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Question 1

(a) Topic: 16.5 (sex hormones in humans)
(b) Topic: 16.5 (sex hormones in humans)
(c) Topic: 16.4 (sexual reproduction in humans)
 

(a)  Fig. 1.1 shows the changes in the concentration of two hormones involved in the menstrual cycle

(i) State the names of the hormones Y and Z in Fig. 1.1.
(ii) On Fig. 1.1, sketch a line to show the levels of progesterone through the 28-day menstrual cycle. 
(iii) State the day in the 28-day menstrual cycle when the egg is most likely to be released from a follicle.
(iv) State the main site of progesterone production during pregnancy.

(b) Egg cells are contained in follicles in the ovary.
At the start of the menstrual cycle, a follicle has an average diameter of 29µm.
Just before an egg is released from the follicle, the follicle has an average diameter of 22mm.
Calculate the percentage increase in the average diameter of the follicle from the start of the
menstrual cycle, until just before an egg is released.
Step 1 Convert the average starting diameter of a follicle to millimetres (mm).
Step 2 Calculate the percentage increase.
Step 3 Give your answer to three significant figures.
(c) Once an egg cell has been released from a follicle it can be fertilised by a sperm cell.
State three adaptive features of a sperm cell.

▶️Answer/Explanation

1.(a)

(i) Y is FSH , Z is LH 

(ii) line drawn:
low until day 14 
increasing until day 21, then a decrease 

(iii) 14 
(iv) Placenta the main site of progesterone production during pregnancy

1.(b)

Step 1: 0.029 (mm)
Step 2: 75 762 
Step 3: 75 800 (%)

1(c)  Adaptive features of a sperm cell:

  • flagellum
  • (many) mitochondria
  • acrosome (containing enzymes)
  • haploid (nucleus)

Question 2

(a) Topic: 7.5 (absorption)
(b) Topic: 9.3 (blood vessels)
(c) Topic: 17.2 (mitosis)
(d) Topic: 7.2 (digestive system)
 

(a) The small intestine is lined with many villi and is adapted to absorb glucose.
Fig. 2.1 shows two villi from the lining of the small intestine.

(i) State the name of structure N in Fig. 2.1.
(ii) Cell M in Fig. 2.1 secretes mucus.
State the name of cell M.
(iii) State one other place in the body where mucus secreting cells are found.

(iv) Describe and explain how the structure of a villus is adapted for its function.

(b) State the name of the main blood vessel that takes blood from the small intestine to the liver.
(c) All cells develop from stem cells.
Describe what is meant by the term stem cell.

(d) Some cells in the small intestine have many mitochondria.
Fig. 2.2 shows the variation in the average number of mitochondria found in three different types of cell.

Explain the differences in the average number of mitochondria in each type of cell

▶️Answer/Explanation

2(a)

(i) lacteal 
(ii) goblet (cell) 
(iii) trachea / bronchi / bronchioles 

(iv) Any four from:

  • microvilli

(microvilli) provide a large surface area

  • epithelium / lining, one cell thick / thin 

ref. to diffusion

ref. to enzyme production

  • good blood supply

(good blood supply) to maintain a steep concentration gradient 

ref. to lacteal / N, and fat transport  

2(b) Hepatic portal vein is the main blood vessel that takes blood from the small intestine to the liver

2(c)Any two from:
unspecialised (cells)
that divide by mitosis  (to produce daughter cells) that become specialised (for specific functions) 

2(d) Any five from:
1 mitochondria are site of aerobic respiration 
2 release energy 
3 heart / intestine (cells), respire more 
4 heart (cells) (continuously) contract 
5 epithelial cells need more energy 
6 active transport in the small intestine 
7 red blood cells need space, for haemoglobin / oxygen 
8 red blood cells, are moved in the blood / do not (actively) move 
9 red blood cells, take up/ release, oxygen by diffusion 
10 so no energy needed for active transport 
11 idea that it is good if RBCs do not use up the oxygen they transport 

Question 3

(a) Topic: 1.3 (features of organisms)
(b) Topic: 14.2 (sense organs)
(c) Topic: 14.2 (sense organs)
 

 (a) (i) Frogs are classified as amphibians.
State two features of amphibians that distinguish them from all other vertebrates.
(ii) Fig. 3.1 is a photograph of a cross-section of a frog’s eye

Identify the structures labelled G and H in Fig. 3.1.

(i) Identify cell structures K, L and M in Fig. 3.2.

(ii) State the names of the two parts of the mammalian central nervous system

(c) Fig. 3.3 is a graph showing the distribution of rod cells and cone cells across the retina in a
human eye.

(i) On Fig. 3.3 draw:
• the letter P to show the location of the fovea
• the letter Q to show the location of the blind spot.
(ii) Describe and explain the distribution of rod cells and cone cells shown in Fig. 3.3.

(iii) Some mammals are nocturnal which means they are active at night and sleep during the day.
Suggest how the number and distribution of rod cells and cone cells across the retina of a nocturnal mammal would differ from a human retina.

▶️Answer/Explanation

(a)(i) Any two from:
eggs laid in / larvae live in, water and adults live on land 
two stage life cycle 
gas exchange occurs through skin (and lungs) 
larva have gills and adults have lungs 
moist skin (described) 

(a)(ii) G cornea 
H lens 

(b)(i) K (cell) membrane 
L cytoplasm 
M nucleus 

(b)(ii) brain and spinal cord 
(c)(i) P draw on the graph in the fovea (area on the graph where there is the highest number of cone cells and no rod cells) 
Q draw on the graph in the blind spot (area on the graph where there are no cone cells or rod cells) 

(c)(ii) Any five from:
Describe:
1 more rod cells than cone cells 
2 (number of) cone cells peak, in the middle / at the fovea 
3 there are no rod cells where the number of cone cells is highest 
4 ref. to uneven distribution of rod cells, either side of the middle / fovea 
5 no rod cells and no cone cells at blind spot 
Explanation:
6 light absorbed (by a pigment) 
7 rods detect low light (intensity) 
8 (rods) do not detect colour 
9 (rods) provide night vision 
10 (cones) detect high light (intensity) 
11 (cones) detect colour 
12 any detail, e.g. three different types of cone 
13 (no rods and cones at blind spot) because of optic nerve 

(c)(iii) more rods present and no / fewer cones present 
rods at the fovea / rods mainly at periphery 

Question 4

(a) Topic: 17.2 & 17.3 (mitosis and meiosis)
(b) Topic: 18.1 (variation)
 

Mitosis and meiosis are both important processes for life.
(a) Complete the sentences about mitosis and meiosis.
Mitosis is a type of nuclear division which produces genetically identical cells.
It is important for growth, ……………………………………. of tissues and
……………………………………. reproduction.
Just before mitosis the chromosomes are replicated and then the chromosomes
……………………………………. so that the chromosome number is maintained in each daughter cell.
Meiosis is another type of nuclear division that is involved in the production of gametes. The chromosome number is halved from ……………………………………. to haploid resulting in genetically different cells. The fusion of the nuclei of two gametes formed by meiosis forms a ……………………………………. . This process is known as ……………………………………. .
(b) Mutations are a source of genetic variation in a population.
(i) Describe what is meant by a gene mutation.
(ii) State two examples of how mutation rates can be increased.

▶️Answer/Explanation

(a) repair 
asexual 
separate 
diploid 
zygote 
fertilisation 

(b)(i) random  change in the base sequence of DNA ;

(b)(ii) ionising radiation 
(named) chemicals 

Question 5

(a) Topic: 20.4 (conservation)
(b) Topic: 20.4 (conservation)
(c) Topic: 20.4 (conservation)
 

Fig. 5.1 shows the changes in the percentage of the total global fish stocks that are overfished and those that are sustainable.

(a) Use the information in Fig. 5.1 to:
(i) State the percentage of fish stocks that were sustainable in 2020.
(ii) State which five-year period had the greatest increase in sustainable fish populations

(b) Overfishing is one reason why populations of fish decline.
Explain the risks to a species if its population size decreases.

(c) Describe and explain how fish stocks can be managed sustainably and how overfishing can be prevented through conservation.

▶️Answer/Explanation

(a)(i) 66%
(a)(ii) 1985 to 1990 ; 1
(b) Any three from:
reduction in genetic variation / reduced gene pool 
inbreeding ;
idea of an increase in the frequency of recessive alleles 
(described) consequence of having too many recessive alleles 
risk of extinction 
idea of unable to find mates

5(c) Any six from:
1 education / awareness 
2 monitoring the populations 
3 ref. to net type 
4 ref. to mesh size 
5 reduced demand (to eat from unsustainable fish stocks) 
6 alternative sources of fish 
7 treaties / licenses / fines / laws / making it illegal 
8 (legal) quotas / restricted catch weight 
9 no-catch zones / nursery zones / protected areas / Marine Protected Areas 
10 fish farms 
11 closed fishing season
12 restocking / captive breeding and release 

Question 6

(a) Topic: 12.3 (lactic acid)
(b) Topic: 12.3 (lactic acid)
(c) Topic: 12.3 (lactic acid)

(a) Fig. 6.1 is a diagram showing how glucose is used by different organisms

(i) State the number or numbers from Fig. 6.1 that identify the processes that:
• release the most energy per glucose molecule
• take place in yeast cells.
(ii) State the balanced chemical equation for anaerobic respiration in a yeast cell.
(iii) State the names of two enzymes that are needed to break down starch into glucose in humans.
(iv) State the main use of the molecule cellulose in a plant

(v) Sucrose and amino acids are transported around a plant.
State the name of:
• the process by which sucrose is transported around a plant
• the tissue that transports sucrose and amino acids around a plant
• the mineral ion that is used to make amino acids

(b) In humans, the build-up of lactic acid creates an oxygen debt.
(i) State the body tissue that produces the most lactic acid during vigorous exercise.
(ii) The oxygen debt needs to be removed after exercise.
State how the breathing and circulatory systems act to remove the oxygen debt.

(iii) State the name of the organ which breaks down lactic acid.

▶️Answer/Explanation

(a)(i)
1 and 3 

(a)(ii) \(C_6H_{12}O_6 → 2C_2H_5OH + 2CO_2\)

(a)(iii) amylase 
maltase 

(a)(iv) (to build) cell walls / provide support 
(a)(v) Translocation is the process by which sucrose is transported around a plant
Phloem is the tissue that transports sucrose and amino acids around a plant
Nitrate(s) is the mineral ion that is used to make amino acids

(b)(i) Muscle is the body tissue that produces the most lactic acid during vigorous exercise.

(b)(ii) Any two from:

continuation of deeper breathing / faster breathing
continuation of fast heart rate
idea of delivering oxygen for the breakdown of lactic acid / delivering lactic
acid to the liver to be broken down

(b)(iii) Liver is the organ which breaks down lactic acid.

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