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IGCSE Biology Part 2- Plant biology and ecology > Ecosystems > Flashcards

Flashcards in Ecosystems Deck (50):

what does the term population mean?

all the organisms of a particular species found in an ecosystem at any one time


what does the term community mean?

the populations of all species found in a particular ecosystem at any one time from the community


what does the term ecosystem mean?

a distinct, self supporting system of organisms interacting with each other and the physical environment


what does the term habitat mean?

the places where the specific organisms live


what is the order of trophic levels?

1. producers
2. primary consumers
3. secondary consumers
4. tertiary consumers
5. decomposers


what should every habitat provide?

- food
- water
- shelter
- space


what are producers?

organisms that produce their own food from the sun (eg. plants photosynthesising)


what are primary consumers?

animals that eat plants; herbivore


what are secondary consumers?

animals that eat primary consumers; omnivore


what are tertiary consumers?

animals that eat secondary consumers; carnivore


what are decomposers?

when any of these organisms die they are broken down by decomposers- fungi and bacteria


what is a food chain?

a food chain shows how energy is passed on from one organism to another. The original source of energy is the sun


what is a food web?

a food web links several animals within a habitat showing what consumes what and what is consumed by what


what are pyramids of number?

pyramids of number show show the number of organisms in a food chain at each trophic level. They usually show that the number of organisms at each trophic level gets smaller towards the top.


what are pyramids of biomass?

pyramids of biomass are a more accurate indication of how much energy is passed on at each trophic level. Biomass is the mass of living material in each organism multiplied by the total number of organisms in that trophic level


what are pyramids of energy?

shows how much energy gets transferred from one trophic level to another


why is the biomass in each trophic level always less than the trophic level below?

because biomass is a measure of the amount of food available. When animals eat, only a small proportion of their food is converted into new tissue, which is the food for the next trophic level.


in what ways is the available energy to an organism predominantly used?

- energy released by respiration is used for movement and other life processes, and is eventually lost as heat to the surrounding
- energy is lost in waste materials, such as faeces


when can energy be passed onto the next trophic level?

if the energy of respiration is used to produce new cells (growth) or used to create offspring it remains fixed in the animal or plant and can be passed onto the next trophic level


why is only about 10% of energy passed onto the next trophic level?

- some parts of food aren't eaten by organisms (eg. bones and roots) so not all energy is taken in
- lots of energy taken in is used by that organism for staying alive (eg. respiration)
- most energy is eventually lost to the surrounding as heat
- only around 10% of total energy available becomes biomass (stored or used for growth)


how can quadrants be used to estimate population size of an organism in two different areas?

- place about a 1m² quadrat on the ground and count all the organisms within it
- multiply the number of organisms, by the total area m² of the habitat to find an estimate
- you can do this in a different area, to compare the population sizes


how can quadrats be used to sample the distribution of organisms in their habitats?

- a sample square is taken at random
- the population of organisms in that square is taken
- this can be repeated in several different areas
- compare results to see which areas are densely populated and which are not


what are the stages of the carbon cycle?

there's only a fixed amount of carbon in the world, so it's constantly recycled via the carbon cycle:
- respiration is carried out by animals and plants to release energy from glucose, this means carbon is produced
- plants use carbon during photsynthesis
- decomposition happens when an animal dies, it is then eaten by a decomposer which releases the carbon in it back into the atmosphere
- combustion is burning, if something with carbon is burnt it will release it into the atmosphere (tree, fossil fuel)


what is decomposition?

where living things are broken down by bacteria and fungi when they die


what are the sources of carbon monoxide?

- car emissions
- burning of fossil fuels without enough air supply (incomplete combustion)


what is carbon monoxide?

a colourless, odourless toxic flammable gas formed by incomplete combustion of carbon


what are the biological consequences of carbon monoxide on humans?

- it binds more strongly to haemoglobin than oxygen does, so the blood will carry less oxygen than it should
- less oxygen available for cell respiration
- death by suffocation
- effects on foetus (underweight, premature birth)


what is sulfur dioxide?

Fossil fuels naturally contain sulfur compounds. These produce sulfur dioxide, a gas with a sharp, choking smell, when the fuel is burned. When sulfur dioxide dissolves in water droplets in clouds, it makes the rain more acidic than normal. This is called acid rain.


what are the sources of sulfur dioxide?

- burning of fossil fuels (eg. coal and oil)
- internal combustion engines in cars and power stations


what are the effects of sulfur dioxide (acid rain)?

- dissolves limestone and stone buildings (statues)
- acidifies lakes, damaging ecosystem as it can kill plants and animals
- damages forests by releasing toxic substances from the soil, making it hard for trees to take up nutrients
- it erodes the waxy cuticle on the surface of leaves, reducing photosynthesis


what are the main greenhouse gases?

- water vapour
- carbon dioxide
- methane
- nitrous oxide
- CFCs (chlorofluorocarbons)


what is a green house gas?

a gas that absorbs heat that is reflected by the earth, this heat is then trapped in the earth's atmosphere warming the earth


how do human activities contribute to carbon dioxide emissions?

- car exhausts
- burning of fossil fuels
- industrial processes


how do human activities contribute to methane emissions?

- natural source: rotting plants in marshland
- manmade source: rice growing and cattle rearing


how do human activities contribute to nitrous oxide emissions?

- released in soils from the use of fertiliser, vehicle engines and industry
- natural source: bacteria in the soil and the ocean


how do human activities contribute to CFC emissions?

- manmade chemicals used in aerosol sprays and fridges
- all man made


how does the greenhouse effect work?

- Electromagnetic radiation at most wavelengths from the Sun passes through the Earth’s atmosphere.
- The Earth absorbs electromagnetic radiation with short wavelengths and so warms up. Heat is radiated from the Earth as longer wavelength infrared radiation.
- Some of this infrared radiation is absorbed by greenhouse gases in the atmosphere.
- The atmosphere warms up.


how does an increase in greenhouse gases lead to global warming?

- the temperature of the earth is balanced between heat from the sun and heat radiated back out to space
- greenhouse gases absorb heat and trap them in the earth's atmosphere
- over time, this heats the earth up (global warming)


what are the consequences of global warming?

- climate change
- polar ice caps melting (flooding)
- damage to animal habitat
- increases sea level and temperature causes more evaporation meaning more rain
- leads to natural disasters like hurricanes or typhoons


what is eutrophication?

- farmers add inorganic fertilisers to add minerals to their soil to increase crop yield
- these minerals are easily leached into water bodies
- these pollutants cause aquatic plant growth of algae, duckweed and other plants
- algae blooms prevent sunlight from reaching plant. The plants die and oxygen in the water is depleted.
- dead plants are broken down by bacteria decomposers, because there is so much food for the bacteria they multiply into large numbers, using up even more oxygen in the water
- oxygen levels reach a point where no life is possible, fish and other organisms die


what are the biological consequences of pollution of water by sewage?

sewage contains nutrients which enable algae to flourish. They take up sunlight and oxygen. Many fish die and other organisms die. Decomposers thrive on their dead bodies; meaning even more oxygen is taken up by microorganisms.


what are the effect of eutrophication on the ecosystem?

- plants below the water surface cannot photosynthesise and so die
- fish that eat the plants also die out
- the water can become so low on oxygen that all life is killed
- the algae can also release toxic poisons into the water that not only make it unsuitable for plants and fish, but also can cause health problems in humans that swim there


what are the causes of deforestation?

- clearcutting
- slow forest degradation
- slash-and-burn
- urban development
- acid rain
- wildfire


what are the effects of deforestation?

- vegetation is degraded
- problems like soil erosion become a bigger problem
- patterns of rainfall are disrupted
- carbon cycle is disrupted


what is soil erosion?

this is the removal of soil by wind, water and the mass movement of soil down a slope


how can we prevent deforestation?

- use wood sparingly
- recycling and using recycled items
- wood factories lessen the production of their products
- reforestaion
- farmers should rotate their crops
- cut down only mature trees


how does deforestation increase leaching?

- trees take up nutrients from the soil and return them to the soil when the leaves die
- when trees are removed, nutrients get leached away (by rain) but don't get replaced, leading to infertile soil


how does deforestation increase soil erosion?

- tree roots help stabilise the soil, preventing the soil from being eroded by heavy rain
- when trees are removed, soil can be washed away by heavy rain, leading to infertile ground


how does deforestation disturb the water cycle?

- trees stop rainwater reaching rivers too quickly
- transpiration from trees release some rainwater back into the atmosphere
- when cut down, rainwater can run straight into rivers, leading to flooding
- it also makes local climate drier


how does deforestation disturb the balance in atmospheric oxygen and carbon dioxide?

- forests take up carbon dioxide by photosynthesis, which is stored in wood, then slowly released when trees decompose
- when cut and burnt, the stored carbon is released at once as carbon dioxide, contributing to global warming
- the fewer the number of trees, the less photosynthesis takes place, so less oxygen is released, and oxygen levels in the atmosphere drop