Biology - Ecology

Ecology: study of the interactions between living things & between organisms and their environment

Biosphere: that part of the planet containing living organisms

• Ecosystem: a group of clearly distinguished organisms that interact with their environment as a unit
• Eg. Grassland – mid temperatures, low rainfall – Steppes of Africa

Population: all members of the same species living in an area

Community: All different populations in an area

• 1. Competition
• Occurs when organisms actively struggle for a resource that is in short supply
• Intra-specific competition: between members of the same species
• Inter-specific competition: Between members of different species

• Contest competition: there is an active struggle between two individual organisms
• Scramble competition: all of competing individuals get some of the resource
• 2. Predation
• The catching, killing & eating of another organism
• Adaptations
• Birds of prey have excellent sight to detect prey
• Ladybirds have strong mouths to chew aphids
• Prey
• Ladybirds are bright to warn that they are poisonous
• Frogs are well camouflaged

• 3. Parasitism
• Two organisms of different species live in close association and one organism obtains its food from, and to the disadvantage to, the host
• Endoparasites: Inside host eg. Liver flukes in sheep
• Exoparasites: Outside host eg. Fleas on a dog
• 4. Symbiosis
• Occurs when two organisms of different species live in close association & at least one of them benefits
• Mutualism: Both benefit from the association

• Abiotic Factors
• Altitude
• Aspect
• Steepness

• Biotic Factors
• Food
• Competition
• Predation
• Parasitism

• Climatic Factors
• Temperature
• Rainfall
• Humidity
• Wind

• Edaphic Factors
• pH
• Humus
• Water content
• Air content

• Aquatic Factors
• Light
• Salt content
• Wave action

• Consumers: Organisms that take food form another organism
• Primary
• Secondary
• Tertiary

• Grazing food chain: A sequence of organisms in which one member is eaten by the next in the chain
• Eg. Buttercup - Caterpillar - Thrush - Fox

• Trophic Level: A feeding stage in a food chain
• 10% of energy in each trophic level is passed on to the next level

Food Web: consists of two are more interlinked food chains

Pyramid of Numbers: Represents the number of organisms at each trophies level in a food chain

• Limitations:
• Do not take into account the size of organisms
• Pyramids cannot be drawn to scale

Ecological Niche: of an organism is the functional role it plays in the community

The way in which elements are exchanged between the living & non-living components of an ecosystem

The process by which carbon from the environment is converted to carbon in living things

• Role of Organisms in the Carbon Cycle
• Plants – remove carbon from the environment by photosynthesis & return it by respiration
• Animals – get their carbon by eating plants & release it through respiration
• Micro-organisms – return carbon to environment when they decompose dead plants & animals

• Rise in carbon dioxide concentration
• Sources: Fossil Fuels
• Deforestation

• CO2 is a ‘greenhouse gas’
• It allows heat radiation pass into atmosphere
• Results: Sea levels may rise
• Weather patterns may alter

Function: To take nitrogen from the air & make it available for use by living things

• Nitrogen Fixation: The conversion of nitrogen gas to ammonia (NH3), ammonium (NH4+) or nitrate (NO3-)
• Happens in lightening & volcanic eruptions
• Nitrogen-fixing bacteria – legumes eg. Clover, soya beans, peas & beans

Nitrification: The conversion of ammonia & ammonium (NH4+) compounds to nitrite then nitrate

Denitrification: The conversion of nitrates to nitrogen gas

• Bacteria: 4 types
• Nitrogen-Fixing Bacteria – Convert nitrogen to nitrates
• Bacteria of decay – Decaying nitrogen to Ammonia
• Nitrifying bacteria – Ammonia to Nitrates
• Denitrifying bacteria – Nitrates to Nitrogen Gas

Fungi: Convert dead plants/animals to ammonia

Plants: Absorb nitrates & use them to form proteins

Animals: Consume plants & use their nitrogen to form animal protein

Pollution: any harmful addition to the environment

Pollutants: substances that cause pollution

Ozone Depletion – an example of air pollution

• Caused by manufactured chemical pollutants:
• · CFCs ( Chlorofluorocarbons)
• · Freon Gas
• · Styrofoam

• Effects:
• Increased numbers of skin cancers, cataracts & weakened immunity
• Damage to crop & plants
• Concern that plankton will be depleted

• Control of Ozone Depletion:
• Reduction & replacement of CFCs with HCFs
• Do not use sprays or foams containing CFCs
• Fridge’s shouldn’t be dumped in landfill sites

• Benefits of Conservation:
• Prevents extinction
• Maintains balance of nature
• Maintains biodiversity
• Organisms may be found to be useful in the future

• Conservation in Fisheries
• Fishing with large-mesh nets does not remove the young, small fish. This allows the fish numbers to be maintained

• In agriculture slurry enters rivers or lakes & minerals in it cause increased algal growth. The algae die & are decomposed by bacteria, depleting the water of oxygen. Aquatic plants & animals die. This is called eutrophication.
• This can be controlled by
• 1. Storing slurry in leak-proof pits
• 2. Spreading slurry on dry land

• Micro-organisms carry diseases, easily spread through water
• Toxic chemicals washed into water
• Nutrients cause eutrophication
• Landfills unsightly
• Poisonous gases