The interaction between the living components and non-living components.
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State the factors that plants may compete for.
Light Space Water Mineral ions from soil
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State the factors that animals might compete for.
Food Mates Territory
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What is intraspecific competition?
Competition within a species.
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What is interspecific competition?
Competition between different species.
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What is interdependence?
Different species in a ecosystem depend on each other for various resources, if one species is removed, the whole community may be affected.
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What is a stable community?
A community in which all the biotic factors (the different species) and all abiotic factors are balanced so that population sizes remain relatively constant.
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What are abiotic factors?
Non-living factors
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State the abiotic factors that may affect an ecosystem.
Light intensity Temperature Moisture Soil pH and mineral content Wind intensity and direction Carbon dioxide level Oxygen level
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Why might light intensity affect an ecosystem?
Different species of plants may have different optimum light intensities for growth.
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Why does temperature affect an ecosystem?
Different species of plants and animals may have different optimum temperatures for growth and survival.
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How does soil pH affect an ecosystem?
Certain plants may grow better in either alkaline or acidic soil. Soil pH may affect the appearance of the plant.
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How does moisture level affect an ecosystem?
Many plants cannot survive in waterlogged soil as their roots cannot respire. Certain plants are adapted to high moisture levels.
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How does wind intensity affect an ecosystem?
Plant seeds are more likely to germinate in locations with lower wind intensity, which may also attract animals that depend on the plant to live nearby.
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How does soil mineral content affect an ecosystem?
Most plants require a high level of soil minerals to grow well.
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Give an example of a type of plants that have adapted to low soil mineral content.
Carnivorous plants catch insects to compensate for the low level of soil mineral content.
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How does carbon dioxide concentration affect an ecosystem?
Higher carbon dioxide concentration leads to more plant growth.
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How does oxygen concentration affect an ecosystem?
Aquatic animals cannot survive in areas with low oxygen concentration
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State the biotic factors that may affect an ecosystem.
Food New predators New pathogens Competition
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What are adaptations?
Features that enable organisms to survive in their living environment.
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What are organisms living in extreme environments called?
Extremophiles
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Give 3 examples of extreme living environments
High temperature High pressure High salt concentration
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Define population
A species that occupy the same habitat.
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Define habitat
The place in which an organism lives.
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Define community
Populations of different species interacting.
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What do food chains show?
Food chains show the feeding relationships of different organisms and the flow of energy between the organisms.
Photosynthetic organisms like green plants and algae that trap energy from the sun.
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What is a primary consumer?
An organism that feeds on producers.
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What is a secondary consumer?
An organism that feeds on primary consumers
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What is a tertiary consumer?
An organism that feeds on secondary consumers.
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What is a predator?
A consumer that kills and eats other animals.
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What is prey?
An animal that is killed and eaten by another animal.
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Describe the pattern of predators and prey in a stable community.
The numbers of predators and prey rise and fall in cycles.
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Why are producers the first trophic level?
Producers provide all biomass for the food chain (production of glucose via photosynthesis). The rest of the food chain involves the transfer of this biomass.
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What piece of apparatus is used to measure the abundance and distribution of organisms in an area?
Quadrat
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What piece of apparatus is used to study the distribution of organisms across a gradient?
Transect
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When considering the abundance of organisms, what is meant the term “mean”?
The average number of organisms.
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When considering the abundance of different organisms, what is meant by the term “mode”?
The most populous organism
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When considering the abundance of organisms, what is meant by the term “median”?
The organism that represents the middle value when the numbers of each organism are arranged from lowest to highest.
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Describe how materials cycle through the living and non-living components of an ecosystem.
Organisms take in elements from their surroundings e.g. soil, air. Elements converted to complex molecules which become biomass. Elements transferred along food chains. Elements returned to environment during excretion and decomposition of dead organisms.
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Give 3 molecules which are cycled through ecosystems
Oxygen, carbon dioxide and water.
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Describe the carbon cycle
Plants fix carbon dioxide into organic molecules during photosynthesis. The organic carbon-containing molecules are passed onto organisms that eat the plants. Carbon dioxide is released back into the atmosphere by respiration from animals and plants. Burning fossil fuels also releases carbon dioxide into the atmosphere.
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Why is the carbon cycle important?
Carbon-containing molecules such as glucose are important for living organisms to grow and provide energy for vital functions within cells.
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Describe the water cycle
Water from lakes and oceans evaporates. The evaporated water condenses into clouds and returns to earth as precipitation. The water from precipitation is useful for life on land. The water then returns to rivers and oceans through surface runoff.
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Why is the water cycle important?
Living organisms require water and the water cycle provides organisms on land with a continuous supply of water.
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Why are microorganisms important for the cycling of materials through an ecosystem?
Microorganisms (bacteria and fungi) return carbon to the environment by releasing carbon dioxide through respiration while they decompose dead matter. The decomposition of dead matter in soil returns mineral ions to the environment for other organisms to use e.g. plants use mineral ions for growth.
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What is meant by decomposition?
The breakdown of dead materials into simpler organic matter
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How do decomposers break down dead matter?
Decomposers release enzymes which catalyse the breakdown of dead material into smaller molecules.
Most decomposers require oxygen for aerobic respiration.
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How does the availability of oxygen affect the rate of decomposition?
As oxygen levels increase, the rate of decomposition increases. As oxygen levels decrease, the rate of decomposition decreases.
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How does soil water content affect the rate of decomposition?
Decomposers require water to survive. In moist conditions the rate of decomposition is high. In waterlogged soils there is little oxygen for respiration so the rate of decomposition decreases.
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Why does decomposition require water?
Water is required for the secretion of enzymes and absorption of dissolved molecules.
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How does temperature affect the rate of decomposition?
Decomposers release enzymes. Rate highest at 50°C (optimum temperature for enzymes). Lower temperatures, enzymes work too slowly, rate decreases. High temperatures, enzymes denature, decomposition stops.
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How is the rate of change calculated when considering the decay of biological material?
Rate of change = Change in value / Change in time
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What is compost?
The nutrient-rich product of the rapid decay of waste biological material (dead plants and animal waste) in optimum conditions set by gardeners and farmers.
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How is compost used?
Used as natural fertiliser to promote growth of crops or garden plants.
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Describe how biogas generators work
Biogas generators provide methane gas for fuel through anaerobic decomposition that occurs in animal waste.
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Describe how environmental conditions affect communities
Environmental conditions e.g. temperature, soil pH, light intensity affect the abundance and distribution of organisms within communities. e.g rising global temperatures have been linked to the extinction of frog species (their thin skin makes them more vulnerable to temperature changes)
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How can different temperatures be bad for certain communities?
If the temperature is too low, growth will be slower as organisms will use more energy to stay warm If the temperature is too high, organisms can die and water will become limited as evaporation increases
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How can changes in water levels affect ecosystems?
Animals may have to migrate to find water. Melting ice caps may destroy the habitats of some animals (either animals living in icy regions or by sea level rise).
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How can atmospheric gases affect ecosystems?
Some organisms cannot survive when certain gases are present. Polluted water can cause illness to animals that drink it.
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What detrimental impacts can sulfur dioxide have on the environment?
Formed when fossil fuels containing impurities are burnt. Sulfur dioxide can dissolve in water to form acid rain which can erode buildings and pollute water sources.
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What detrimental impacts can carbon monoxide have on the environment?
Carbon monoxide is formed from the incomplete combustion of fossil fuels. Carbon monoxide binds irreversibly to haemoglobin which prevents it from carrying oxygen. Too much exposure can cause unconsciousness and death.
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Give 3 human activities that contribute to greenhouse gases
Burning fossil fuels Deforestation Large scale livestock farming
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How do greenhouse gases lead to global warming?
Greenhouse gases allow heat from the sun to enter the atmosphere. The gases act as a ‘blanket’ and trap the heat in the atmosphere.
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State 3 negative consequences of global warming
Sea level rise caused by melting icebergs. Disrupted farming and agriculture. Increased spread of diseases in warmer climates.
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What is biodiversity?
The variety of the different species on\earth or within an ecosystem.
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What is the importance of biodiversity?
To maintain the stability of an ecosystem.
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How does biodiversity ensure the stability of an ecosystem?
It reduces the dependence on particular species for resources eg. food and shelter, so that even if one species is removed other species can still survive.
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Why have humans’ consumption of resources and waste production increased?
Rapid rise in human population Increase in standard of living
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Where does pollution occur?
Air Land Water
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State an example of water pollutants.
Sewage Fertiliser Chemicals
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How does eutrophication occur?
Fertiliser from farms pollute the water, causing excessive algae growth, depleting the oxygen in the water, causing other plants and animals to die. Dead plants are decomposed by bacteria and the oxygen level decreases further.
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State an example of air pollutants.
Smoke Acidic gases
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State an example of land pollutants.
Landfill waste Chemicals
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Which human activities reduce the land available for animals and plants?
Building Farming Quarrying Disposing of waste
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Why have peat bogs been destroyed?
To produce compost to increase food production.
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Why does the destruction of peat bogs greatly contribute to the greenhouse effect?
Peat bogs are stores of carbon (carbon sinks) and burning them releases a large volume of carbon dioxide into the atmosphere.
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Why have large-scale deforestation activities occurred?
To provide land for cattle or rice fields To grow crops to produce biofuels
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What is the greenhouse effect?
Greenhouse gases trap energy from the Sun as heat in the atmosphere, keeping the temperature on earth suitable for life.
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What is causing global warming?
The increase in levels of greenhouse gases eg. carbon dioxide and methane, causing the temperature on earth to increase.
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What are the harmful effects of deforestation?
Destruction of many animals’ habitats Releases large amounts of greenhouse gases
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State the consequences of global warming.
Rising sea levels Melting polar ice caps Changing weather patterns Migration of animals to find suitable habitats Tropical diseases becoming more common Extinction of species
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Describe the steps taken to maintain biodiversity
Breeding programmes for endangered species. Protection and rebuilding habitats. Replanting field margins and hedgerows. Reduce deforestation. Reduce carbon dioxide emissions. Recycling rather than disposing in landfills.
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What is the purpose of replanting hedgerows and field margins?
There is higher biodiversity in the margins than the fields that they surround.
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What does a food chain show?
It describes the feeding relationships between organisms and the resultant stages of biomass transfer.
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What are trophic levels?
The stages in a food chain
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How are trophic levels represented?
Trophic levels are represented by numbers, starting from 1. After 1, trophic levels are numbered according to far along the organism is in the food chain
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What is an apex predator?
A carnivore with no predators
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Why is dry mass used for biomass?
Because the wet mass varies as the volume of water in the organism varies
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How do you calculate the efficiency of biomass transfer?
efficiency = (energy transferred / total energy available) × 100
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What percentage of the incident energy from light for photosynthesis do producers transfer?