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33 Cards in this Set
- Front
- Back
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On soils with a low conc of nitrate ions, leguminous plants often grow better. Why? |
Fix nitrogen (n2) from the atmosphere to produce ammonia/ammonium compounds Ammonia used to prouce proteins. |
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Applying high conc of fertiliser to the soil can reduce plant growth. why? |
(Weeds) Reduce water potential Less osmosis |
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2 factors that decrease death rate in humans |
Improved medical care Improved nutrition good sanitation improved economy less disease |
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Changes in a survival curve show a demographic transition. Explain how. |
Increase in life expectancy Low death rate/more older people (lower birth rate?) |
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Why are observed phenotypic ratios not equal to expected ratios? |
Not large enough sample size Selection advantage or disadvantage Fertilisation and fusion of gametes is random |
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Why are males more likely to inherit a sex-linked disease? |
Males have one ALLELE Females need two/must be homozygous |
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What evidence shows succession has occured? |
Less bare ground Change in diversity/more soil/less hostile Increase in depth of soil as humus formed |
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What conditions must be met for mark release recapture method to be valid? |
Marking is not removed/does not affect survival/predation No immigration/emigration Sufficient time for indiciduals to mix and distribute evenly No deaths/births Same sampling method |
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Why would oxygen uptake of yeast p opulation in a sealed container decrease after exponential increase |
Glucose/nutrients/oxygen decreases and becomes limiting OR cells die as toxins form/ethanol produced |
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2 advantages of carrying out experiments in natural habitats |
Can see effects of other biotic factors Can see effects of other abiotic factors |
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What happens during the LDR? |
Chlorophyll absorbs light energy Electrons gain energy (excited), move to a higher energy level, and leave molecule. electrons move along electron transport chain releasing energy Energy used to join ADP and Pi to form ATP Photolysis of water produces protons electrons and oxygen Protons and electron reduce NADP |
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Describe the reasons for the low efficiency of energy transfer through ecosystems |
Most light energy not of right wavelength/does not strike chlorophyll molecule/reflected Heat loss Through respiration Loss via faeces Excretion |
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How does a new species evolve? |
Geographical isolation no interbreeding so separate gene pool Variation due to mutation Different environmental conditions creates different selection pressures, so diff reproductive success. Some with ALLELE to survive in conditions are more likely to survive and reproduce Increase in frequency of allele (takes a long time) |
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3 reasons why increase in size of human population may reduce size of other populations |
Pollution Hunting Destroy habitats Competing for same resource
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2 factors that might result in a less-than-estimate increase in population size |
War Disease famine Contraception Poor healthcare |
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Explain the typical changes in the size of a new population |
Initial increase due to high food-availability (low environmental resistance) + less competition Slow intial rise as few individuals Decreases due to density dependent factors such as disease and intra-specific competition for food Stable as environment reaches carrying capacity |
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What would be the effect of introducing a predator into a population? |
Population size decreases and then stabilises |
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How do you know if a sample is representative? |
Running mean |
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Explain the difference between density dependent factors and density independent factors |
DDF - greater effect on pop. of larger size (food, space and disease) DIF - rainfall, temp, light availability not affected by pop. size |
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Different species of plant occupy different niches. Why? |
Different adaptations, suited to different environments. Compettive exclusion principle |
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Why are populations with a large genetic diversity more likely to survive changing conditions? |
Some individuals possess adaptations to survive |
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It takes longer for nitrogen-containing substances to get into a lake when organic fertiliser is used as opposed to inorganic fertiliser |
Organic fertiliser has to be broken down by decomposibg backteria |
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The % increase in crop yield decreases at higher fertiliser applications. Why? |
Encourage the growth of weeds Lower the pH and reduce enzyme activity Finite number of carrier protiens so no further uptake |
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Advantages of inorganic fertiliser |
Easy to store, apply and spread More control (specific nutrients) Higher conc + fast-acting |
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Disadvatnages of inorganic fertiliser |
No eutrophication/leaching Cost |
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2 features of ATP molecule that make it biologically useful |
Releases energy in a single-step hydrolysis reaciton Releases small, manageable amoutns of energy Soluble Readily available |
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When conc of CO2 is reduced, why does conc of RuBP increase? |
Less RuBP combining with CO2, but RuBP still being produced |
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Why do you radioactively label carbon dioxide in lollipop experiment? Why is a rapid action tap used? Why is hot methanol used? |
Allows detection of any carbon compounds formed from CO2 Take samples at precise, short time intervals Denature any enzymes |
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Explain why the rate of CO2 uptake decreases in cloudy conditions |
CO2 taken up in photosynthesis Low light intensity limits rate of photosynthesis |
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Explain why CO2 uptake decreases at midnight |
No photosyntehsis at midnight Stomata closed and smaller CO2 gradient |
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Explain advantage of having pigments other than chlorophyll |
more wavelengths absorbed more efficient photosynthesis can occur |
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Explain why the LIR slows down at lower temperatures. Explain why the LDR is unaffected by temp. |
Less KE Fewer collisions Fewer E-S complexes
Physical reaction/no direct enzyme involvement |
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What is the advantage of collecting a large number of results? |
More reliable MEAN Statistical tests |
