M22 Biology Paper 2

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