ecology Flashcards
DEFINITIONS-
habitat?
population?
producer?
consumer?
decomposer?
trophic level?
climax community?
habitat = the place where an organism lives eg a rocky shore or field
population = all the organisms of one species in a habitat
producer = an organism (plants) that convert light energy to chemical energy
consumer = an organism that eats other organisms eg. animals and birds
decomposer = an organism that breaks down or undigested organic material eg. bacteria and fungi
trophic level = a stage in a food chain occupied by a particular group of organisms, eg. producers are the first trophic level in a food chain.
climax community = community is stable
what is an ecosystem?
what does an ecosystem include?
what are biotic factors?
what are abiotic factors?
- all the organisms living in a certain area and all the non-living factors (conditions) found there. It is a dynamic system, means it is changing all the time
-biotic and abiotic factors
-biotic = the living features of an ecosystem. E.g the presence of predators or food
-abiotic = the non-living features of an ecosystem. E.g temperature, rainfall,, shape of the land (topology) and soil nutrient availability. In an aquatic ecosystem, this may include pH and salinity of the water.
BIOTIC AND ABIOTIC FACTORS OF ECOSYSTEMS-
rock pools?
-Biotic factors = seaweed can be a food source for consumers such as limpets that graze on this producer. Intense competition for food (such as seaweed) can limit the number of organisms that are present in a small rock pool ecosystem.
-Abiotic factors = rock pools are heavily influenced by the tides. At high tide they are completely submerged by the ocean so experience similar abiotic factors (eg. pH, salinity, temp) to the ocean ecosystem. HOWEVER, at low tide they experience more extreme abiotic conditions and only some organisms can tolerate these conditions (eg. higher salinity and temps).
BIOTIC AND ABIOTIC FACTORS OF ECOSYSTEMS-
playing field?
-biotic factors = producers are grass and other plants, eg. daisies, clover and dandelions. The large amount of these plants may attract a large number of organisms that use them as a food source (eg. rabbits, caterpillars).
-abiotic factors = rainfall and sunlight affect the growth of the producers in the ecosystem. In a very wet year, the soil may become waterlogged, making it difficult for plants to grow. Poor plant growth may decrease the number of consumers the ecosystem is able to support.
BIOTIC AND ABIOTIC FACTORS OF ECOSYSTEMS-
large tree?
-biotic factors = insects (eg. caterpillars), can use the leaves of a tree as a food source. However, if they consume all the leaves on a tree (defoliation), they can slow the tree growth and can lead to its death.
-abiotic factors = drought condition can negatively impact the growth of a tree. Can lead to parts or all of the tree dying.
how is energy transferred through ecosystems?
- The main route energy enters an ecosystem is photosynthesis. Some energy enters sea ecosystems when bacteria use chemicals from deep sea vents as an energy source.
- plants are producers that store photosynthesised energy (sunlight energy) as biomass. Biomass = the mass of living material eg. the mass of plant material.
- energy transfers through ecosystems = biomass transfers.
- energy is transferred through living organisms of an ecosystem when organisms eat other organisms eg. producers are eaten by primary consumers, then they are eaten by secondary consumers, then they are eaten by tertiary consumers.
- Food chains and food webs show how energy is transferred through an ecosystem.
Food chains = show simple lines of energy transfer.
Food webs = show lots of food chains in an ecosystem and how they overlap - energy that is in bones and faeces (things that cant be eaten) gets recycled back into the ecosystem by decomposers.
not all the energy is transferred to the next trophic level, why?
- around 90% of the total available energy is lost in various ways
- some of the available energy (60%) is never taken in by the organisms in the first place because:
-plants cant use all the light energy that reaches their leaves = some is the wrong wavelength, some is reflected, some passes straight through the leaves.
-some sunlight cant be used because it hits parts of the plant that cant photosynthesise eg. bark of a tree
-some parts of food eg. roots or bones aren’t eaten by organisms soo the energy isn’t taken in = they pass to decomposers
-some parts of food are indigestible so pass through organisms and come out as waste eg. faeces = passes to decomposers. - the rest of the available energy is (40%) is absorbed = called gross productivity. BUT not all of this is available for the next trophic level.
- 30% of the total energy available (75% of the gross productivity) is lost to the environment when organisms use energy produced from respiration for movement or body heat = called respiratory loss.
- 10% of the total energy available (25% of the gross productivity) becomes biomass (stored or used for growth) = called net productivity. - net productivity (biomass) is the amount of energy thats available to the next trophic level. The flow of energy transfer continues at the next trophic level and the process starts again from the beginning.
how is net productivity calculated?
how to calculate how efficient organisms from one trophic level are at converting what they eat into energy for the next trophic level?
-net productivity = gross productivity - respiratory loss
- (energy transferred / energy intake) x 100
how can energy transfer between trophic levels be measured?
what are the problems with this method?
- need to calculate the difference between the amount of energy in each level (the net productivity of each level)
- do this by measuring dry mass of organisms (biomass)
- first, calculate amount of biomass in a sample of organisms eg. 1m2 area of wheat or a single mouse that feeds on the wheat
- then multiply the results of the sample by the size of total population eg. a 10,000 m2 field of wheat or the number of mice in the population, to give the total amount of energy in the organisms at that trophic level
- the difference in energy between the trophic levels is the amount of energy transferred
- eg. consumers (mice) may have taken in energy from sources other than the producer measured = difference between the two figures wouldn’t be an accurate estimate or the energy transferred between only those two organisms.
-for an accurate estimate, you’d need to include all the individual organisms in each trophic level
how do human activities increase the transfer of energy through an ecosystem?
some farming methods increase productivity by increasing transfer of energy:
-herbicides kill weeds that compete with agricultural crops for energy. Reducing competition means crops receive more energy = grow faster, become larger, increasing productivity
-fungicides kill fungal infections that damage agricultural crops = crops then use more energy for growth and less for fighting infection = grow faster and become larger, increasing productivity
-insecticides kill pests that eat and damage crops = so less biomass lost from crops = grow larger = productivity is greater
-natural predators introduced to the ecosystem eat the pest species eg. ladybirds eat greenfly = crops lose less energy and biomass = increasing productivity
-fertilisers are chemicals that provide crops with minerals needed for growth eg. nitrates. crops use up minerals in the soil as they grow = so growth is limited when aren’t enough minerals. Adding fertiliser replaces lost minerals = more energy from the ecosystem can be used to grow, increasing the efficiency of energy conservation
-rearing livestock intensively involves controlling the conditions they live in = so more energy used for growth and less used for other activities.
-Efficiency of energy conservation is increased = so more biomass produced = productivity is increased. EXAMPLES:
-animals kept warm and indoors= less energy wasted keeping them warm and moving around
-reduce animal movement
-feed animals high energy food = increases energy input = more energy available for growth
-vaccination or routine antibiotics for animals
-selective breeding for improved animals
-slaughter just before full size
benefits of human activities increasing transfer of energy?
Disadvantage?
-more food produced in a shorter space of time often at lower cost
-intensive rearing raises ethical issues, as conditions may cause pain, distress or restriction of natural behaviour so shouldn’t be done
How to use a belt transect of a field which contained a pond, buttercups looked slightly different near the pond compared to slightly further away
-lay a tape measure out from the edge of a pond
-place a quadrat beside the tape measure
-identify species of buttercup in the quadrat
-count number of plants of each species in the quadrat
-repeat for positions of quadrat along the tape
outline the process of primary succession and explain why heather moorland is an example of deflected succession
-pioneer community = begins with bear rock,
arrival as seeds or spores, pioneer species have certain adaptations eg. nitrogen fixation
-intermediate community = herb species including grasses, followed by shrubs and trees
-climax community = dominance by a few tree species, little change over time
-general principles to have in the 6 marker = several stages, community and decomposition changes composition of soil, increased organic; nitrate or water content
-deflected succession because = climax community is prevented from developing, as a result = plagioclimax, heather is a shrub
describe the differences between these terms:
- pioneer and climax community?
- decomposition and denitrification?
- conservation and preservation?
- nitrogen fixation and nitrification
- -pioneers arrive first, climax arrives last
-pioneer communities subject to more succession
-pioneer community has less biomass
-pioneer usually has less biodiversity
-species in pioneer are better adapted to abiotic factors eg. wind and those in climax are better adapted to biotic factors eg. competition between species - -decomposition is breakdown of waste OR decomposition is the conversion of organic matter to inorganic eg. carbon dioxide, water, ammonium compounds
-denitrification is the conversion of nitrates to nitrogen gas
-decomposition increases nitrate supply and denitrification reduces nitrate supply - -conservation involves active management of the ecosystem
-preservation leaves ecosystems undisturbed - -nitrogen fixation is the conversion of atmospheric nitrogen into ammonium ions
-nitrification is the conversion of ammonium ions into nitrite/nitrate
-Examples: nitrogen fixation involves Rhizobium/ Azotobacter and nitrification involves Nitrosomonas/ Nitrobacter
outline the role of decomposes in the decomposition of leaves?
-bacteria/fungi
-external digestion (saprophytic)
-by enzymes such as cellulase/lignase
-absorption of breakdown products
-release of carbon dioxide and water
-breakdown of protein makes ammonium ions/ NH4+
carbon cycle?
- Carbon in the form of CO2 is absorbed by plants when they carry out photosynthesis and becomes carbon compounds in plant tissues
- carbon is passed on to primary consumers when they eat the plants and then passed onto secondary and tertiary consumers.
- living organisms die and the carbon compounds in the dead organic matter is digested by decomposes, this is called saprophytic nutrition.
4.carbon and water is returned to the atmosphere through respiration of living organisms which produces CO2
- if DOM ends up in deep oceans or bogs (where there aren’t any decomposes), their carbon compounds can be turned into fossil fuels by heat and pressure
- the carbon in fossil fuels (eg oil and coal) is released when they’re burnt- combustion
- in the ocean, limestone and chalk are mainly composed of calcium carbonate and comes from marine organisms like crabs and mussels that utilise this compound in their development eg. to form shells
- carbon is then returned to the atmosphere by volcanoes from movement of tectonic plates.
- the rocks can eventually become land which is then weathered. can happen chemically by slightly acidic rain water (CO2 dissolved in it) and can happen physically by plant roots or animals. chemical weathering causes mineral ions and bicarbonate ions to be released from the rock into solution and enter groundwater and is transported into rivers and oceans and combine to form carbon containing compounds such as CaCO3.
- CO2 can dissolve directly into oceans from the atmosphere and be transported by deep underwater currents (physical process) and remain in these for years before returning to the surface and being released back into the atmosphere.
nitrogen cycle-
- nitrogen fixation-
-when nitrogen gas in the atmosphere is turned into ammonia by Rhizobuim and Azotobacter bacteria
-the ammonia can then be used by plants
-Rhizobium are found in the root nodules of leguminous plants (peas, beans, clover)
-they form a mutualistic relationship with other the plants as they provide the plant with nitrogen compounds and the plant provides them with carbohydrates.
-Azotobacter are found in the soil and don’t form mutualistic relationships with plants
- atmospheric nitrogen gas can also be fixed into the soil by lighting or by artificial fertilisers produced in the harber process - Ammonification
-ammonification is when nitrogen compounds from dead organisms are turned into ammonia by decomposes which then forms ammonium ions
-animal waste also contains nitrogen compounds and are turned into ammonia by decomposes which then form ammonium ions - Nitrification
-nitrification is when ammonium ions in the soil are changed into nitrates that can then be used by plants
-first, nitrifying bacteria called nitrosomonas change ammonium ions to nitrites
-then nitrobacter change nitrites to nitrates - Denitrification
-denitrification is when nitrates in the soil are converted into nitrogen gas by denitrifying bacteria, they use nitrates in the soil to carry out respiration and produce nitrogen gas
-this happens under anaerobic conditions eg. in waterlogged soils
what is primary succession?
what is secondary succession?
-happens on land that has been newly formed or exposed, eg. where a volcano has erupted to form a new rock surface. there is no soil or organic material to start with, just bare rock
-happens on land that’s been cleared of all the plants, but where the soil remains eg. after a forest fire or after deforestation
succession stages-
- primary succession:
-starts when a species colonise a new land surface
-seeds and spores are blown in by the wind and begin to grow. The first species that colonise the area are called pioneer species
-the abiotic conditions are harsh eg. no soil to retain water = pioneer species are specialised to grow with harsh conditions (marram grass can grow on sand dunes because it has deep roots and can tolerate salty environment).
-the pioneer species change the abiotic conditions = they die and microorganisms decompose the dead organic material (humus) = forms basic soil
-this makes conditions less harsh = soil retains water = new organisms can grow = these die and are decomposed = adding more organic material = making soil deeper and richer in minerals = larger plants like shrubs can grow which retain more water = more plants = more habitats = more animals. - Secondary succession happens in the same way but starts at a later stage as there is already a soil layer- the pioneer species are larger plants eg. shrubs
- at each stage, better plants and animals that are better adapted for the improved conditions move in, then out compete the plants and animals that are already there and become the dominant species in the ecosystem
- as succession goes on, the ecosystem becomes more complex. new species move in alongside existing ones which means the species diversity increases
- amount of biomass increases because plants at later stages are larger and more dense eg. woodland
- final stage is called the climax community- the ecosystem is supporting the largest and most complex community of plants and animals it can. It is at a steady state and will not change much more.
