yield by killing off pests, such as small insects or plant pathogens, which would otherwise feed on or damage crops.
• Some of these chemicals can remain in the soil for long periods, polluting the land, and they may be washed up into rivers, lakes, and seas. There can also be consequences further up the food chains within an ecosystem - pollution disrupting food chains or accumulating to toxic levels.
• Examples of land pollution include household waste in landfill sites, buried nuclear waste, toxic chemicals (pesticides and herbicides)

Air Pollution

• Air pollutant: Smoke
• Source: Incomplete combustion of fossil fuels
• Effect: Tiny solid particles, called particulates, can damage the lungs when breathed in. They also reduce the light that reaches Earth resulting in a dimming and cooling effect. Soot is deposited on buildings and trees causing them damage. Global dimming, lung problems.
• Air pollutant: Acidic gases such as sulfur dioxide
• Source: Combustion of fossil fuels, eg coal, with sulfur impurities in them
• Effect: Contributes to acid rain. This can cause the weathering of buildings and damage to aquatic ecosystems and forests.

Decay

• Bacteria and fungi decay things
• Conditions for decay: Oxygen (for aerobic decay which is quicker), the right pH level, warm, moist

Deforestation

• Large scale deforestation in tropical areas has occurred to provide land for cattle and to grow crops for biofuels.
• Deforestation is when trees are cut down on a large scale. It is the destruction of forests by cutting down trees.
• Forests act as a carbon sink which means that they trap away lots of carbon. Therefore, when deforestation occurs, that carbon won't have anywhere to go so it gets released into the atmosphere. Burning wood also releases carbon dioxide. Trees take in carbon dioxide during photosynthesis.
• We could be destroying lots of plants which could be used as drugs due to deforestation.
• Deforestation reduces biodiveristy as if forests are cut down then lots of animals will lose their habitats. Forests and rainforests are vital as they provide habitats for different species.

Peat Bogs

• Peat bogs store carbon and are anaerobic and slightly acidic so decay is slow.
• Peat can be dried and used for fuel. It can also improve soil structure.
• Peat is formed over thousands of years by the growth of mosses and other plants which absorb and lock away carbon dioxide during photosynthesis.
• Peat bogs take carbon dioxide out of the atmosphere, so when they're destroyed the carbon is released back into the environment, contributing to global warming. Destruction of peat bogs also means the destruction of many habitats. If peat is exposed to soil then it will lose its carbon as it gets released into the soil.
• Peat is formed in waterlogged, acidic fens and bogs over thousands of years by the growth of mosses and other plants, which absorb and lock away carbon dioxide during photosynthesis. When the moss dies, the waterlogged bog provides anaerobic conditions which, together with the acidity of the bog, prevent the total decomposition of the moss. It accumulates in the bogs in a partially decomposed state, forming peat. Peat bogs cover nearly 2-3% of the Earth's surface and are an important carbon sink, containing more locked away carbon than the Earth's forests. However, peat can be dried and burnt as fuel, which make it an important energy source in some countries. Peat also has valuable properties when mixed with soil including improved soil structure, mineral retention, water retention and acidity, making it valuable in agriculture and gardening. Many peat bogs have been drained to allow the peat to be extracted. However, the use of peat has caused problems. Burning the peat releases its carbon back into the atmosphere as carbon dioxide. Peat mixed with soil gets exposed to its anaerobic conditions and begins to decompose causing carbon dioxide to be released. The destruction of peat bogs contributes to global warming and destruction of important habitats.

Biodiversity

• Loss of biodiversity is the loss of plants and animals in a certain area.
• Biodiversity is the variety of all the different species of organisms on Earth / in an ecosystem.
• Pollution reduces biodiversity
• Biodiversity is important as it makes ecosystems sable and it reduces the dependency of one species on another.

People and Population

• People are producing more waste than ever now due to an increased population and a higher standard of living.
• Humans reduce the amount of land available for other animals and plants by building, quarrying, farming, and dumping waste. The destruction of peat bogs and other areas of peat to produce garden compost, reduces the area of this habitat and thus the variety of different plant, animal and microorganisms species that live there (biodiversity)

Global Warming

• The gradual increase in the temperature of the Earth.
• Many scientists believe that it is caused by changes in the amounts of various gases in the atmosphere caused by pollution and deforestation. These gases include carbon dioxide and methane.
• An increase in the Earth's temperature by only a few degrees celsius could:
• Cause big changes in the Earth's climate, cause a big rise in sea level resulting in a loss of habitat, reduce biodiversity, cause changes in the migration patterns for example in birds, result in changes to the distribution of species

Facts

• A stable ecosystem is where there is little change in the population sizes over time
• Acid rain kills animals and plants, change the pH of soils and waterways, can damage buildings
• Monoculture is the cultivation of a single crop in a given area. Monoculture reduces biodiversity
• An increase in concentration of carbon dioxide is the atmosphere causes an increase in air temperature because there would be less loss of heat
• CO2 traps long wave radiation

Biomass and Trophic Levels

• Biomass is the mass of living material in plants and animals
• Trophic levels represent an organism's position in a food chain
• Level 1: Plants and algae make their own food and they're called producers
• Level 2: Herbivores eat plants and algae and they're called primary consumers
• Level 3: Carnivores eat herbivores and they're called secondary consumers
• Level 4: Carnivores that eat other carnivores are called tertiary consumers. Apex predators are carnivores with no predators
• Decomposers break down dead plant and animal matter by secreting enzymes into the environment. Small soluble food molecules then diffuse into the microorganism.

Biomass and Trophic Levels

• Pyramids of biomass represent the relative amount of biomass at each level of a food chain. Trophic level one is always at the bottom.