Ecology

Habitat: the place where an organism lives

Population: all the organisms of one species in a habitat

Community: all the different species in a habitat

Ecosystem: all the organisms living in a particular area and all the non-living conditions

Abiotic factors:

• Environmental factors that are not living

• These include:

  • Light intensity

  • Humidity

  • Temperature

  • Pollution

  • Air quality

  • Climate change

Biotic factors

• Relating or as a result of living organisms

• These include:

  • Introduction of species

  • Parasites and diseases

  • Removal of predators

  • Competition between organisms

  • Availability of food

Quadrats: a square frame enclosing in a known area

How to use quadrats to compare population size of an organism in two sample areas:

1. Place the quadrat on the ground at a random point in the first sample area, it can be done by dividing the sample area into girds and using a random number generator to pick the coordinate where the quadrat will go to, this makes results representative

2. Count all organisms that you are studying that are inside the quadrat

3. Repeat step 1 and 2 multiple times

4. Work out the mean number of organisms per quadrat within the first sample area

5. Repeat steps 1-4 in the second sample area

6. Compare the two means

Mean: total number of organisms/number of quadrats placed

Estimating population size from a small sample area

• Find the mean number of organisms per metre squared

• Multiply this number by the total area in metre squared of the habitat

Pyramids of numbers

• They show the number of organisms at the stage of the food chain

• The more organisms there are, the longer the bar

• Normally as you go up trophic levels, the number of organisms goes down as it takes a lot of food from the level below to keep one animal alive

• It will not always look like a pyramid

Pyramids of biomass

• Each bar shows the mass of living material at that stage of the food chain

• How much all the organisms at each level would weigh if you put them all together

• It will always have the right shape

Pyramids of energy transfer

• Shows the energy transferred to each trophic level in a food chain

• Always the right shape, a regular pyramid

Energy transfer

• Energy is sourced from the Sun for nearly all life on Earth

• Plants use sunlight to make food during photosynthesis and the energy will continue to go around the food chain as animals eat plants and each other

• Not all energy is able to pass to the next trophic level, around 90% is lost in various ways

• Energy that does get taken in is for staying alive, like respiration

• Some parts of food like roots or bones don’t get eaten so energy there isn’t taken in, some parts are indigestible so they come out as waste

• Most of this energy is eventually transferred to the surroundings by heat

• Only around 10% of the total energy available becomes biomass for storage or growth

• This is the energy that gets transferred from one trophic level to the next

Sulphur dioxide - Acid rain

• Sulphur dioxide is released by burning fossil fuels

• It dissolves in rainwater to create sulphuric acid which forms acid rain

• Acid rain kills trees and damages leaves, releasing toxic substances from the soil that stops minerals from being absorbed

• This also acidifies the water in lakes which kills many plants and animals sensitive to pH

Carbon Monoxide - CO

• Happens during incomplete combustion

• CO binds with haemoglobin so it cannot transport oxygen which slowly kills your body

• It comes from car emissions

Greenhouse gases

• Water vapour

• Carbon dioxide

• Methane

• Chlorofluorocarbons

• Nitrous oxide

Greenhouse gas: a gas that traps energy from the Sun, without them, we would get very cold without any heat

Human activity on global warming

• Increasing the amount of carbon dioxide, CFC’s and nitrous oxide

• This causes rising sea levels, habitat loss and extreme weather