topic 7 - ecology Flashcards
what is an ecosystem?
an ecosystem is the interaction of a community of living organisms (biotic) with the non-living (abiotic) parts of their environment
what is a habitat?
the environment in which an organism lives
what is a population?
the total number of organisms of the same species living in the same geographical area
what is a community?
the populations of all the different species that live in the same habitat
what are the levels of organisation in an ecosystem?
- individual
- population
- community
- ecosystem
what are the factors that plants may compete for?
- light
- space
- water
- mineral ions from soil
what are the factors that animals may compete for?
- food and water
- mating partners
- territory
what is interdependence?
- when within a community, each species depends on other living organisms for food
what is a stable community?
- a community where all the species and environmental factors are in balance so that population sizes remain fairly constant
how does the availability of food affect a community?
- if the availability of food falls, then the number of organisms in that community will also fall
how does the arrival of a new predator affect a community?
- this can cause the population of a prey species to fall
- a new predator can also affect existing predators for example if they are competing for the same prey
how does the competition of species affect a community?
- if a species is outcompeted then its population can fall so much that numbers are no longer sufficient to breed and the species may become extinct
how do new pathogens affect a community?
- if an infectious disease emerges and then spreads it can wipe out the population of a species
what are biotic factors which can affect a community?
- availability of food
- new predators arriving
- new pathogens
- one species outcompeting another so the numbers are no longer sufficient to breed
what are abiotic factors which can affect a community?
- light intensity
- temperature
- moisture levels
- soil pH and mineral content
- wind intensity and direction
- carbon dioxide levels for plants oxygen levels for aquatic animals
how does light intensity affect a community?
- all plants need light to carry out photosynthesis, however, if the light intensity is too low then the rate of photosynthesis falls and plants will grow more slowly
- this can have a major impact on a community
- this is because if plants grow more slowly, then animals which feed on plants may not have enough food
how does temperature affect a community?
- if the temperature of an environment changes then this could cause the distribution of species to change
how does water affect a community?
- both plants and animals need water to survive
- many species are adapted to deal with low levels of water
how do the pH and mineral content of the soil affect a community?
- many plants cannot grow on soil which is too acidic or too alkaline
- plants also need certain minerals in the soil e.g nitrate which is used to make amino acids for proteins
how do the wind intensity and direction affect a community?
- strong winds blowing inland from the sea can cause plants to lose water
- so plants growing in sand dunes are often adapted to reduce water loss
how do carbon dioxide and oxygen affect a community?
- carbon dioxide is needed for plants to photosynthesise and if carbon dioxide levels fall then the rate of photosynthesis can also decrease
- oxygen is needed for aerobic respiration. The level of oxygen in the air stays fairly constant.
- However, the level of dissolved oxygen in water can fall e.g. on hot days. This can be harmful to aquatic organisms such as fish
what are adaptations?
features that enable organism to survive in their living environment
what are extremophiles?
organisms living in extreme environments
what are 3 examples of extreme living environments?
- high temperature
- high pressure
- high salt concentration
where can extremophile bacteria be found?
in deep sea vents
what do food chains show?
- food chains show the feeding relationships of different organisms and the flow of energy between the organisms
describe a simple food chain
producer -> primary consumer -> secondary consumer -> tertiary consumer
why are producers important in food chains?
- they synthesise complex molecules
- the source of all biomass
what is biomass?
- the total mass of living material
what is random sampling?
- random sampling is used to compare the numbers of organisms in different areas
what is a quadrat?
- a wooden or plastic square
how do you use a quadrat?
- to use a quadrat, we place it on the ground and then count the number of organisms inside the quadrat
- this technique can be used to sample plants or slow-moving animals
how do you calculate the total population size of a species in an area?
total population size = total area/area sampled x number of organisms of that species counted in sample
why is sampling along a transect used?
- sampling along a transect is used to investigate whether the number of species changes as we move across a habitat
what is a transect?
- a transect is simply a line such as a tape measure or a piece of rope
how do you use a transect?
- place the transect so it runs across the habitat
- use a quadrat to count the number of organisms at intervals on the transect
how to measure random sampling?
- use a quadrat 0.5m by 0.5m
- place two tape measures at right angles
- these tape measures should be 20m in length
- we then need two bags and each bag contains the numbers 1 to 20
- the first student removes a number from the bag -> e.g. 8
- this student now moves to the 8m point on one of the tape measures
- the second student now selects a number from their bag and moves to that point on the other tape measure - e.g. 12
- now the third student places a quadrant on the ground at the 8m by 12m point
- the students now record the number of daisies in the first quadrat
- the students then repeat this process nine more times
- then calculate the total population size
how does carbon enter the carbon cycle?
- by photosynthesis
how does the carbon cycle work?
- plants and algae take in carbon dioxide from the atmosphere in photosynthesis
- the carbon is used to make carbohydrates, fats and proteins which make up the cells of plants and algae
- plants and algae respire so some of the carbon is released back into the atmosphere as carbon dioxide
- plants and algae can be eaten by animals and then these animals can be eaten by other animals
- at this point, the carbon in the plants becomes part of the carbohydrates, fats and proteins in the cells of animals
- just like plants, animals respire, so some of the carbon is released back into the atmosphere as carbon dioxide
- animals release waste products such as faeces and eventually all animals and plants die
- now we have carbon in waste products and dead remains
- the waste product and dead remains are then broken down by decomposing microorganisms e.g. bacteria and fungi
- and when decomposers carry out respiration, the carbon in the waste and dead remains are returned to the atmosphere as carbon dioxide
why are decomposers important?
- they cycle materials through an ecosystem
- as well as returning carbon to the atmosphere as carbon dioxide, they also release mineral ions to the soil
what happens if decomposers cannot function effectively?
- the carbon in dead remains can slowly be converted to fossil fuels
how does the water cycle work?
- energy from the sun causes the water to evaporate from the surface of the sea
- the water vapour now travels into the air and cools down
- when it cools, the water vapour condenses to form clouds
- the water in clouds then falls to the ground as precipitation
- all forms of precipitation contain fresh water
- once the water hits the ground, some of it evaporates back into the atmosphere as water vapour
- some of the water passes through rocks and forms aquifers
- and a lot of the water from rivers or streams
- the water in rivers and streams eventually drains back into the sea
how do living organisms play a role in the water cycle?
- plants take up water in their roots
- this water moves up the plant in the xylem and passes out of the leaves through stomata as water vapour (transpiration)
- animals take in water from drinking and eating, they then release water in their urine, in their faces and when they exhale
what is meant by decomposition?
the breakdown of dead materials into simpler organic matter
how do decomposers break down dead matter?
decomposers release enzymes which catalyse the breakdown of dead material into smaller molecules
what are the two types of decomposition?
- aerobic decomposition
- anaerobic decomposition
what factors affect the rate of decomposition?
- oxygen availability
- temperature
- water content
why is oxygen required for decomposition?
- most decomposers require oxygen for aerobic respiration
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
why can decomposition still occur in the absence of oxygen?
- some decomposers respire anaerobically
- however, the rate of decomposition is slower as anaerobic respiration produces less energy
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
why does decomposition require water?
- water is required for the secretion of enzymes and absorption of dissolved molecules
how does temperature affect the rate of decomposition?
- the optimum temperature at 50° C
- lower temperatures, enzymes work too slowly, rate decreases
- high temperatures, enzyme denature, decomposition stops
how is the rate of change calculated when considering the decay of biological material?
rate of change = change in value/ change in time
what is compost?
- the nutrient-rich product of the rapid decay of waste biological material in optimum conditions set by gardeners and farmers
how is compost used?
- used as natural fertiliser to promote growth of crops or garden plants
how do biogas generators work?
- biogas generators provide methane gas for fuel through anaerobic decomposing that occurs in animal waste
how do environmental conditions affect communities?
- environmental conditions e.g. temperature, soil pH, and 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
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
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
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
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
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
what are 5 greenhouse gases?
- water vapour
- carbon dioxide
- nitrous oxide
- methane
- CFCs
what are 3 human activities that contribute to greenhouse gases?
- burning fossil fuels
- deforestation
- large scale livestock farming
how do greenhouse gases lead to global warming?
- green house gases allow heat from the sun to enter the atmosphere
- the gases act as a ‘blanket’ and trap the heat in the atmosphere
what are 3 negative consequences of global warming?
- sea level rise caused by melting icebergs
- disrupted farming and agriculture
- increased spread of diseases in warmer climates
what is biodiversity?
the variety of the different species on earth or within an ecosystem
what is the importance of biodiversity?
- to maintain the stability of an ecosystem
how does biodiversity ensure the stability of the ecosystem?
- it reduces the dependence on particular species for resources, so that even if one species is removed other species can still survive
why has humans’ consumption of resources and water production increased?
- a rapid rise in the human population
- increase in the standard of living
where does pollution occur?
- air
- land
- water
what are examples of water pollutants?
- sewage
- fertiliser
- chemicals
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
what human activities reduce the land available for animals and plants?
- building
- farming
- quarrying
- disposing of waste
why have PEAT bogs been destroyed?
- to produce compost to increase food production
why does the contribution of PEAT bogs greatly contribute to the greenhouse effect?
- PEAT bogs are stores of carbon and burning them releases a large volume of carbon dioxide into the atmosphere
why have large-scale deforestation activities occurred?
- to provide land for cattle or rice fields
- to grow crops to produce biofuels
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
what is causing global warming?
- the increase in levels of greenhouse gases causing the temperature on earth to increase
what are the harmful effects of deforestation?
- the destruction of many animals’ habitats
- releases large amounts of greenhouse gases
what are 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
what is 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
what is the purpose of replanting hedgerows and field margins?
- there is higher biodiversity in the margins than the fields that they surround
what are trophic levels?
- the stages in a food chain
what is trophic level 1?
- plants and algae which make their own food (through photosynthesis) - called producers
what is trophic level 2?
herbivores which eat producers - called primary consumers
what is trophic level 3?
- carnivores that eat herbivores - called secondary consumers
what is trophic level 4?
carnivores that eat other carnivores - called tertiary consumers
what is an apex predator?
a carnivore with no predators
how do decomposers break down dead matter?
- decomposers release enzymes which catalyse the breakdown of dead material into smaller molecules
- soluble small food molecules then diffuse into the microorganisms
what is biomass?
- the dry mass of all of the living organisms in an area
why is dry mass used for biomass?
- because the wet mass varies as the volume of water in the organism varies
how do you calculate the efficiency of biomass transfer?
efficiency = (energy transferred / total energy available) x 100
what percentage of the incident energy from light for photosynthesis do producers transfer?
1%
what percentage of the biomass from one trophic level is transferred to the level above it in feeding?
approximately 10%
why are biomass transfers not 100% efficient?
energy is lost through:
- egestion (removal of faeces)
- excretion (removal of waste products e.g. urine containing urea and water)
- respiration (loss of carbon dioxide and water) in which large amounts of glucose are used
- the production of inedible bones and shells
how does the efficiency of biomass transfers affect the number of trophic levels in a biomass pyramid?
- the less efficient the transfers, the fewer trophic levels and the fewer organisms in higher trophic levels
what is a biomass pyramid?
- a pyramid that shows the total dry mass of organisms at each trophic level
what is food security?
- having enough food to be able to feed a population
what are the biological factors threatening food security?
- rising birth rates
- changing diets in developed countries -> food is transported around the world
- new pests and pathogens
- environmental changes affecting food production
- increased cost of agriculture
- armed conflicts
how does intensive farming increase the production of animals?
- feed animals high-protein foods to increase growth
- reduce their energy loss to the environment by limiting movement or regulating their surrounding temperature
- feed animals antibiotics to prevent diseases
what are the advantages of intensive farming?
- higher yield of food
- more efficient
- allows easier quality control
what are the disadvantages of intensive farming?
- may lead to antibiotic resistance
- cost is high
- ethical objections
- biodiversity may be reduced
how can fish stocks be conserved?
- control the size of gaps in fishing nets to prevent juvenile fish from being killed before reaching reproductive maturity
- introduce fishing quotas
what is a transgenic organism?
- an organism that has been genetically modified to contain genetic material from another source
what is an example of a genetically modified food?
golden rice
why might crops be genetically modified?
- to improve the nutritional value
- to be pest resistant
- to be pesticide resistant
what are the advantages of golden rice?
- it contains additional beta-carotene which can be converted to vitamin A in the body, supplementing people who do not obtain enough Vitamin A in their diet to prevent night blindness from forming
what is mycoprotein?
a protein-rich substance used to make meat substitute food for vegetarians and vegans
how is mycoprotein produced?
- Fusarium, a fungus, is grown on glucose syrup, in aerobic conditions and the biomass is harvested and purified to get the mycoprotein
