The most common source of air pollution is the combustion of fossil fuels. Sulphus dioxide is released if the fuel contains sulphur compounds. This usually contributes to acid rain.
These are plants that grow in exposed places such as rocks or tree bark. They need to be very good at absorbing water and neutrient to live there; therefore rainwater contains just enough neutrient to keep them alive. Air pollutant in the rainwater can damage lichens and prevent them from growing. This makes them good indicators of pollution.
- Bushy lichens show that the air is very clean
- Leafy lichens show that there is a small amount of air pollution
- Crusty lichens show that there is quite a lot of air pollution
This is caused by the discharge of harmful substances into rivers, lakes and seas.
Indicators of water pollution
Many aquatic invertabrate animals cannot survive in polluted water; so their presence or absence indicates the extent to which water is polluted.
- Mayfly larva show that the water is clean
- Freshwater shrimp show that there is a low amount of pollution
- Water louse show that there is a high amount of pollution
- Rat-tailed maggot and sludge worm show that there is a very high amount of pollution
How does sewage kill fish?
- Sewage/fertiliser gets into the water
- makes plants grow
- Plants have short lives so they die
- Number of dead plants in water increases causing bacteria to decompose and eat the dead bodies.
- Bacteria use oxygen during respiration causing oxygen levels to decrease
- Fish die due to the reduced oxygen levels.
How do heavy metals build up in the food chain?
- Factories release heavy metals into the water
- Algae and small plants absorb mercury from the water
- Fish eat the small plants and mercury levels increase in the fish
- Fishermen catch the fish and eat them
- Mercury level increase and build up in the person, to poisonous levels
- The person can become ill or can die.
Adaptions to cold climates
The artic is cold and windy, with very little rainfall.
Plants there often grow very close to the ground and have small leaves. This helps to conserce water and to avoid damage by wind.
Polar bears have a white appearance which is used as camouflage from prey. They also have thick layers of fat and fur for insulation against the cold.
Adaptions to hot climates
Camels live in deserts that are hot and dry during the day but cold at night. Their adaptions include:
- Large, flat feet to spread out their weight on the sand to prevent them from sinking
- The ability to go without water for a long time.
- Two rows of eyelashes to prevent the sand from getting into their eyes.
Desert plants include cacti, their adaptions include:
- Stems which store water
- Spines instead of leaves, to protect from predators.
- Widespread root systems which help collect water.
Factors that affect population
- Birth and death rates
All the conditions that surround a living organism
The place where an organism lives
Habitats have limited amounts of resources needed by living organisms. Organisms can only survive if they can get enough of these resources. Therefore they must compete for them.
The resources animals compete for (grey squirrels and red squirrels)
The resources plants compete for:
- Mineral salts
These are organisms that live in very extreme environments and can survuve in conditions that would kill most other organisms. These extreme conditions include:
- High temperatures
- High concentrations of salt in water
- High pressures
This is used to produce meat or crops quickly by controlling food, temperature, space, predators and disease in an area. However most people believe that this is animal cruelty.