unit 4 bio flashcards

Frage	Antworten
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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