Biology 0610 | Paper 3 Mock 01 | Theory (Core)
Question 1 Report
During hard exercise a runner's leg muscles respire more quickly to release the energy needed for contraction. Aerobic respiration produces carbon dioxide as a waste product, so the concentration of carbon dioxide dissolved in the blood begins to rise. The body monitors this concentration closely and acts to bring it back within its normal range once the exercise is over. In the investigation shown, a runner exercised for a fixed period and then rested, while the concentration of carbon dioxide in her blood was measured at regular intervals. The graph below plots blood carbon dioxide concentration against time in minutes, with the exercise period and the recovery period marked above the curve. The concentration climbs during the exercise, reaches a peak, and then falls back during recovery. Use the graph and your own knowledge of control systems to answer the questions.
(a) State the part of the brain that monitors the composition and temperature of the blood. [1]
(b) Using the graph to help you, describe how negative feedback returns the raised blood carbon dioxide concentration to normal during the recovery period. [3]
The graph shows blood carbon dioxide concentration rising during exercise and falling back during recovery, which is an example of negative feedback.
(a) The part of the brain that monitors the composition and temperature of the blood is the hypothalamus (the brain stem is also accepted for CO2 monitoring). [1]
(b) Negative feedback returns the raised CO2 to normal during recovery as follows [3]: the rise in carbon dioxide is detected by receptors in the brain [1]; the breathing rate and depth (and heart rate) increase [1]; so more carbon dioxide is removed/exhaled at the lungs, returning its concentration to normal [1]. Negative feedback means the correction acts to reverse the change and switches off once the normal level is restored, which is why the curve levels out at the end.
Answer Details
The graph shows blood carbon dioxide concentration rising during exercise and falling back during recovery, which is an example of negative feedback.
(a) The part of the brain that monitors the composition and temperature of the blood is the hypothalamus (the brain stem is also accepted for CO2 monitoring). [1]
(b) Negative feedback returns the raised CO2 to normal during recovery as follows [3]: the rise in carbon dioxide is detected by receptors in the brain [1]; the breathing rate and depth (and heart rate) increase [1]; so more carbon dioxide is removed/exhaled at the lungs, returning its concentration to normal [1]. Negative feedback means the correction acts to reverse the change and switches off once the normal level is restored, which is why the curve levels out at the end.
Question 2 Report
The photograph was taken through a light microscope and shows a single-celled microorganism greatly magnified. Microorganisms are extremely small and often look similar to one another, so they cannot be sorted into groups by their appearance alone. Instead, biologists examine features such as whether the cell contains a true nucleus, what material the cell wall is made from, and whether the organism is made of one cell or many. Viruses are sometimes studied alongside microorganisms because they too are very small and can cause disease, but a virus is not placed in any kingdom of living organisms.
(a) State the kingdom in which a microorganism whose cells have no true nucleus is placed. [1]
(b) State two features that could be used to decide whether a microorganism is a fungus or a bacterium. [2]
(c) Explain why a virus is not classed as a living organism in the same way as the microorganism shown. [2]
(d) Explain why the cell structure of a microorganism is a more reliable basis for classification than its overall size. [2]
This question is about classifying microorganisms by cell structure, and why viruses are not classed as living.
- Kingdom with no true nucleus [1]. The prokaryotes (Prokaryotae) [1] - for example bacteria.
- Two features separating a fungus from a bacterium [2, any two]. A fungus has a true nucleus while a bacterium does not; a fungal cell wall is made of chitin while a bacterial wall is not; a fungus is often multicellular (with hyphae) while a bacterium is a single cell. Any two.
- Why a virus is not living [2]. A virus is not made of cells and has no cytoplasm or organelles [1]; it cannot carry out the characteristics of living organisms on its own and can only reproduce inside a host cell [1].
- Why cell structure is more reliable than size [2]. Cell structure (such as having a nucleus or a particular cell wall) is a constant, shared feature of a group [1]; overall size varies between individuals and overlaps between different groups, so it cannot reliably separate them [1].
Answer Details
This question is about classifying microorganisms by cell structure, and why viruses are not classed as living.
- Kingdom with no true nucleus [1]. The prokaryotes (Prokaryotae) [1] - for example bacteria.
- Two features separating a fungus from a bacterium [2, any two]. A fungus has a true nucleus while a bacterium does not; a fungal cell wall is made of chitin while a bacterial wall is not; a fungus is often multicellular (with hyphae) while a bacterium is a single cell. Any two.
- Why a virus is not living [2]. A virus is not made of cells and has no cytoplasm or organelles [1]; it cannot carry out the characteristics of living organisms on its own and can only reproduce inside a host cell [1].
- Why cell structure is more reliable than size [2]. Cell structure (such as having a nucleus or a particular cell wall) is a constant, shared feature of a group [1]; overall size varies between individuals and overlaps between different groups, so it cannot reliably separate them [1].
Question 3 Report
Fig. 4.1 shows a synapse, the junction between two neurones, labelled X and Y, in the spinal cord. Where they meet the two neurones do not quite touch, and a very small gap, labelled G, separates the end of neurone X from the start of neurone Y. When a nerve impulse travelling along neurone X reaches this point, it cannot simply jump across the gap as an electrical signal. Instead the signal is carried across by a chemical released from neurone X. Fig. 4.1 shows the ending of neurone X, the gap G and the membrane of neurone Y beyond it.
(a) Name the small gap labelled G between the two neurones. [1]
(b) Name the chemical that is released to carry the signal across gap G. [1]
(c) Describe how an impulse is passed from neurone X to neurone Y across the synapse. [4]
(d) Explain why an impulse can cross this synapse in one direction only. [2]
(e) Suggest one reason why some drugs change a person's mood by acting at synapses. [1]
(a) The small gap G is the synaptic gap (synaptic cleft). [1]
(b) The chemical released to carry the signal across the gap is a neurotransmitter. [1]
(c) Four linked steps (1 mark each): the impulse reaches the end of neurone X; the vesicles release a neurotransmitter into the gap; the neurotransmitter diffuses across the gap; and it binds to receptors on neurone Y, triggering a new impulse. [4]
(d) The neurotransmitter is released only from neurone X [1], and the receptors are only on neurone Y [1], so the signal can pass from X to Y but never the other way. [2]
(e) Many mood-changing drugs work because they add to, imitate or block the neurotransmitter (or its receptors) at the synapse, altering the impulses that reach the brain. [1]
Answer Details
(a) The small gap G is the synaptic gap (synaptic cleft). [1]
(b) The chemical released to carry the signal across the gap is a neurotransmitter. [1]
(c) Four linked steps (1 mark each): the impulse reaches the end of neurone X; the vesicles release a neurotransmitter into the gap; the neurotransmitter diffuses across the gap; and it binds to receptors on neurone Y, triggering a new impulse. [4]
(d) The neurotransmitter is released only from neurone X [1], and the receptors are only on neurone Y [1], so the signal can pass from X to Y but never the other way. [2]
(e) Many mood-changing drugs work because they add to, imitate or block the neurotransmitter (or its receptors) at the synapse, altering the impulses that reach the brain. [1]
Question 4 Report
The photograph shows one example animal taken from each of the five groups of vertebrates, and the table underneath compares the same five groups. All of these animals have a backbone, but the groups differ from one another in several ways. The table records the kind of covering found on the outside of the body, the organ that the adult animal uses for gas exchange, the type of egg that is produced, and the way in which the body temperature is controlled. Biologists use features of this kind to place an unknown vertebrate into the correct group.
| Feature | Fish | Amphibian | Reptile | Bird | Mammal |
|---|---|---|---|---|---|
| Body covering | wet scales | moist skin | dry scales | feathers | hair / fur |
| Gas exchange (adult) | gills | lungs and skin | lungs | lungs | lungs |
| Eggs | soft, laid in water | soft, laid in water | leathery shell, on land | hard shell, on land | develop inside female |
| Body temperature | ectothermic | ectothermic | ectothermic | endothermic | endothermic |
(a) State the type of body covering found on a bird. [1]
(b) State one feature, shown in the table, that distinguishes a mammal from a reptile. [1]
(c) Describe three ways in which a fish is adapted to life in water. [3]
(d) Explain why reptile eggs can survive on dry land but the eggs of most fish and amphibians cannot. [3]
(e) State the meaning of the term endothermic. [2]
(f) Suggest one advantage to a mammal of allowing its young to develop inside the body. [2]
Labelled answer diagram:
(a) Body covering of a bird [1]
Feathers.
(b) One feature distinguishing a mammal from a reptile [1, max 1]
Any one from the table: a mammal has hair / fur whereas a reptile has dry scales; or a mammal is endothermic whereas a reptile is ectothermic; or a mammal's young develop inside the female whereas a reptile lays eggs.
(c) Three adaptations of a fish to life in water [3, max 3]
Any three of: gills to obtain (dissolved) oxygen from the water [1]; a streamlined body and scales to reduce resistance to movement through water [1]; fins for movement and steering [1]; large numbers of eggs fertilised externally in the water [1].
(d) Why reptile eggs survive on dry land but most fish and amphibian eggs cannot [3]
Reptile eggs have a waterproof, leathery shell that stops the egg drying out in air on land [1]; fish and amphibian eggs have no shell, only a soft jelly coat, so they lose water and dry out in air [1]; also, fertilisation in fish and amphibians is external and needs water, which land does not provide [1].
(e) Meaning of endothermic [2]
An endothermic animal keeps its internal body temperature (almost) constant [1]; independent of the temperature of its surroundings [1].
(f) One advantage of young developing inside the body [2, max 2]
The young are protected inside the mother's body [1]; and are kept warm and supplied with food and oxygen, improving their chance of survival [1].
Answer Details
Labelled answer diagram:
(a) Body covering of a bird [1]
Feathers.
(b) One feature distinguishing a mammal from a reptile [1, max 1]
Any one from the table: a mammal has hair / fur whereas a reptile has dry scales; or a mammal is endothermic whereas a reptile is ectothermic; or a mammal's young develop inside the female whereas a reptile lays eggs.
(c) Three adaptations of a fish to life in water [3, max 3]
Any three of: gills to obtain (dissolved) oxygen from the water [1]; a streamlined body and scales to reduce resistance to movement through water [1]; fins for movement and steering [1]; large numbers of eggs fertilised externally in the water [1].
(d) Why reptile eggs survive on dry land but most fish and amphibian eggs cannot [3]
Reptile eggs have a waterproof, leathery shell that stops the egg drying out in air on land [1]; fish and amphibian eggs have no shell, only a soft jelly coat, so they lose water and dry out in air [1]; also, fertilisation in fish and amphibians is external and needs water, which land does not provide [1].
(e) Meaning of endothermic [2]
An endothermic animal keeps its internal body temperature (almost) constant [1]; independent of the temperature of its surroundings [1].
(f) One advantage of young developing inside the body [2, max 2]
The young are protected inside the mother's body [1]; and are kept warm and supplied with food and oxygen, improving their chance of survival [1].
Question 5 Report
The volume of gas released by an aquatic plant can be used to measure the rate of photosynthesis. The apparatus shown was used to measure the rate of photosynthesis of a piece of pondweed placed in a test tube of water. The gas released from the cut end of the stem was collected in an inverted tube and its volume was measured over a fixed period of time. Before starting, sodium hydrogencarbonate solution was added to the water surrounding the plant. A bright lamp provided a constant light intensity and the temperature of the water was kept steady throughout the investigation. A student used this arrangement to measure the rate of photosynthesis and to confirm which factors were needed for the process to take place.
(a) Name the gas collected in the apparatus. [1]
(b) Describe how you would use this apparatus to measure the rate of photosynthesis. [3]
(c) Explain why sodium hydrogencarbonate solution was added to the water. [2]
(d) Suggest a control that would show the gas is produced by photosynthesis. [2]
(e) Name the green pigment needed for photosynthesis. [1]
(a) Gas collected [1]. The gas given off by the illuminated pondweed is oxygen [1], the by-product of photosynthesis.
(b) How to measure the rate [3]. Measure the volume of gas collected in the inverted tube [1]; over a fixed, measured period of time (using a stopwatch) [1]; then calculate \(\text{rate}=\dfrac{\text{volume of gas}}{\text{time}}\), repeating and taking a mean for reliability [1]. (An equivalent accepted method is to count the bubbles released per minute.)
(c) Why sodium hydrogencarbonate was added [2]. It slowly releases/supplies carbon dioxide to the water [1]; this ensures carbon dioxide is plentiful so that it does not become the limiting factor, and the rate then reflects the factor being studied (light) rather than a shortage of \(\text{CO}_2\) [1].
(d) A control to show the gas is from photosynthesis [2]. Set up identical apparatus but place it in the dark / cover it so no light reaches the plant [1]; little or no gas is then produced, showing that light (and therefore photosynthesis) is needed for the gas to be released [1].
(e) Green pigment [1]. Chlorophyll [1], which absorbs the light energy used to drive photosynthesis.
Answer Details
(a) Gas collected [1]. The gas given off by the illuminated pondweed is oxygen [1], the by-product of photosynthesis.
(b) How to measure the rate [3]. Measure the volume of gas collected in the inverted tube [1]; over a fixed, measured period of time (using a stopwatch) [1]; then calculate \(\text{rate}=\dfrac{\text{volume of gas}}{\text{time}}\), repeating and taking a mean for reliability [1]. (An equivalent accepted method is to count the bubbles released per minute.)
(c) Why sodium hydrogencarbonate was added [2]. It slowly releases/supplies carbon dioxide to the water [1]; this ensures carbon dioxide is plentiful so that it does not become the limiting factor, and the rate then reflects the factor being studied (light) rather than a shortage of \(\text{CO}_2\) [1].
(d) A control to show the gas is from photosynthesis [2]. Set up identical apparatus but place it in the dark / cover it so no light reaches the plant [1]; little or no gas is then produced, showing that light (and therefore photosynthesis) is needed for the gas to be released [1].
(e) Green pigment [1]. Chlorophyll [1], which absorbs the light energy used to drive photosynthesis.
Question 6 Report
The key separates four classes of vertebrates. The same species can also show inherited variation, such as coat colour in mammals.
(a) Using the key, name the class of an animal that has wet scales and lays its eggs in water. [1]
(b) State the term used for animals whose body temperature changes with their surroundings. [1]
(c) Explain one advantage to a mammal of keeping a constant body temperature. [2]
(d) State two features, other than fur and live young, that are characteristic of mammals. [2]
(e) In a mammal, coat colour is controlled by a dominant allele B (black) and a recessive allele b (brown). State what is meant by a dominant allele. [2]
(f) A heterozygous black individual (Bb) is crossed with a brown individual (bb). State the genotypes of the offspring and the expected ratio of black to brown. [3]
(g) Explain why members of the same mammal species can differ in coat colour. [2]
This question tests using a classification key, vertebrate features, and a monohybrid cross.
(a) Class with wet scales, eggs in water. [1] Following the key (scales, then wet), the animal is a Fish [1].
(b) Term for changing body temperature. [1] Ectothermic (accept cold-blooded / poikilothermic) [1].
(c) One advantage of a constant body temperature. [2] The body's enzymes can work at a constant optimum rate [1]; so the mammal stays active in cold conditions / can live in a wider range of habitats [1].
(d) Two mammal features other than fur and live young. [2] Any two of: mammary glands that produce milk; external ears (pinnae); a diaphragm; different types of teeth; sweat glands [2, 1 each].
(e) Meaning of a dominant allele. [2] An allele that is expressed/shown in the phenotype whenever it is present [1], even in the heterozygote, where it masks the recessive allele [1].
(f) Cross Bb x bb. [3] The black parent (Bb) makes gametes B and b; the brown parent (bb) makes only b gametes:
| gamete B | gamete b | |
|---|---|---|
| gamete b | Bb | bb |
| gamete b | Bb | bb |
Offspring genotypes are Bb (black) and bb (brown), in the ratio 1 black : 1 brown [3: 1 for each correct genotype, 1 for the ratio].
(g) Why members of the same species differ in coat colour. [2] They carry different alleles/genotypes for coat colour [1], inherited from their parents (accept mutation as a source of new alleles) [1]. Exam tip: dominant needs the "even in the heterozygote" idea to score the second mark.
Answer Details
This question tests using a classification key, vertebrate features, and a monohybrid cross.
(a) Class with wet scales, eggs in water. [1] Following the key (scales, then wet), the animal is a Fish [1].
(b) Term for changing body temperature. [1] Ectothermic (accept cold-blooded / poikilothermic) [1].
(c) One advantage of a constant body temperature. [2] The body's enzymes can work at a constant optimum rate [1]; so the mammal stays active in cold conditions / can live in a wider range of habitats [1].
(d) Two mammal features other than fur and live young. [2] Any two of: mammary glands that produce milk; external ears (pinnae); a diaphragm; different types of teeth; sweat glands [2, 1 each].
(e) Meaning of a dominant allele. [2] An allele that is expressed/shown in the phenotype whenever it is present [1], even in the heterozygote, where it masks the recessive allele [1].
(f) Cross Bb x bb. [3] The black parent (Bb) makes gametes B and b; the brown parent (bb) makes only b gametes:
| gamete B | gamete b | |
|---|---|---|
| gamete b | Bb | bb |
| gamete b | Bb | bb |
Offspring genotypes are Bb (black) and bb (brown), in the ratio 1 black : 1 brown [3: 1 for each correct genotype, 1 for the ratio].
(g) Why members of the same species differ in coat colour. [2] They carry different alleles/genotypes for coat colour [1], inherited from their parents (accept mutation as a source of new alleles) [1]. Exam tip: dominant needs the "even in the heterozygote" idea to score the second mark.
Question 7 Report
A student collected five small animals from a freshwater pond and labelled them P to T. The photograph shows the five specimens, and the table below records four external features for each one: the number of legs, and whether wings, antennae and a shell are present or absent. Four of the animals have jointed legs, while the other has a soft body protected by a shell. The student wants to build a dichotomous key so that other pupils can identify each animal from a series of paired choices.
| Animal | Number of legs | Wings | Antennae | Shell |
|---|---|---|---|---|
| P | 6 | present | present | absent |
| Q | 8 | absent | absent | absent |
| R | 0 | absent | absent | present |
| S | 14 | absent | present | absent |
| T | 6 | absent | present | absent |
(a) State how many of the five animals are arthropods. [1]
(b) State the feature, shown in the table, that shows animal R is not an arthropod. [1]
(c) Name the arthropod group to which animal Q belongs and give the feature you used to decide. [2]
(d) Construct a dichotomous key that separates animals P, Q, S and T using the features in the table. [4]
(e) Explain why the colour of an animal is a poor feature to use in a dichotomous key. [2]
(f) Describe how the body length of one of these animals could be measured accurately. [3]
This question tests classification of arthropods and the construction of a dichotomous key from a table of features.
(a) How many are arthropods [1] Four (P, Q, S and T) - they all have jointed legs.
(b) Feature showing R is not an arthropod [1] R has no (jointed) legs / has a shell / has a soft body. Arthropods must have jointed legs, which R lacks.
(c) Arthropod group of Q, with reason [2] Q is an arachnid (1); because it has four pairs of legs (eight legs) (1). Arachnids have 8 legs, insects 6.
(d) Dichotomous key for P, Q, S and T [4] A key uses paired, opposite statements that split the group step by step:
- Six legs .......... go to 2
More than six legs .......... go to 3 - Wings present .......... P
Wings absent .......... T - Eight legs .......... Q
Fourteen legs .......... S
Award 1 mark for using paired opposite statements and 1 mark each for correctly separating P, Q, S and T (max 4).
(e) Why colour is a poor key feature [2] The colour of an animal can vary between individuals or change with age, diet or surroundings (1); so it is not a reliable or constant feature for identification (1). A good key uses fixed, easily observed features.
(f) Measuring body length accurately [3] Place the animal against a ruler marked in millimetres (1); straighten the body and measure in a straight line from one end to the other, reading at eye level to avoid parallax (1); repeat and take an average to improve accuracy (1).
Answer Details
This question tests classification of arthropods and the construction of a dichotomous key from a table of features.
(a) How many are arthropods [1] Four (P, Q, S and T) - they all have jointed legs.
(b) Feature showing R is not an arthropod [1] R has no (jointed) legs / has a shell / has a soft body. Arthropods must have jointed legs, which R lacks.
(c) Arthropod group of Q, with reason [2] Q is an arachnid (1); because it has four pairs of legs (eight legs) (1). Arachnids have 8 legs, insects 6.
(d) Dichotomous key for P, Q, S and T [4] A key uses paired, opposite statements that split the group step by step:
- Six legs .......... go to 2
More than six legs .......... go to 3 - Wings present .......... P
Wings absent .......... T - Eight legs .......... Q
Fourteen legs .......... S
Award 1 mark for using paired opposite statements and 1 mark each for correctly separating P, Q, S and T (max 4).
(e) Why colour is a poor key feature [2] The colour of an animal can vary between individuals or change with age, diet or surroundings (1); so it is not a reliable or constant feature for identification (1). A good key uses fixed, easily observed features.
(f) Measuring body length accurately [3] Place the animal against a ruler marked in millimetres (1); straighten the body and measure in a straight line from one end to the other, reading at eye level to avoid parallax (1); repeat and take an average to improve accuracy (1).
Question 8 Report
Human reproduction is controlled by several hormones, each of which has a particular role in the reproductive system. Table 17.1 lists four hormones involved in human reproduction together with their roles, but some of the information in the table has been left out. Study the entries that are already given in the table and use them, together with your own knowledge, to help you work out and complete the missing details.
| Hormone | Main role |
|---|---|
| FSH | |
| LH | |
| Oestrogen | |
| Progesterone | maintains the thick uterus lining |
Use Table 17.1 and your knowledge of reproductive hormones to answer the questions that follow.
(a) Complete Table 17.1 by giving the main role of FSH, LH and oestrogen. [3]
(b) State the organ in which oestrogen is produced. [1]
(c) State what is meant by the term hormone. [2]
(d) Explain how a hormonal contraceptive pill prevents a pregnancy. [3]
(e) State one hormonal and one non-hormonal method of contraception. [2]
(f) Suggest two reasons why a couple might choose a non-hormonal method of contraception. [2]
This question is about the four main hormones of human reproduction. Part (a) asks you to complete Table 17.1, so the finished table is shown below.
| Hormone | Main role |
|---|---|
| FSH | stimulates an egg/follicle to mature in the ovary and stimulates the ovary to release oestrogen |
| LH | causes ovulation (release of the egg) |
| Oestrogen | repairs and thickens the uterus lining (and inhibits FSH) |
| Progesterone | maintains the thick uterus lining |
- Completed roles [3]. FSH matures a follicle/egg and triggers oestrogen release [1]; LH causes ovulation [1]; oestrogen repairs and thickens the uterus lining [1].
- Where oestrogen is made [1]. The ovary [1].
- Meaning of hormone [2]. A hormone is a chemical substance (messenger) produced by a gland [1] that is carried in the blood to alter the activity of a target organ [1].
- How the pill prevents pregnancy [3]. The pill contains oestrogen and/or progesterone [1]; these inhibit the release of FSH from the pituitary [1]; so no egg matures or is released and ovulation is prevented [1].
- One hormonal and one non-hormonal method [2]. Hormonal: the contraceptive pill, implant or injection [1]. Non-hormonal: a condom, diaphragm, IUD or abstinence [1].
- Why choose a non-hormonal method [2, any two]. A condom also protects against sexually transmitted infections; to avoid the side effects of hormones; for religious or personal reasons; or because hormonal methods are not always available. Any two.
Answer Details
This question is about the four main hormones of human reproduction. Part (a) asks you to complete Table 17.1, so the finished table is shown below.
| Hormone | Main role |
|---|---|
| FSH | stimulates an egg/follicle to mature in the ovary and stimulates the ovary to release oestrogen |
| LH | causes ovulation (release of the egg) |
| Oestrogen | repairs and thickens the uterus lining (and inhibits FSH) |
| Progesterone | maintains the thick uterus lining |
- Completed roles [3]. FSH matures a follicle/egg and triggers oestrogen release [1]; LH causes ovulation [1]; oestrogen repairs and thickens the uterus lining [1].
- Where oestrogen is made [1]. The ovary [1].
- Meaning of hormone [2]. A hormone is a chemical substance (messenger) produced by a gland [1] that is carried in the blood to alter the activity of a target organ [1].
- How the pill prevents pregnancy [3]. The pill contains oestrogen and/or progesterone [1]; these inhibit the release of FSH from the pituitary [1]; so no egg matures or is released and ovulation is prevented [1].
- One hormonal and one non-hormonal method [2]. Hormonal: the contraceptive pill, implant or injection [1]. Non-hormonal: a condom, diaphragm, IUD or abstinence [1].
- Why choose a non-hormonal method [2, any two]. A condom also protects against sexually transmitted infections; to avoid the side effects of hormones; for religious or personal reasons; or because hormonal methods are not always available. Any two.
