Question 1
(a) Topic: 2.1 (cell structure) (b) Topic: 3.2 (osmosis)
Fig. 1.1 is a diagram of an animal cell.
(a) Complete Table 1.1 by writing the name and function of each of the labelled parts of the cell shown in Fig. 1.1.
(b) (i) Explain how water moves into and out of animal cells.
(ii) A sample of red blood cells was taken from a person. The red blood cells were put into three test‑tubes. Each test‑tube contained a different liquid:
• blood plasma
• pure water
• a very concentrated salt solution.
Fig. 1.2 shows the appearance of the red blood cells when examined using a microscope. Identify the liquids the red blood cells were immersed in. Write your answers in the spaces provided in Fig. 1.2.
(iii) State the name of the molecule in red blood cells that combines with oxygen.
(iv) Fig. 1.3 shows a drawing of a white blood cell.
Identify the type of white blood cell shown in Fig. 1.3.
▶️Answer/Explanation
Ans
(a) (b)(i) any three from:
by osmosis ;
from high(er) water potential to low(er) water potential / down a water
potential gradient ;
through a partially permeable membrane ;
ref. to, kinetic energy / random motion of molecules
(ii) in this order vertically:
(blood) plasma
(a very concentrated) salt solution
(pure) water
(iii) haemoglobin
(iv) phagocyte
Question 2
(a) Topic: 1.3 (features of organisms) (b) Topic: 16.1 (Asexual reproduction) (c) Topic: 16.3 (sexual reproduction in plants) (d) Topic: 16.3 (sexual reproduction in plants)
Fig. 2.1 is a photograph of a spider plant, Chlorophytum comosum. Spider plants can reproduce by producing an identical plantlet, which grows away from the single parent plant.
(a) (i) Identify one feature in Fig. 2.1 that shows that spider plants are monocotyledons.
(ii) Describe the advantages and disadvantages of asexual reproduction in a population of spider plants in the wild.
(b) Fig. 2.2 shows pollen that has been released from the flowers of a hazel tree, Corylus avellana. These flowers are wind‑pollinated.
(i) Explain why a hazel tree has to produce very large amounts of pollen.
(ii) Describe how a stigma from a wind‑pollinated plant is adapted for pollination.
(c) The hazel tree uses cross‑pollination rather than self‑pollination. Describe cross‑pollination.
(d) Outline the events that occur in the flower after pollination.
▶️Answer/Explanation
Ans
(a)(i) any one from:
strap-shaped / narrow / AW, leaves ; parallel / not branched, veins
(ii) any four from:
advantages
1 fast ;
2 no need for, pollination / pollinators ;
3 no need for, pollen / gametes / fertilisation ;
4 offspring adapted to parent’s environment ;
disadvantages
5 no / low, (genetic) variation ;
6 more susceptible to (named) environmental change ;
7 more susceptible to a new disease OR disease spreads fast through a population ;
8 offspring are, very close / in competition ;
9 AVP
(b)(i) increases the chance of reaching a, stigma / plant / AW
(ii) large / long / feathery / (hanging) outside the flower
(c) the transfer of pollen grains from the anther to the stigma ; on a different plant of the same species
(d) any four from:
1 pollen tube growing from a pollen grain ;
2 pollen (tube / grain) releases enzymes ;
3 (pollen tube) grows down style / grows into ovary ;
4 pollen / male, nucleus travels down the pollen tube ;
5 pollen tube grows / pollen nucleus or male nucleus moves, through the micropyle / (in)to the ovule ;
6 fertilisation occurs ;
7 pollen / male, nucleus fuses with female nucleus ;
8 zygote formed ;
9 AVP
Question 3
(a) Topic: 4.1 (biological molecules) (b) Topic: 5.1 (enzymes)
(a) Proteins are biological molecules. Explain how proteins are made.
(b) Fig. 3.1 is a diagram of enzyme 1 catalysing the breakdown of molecule A into two smaller molecules, B and C.
Molecule D, shown in Fig. 3.2, is added to the mixture shown in Fig. 3.1. This causes the rate of production of molecules B and C to decrease.
(i) Using the information in Fig. 3.1 and Fig. 3.2, suggest why the rate of production of molecules B and C decreases after molecule D is added.
(ii) Fig. 3.3 shows enzyme 1 after a change in its environmental conditions.
Suggest two changes that could cause the effect on enzyme 1 shown in Fig. 3.3
▶️Answer/Explanation
Ans
(a) any six from:
messenger RNA (mRNA) is a copy of, a gene / DNA ;
mRNA is made in the nucleus ;
the gene (coding for the protein) / DNA, remains in the nucleus ;
mRNA moves to the, cytoplasm / ribosome ;
mRNA passes through ribosomes ;
the ribosome assembles amino acids into, polypeptide / protein ;
the (specific) sequence of amino acids is determined by the sequence of
bases in mRNA ;
AVP
(b)(i) any two from:
(molecule) D has a similar shape to (substrate) A ;
shape of (molecule) D is complementary to the active site ;
(molecule) D, binds to / fits, the active site ;
reduces / prevents, (substrate) A binding to enzyme ;
idea of (substrate) A cannot be broken down / less substrate A is broken down
(ii) increased temperature ;
(increased / decreased / extreme) pH
Question 4
(a) Topic: 17.1 (chromosomes, genes and proteins) (b) Topic: 17.4 (monohybrid inheritance) (c) Topic: 17.4 (monohybrid inheritance)
Characteristics of plants are controlled by genes. Alleles are alternative forms of a gene.
(a) Explain how new alleles are formed.
(b) The number of hours of daylight affects when plants produce flowers. This ensures that flowers are produced at an appropriate time of year for each species. This response to the number of hours of daylight is controlled by genes.
(i) Wheat is a crop plant. A farmer wants to produce a type of wheat that flowers when there are fewer hours of daylight. Describe how the farmer could selectively breed this type of wheat.
(ii) Wheat is grown from seeds. State two conditions needed for the germination of seeds.
(iii) Different types of wheat have also evolved through natural selection. Explain how natural selection differs from artificial selection.
(c) Scientists can selectively breed for increased pest resistance in wheat. Explain the benefits of growing wheat with increased pest resistance.
▶️Answer/Explanation
Ans
(a) any two from:
through mutation ;
(mutation is ) a change in the base sequence of DNA ;
(mutation is) caused by, ionising radiation / chemicals
(b)(i) any three from:
selection of individual plants which, flower in fewer hours of daylight / show the desirable feature ;
crossing these individuals to produce the next generation ;
selection of offspring that show the desirable feature ;
repeat for (many) generations ;
AVP
(ii) any two from:
water ;
oxygen ;
a suitable temperature
(iii) any three from:
in natural selection
selection pressure / AW, comes from the environment ;
better adapted individuals (survive and) reproduce ;
(always) produces characteristics suitable for the (new) environment ;
slower ;
affects many characteristics
(c) any two from:
less pesticides used ;
less contamination of food with pesticides ;
less pollution / described ;
less damage to / higher yield of / higher quality of, crop ;
less risk to pollinators / non target species ;
improve health of farm workers ;
less spread of plant disease ;
increases biodiversity
Question 5
(a) Topic: 6.1 (photosynthesis) (b) Topic: 19.2 (food chains and food webs) (c) Topic:7.1 (diet) (d) Topic: 7.4 (chemical digestion)
Phytoplankton are microorganisms that photosynthesise.
(a) State the chemical equation for photosynthesis.
(b) A scientist made notes about a marine food web. Fig. 5.1 shows the notes she made.
(ii) State the principal source of energy for this food web.
(iii) Table 5.1 describes features of the food web in Fig. 5.2. Complete Table 5.1, using the information in Fig. 5.2
(iv) Fig. 5.3 is a photograph of an orca.
Using the information in Fig. 5.2, predict and explain the most likely effect of a decrease
in the orca population on the population size of:
krill …………………………………………………………………………………………………………………….
leopard seals. ……………………………………………………………………………………………………..
(c) Krill and seals can be harvested to produce omega‑3 fatty acids. Many people take omega‑3 fatty acids as a dietary supplement as they are thought to have health benefits in humans.
(i) List the chemical elements found in all fats.
(ii) Using the information in Fig. 5.2, explain why it is more energy efficient to use krill as a source of omega‑3 fatty acids rather than seals.
(d) Describe how fats ingested by humans are digested and absorbed.
▶️Answer/Explanation
Ans
(a) \(6CO_2 + 6H_2O \to C_6H_{12}O_6 + 6O_2\)
(b)(i) phytoplankton and zooplankton in the correct positions ; herring (fish) and cod (fish) in the correct positions
(ii) the Sun / sunlight
(iii)
(iv) krill:
decrease (in population size) as more predation (by crabeater
seal / Adélie penguin) ;
leopard seal:
increase (in population size) as less predation (by orca)
(c)(i) carbon, hydrogen and oxygen
(ii) 1 energy is lost at each trophic level / AW ;
2 & 3 (energy lost through) metabolism / excretion / movement / faeces / indigestible parts / active transport / thermoregulation ;;
4 krill is at a lower trophic level than seals ; ora
(d) any four from:
physical / mechanical digestion ;
emulsified by bile (in the small intestine) ;
increase the surface area of fats (for enzymes) ;
(fats digested by) lipase ;
(lipase) secreted / produced, by pancreas ;
(lipase) breaks fat down into glycerol and fatty acids ;
absorbed by, lacteals / (micro)villi ;
(absorbed) in small intestine
Question 6
(a) Topic: 1.2 (concept and uses of classification systems) (b) Topic: 19.4 (populations) (c) Topic: 19.4 (populations) (d) Topic: 20.4 (conservation)
Fig. 6.1 shows a boreal toad, Anaxyrus boreas. This toad is listed as an endangered species.
(a) State the genus of the boreal toad.
(b) One reason for the boreal toad’s recent decrease in population is a disease caused by chytrid fungus. State two reasons other than disease that could cause the boreal toad to become endangered.
(c) Scientists investigated whether increasing the number of beneficial bacteria that live on the toads’ skin could provide protection against the fungus. The scientists took 42 toads and placed 21 in group 1 and 21 in group 2.
• Group 1 – the toads’ skin was treated with beneficial bacteria.
• Group 2 – the toads’ skin was not treated with beneficial bacteria.
The scientists measured the number of toads that became infected with the fungus.
Table 6.1 shows the results.
(i) Calculate the percentage of the 21 toads that have the fungal infection after 100 days in group 1 in Table 6.1. Give your answer to two significant figures. Space for working.
(ii) Using the information in Table 6.1, describe the effect of treating the toads with beneficial bacteria.
(d) There are conservation programmes to reintroduce boreal toads into their natural habitat.
(i) Describe why conservation programmes are set up for animals like the boreal toad.
(ii) Conservation programmes for other endangered animals, such as birds, use artificial insemination as part of a captive breeding programme. Describe how artificial insemination is carried out as part of a captive breeding programme.
▶️Answer/Explanation
Ans
(a) Anaxyrus
(b) any two from:
climate change / global warming ;
habitat destruction / deforestation ;
hunting ;
pollution ;
introduced species ;
overharvesting ;
AVP
(c)(i) 62 (%)
(ii) any two from:
bacterial treatment reduces the number of toads with fungal infection ;
there is no effect of treatment in 0 to 20 / (first) 40 days ;
bacteria treatment reduces fungal infections from, 40 to 100 / 60 to 100 days ; suitable comparative data quote
(d)(i) any three from:
maintaining / increasing, biodiversity ;
reducing extinction / increase population size / repopulate ;
maintaining food, webs / chains ;
maintaining source of future, food / drugs / genes ;
protecting vulnerable, ecosystem / habitat ;
ref. to effects on nutrient cycles ;
AVP ;
(ii) any four from:
collect, sperm / gamete / semen (from male) ;
males can be chosen from different breeding programmes ;
to maximise genetic variation ;
sperm, screened / quality checked / AW ;
sperm / semen, frozen ;
(female) given drugs to induce ovulation ;
sperm / semen, placed in, vagina / uterus / oviduct ;
sperm / semen, inserted at appropriate time for ovulation