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Description
Flashcards by joannalivesey, updated more than 1 year ago
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Created by joannalivesey
almost 10 years ago
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| Question | Answer |
| Why would cattle farmers want to grow clover in grassland? | • Clover contains nitrogen fixing bacteria • When the clover dies they will add lots of nitrogen compounds for soil- more grass for more cows • Farmers need to apply less fertiliser |
| why does pioneer species population decline? | out-competed by other species that are better adapted to the changed environmental conditions |
| effects of succession | • greater nutrient content in soil • more biodiversity and biomass • more niches/habitats/food sources • more complex food webs • less hostile conditions |
| what limits the size of population in a climax community? | • numbers of producers and their rate of photosynthesis to provide energy for food chains- limited by nitrates concentration/light intensity/CO2 • disease- members of species are killed • space for nest building • intra/inter specific competition for a limited resource e.g. food • predation |
| how might introduction of a new plant species reduce diversity? | • new plant competes for CO2/light/nutrients so less available for original plants • reduction in number of original plants and some species may die out altogether • loss of habitats/niches/shelter/food sources • consumers die or some migrate elsewhere |
| why does net primary production not represent total plant biomass formed by photosynthesis | • net productivity = gross productivity - respiratory losses • some biomass is respired and lost as CO2 |
| why is not all energy ABSORBED by plants transferred to organic molecules? | • energy losses in photosynthesis • energy absorbed is of wrong wavelength • energy losses due to radiation/evaporation/transpiration |
| why might nitrogen concentration increase in a river? | • fertiliser run-off (leaching) • breakdown of dead organic matter (nitrification) • sewage effluent • nitrogen fixation by bacteria in water |
| why are pests a bigger problem in monocultures? | • eggs/larvae/weeds left in soil • plentiful supply of the same food source for pest • overuse of pesticide leads to resistance • all results in rapid growth of pest population and decreased crop yield |
| Why do plants have a higher C:N ratio than animals? | • high proportion of carbohydrate in plant tissues (e.g. starch) • cellulose in cell walls • more protein in animal cells (such as muscle) |
| How do Venus fly traps get nitrogen compounds from eating insects? | • insects contain proteins • digested to amino acids • which can be absorbed into leaf |
| Comparisons of many things with one standard thing (e.g. why compare CO2 given out by burning lots of different biofuels with CO2 given out by burning petrol?) | • (petrol) Is widely and commonly used • Provides a benchmark |
| When talking about ‘correlation does not equal causation’, make sure to clearly state what the correlation is between | remember this! |
| What is water needed for in plants? | • expansion of fruit • maintain leaf turgidity • maintain stomatal opening • replace water lost in transpiration • used in photosynthesis |
| Evidence for succession | • Decrease in percentage cover of bare ground/water because there are is an increase in plant coverage • Pioneer species replaced due to competition • Increase in depth of soil as plants die and humus formed |
| Not always expected ratio because... | • Offspring ratios are a probability • Fertilisation is random • gametes may not be produced in equal numbers • Small population, so small sample • Selection advantage/disadvantage • Lethal allele |
| why does anaerobic respiration lead to muscle fatigue? | • Production of lactate • increase in H+ ions and therefore decrease in pH • Influences enzyme activity/muscle protein/contraction |
| why must animals digest plant proteins to amino acids if these proteins are to be used for? growth | • Proteins cannot be absorbed by the gut (too large and correct carrier proteins not present) but amino acids can • Animal proteins contain a different sequence of amino acids |
| why are hedges good? | • increase biodiversity • habitat for pollinators • hedge plants add different nutrients to soil (not a monoculture) • reduces wind speed so less water loss due to transpiration |
| why are hedges bad? | • Competition for nutrients/water • Lack of light (block it out) • Pests may be present in hedge • less land for crops • harder to use large machinery |
| why is it an advantage to have different niches? | • Reduce interspecific competition for resources e.g prey • Stops one species being eliminated by another |
| components of a niche | • where and what the species eats • environmental conditions required by the species • habitat • how the species responds to the abiotic/biotic environment |
| why is growing crops more efficient that rearing cattle in terms of total food production? | • energy is lost between each trophic level • shorter food chain so fewer trophic levels • crops are producers, cattle are consumers |
| environmental impact of monocultures | • Reduction in diversity- since smaller variety of niches / habitats / food sources • Reduction in soil fertility- same nutrients continually removed • Increased risk of disease- more crop-specific pests • Hedges removed- e.g. increases soil erosion |
| nitrogen fixing bacteria convert atmospheric nitrogen into... | AMMONIUM ions |
| why does water-logged soil have low nitrate concentration? | • Anaerobic conditions • Favour growth of denitrifying bacteria • Bacteria convert nitrates to atmospheric nitrogen |
| how might introduction of a new animal affect local population? | • interspecific competition for niche/resources- may outcompete • no natural predators, so increase in numbers • introduced species are a new predator species • introduce new disease |
| how you would decide the number of quadrats to use in order to collect representative data? | • Calculate running mean • When enough quadrats, this shows little change (graph levels out) • large number needed to be enough to carry out a statistical test and make sure results are representative • Need to make sure work can be carried out in the time available |
| what does the Hardy-Weinberg principal predict | The frequency of alleles of a particular gene will stay constant from one generation to the next |
| conditions of Hardy-Wienberg | • population is large- chance events (e.g. genetic bottlenecks) have smaller effect • no migration- no alleles enter or leave gene pool • there are no mutations- no new different alleles of the same gene introduced • there’s random mating- equal probability of any allele being passed on to next generation • all genotypes have same reproductive success |
| why does nitrate concentration in the soil increase with succession? | • more dead organisms and humus means more nitrification • more nitrogen fixation |
| ways in which the properties of ATP make it a suitable source of energy in biological processes | • energy released in small amounts - manageable and little waste • soluble - easily transported round cell • involves a single reaction - energy readily released |
| why should you use random sampling? | • Avoids bias • Data representative • Allows use of statistical tests |
| Suggest how the shape of mouth is an adaptation to its niche | • fish with different mouth shape eat different food • this reduces interspecific competition |
| when talking about eutrophication remember to say... | saprobionts break down dead plant matter |
| why ATP? | • Releases energy in small and manageable amounts • Broken down in a one step reaction • Immediate energy source- makes energy available rapidly • Phosphorylates substance which makes them more reactive so lowers activation energy • easily reformed ADP + Pi -> ATP |
| similarities between mitochondria and chloroplasts | • Two surface membranes (envelope) • Smooth outer membrane • DNA • Ribosomes • Electron carriers • Internal membranes that give large SA |
| why carry out a stat test? | • To see if difference is significant or due to chance • So they can reject/support the null hypothesis |
| why should we stop something going extinct? | • Maintaining genetic diversity • Ethical reasons/tourism • Avoid damage to food webs (e.g. predators have less food) • May have/produce useful genes/chemicals that we can use to treat diseases |
| advantage of using % cover | • Data can be collected rapidly • Does not require defining individual plants |
| when talking about mark, release, recapture... | always say how you would mark e.g. snail varnish |
| why does less mowing increase the number of insect species found on a roundabout? | • Mowing prevents growth of woody plants • By cutting off growing point • Less mowing means succession can progress further so diversity of plants increases • More food sources/habitants/niches available for insects |
| why are males more likely to get a sex linked recessive disease? | • MALES HAVE ONE ALLELE, so only need to inherit one faulty allele to get the disease • Females need two recessive alleles |
| advantages of carrying out investigations in natural habitats | • can see effect of other biotic/abiotic factors • can see effect on other organisms • causes less stress to animals |
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