Studied by 4 people
Timezone 2. Questions with answers. NB! Specific formulations chosen based on markscheme.
Describe the effect of neonicotinoid pesticides on the nervous system of insects.
They block synaptic transmission They bind to receptors
State the cumulative increase in the mass of control colonies at 7 weeks.
230 grams
Compare and contrast the cumulative increase in mass of three groups of colonies once they were placed in the field.
All three groups decreased in cumulative mass gain after 6 weeks Colonies exposed to high concentration always had the lowest cumulative gain
Suggest a reason for the changes in mass in the colonies between week 6 and 8
Less production of honey Fewer bees
Using the data in the graph, predict how the use of neonicotinoid pesticides will affect bumblebee populations.
A number of populations will decrease Without new queens, new colonies cannot be founded New colonies are essential to maintain bumblebee populations
Identify the species whose eggs are most affected by a high dose of neonicotinoid.
B. locorum
Describe the overall effects of low and high doses of neonicotinoid on the egg lengths of all four species.
Low doses caused a decrease in the average egg length in 3 species High doses caused lower average results in all 4 species compared to the control
Deduce, based on the data presented, whether the levels of neonicotinoids used in agriculture cause direct harm to B. terrestris
Yes, as both doses affect the overall development of colonies negatively Yes, as decreased numbers of queens will likely affect their reproductive capabilities
State the main characteristic of stem cells
Undifferentiated Can differentiate into any type of cells
State one therapeutic use of stem cells
Treatment of Stargardt's disease/leukemia
Discuss how the use of stem cells to treat hereditary diseases could affect the person who received the treatment and their progeny.
It could improve the quality of life of the treated person The disease could still be passed on to progeny if the defective gene is not changed
Describe anaerobic respirations in humans and in yeast
Anaerobic respiration occurs when there is no oxygen Anaerobic respiration in yeast produces ethanol and CO2 + yields a small amount of ATP Anaerobic respiration in humans happens in muscles where lactate is produced
Distinguish between the thermal properties of water and methane
Water has a higher boiling point Water has a higher specific heat capacity
Explain the role of methane in climate change
Methane is one of the most powerful greenhouse gasses Which causes an increase in temperature in the atmosphere Methane has a shorter lifespan than CO2, but is more powerful than it
State where melatonin is produced in the body
Pineal gland
Describe one difference between melatonin levels of the day and night workers
Melatonin levels are lower in night workers
Deduce, with reason, what time of day would be a good time to take melatonin if you have traveled over several different time zones and are jet-lagged on your arrival.
Time that is in the range of local standard bed time To reestablish the circadian rhythm
Explain how the appearance of membranes in electron micrographs was used as evidence to support the Davson-Danielli model.
The black lines represent proteins 2 membrane layers can be seen There is a clear layer in the center that is composed of phospholipids
Explain the decrease in activity of the enzyme on either side of the optimum temperature
As the temperature increases, the enzyme becomes denatured As the temperature decreases, the enzyme molecules have less kinetic energy
In biotechnology, enzymes are used to transfer genes to bacteria. Outline how two specific enzymes are used for the transfer.
Restriction enzymes work by targeting a specific sequence of base pairs in DNA causing both strands of the DNA to break apart
DNA ligase attaches the gene to the plasmid
Outline energy flow through a community in a natural ecosystem
Communities are made up of populations of different species Plants receieve energy from sunlight Plants convert the sunlight energy into chemical energy through photosynthesis Chemical energy is stored in organic compounds The energy is passed through the community through the food chain Respiration converts the chemical energy to other useful forms of energy Eventually, throughout the food chain, the chemical energy is lost as heat energy Energy is thus lost from the community
Energy losses between trophic levels limit food chains
Explain how natural selection can cause traits such as drought resistance to develop in wild plants
Natural selection occurs if there is variation in the degree of drought resistance among the members of species
Variation is caused by mutations Variations may occur during meiosis as chromosomes separate or during sexual reproduction as different alleles combine
Some variations make plants more drought-resistant Examples: deeper roots, more storage tissue for water, less opening of the stomata, etc.
The variations within a species mean the better adapted (drought resistant) survive and reproduce more As they reproduce, their characteristics are passed onto offspring who are then more fit to survive
Natural selection thus increases the frequency of the adapted characteristics This leads to evolution in a species where they become more drought resistant
Suggest possible benefits and risks of using genetic modification to develop varieties of crop plants with traits such as drought resistance
Benefits: It increases crop growth It requires less water
Risks: These plants may out-compete other species in the community which can cause extinction + affect the food chain The modified gene may pass to other organisms uncontrolled GMO may always have health effects in consumers
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