2010 STAGE 3 HUMAN BIOLOGICAL SCIENCE

SOLUTIONS

Section One Multiple Choice 40 Marks

1 B 11 A

2 D 12 C

3 C 13 C

4 D 14 A

5 A 15 C

6 A 16 B

7 C 17 B

8 D 18 A

9 D 19 D

10 B 20 C

Section Two Short Answers 100 Marks

Question 21

(a) Transcription (1)

(b) Nucleus (1)

(c) To produce a copy of the DNA that can leave the nucleus (1) and move to the ribosome for protein production (1). (2)

(d) Ribosome (1)

(e) A codon is a sequence of three bases in a mRNA molecule (1) and this codes for one amino acid and carried to a specific tRNA molecule. (1) (2)

(f) Regulator genes inhibit transcription (1). Operator genes activate production of mRNA (1) Promoter genes facilitates transcription(1) (3)

Question 22

(a)

Non-skeletal structure Description

Feet Two arches present (longitudinal and transverse)

Ist digit –non-opposable

Pelvis Broad and short/bowl

Vertebrae Wedge shape lumbar

Spine ‘S’ Curvature

Knee Shows a carrying angle buttressing for load bearing

(Any three structures @ 1 mark each) (3)

(b) An absolute dating or radiometric technique or potassium/argon dating (1). This is based on the presence of radioactive isotopes that decay over time at a fixed rate (1). The older the fossil the less amount of radioactive isotope it contains (1).

(3)

(c) Previous Hominins (extinct) common to both modern apes and humans possessed an U-shaped dental arcade (1) and through evolution humans now possess a parabolic or horse-shoe shaped dental arcade (1) (2)

(d) Teeth size/prominence and shape can infer diet. Large canine and large molars suggest a tearing and chewing plant material (1) whereas humans with smaller teeth an omnivorous diet containing meat(1) (2)

Question 23

(a) More than two alleles for that gene are found in the population. (1)

(b) Mother IAi (1) Father IBi (1) (2)

(c) AB, A, B or O (1/2 each) (2)

(d) DNA has negative charge and moves towards the positive electrode (1). The shorter or lighter fragments move faster and travel further in the gel (1) and the longer or heavier fragments move slower and are found closer to the neg electrode (1) (3)

(e) Yes (1) 60nt DNA fragment found in the son (1) (2)

Question 24

(a) Joints decrease mobility (1)

(b) Joint Pain/stiffness/inflammation (any two) (1)

(c) Weight control to lessen stress on joints/artificial joints/ Anti-inflammatories (any two) (2)

(d) Stem cell therapy involves finding ways to re-program adult stem cells so that they will differentiate into the required tissue type. (2)

(e) The articular cartilage will regenerate in the joint (1) and will limit the need for ongoing medical intervention and rejection issues such as joint replacement (1) (2)

Question 25

(a) Chemical messenger that carries the nerve impulse across the synapse (1) acetylcholine or noradrenaline or (1) (2)

(b) (synaptic knob) the expanded end of a nerve cell (1)/(synapse) a gap between nerve cells or a nerve cell and muscle(1)/the junction between a motor nerve and muscle (1) (3)

(c)

ACTIN MYOSIN Z LINE

I BAND H ZONE

(5)

(d) The Myosin (thick filament) head attaches to the Actin (thin filament) or cross bridge forms (1) and then a pulling action occurs and the actin slides over the myosin (1) causing the muscle tissue to shorten (1) (3)

Question 26

(a) Right handed people are right eye dominant. (1)

(b) (ind) Handedness (1) and (dep) dominant eye (1) (2)

(c) Room lighting/both eyes have good vision/size of distant object/age/gender (any two) (2)

(d) Right eye people showed right eye dominance (1)

(e) A large sample of people used including both left and right handed/repeat experiment/large number of trials (any one) (1)

(f) There are a large number of people who are not left hand are right eye dominant or most people’s dominant eye matches their dominant hand(1)

Question 27

(a) Lower blood glucose levels (1)

(b) Islets of Langerhans/Beta cells (1)

(c) Increased respiration rate/Increased glycogen storage(glycogenesis)/Increased fat storage (excess)/Increased protein synthesis (gluconeogenesis) (any two) (2)

(d) NPH 14 hours/LANTUS 22 hours (2)

(e) Careful ‘healthy diet/regular physical exercise/maintaining a healthy body weight/possibly medication initially (any two) (2)

Question 28

(a) (i) Chimpanzee (1)

(ii) The organism with the least number of mutations (amino acid differences) would have had a common ancestor most recently. (2)

(b) The codes are virtually the same or the DNA codes may vary without producing a significant change in the amino acid sequence of the haemoglobin. (2)

(c) Fossils/Comparative Studies of DNA/embryology/anatomy/vestigial structures/Absolute Dating (any two) (2)

(d) (i) DNA makeup in an individual’s chromosomes (as well as mitochondrial)(1)

(ii) HGP will aid doctors in the diagnosis/treatment and preventation of many diseases/screening for genetic disorders assisting rapid intervention. (2)

Question 29

(a) C-cerebellum E-hypothalamus (2)

(b) Cerebrum cortex (1)

(c) Cerebrospinal fluid (1)/Shock absorption(1)/delivers nutrients and removes wastes from the CNS(1) (3)

(d) X-connector neuron or inter-neuron (1) Y-receptor (1) (2)

(e) The physical pathway of the impulse is shorter and the lower number of synapses allows a rapid reflex response (1). Conscious recognition of the reflex in the cerebrum will therefore occur at a later point (1). (2)

(f) The charge becomes more positive or becomes oppositely charged (1)

(g) Nerve impulse jumps from node to node in a myelinated fibre (1) and travels continuous in an unmyelinated fibre (1). Unmyelinated nerve fibres shows continuous conduction whilst myelinated nerve fibres shows saltatory conduction(1). (3)

Question 30

(a) A joint surrounded by a capsule and filled with synovial fluid (1)

(b) Articular cartilage on surface (1)bursae or menisci (1) joint capsule (1) Synovial fluid (1) (any two) (2)

(c)

(any three) (3)

(d) Flexion where joint angle decreases (less than 90o) (1) and extension where joint angle increases (greater than 90o) (1) (2)

(e) Ligament (1)

Ball and Socket Shoulder or hip

Gliding Carpal and tarsal bones

Pivot Radius and ulna/atlas and axis

Saddle Thumb joint

Section Three Extended Answers 60 marks

Question 31

(a)

A chemical that is able to inhibit the growth or kill micro-organisms

Antibiotics are administered when a bacterial infection is present.

Antibiotics work on bacterial cell walls, cell membranes and metabolism.

Antibiotics block translation during protein synthesis

Natural genetic variation within the bacterial population is high

Due to high mutation rate of bacteria

When treated with antibiotics, some of resistant bacteria survive (small numbers)

These produce colonies of antibiotic resistant bacteria

If same selection mechanism used (same antibiotic)

Increased number of antibiotic resistant exist and antibiotic is longer effective

This antibiotic no longer effective and new antibiotic(s) needed

Herd Immunity

(10 marks)

Question 31

(b) (12 marks)

A vaccine is an antigen preparation (dead bacteria/weakened/less virulent strain) injected into a person.

The vaccine causes the immune response to occur without causing the disease.

Individual is exposed to the vaccine through oral ingestion or injection.

Specific B lymphocytes are sensitized as part of the humoral response

The specific B lymphocytes form clones.

Some clones form specific Plasma cells which are capable of producing antigen specific antibodies.

Some clones form antigen specific Memory cells.

Memory cells spread to all body tissues to allow the immune response to occur more rapidly when the individual is exposed to the same antigen again.

The cell-mediated response involves specific T-cells becoming sensitized.

The specific T lymphocytes form clones

Some clones form antigen specific Killer T-cells which move to the site of infection.

Some clones form antigen specific Memory cells.

Again, memory cells spread to all body tissues to allow the immune response to occur more rapidly when the individual is exposed to the same antigen again.

The disease will not be spread due to the lack of illness developing in people

Question 31

(c) (8 marks)

Type of Immunity Mechanism Example

Natural Active After infection with a pathogen, tissues retain specific memory cells from the bodies’ immune response which confers immunity for many years.

Baby or Child is exposed to Chickenpox (varicella zoster virus), becomes ‘ill’ but does not suffer chickenpox again.

Artificial Active After vaccination with antigens, tissues retain specific memory cells from the bodies’ immune response which confers immunity for many years.

Baby and children are given a vaccine (eg: rubella) and they do not develop the disease at any time.

Natural Passive Antibodies transferred from one person to another. Short-lived immunity with no immune memory conferred.

Antibodies cross the placenta from mother to child in the developing foetus (also in breast milk).

Artificial Passive An injection of antibodies, antitoxins or antivenins. Short-lived with no immune memory conferred.

(11/2 marks)

Antibodies injected into person. eg: tetanus antibodies

(1/2 marks)

Question 32

(a) 1 mark for comparison and ½ for each example (10 marks)

Feature Sympathetic NS Thyroxine

Speed Immediate(1)

Eg: Medulla sends a message to

the arterioles of the skin for

vasoconstriction to occur.(1)

Delayed(1)

Eg: Anterior pituitary releases

thyroid stimulating hormone

(TSH) and this will eventually

stimulate the thyroid to produce

and secrete more thyroxine.(1)

Specificity Specific target organ/cell (1)

Eg: Medulla sends a message to

the heart only (atrioventricular

node) to increase heart rate.(1)

Many targets(1)

Eg: Thyroxine will stimulate

most cells to increase

respiration/metabolism.(1)

Duration of effect Short(1)

Eg: Cerebral cortex sends a

message to the iris and dilation of

the pupil occurs immediately.(1)

Long(1)

Eg: The cellular stimulation of

the thyroid will be evident in the

body for minutes/hours.(1)

Type Electrochemical(1)

Eg: salutatory conduction along a

sympathetic nerve fibre involves

the movement of an action

potential via membrane

depolarisation(1)

Chemical(1)

Eg: Thyroid stimulating hormone

(TSH) is a chemical/protein

substance.(1)

Means of transmission Nervous(1)

Eg: Conduction is via

sympathetic nerve fibres(1)

Blood(1)

Eg: Thyroxine is secreted from

the thyroid into the bloodstream

to move to the target cells.(1)

Type of Response Physiological or Behavioural (1)

Eg: A decrease in saliva

production in the mouth or the

creation of complete panic in

some people!

Physiological(1)

Eg: Thyroxine produces an

increase in metabolism.

Effectors Exocrine glands or smooth or

cardiac muscle(1)

Eg: A decrease in saliva

production.

Endocrine glands or body cells(1)

Eg: TSH stimulating the thyroid

gland or Thyroxine increasing

respiration in body cells.

Question 32

(b) (10 marks)

Hypothalamus contains the thermoregulatory centre

Receives information from peripheral thermoreceptors in skin & central in hypothalamus

Sweating –sweat is secreted onto skin

Evaporation of sweat draws heat from the circulating blood.

Vasodilation -muscular walls of the arterioles near the skin relax

Due to decreased sympathetic stimulation/ increased parasympathetic

Increase blood flow and increase heat loss

Via radiation, conduction and convection

Reduced metabolism by decreasing secretion of thyroxine

Reduced physical activity therefore decreasing muscular contraction reducing heat energy production (respiration)

Question 32 (c) (10 marks)

Stimulus: blood oxygen levels are low

Due to a decrease in alveolar surface area (emphysema)

Receptors: chemoreceptors in aortic, carotid bodies

and medulla oblongata.

Control Centre: Respiratory centre in medulla oblongata.

Effectors: Respiratory muscles (diaphragm and intercostals).

Response: Increased rate of breathing.

Depth does not increase (generally) as alveoli are damaged.

Feedback: negative as oxygen levels in the blood will increase.

Continue damage or breakdown of the alveoli tissue will result in very limited oxygen/blood exchange.

During exertion, the oxygen exchange is insufficient to cope with the needs of the active cells.

Question 33 (a) (8 marks)

Gene pool-the sum of all the alleles carried by members of a population.

Allele-an alternative form of a gene that occurs at a given point on a chromosome.

Interbreeding-Different populations of the same species reproducing.

Blood groups provide no adaptive significance/not subject to selection so

Assuming populations are/were small

Random Genetic Drift (founder effect) has occurred

The different allele frequencies arose by chance mutation/variation in original population

Populations were isolated

When compared to population B

IB frequency would increase as dominant to i

similar trend with IA and

i would decrease

Eventually one homogenous group

Question 33 (b) (10 marks)

Hominins refers to a primate family consisting of man’s extinct upright ancestors and humans.

Hominins possess adaptations for upright posture

and bipedal locomotion

Mutations cause changes in base sequence of genes

DNA or gene mutation has occurred in the Homininidae

Amino acids determined by DNA code.

Mutated genes will alter their expression, hence alter amino acid sequences in proteins

The shorter the period of time, the less number of base changes in DNA

More closely related Hominins will have fewer DNA/amino acid differences for the same genes

Comparisons of similar DNA and amino acids sequences between different species suggest they evolved from a common ancestor.

Other comparative studies explained

Homologous structures

Comparative vertebrate embryology

Vestigial organs

Fossil evidence

Question 33 (c) (12 marks)

Biological evolution is the gradual change of physical characteristics that can be observed and measured (anatomical features).

Fossilised craniums showing an increase in cranial capacity/brain size.

Approx 400 to 1350cm3

Prognathism was pronounced now flat face.

No chin to chin development

Brow ridge to less prominent brow ridge.

Improved bipedalism:

Foot – big toe, arches, robust tarsals, digits aligned

Knee - carrying angle, robust

Legs – length, angled inward, large protuberance of femoral head

Trend towards a parabolic jaw from U shaped

Trend towards smaller teeth

(7 marks)

Cultural evolution refers to the change in “way of life” of Hominins.

It is learned behavior, ie: behaviour acquired through learning. It can be inferred from artefacts.

Toolmaking-reduced the environmental pressure on natural selection for physical characteristics. Eg: teeth size, jaw muscle

Use of Fire-reduced the selective pressure for physical characteristics Eg: warmth, cooked food, killed bacteria, increased tenderness of food…allowed for reduced jaw & teeth, allowed for an increase in cranial capacity by encouraging tool manufacture, passage of knowledge, planning hunts etc…

Agricultural Revolution-larger groups formed increasing survival but also retaining weaker/sick/inferior genes. Also increased allele combinations and allowed for larger populations

Writing/Language-influence of environmental selection pressures decreased. However, again weaker/inferior genes retained in gene pool(s). Reduced jaw & cerebral development for speech.

(5 marks)

End of Solutions