Excel Revise in a Month: TEE Human BiologyTips for TEE examinationPreparation

One month before the exam, make an organised study schedule that gives the entire course an even coverage. Organise your notes and coursework into a sequential format, and rewrite your class notes to make study notes. Working through past papers (especially those from the last 4 years) can also help in your preparation

On the night before your exam, read over your study notes, then go to sleep at your regular time. Don’t stay up excessively late studying. It’s also a good idea to have a plan for how you will tackle the exam – see the sample plan below for ideas

On the day of the exam, get up early enough to prepare to go to the exam in a relaxed manner. Know what time your exam starts, which room it is in and how you are going to get to school. Wear comfortable clothing, and take the necessary equipment and a drink bottle

Try to avoid last-minute study, but having a friend quiz you on easy parts of the course will get your brain into ‘information output’ mode. Don’t stand around in large groups of people before the exam, especially those who are discussing the exam – it will only make you nervous

Sample ‘plan’ for the Human Biology TEE exam When you enter the exam room, read the front of the exam and make a conscious effort to

relax, calm down and let your brain function Spend the first 5 minutes of reading time going through Part II of the paper. Choose the

easiest question to start on and sequence the others in order of difficulty. In the second 5 minutes, read the Part III extended answer questions and choose the two you will be doing. Start making up a list of key words in your head. DO NOT read the multiple-choice questions – you will put 120 ‘wrong’ ideas in your head!

When working time has started, write down your list of key words for Part III. This will take about 5 minutes

Answer Part II, starting on the easiest questions first. Part II should take around 70 minutes. Note the mark allocation – one main idea is normally associated with one mark

Answer Part III, make sure you stick to the point of the question, give at least 20 ‘points’ to get the 20 marks and write legibly. Part III should take 50 minutes

Answer Part I. Once you have read the ‘stem’ of the question, think of the answer based on your learning and then see if this matches the alternatives given. Once you have chosen an answer, don’t change it unless you are absolutely sure, and NEVER leave a multiple-choice question unanswered. This section should take you 50 minutes.

Spend the last 5 minutes reading through your answers to Parts II and III Don’t leave the exam early. It will not improve your mark, and it could stop you from

finding a simple mistake that is easily fixed

INTRODUCTION – Introductory topics1. Cells that are suited to a particular function are said to be specialised. The body structure

consists of a hierarchy. Tissues are composed of cells, organs of tissues and systems of organs. Cellular respiration is a process by which cells convert glucose and oxygen into energy for use in bodily functions.

2. The making of new substances is termed synthesis. The building up of large molecules from simpler ones is termed anabolic synthesis and the breaking down of large molecules into small is termed catabolic synthesis.

3. Growth is an increase in size of an individual. It is normally brought about by an increase in cell size and/or number. Increases in cell size are limited by each cell’s surface area to volume ratio. Increasing the number of cells by the process of mitosis is the major contributor to growth.

4. Cells are interdependent, relying on each other for survival. The respiratory system supplies oxygen and removes carbon dioxide, the digestive system supplies nutrients, the

excretory system removes metabolic wastes and the circulatory system moves these materials around the body.

5. Humans exist in an amazing variety of environments but in spite of this they maintain a constant internal environment at an optimal level. Optimal conditions are those that best suit the cell and therefore the organism. The maintenance of a constant optimal internal environment in the body irrespective of the external environment is called homeostasis. This makes the body independent of the external environment.

6. The internal fluid environment of the body consists of intracellular fluid (made up of cytoplasm and nucleoplasm), intercellular fluid (the fluid between cells), plasma and lymph. Together, the intercellular fluid, plasma and lymph are called extracellular fluid.

7. To work efficiently, the human body must maintain relatively constant levels of carbon dioxide, oxygen, temperature, blood glucose and fluid levels. Human cells have become adapted to operate at their optimum at specific levels of these substances.

NERVOUS AND HORMONAL CONTROL – Homeostasis1. Humans exist in an amazing variety of environments but in spite of this they maintain a

constant internal environment at an optimal level. Optimal conditions are those that best suit the cells and, therefore, the organism. The maintenance of a constant optimal internal environment in the body irrespective of the external environment is called homeostasis.

2. The internal fluid environment of the body consists of intracellular fluid, intercellular fluid, plasma and lymph. These fluids are constantly being exchanged with each other.

3. For the efficient functioning of the cell, factors in the internal environment must be maintained at a constant level. These include oxygen and carbon dioxide concentrations, temperature, blood glucose and fluid levels.

4. Control mechanisms function at the level of cells, physiological systems and behaviour, and compensate for changes in the external environment or internal environment. To maintain homeostasis, the body requires control mechanisms that operate automatically. These mechanisms usually occur as steady-state models. Steady-state models are usually presented as follows:

Stimulus Receptor Modulator Feedback Response Effector

The stimulus is the factor that changes and causes the system to operate. The receptor detects the change in the stimulus and the modulator processes information from the receptor and sends an electrical (nervous) or chemical (hormonal) message to the effector. The effector carries out the response, which is the change made by the effector to maintain homeostasis. The feedback is how the response modifies the stimulus.

5. The nervous system is broken up into the following divisions:Nervous system

Central Peripheral

Spinal cord Brain Autonomic Somatic

Parasympathetic Sympathetic

HINT: The sympathetic division speeds processes up. Sympathetic and speed both start with‘s’. Words beginning with ‘para’ (e.g. ‘paralysed’ and ‘paralytic’) relate to the idea of ‘slow’.

NERVOUS AND HORMONAL CONTROL – The central nervous system1. The nervous system is composed of the central and peripheral nervous systems. The central

nervous system (CNS) comprises the brain and spinal cord.

2. The bones of the skull enclose the brain, and the spinal cord is enclosed in the spinal canal which is formed by the vertebrae. The brain and spinal cord are also protected by a jacket of fluid and connective tissue.

3. The brain and spinal cord are surrounded by a fluid called cerebrospinal fluid (CSF). It acts as a cushion or shock absorber and circulates around the brain and spinal cord, supplying nutrients and oxygen, and removing wastes. The connective tissue is called the meninges and is made up of three layers (Dura matter, Arachnoid, Pia matter).

4. The brain’s role in the nervous system is that of a receiver, analyser, coordinator ‘storer’ and initiator of nerve impulse. The diagram below shows the different parts of the brain.

The medulla is the control centre for breathing and circulation. It also regulates a number of other body functions.

The pons coordinates and transmits information between the cerebral cortex, cerebellum and spinal cord.

The pituitary gland sometimes referred to as the master endocrine gland, controls other endocrine glands by producing hormones.

The hypothalamus regulates basic body functions such as thirst and hunger. It is mostly concerned with homeostasis and body temperature control.

The cerebrum (cerebral cortex) is concerned with memory, reasoning, imagination, problem solving and ‘higher’ thought processes.

The cerebellum controls balance, posture, muscle tone and coordination of movement.

The thalamus acts as a relay station. All sensory information entering the brain passes through the thalamus before being relayed to the cerebral cortex (cerebrum).

5. The function of the spinal cord is to receive nervous impulses from sensory neurons and carry these impulses to the brain. It also carries impulses initiated in the brain to motor neurons and links together sensory and motor neurons. The diagram below shows the different parts of the spinal cord.

Grey matter is mainly made up of nerve cell bodies and unmyelinated nerve fibres. White matter is made up of myelinated nerve fibres 9sensory and motor neurones).

The myelin gives it its white appearance. In the brain the white matter is on the inside and the grey matter is outside. In the

spinal cord the white matter in on the outside and the grey matter is inside.

The ventral root of the spinal cord is mainly composed of the axons of motor neurons.

The dorsal root of the spinal cord is mainly composed of sensory neurons, with the ganglion consisting primarily of sensory nerve cell bodies.

NERVOUS AND HORMONAL CONTROL – The peripheral nervous system1. The peripheral nervous system (PNS) consists of cranial and spinal nerves and their

associated ganglia. It is divided into the afferent and efferent divisions. It is involved in transferring information to and from the central nervous system (CNS).

2. The afferent division of the PNS consists of sensory nerve fibres that carry sensory nervous impulses towards the CNS. The efferent division consists of motor neurons that carry impulses initiated on the CNS to the body’s effectors.

3. The efferent nerve fibres that convey impulse to the skeletal muscles are termed somatic. The somatic division is generally involved with voluntary movement of the body. Nerve fibres that carry impulses to the organs and involuntary muscles are termed autonomic.

4. The autonomic division is involved in movement (e.g. breathing and other processes within the body such as digestion that are essential for life) and is generally thought of as automatic. Most parts of the body that are under autonomic control have two types of nerve fibres that carry impulses from the CNS. These are termed sympathetic and parasympathetic. In general, the sympathetic division is involved with changes and responses that prepare the body for increased levels of physical activity. The parasympathetic division is involved in returning the body to, or maintaining a state of, rest.

5. The sympathetic division of the PNS, under the direction of the CNS, is responsible for what is called the ‘flight or fight’ response. This response occurs when a person is in a situation where they feel physically threatened. It increases the body’s ability to fight or to run away from the threat in order to survive.

6. The following table lists the sympathetic and parasympathetic stimulation of selected organs.

Organ Sympathetic stimulation Parasympathetic stimulationLungs Bronchioles dilate (increases O2) Bronchioles contract (decreases O2)Heart Cardiac output increases Cardiac output decreasesEye Dilation of pupil increases light Contraction of pupil decreases lightSweat glands Sweating and heat loss increases Sweating and heat loss decreasesSkin blood vessels Vasoconstriction MinimalSkeletal blood vessels Vasodilation increasing blood flow MinimalStomach/intestines Decreased movement Increased movementSalivary glands Decreased secretion Increased secretion

HINT: ‘Efferent’ sounds like ‘effluent’, which is waste that is removed from a house. HINT: ‘Autonomic’ sounds like ‘automatic’. HINT: The prefix ’para’ in words such as ‘paralysed’ and ‘paralytic’ means ‘slow’.

NERVOUS AND HORMONAL CONTROL – The neuron1. The neuron is the structural and functional unit of the nervous system. Neurons consist of

three major parts: the cell body, dendrites and axons.2. The three main types of neurons are the connector, motor and sensory neurons. Motor

neurons are responsible for transferring impulses from the CNS to the PNS. Sensory neurons relay impulses from the sensory receptors to the CNS. Connector neurons connect motor and sensory neurons together in the CNS.

3. The diagram below illustrates a typical motor neuron.

The cell body contains the nucleus (which control the activities of the neuron), cytoplasm and organelles.

The myelin sheath insulates and protects the axon. It speeds up nerve impulses. The gaps in the myelin sheath are called the nodes of Ranvier and the gaps between

the axon of one neuron and the dendrite of another are called synapses. A membrane called the neurilemma, which helps to repair damaged nerve fibres,

covers the myelin sheath. Dendrites carry nervous impulses to the cell body and axons carry nervous impulses

from the cell body. Schwann cells are responsible for the regeneration of nerve fibres and the production

of the myelin sheath. The motor end plate is the point where an impulse passes to a muscle, causing

contraction. It is joined to an axon by the filament.

4. In some cases, the time it would take for an impulse to travel to the CNS and be processed and then for an impulse to be sent to an effector would be detrimental. In these cases the body has incorporated spinal reflexes which reduce the time taken for a response to a particular stimulus, as there is a decreased distance that the impulse has to travel. This decreases the chance of injury.

5. In a spinal reflex arc (due to the arrangement of the neurons and the distances involved) a response occurs before the impulse reaches the brain and causes a sensation. The diagram below illustrates a spinal reflex arc.

The receptor detects any change in the external environment. The sensory neuron transmits an impulse from the receptor to the connector neuron

in the spinal cord. The connector neuron ‘splits’ the impulse and relays it to the brain via the

ascending tract and also directly to the motor neuron. The motor neuron transmits the impulse from the connector neuron to the effector. The effector receives impulses from the motor neuron and activates the appropriate

response.HINT: Use the basic shape to identify the type of neuron shown and then remember ‘axon’ and ‘away’ both start with ‘a’: axons carry impulses away from the cell body.

NERVOUS AND HORMOONAL CONTROL – Hormones1. The endocrine system consists of a collection of endocrine glands that are linked by the

circulatory system. Endocrine glands are ductless glands that secrete hormones directly into the bloodstream.

2. A hormone is a chemical substance that circulates in the bloodstream and binds to receptor molecules on target cells, changing the activity of the cell. Only cells with the receptor molecules can be affected by a particular hormone.

3. The table below lists the differences between nervous and hormonal control.

The endocrine system is more effective than the nervous system because hormones in the plasma can reach all body cells while nerves only reach muscles and glands.

4. The diagram below illustrates the major endocrine glands.

5. Overall control of the endocrine system is achieved through the hypothalamus (part of the brain) which controls the pituitary gland (master gland), using nerves and releasing and inhibiting factors.

6. The posterior pituitary is controlled by nervous impulses, whereas the anterior pituitary is controlled by releasing and inhibiting factors. Pituitary hormones, in turn, control other endocrine glands.The table below lists the anterior pituitary hormones, their target tissues and the function of each hormone.

Anterior pituitary hormone

Target tissue Function of hormone

FSH (female) Ovaries Stimulates development of follicles and causes ovary to produce oestrogen

FSH (males) Testes Stimulates the production of spermLH (females) Ovaries Causes ovulationLH (males) Testes Stimulates cells in testes to produce

testosteroneTSH Thyroid Stimulates the production of thyroxineProlactin Mammary glands Initiates and maintains milk productionGrowth hormone Body cells Increases growth rate of cellsACTH Adrenal cortex Causes adrenal cortex to produce aldosterone

and cortisol

Nerves HormonesSpeed Fast acting Slow actingSpecificity Specific (one motor neuron

goes to one muscle or gland)General (some hormones are more general than others)

Nature of transfer Electrochemical Chemical (hormones in blood)

Transport of message Nerve cells BloodstreamPersistence of action Short term (seconds) Long term (hours/years)

The table below lists the posterior pituitary hormones, their target tissues and the function of the hormone.

Posterior pituitary hormone

Target tissue Function of hormone

Oxytocin Uterus and mammary glands

Stimulates the contraction of uterus and mammary glands

ADH kidneys Increases tubule permeability, causing more water to be absorbed back into the bloodstream from kidney tubules

7. The table below lists other endocrine glands, their hormones, target tissues and the function of the hormone.

Gland Hormone Target tissue Function of hormoneTestes Testosterone Body cells

Sperm cells

development of secondary sex characteristicsmaturation of sperm

Follicle cells Oestrogen Body cells

Uterus

development of secondary sex characteristicsbuilds up endometrium

Corpus luteum Oestrogen

Progesterone

Body cells

UterusUterus

Development of secondary sex characteristicsBuilds up endometriumMaintains endometrium

Thyroid Thyroxine Body cells Controls basal metabolic rateAdrenal cortex Cortisol

AldosteroneBody cellsKidney

Helps the body adapt to stressRegulates salt level, reduces amount of sodium and increases amount of potassium in urine

Adrenal medulla Adrenalin

Noradrenalin

Body cells

Body cells

Prepares body for ‘flight or fight’ responsePrepares body for ‘flight or fight’ response

Islets of Langerhans InsulinGlucagon

Body cells; liverLiver

Reduces glucose level in bloodIncreases glucose level in blood

HINT: Between the hormone and action there is a ‘target tissue’ for question asking for naming a gland, a hormone it produces and its function/action.HINT: All hormonal control starts at the hypothalamus.

NERVOUS AND HORMONAL CONTROL – Feedback loops1. Levels of particular hormones in the blood may influence the release of similar and in some

cases, different hormones – this is termed feedback. Positive feedback is when the increase in the concentration of one hormone leads to an increase in the concentration of another hormone. Negative feedback is when an increase in the concentration of one hormone leads to a decrease in the concentration of another.

2. Control of the basal metabolic rate is an example of a feedback loop and steady state control. Metabolism involved all of the chemical reactions occurring in the body when the body is at rest. Thyroxine is a hormone that is directly involved with the regulation of the basal metabolic rate.

3. Low metabolic rate is detected by receptors in the hypothalamus, which releases more TSH releasing factor. This causes the anterior lobe of the pituitary to release more TSH, which then acts on the thyroid gland to release more thyroxine resulting in body cells increasing their metabolic rate.

Reduced core Hypothalamus Increased TSH-rf release Anterior pituitary temperature Increased heat production Increased thyroxine Thyroid Increased TSH in body cells

4. High metabolic rate is detected by receptors in the hypothalamus, which release less TSH releasing factor. This causes the anterior lobe of the pituitary to release less TSH, which then acts on the thyroid gland to release less thyroxine, resulting in body cells decreasing their metabolic rate.

Increased core Hypothalamus Decreased TSH-rf release Anterior pituitary temperature Decreased heat production Decreased thyroxine Thyroid Decreased TSH in body cells

5. A hyperthyroid person has an overactive thyroid gland. This increases the rate of metabolism causing heat gain (the person feels hot), weight loss and an increased level of activity.

6. A hypothyroid person has an underactive thyroid gland. This decreases the rate of metabolism causing heat loss (the person feels cold), weight gain and a decreased level of activity.

7. The menstrual and ovarian cycles are controlled by the hypothalamus; the hormones are under cyclic control. The menstrual cycle involves the build up and breakdown of the endometrium over 28 days. The ovarian cycle involves the development of follicles, ova and corpus luteum.

8. The diagram below outlines the sequence and events in the menstrual and ovarian cycles as well as the action of the hormones involved.

9. The sequence of steps in the menstrual and ovarian cycle is as follows:

Pituitary

Follicle Corpus luteum

a. The hypothalamus stimulates the anterior pituitary to secrete FSH by releasing FSH-rf. FSH causes the follicle to develop in the ovary and the follicle secretes oestrogen.

b. Higher levels of oestrogen cause the endometrium to build up and the hypothalamus to secrete LH-rf. Tis in turn causes the anterior pituitary to secrete LH (positive feedback).

c. The surge in LH acts on the follicle, causing it to burst (ovulation) and releases an ovum. The remains o the follicle is called the corpus luteum.

d. The corpus luteum continues to produce oestrogen and starts to make progesterone, which vascalorises and maintains the endometrium.

e. High levels of oestrogen and progesterone from the corpus luteum are detected by the hypothalamus. It stops releasing FSH-rf and LH-rf (negative feedback) and, as a result, the anterior pituitary stops releasing LH and FSH.

f. If the ovum is fertilised, the corpus luteum continues to produce oestrogen and progesterone. This leads to continued negative feedback and, therefore, no further follicle development.

g. If the ovum is not fertilised, after about seven days the corpus luteum breaks down and stops producing oestrogen and progesterone.

h. Low levels of oestrogen and progesterone result in no negative feedback on the hypothalamus, which begins to produce FSH-rf, starting the cycle again.

10. The model below describes the hormonal regulation of the ovarian cycle.

FSH-rf LH-rf

Inhibits FSH-rf LH-rf Inhibits

Oestrogen Progesterone

11. The contraceptive pill contains high levels of the hormones oestrogen and progesterone which are detected by the hypothalamus and inhibit the release of FSH-rf and LH-rf (negative feedback). The anterior pituitary is therefore inhibited from releasing FSH and LH. Thus no ovarian follicles are developed during the cycle (no ova are released). The oestrogen and progesterone in the pills replace the hormones normally produced by the follicle/corpus luteum so that the endometrium develops normally and the secondary sex characteristics are maintained.

REGULATION – Regulation of the heart1. The amount of blood that leaves the heart in a minute is called cardiac output. It is

calculated on the basis of heart rate (beats per minute) and stroke volume (in mL).2. When we exercise a great many changes take place inside our bodies which must, therefore,

adjust to maintain homeostasis. Responses to exercise are generally divided into two stages: responses before exercise and responses during exercise.

3. As a person is about to begin exercising, there is an anticipatory response brought about by the cerebral cortex acting through the autonomic nervous system. The sympathetic division of the ANS stimulates the adrenal medulla to release adrenalin.

Hypothalamus

Secondary sex characteristics

Promotes growth of and maintains

endometrium

Adrenalin causes increased cardiac output, increased breathing rate, redistribution of blood to muscles away from the intestines, increased blood pressure and the breakdown of glycogen to glucose.

4. As the demand for energy increases during exercise, so does the rate of cellular respiration. For this to happen inputs must increase and the removal of waste must also increase.

5. In order to maintain homeostasis, breathing rate and depth increase, heart rate and stroke volume increase, glycogen and fat are converted into glucose, heat loss mechanisms start to operate and there is a redistribution of blood. During exercise the increase in heart rate is maintained by a number of factors. The active muscles are producing carbon dioxide, blood pressure is increasing and the major joints are moving.

6. The main stimuli for an increase in heart rate are: a decrease in the pH of the blood due to an increase in the carbon dioxide concentration in the blood (detected by chemoreceptors in the medulla/hypothalamus); increased blood pressure (detected by pressoreceptors (baroreceptors) in the carotid arteries/aorta) and movement in the joints (detected by proprioceptors (stretch receptors)).An increased heart rate allows more blood to be pumped to the muscles, supplying oxygen and glucose and removing carbon dioxide, lactic acid and heat (feedback).

7. Information from the receptors is passed to the medulla (modulator). The medulla then acts through the sympathetic nervous system, stimulating the sinoatrial node in the heart (effector) to increase the heart rate (response).

REGULATION – Regulation of breathing1. To help maintain constant levels of CO2 and O2, the body varies the rate of breathing. These

levels must be maintained as O2 is required by cells for respiration, and CO2 is a waste product of cellular respiration, which if allowed to accumulate, will decrease the cells metabolic efficiently.

2. The concentration of carbon dioxide in the blood lowers the pH which is the main stimulus for the control of breathing rate. If CO2 levels are high (when exercising) breathing rate increases. If CO2 levels are low (during rest) breathing rate decreases.

3. The table below highlights the components involved in the control of breathing.Component How it controls breathing LocationChemoreceptors Chemoreceptors detect changes

in pH and CO2 concentration in blood

Aortic and carotid bodies

Respiratory centre Controls breathing rate and depth

Medulla

Stretch receptors Overstretching of lungs causes expiration (protective function)

Lungs

4. The control of breathing during exercise (high CO2) can be represented by the following steady-state feedback model:Stimulus -------- Receptor -------- Modulator(high concentration (chemoreceptors in the (respiratory centre in the of CO2 in blood) respiratory centre, aorticmedulla) and carotid bodies) Feedback -------- Response -------- Effector(lower CO2 in blood) (increased rate and depth (intercostals muscles

of breathing) and diaphragm)5. The control of breathing during rest (low CO2) can be represented by the following steady-

state feedback model:Stimulus -------- Receptor -------- Modulator(low concentration (chemoreceptors in the (respiratory centre in the of CO2 in blood) respiratory centre, aorticmedulla)

and carotid bodies) Feedback -------- Response -------- Effector(higher CO2 in blood) (decreased rate and depth (intercostals muscles

of breathing) and diaphragm)6. Due to anticipation, breathing rate increases before exercise under the control of the

sympathetic division of the autonomic nervous system (ANS). The sympathetic division of the ANS causes the adrenal medulla to release the hormone adrenalin. Adrenalin is responsible for increasing the rate of breathing.

7. During exercise the muscles use large amounts of oxygen and glucose producing carbon dioxide. The high levels of carbon dioxide (which lower the pH of the blood) are detected by chemoreceptors located in the aortic and carotid bodies, and the medulla.Chemoreceptors pass on information on carbon dioxide levels via nervous impulses to the respiratory centre located in the medulla, which acts as the modulator. This then causes the effectors (intercostals muscles and diaphragm) to increase the rate and depth of breathing (response).

8. The increased rate and depth of breathing allows the high levels of carbon dioxide to be removed from the blood and the oxygen level to be increased. This is important, as oxygen is required for respiration in the active muscle. Carbon dioxide is a waste product that, if allowed to accumulate, increases the activity of the blood and can denature enzymes.

9. Hyperventilation is rapid, deep breathing to decrease the amount of carbon dioxide in the blood (it has little effect on the concentration of oxygen). It is especially dangerous to hyperventilate and then go under water. Because of the low initial concentration of carbon dioxide in the blood, it would take a long time for the carbon dioxide to build up to a level at which the decreased pH of the blood would stimulate the respiratory centre to make you take a breath. During this time your oxygen concentration may decrease to such a level that you pass out before the urge to take a breath occurs. Then, when you are forced to breathe, you will take in water and drown.

REGULATION – Regulation of blood glucose1. Blood glucose levels must remain fairly constant as glucose is required for metabolic

processes in cells. Glucose is a simple sugar that is used in cellular respiration to produce energy.

2. Nervous tissue (brain) and the retina (eye) are very sensitive to changes in blood glucose levels. An excess or deficiency of blood glucose levels for more than a few hours can result in loss of consciousness and brain damage. Glucose can be converted to glycogen (a ‘stored’ version of glucose), which does not cause harm to tissues.

3. The Islets of Langerhans are special areas in the pancreas which have a number of roles. They have chemoreceptors that detect the glucose level of the blood.

If the blood glucose level is found to be low, alpha cells in the Islets of Langerhans produce glucagon. Glucagon acts in a number of ways to increase the blood glucose level.

If the blood glucose level is found to be high, beta cells in the Islets of Langerhans produce insulin. Insulin acts in a number of ways to decrease the blood glucose level.

4. The body has a number of ways of increasing blood sugar levels when they are too low. The main method is glycogenolysis. This involves the breakdown of glycogen into glucose. Lipolysis can also occur where lipids where lipids are broken down and used directly by cells. Glucose is saved for the brain cells. Gluconeogenesis can also occur, in which fats and amino acids combine to produce glucose.

5. The body has a number of ways of decreasing blood sugar levels when they are too high. In glycogenesis glucose molecules are combined to produce glycogen; in translocation glucose moves from the blood into cells; and in lipogenesis glucose is converted into lipids (fat). High

levels of glucose can also lead to increased protein synthesis (an anabolic process that uses up energy) which helps reduce the blood glucose level.

6. A high level of glucose in the blood, for example after a meal, would be controlled in the following way.Stimulus -------- Receptor -------- Modulator(high levels of glucose (Islets of Langerhans (beta cells in Islets of in blood) in pancreas) Langerhans produce insulin) Feedback -------- Response -------- Effector(lower glucose in blood) (glycogenesis; translocation; (liver; body cells; muscle

lipogenesis) cells)7. During exercise, blood glucose levels will drop, as the glucose is being used by respiring

muscle cells. This is controlled in the following way:Stimulus -------- Receptor -------- Modulator(low levels of glucose (Islets of Langerhans (alpha cells in Islets of in the blood) in pancreas) Langerhans produce

glucagon) Feedback -------- Response -------- Effector(higher glucose in blood) (glycogenesis; (liver; body cells)

gluconeogenesis; lipolysis)8. During exercise the adrenal medulla is stimulated to produce adrenalin. Adrenalin is a very

fast-acting hormone which behaves in a similar way to glucagon acting to raise blood glucose levels quickly when required.

9. The hypothalamus controls behaviour (through the cerebral cortex) in response to high and low blood glucose levels. When blood glucose levels are high, there is a decrease in appetite. When blood glucose levels are low, appetite increases and a person seeks out food (sugar cravings).

HINT: Break the word up into parts: ‘gluco’ (glucose), ‘neo’ (new), ‘genesis’ (make).

REGULATION – Regulation of temperature1. Homeothermic organisms are able to maintain a relatively constant internal body

temperature independent of the extern al temperature. The internal temperature of humans is 37C.It is necessary for humans to maintain a constant internal temperature, as the metabolic reactions occurring in cells require an optimal temperature. At temperatures higher than 37C enzymes start to denature; lower than 37C and the chemical reactions in the body start to slow, possible to a level where cell function is compromised.

2. Conduction is a type of heat transfer in which heat energy moves from a warmer object to a cooler object when they are in direct physical contact. If you touch an object that is cooler than your body, heat passes from your body to the cooler object. The reverse happens when you touch an object that is hotter than your body.

3. Convection is a type of heat transfer in which heat energy is transferred by the movement of fluids. Warm air (created by contact with a warm body) rises and is replaced by cooler air. The currents of moving air remove heat energy from the body.

4. Radiation is a type of heat transfer in which heat energy moves from a warmer object to a cooler object across space: no contact between the bodies is necessary. If your body has a higher temperature than the environment, it will radiate heat into the environment, which cools the body. If your body is cooler than the environment then it will gain heat through radiation.

5. Evaporation occurs when liquid water is converted to water vapour. This process requires energy which is taken from the body in the form of heat, thus cooling the body. When a person sweats, the evaporation of the liquid from the skin cools the body.

6. The receptors responsible for changing body temperature are thermoreceptors. They are located in the skin and hypothalamus. The modulator for temperature regulation is the hypothalamus. The main effectors for temperature regulation are the skin, blood vessels, body cells, muscles and sweat glands.

7. As temperature regulation steady-state model for a low body temperature is shown below:Stimulus -------- Receptor -------- Modulator(low body temperature) (thermoreceptors in skin(hypothalamus) and hypothalamus) Feedback -------- Response -------- Effector(higher body temperature) (increased metabolic rate; (body cells; muscles;

shivering; vasoconstriction skin blood vessels;of blood vessels in skin; cerebral cortex)change in behaviour)

8. A temperature regulation steady-state model for a high body temperature is shown below:Stimulus -------- Receptor -------- Modulator(high body temperature) (thermoreceptors in skin(hypothalamus)

and hypothalamus) Feedback -------- Response -------- Effector(higher body temperature) (decreased metabolic rate; (body cells; muscles;

increased sweating; skin blood vessels;vasodilation of blood vessels cerebral cortex)in skin; change in behaviour)

9. Temperature regulation involves a balance between heat loss and heat gain. The table below outlines how heat gain and loss is modified in hot and cold conditions.

Physiological methods Behavioural methodsHot conditionsNeed to reduce heat gainNeed to increase heat loss

Reduce metabolic rateVasodilation of blood vessel in skin and sweating

Find somewhere coolFind somewhere cool, go or a swim, remove clothing

Cold conditionsNeed to increase heat gain and shiveringNeed to reduce heat loss

Increased metabolic rate

Decreased sweating, vasoconstriction of skin blood vessels

Deliberate movement and exerciseIncrease insulation by putting on clothing

REGULATION OF THE COMPOSITION OF BODY FLUIDS – Body fluids and metabolic wastes1. The internal environment comprises the fluid environment of the body which consists of

intracellular fluid, intercellular fluid and plasma.2. The diagram below illustrates the relationship between these fluids.

3. Intercellular (tissue) fluid is found between the cells. Intracellular fluid (cytoplasm) is found inside the cells. Plasma is the liquid part of the blood within the blood vessels. Blood plasma plus intercellular fluids is called extracellular fluid.

4. Regulation of the composition of body fluids is needed to maintain the efficient functioning of cells. The five main components of body fluids are pH, concentration of nutrients, concentration of wastes, dissolved gas concentrations and water levels.

5. It is important to maintain constant levels of the components of body fluids or the efficiency of cellular reactions may decrease. A constant pH needs to be maintained, as a build-up of hydrogen ions will denature enzymes, reducing cell efficiency. Nutrients and oxygen are required by respiring cells, and so they must remain constant. Wastes are toxic and, if allowed to accumulate, will slow down cell reactions, reducing cell efficiency. Carbon dioxide is a waste product that, if allowed to accumulate, reduces the pH of blood denaturing enzymes, reducing cell efficiency. A decrease in water level will affect chemical reactions and osmosis/osmotic pressure.

6. Metabolic wastes are products of metabolism that are of no more use to the body. These wastes need to be excreted, as some of them may be harmful if they are allowed to build up in the body. The removal of metabolic wastes from the body is called excretion. The removal of a substance that was not involved in the body’s metabolism is called elimination (e.g. the passing of faeces is elimination, not excretion, as it consists mainly of undigested food, not products of metabolism).

7. There is a constant exchange of materials between plasma, intercellular fluid and intracellular fluids. The concentration of small molecules in the plasma directly affects concentrations in the intercellular fluid and, in turn, the cytoplasm. The molecules move from a high to a low concentration gradient. Nutrients diffuse from the plasma through the intercellular fluid to the cytoplasm. The opposite occurs for small molecules moving from the cytoplasm to the plasma (e.g. carbon dioxide). Large molecules such as proteins are limited in their movement because of the permeability of the walls of the blood vessels and the cell membrane.

8. The table below illustrates the source and excretory pathway for a number of metabolic wastes.

Type of waste Source of waste Excretory pathwayCarbon dioxide Cell respiration Breathed out from lungsWater Cell respiration

Sweat from skinUrine from kidney

Breathed out from lungs

Urea, uric acid, creatinine, ammonia

Occurs in liver Breakdown of nucleic acids

Breakdown of proteins (deamination) Removed by kidneyExcreted in urine

Bile salts and pigmentsMinerals

Through cellsCell breakdown

FaecesUrine and sweat

9. As well as carbohydrates and fats, proteins can be used as a source of energy. In the liver, an amino acid (simplest unit of protein) can have its amino group (NH3) removed, leaving a carbohydrate-like compound. The removal of an amino group from an amino acid is known as deamination. In deamination, the amino group is converted to ammonia, which is highly toxic to the cell. To avoid this toxicity, ammonia is rapidly converted to a low-toxicity substance called urea. This chemical change occurs in the liver; the urea is constantly removed from the blood by the kidneys.

REGULATION OF THE COMPOSITION OF BODY FLUIDS – Structure and function of the nephron

1. The nephron is the functional unit of the kidney. There are over one million nephrons in each kidney. The basic function of the nephron is to filter unwanted material out and then reabsorb those substances that the body needs to retain.

2. The diagram below illustrates the structure of a nephron.

3. The glomerulus is a knot of capillaries that works in conjunction with the glomerular capsule to filter the blood. Large substances, such as red and white blood cells and proteins, that are too large to pass through the membranes of the glomerulus and capsule remain in the bloodstream. Small molecules, such as water, glucose, slats, amino acids, urea and hormones, pass through the membrane into the capsule.

4. The proximal convoluted tubule is responsible for the reabsorption into the bloodstream of glucose, amino acids, sodium and potassium (all selective reabsorption by active transport) plus water (by passive osmosis).

5. The loop of Henle is responsible for reabsorption (selective by active transport) of sodium back into the tissue fluid. This helps maintain suitable conditions for the removal (osmosis) of water from the filtrate as it moves down the collecting duct.

6. The distal convoluted tubule is responsible for the selective reabsorption of sodium by active transport. It is also involved in the secretion of hydrogen ions, potassium and creatinine into the tubule. The movement if hydrogen ions helps to control the pH of the plasma and thus other body fluids.

7. The collecting duct is responsible for the reabsorption of water back into the bloodstream. This occurs by osmosis and is under the influence of anti-diuretic hormone (ADH). The high sodium concentration outside the duct helps the water move by osmosis.

8. The afferent arteriole supplies the nephron with blood and forms a ball of capillaries called the glomerulus. The efferent arteriole takes blood away from the glomerulus. It is smaller in diameter than the afferent arteriole, resulting in raised blood pressure in the glomerulus, and it branches into the peritubular capillaries. The peritubular capillaries surround the tubules and collecting duct. Substances in the tubules requires by the body can be reabsorbed back into the bloodstream.

9. The formation of urine by the nephrons of the kidneys involves three major processes: glomerular filtration, selective reabsorption and tubular secretion.

10. Filtration takes place in the glomerulus and glomerular capsule. Blood in the glomerulus is under high pressure as the afferent arteriole is wider than the efferent and the renal artery is short and connected directly to the aorta. The high pressure forces small molecules such as water, glucose, amino acids, urea, sodium, potassium and hormones across the membranes of the glomerulus and into the glomerular capsule. This fluid is termed filtrate. Large molecules like erythrocytes, leucocytes and proteins are too large to pass through the membranes and remain in the glomerulus. They move out of the efferent arteriole.

11. Many substances in the filtrate are useful to the body and, therefore, are returned to the blood by selective reabsorption. In the proximal convoluted tubule, glucose, amino acids, sodium and potassium are selectively reabsorbed by active transport and water is reabsorbed by osmosis (passive). In the distal convoluted tubule, sodium is reabsorbed by active transport and water by osmosis under the influence of ADH. In the collecting duct, water is reabsorbed by osmosis (passive) under the influence of ADH. Urea is not reabsorbed and passes out as urine.

12. Tubular secretion occurs in the distal convoluted. Unwanted substances such as H+, NH3 and drugs are added to the filtrate.

13. The movement of particles in glomerular filtration, selective reabsorption and tubular secretion rely on the processes of diffusion, osmosis and active transport. Diffusion is the movement of particles (or molecules) from areas of high concentration to areas of low concentration. Osmosis is the movement of water molecules from an area of high concentration of water (low concentration of ions) to an area of low concentration of water (high concentration of ions) through a semi-permeable membrane. (A semi permeable membrane allows the movement of some molecules through it but not others.) Substances are moved from areas of low concentration to areas of high concentration (against the concentration gradient) by active transport. It occurs across cell membranes and is an active process requiring energy in the form of ATP.

REGULATION OF THE COMPOSITION OF BODY FLUIDS – Water balance1. The level of water in the plasma and tissue fluid is regulated by varying the amount of water

taken into the body (drinking) and the amount reabsorbed from the filtrate in the nephron tubules.

2. Osmoreceptors in the hypothalamus detect the osmotic potential of the blood. The hypothalamus controls the secretion of anti-diuretic hormone from the posterior pituitary.

3. Water is reabsorbed from the filtrate in the distal convoluted tubule and the collecting duct. Some of the water moves naturally because of concentration gradients (e.g. obligatory reabsorption). Some water reabsorption is controlled by the level of ADH in the blood e.g. facultative reabsorption.

4. ADH increases the amount of water reabsorbed from the tubular filtrate back into the plasma. This is achieved by increasing the permeability of the walls of the distal convoluted tubule and the collecting duct.

5. Water levels in body fluids can change the osmotic pressure of the blood. The following steady-state control models show how water levels are returned to normal.

Low water level: Stimulus -------- Receptor -------- Modulator(low plasma water (osmoreceptors in (posterior pituitary level resulting in increased the hypothalamus) releases more ADH)osmotic pressure) Feedback -------- Response -------- Effector(decrease in the (increased reabsorption (increase in theosmotic pressure) of water into permeability of

capillaries) DCT and CT walls)6. High water level:

Stimulus -------- Receptor -------- Modulator(high plasma water (osmoreceptors in (posterior pituitary level resulting in decreased the hypothalamus) releases less ADH)osmotic pressure) Feedback -------- Response -------- Effector(increase in the (decreased reabsorption (decrease in theosmotic pressure) of water into permeability of

capillaries) DCT and CT walls)

HINT: ADH increases the permeability of the tubule walls.HINT: Alcohol and caffeine are diuretics.

PREVENTION AND CONTROL OF INFECTION – Causes and prevention of infection1. An antigen is a ‘foreign’ substance that can cause a specific immune response within the

body. In many cases, antigens consist of ‘molecules’ on the surface of invading micro-organisms

2. An antibody is a specific protein that is produced within the body and can combine with its ‘matching lock/key’ antigen. Once combines into an antigen/antibody complex, the antigen or antigen-carrying micro-organisms can be removed or deactivated.

3. An antibiotic is a chemical substance produced by bacteria or fungi. It is able to suppress, inhibit or kill the growth o other micro-organisms without causing harm to human cells.

4. A vaccine is an antigen (prepared in a relatively harmless form) which is used to develop immunity by activating the immune system to produce memory cells and antibodies.

5. A vaccination introduces a vaccine into the body as the primary stimulus to develop the immune memory for a particular disease (pathogen). It increases the speed at which the pathogen is detected in subsequent exposures.

6. There are three main types of vaccines: dead pathogens, living pathogens and toxoid vaccines.

7. In dead pathogen vaccines the pathogen has been ‘killed’ so that it cannot reproduce but it still contains the surface antigens that are detected in the plasma. While the antigens start the immune response, the pathogen is not able to cause any harm. These vaccines are used for dangerous diseases, such as cholera and typhoid.

8. In living pathogen vaccines, the pathogen is still living but it has been modified (attenuated) so that it cannot reproduce. The antigens are recognised and the immune response occurs but symptoms of the disease do not occur. (If the disease is contracted the symptoms are not severe). The majority of vaccines are of this type (e.g. polio, tuberculosis and rubella).

9. With toxoid vaccines pathogens cause a disease by releasing toxins into the body. The pathogens are cultured in an artificial medium and the toxins are obtained by filtration. The toxins are then modified so that they do not cause disease symptoms but are still detected by the body, leading to an immune response. These vaccines are used where the toxin is the major cause of the disease (e.g. tetanus and diphtheria).

10. Immunity is the ability to combat a particular antigen should it enter the body. Immunity can be classified as natural or artificial, and active or passive.

11. Natural immunity occurs without any human intervention. Artificial immunity occurs following human intervention. It results from being vaccinated with antibodies or an antigen that triggers the immune response. Passive immunity results from introducing ready-made antibodies to the body. The body does not produce its own antibodies. Active immunity occurs when the body produces its own antibodies in response to an antigen.

12. Active natural immunity occurs when, you are able to make your own antibodies against a disease because of a previous unplanned exposure to a particular pathogen/antigen (e.g. once you have had chickenpox/measles you rarely will get it again).

13. Passive artificial immunity involves injecting antibodies against a particular antigen directly into the bloodstream. There is no future ability to produce these antigens again (e.g. anti-venee for snake/spider bite).

14. Active artificial immunity occurs when you are able to make your own antibodies against a particular antigen/pathogen because you had a vaccination of that particular antigen (pathogen).

15. Passive natural immunity is a special case where babies obtain their mother’s antibodies via the placenta or breast milk. A breastfeeding baby will have the same antibodies as the mother.

PREVENTION AND CONTROL OF INFECTION – Prevention and control of infection 21. Antibody-mediated immunity (humoral response) is based around B-lymphocytes. These

are produced and mature in bone marrow and then migrate to the lymph nodes and tissues. They recognise pathogens by their antigens and produce antibodies.

2. Lymphocytes are able to distinguish between different invading pathogens which have different antigens on their surface. An antigen is any substance that can trigger the production of antibodies. Each antibody is specific to its antigen.

3. As antigens flow through the lymph nodes they encounter thousands of B-lymphocytes. On the surface of these B-lymphocytes are antibodies, which will combine with a ‘matching’ antigen located on a pathogen. This combination gives the B-lymphocyte the signal to divide and form clones.

4. Some clone cells change into plasma cells and begin to produce antibodies, which are released via the lymphatic system into the plasma. Antibodies destroy the pathogens by combining with them and inactivating them, by agglutination and by helping phagocytes remove them. Other cells remain as B-lymphocytes and become memory cells. They can quickly develop into plasma cell to produce antibodies if they recognise the same antigen again.

5. The diagram below illustrates the process outline in points 3 and 4.

6. The response of the antibody-mediated immunity (humoral response) on its first contact with an invading organism is called the primary response. The secondary response is triggered by a reintroduction of the pathogen/antigen at a later time. The secondary response is due to the immune memory comprising memory cells called lymphocytes. During the primary response, those lymphocytes sensitive to the particular antigen divide creating more memory cells. Should a second infection occur, a large population of memory cells is primes to change rapidly into plasma cells. These persist longer and are capable of more rapidly producing higher concentrations o antibodies.

7. The graph below illustrates the difference in speed of production and number of antibodies produced in plasma after a first and second exposure to antigens.

8. Cell-mediated immunity is also specific and exhibits an immune memory but, unlike antibody-mediated immunity, it does not employ antibodies. It is based around T-lymphocytes, which are produces on bone marrow, mature in the thymus and then migrate to the lymph nodes and tissues.

9. The initial antigen recognition process for cell-mediated immunity is similar to that for antibody-mediated immunity. Once a T-lymphocyte encounters a ‘matching’ antigen it is sensitised, enlarges and divides into clones. Some of the clones become killer T-cells. They leave the lymph nodes and migrate around the body, actively seeking pathogens with the ‘matching’ antigen/ Some T-cells remain as memory cells which can recognise the original invading antigen id it re-enters the body at a later time and initiate a much faster response.

10. The diagram below illustrates the process outline point 9.

11. Killer T-cells can encourage phagocytosis by macrophages, attract macrophages by chemotaxis, sensitise more lymphocytes, and attach to the pathogen and destroy it. Cell-mediate immunity is associated with graft rejection (organ transplants), and fighting cancer cells and AIDS.

GENETICS – Mechanisms of and evidence for evolution1. Evolution is the statistical change in the gene pool of a population over time. It results in a

gradual change in the characteristics of a species over many generations.2. There are four main principles involved in evolution: Variation – each individual of a

species differs slightly in behaviour, structure and function (due to sexual reproduction, gene mutations, and chromosome mutations); Competition – a population that produces more offspring than can survive and reproduce. This results in competition between individuals for limited resources. Selection – individuals with variations that are better suited to a particular environment have a better chance of surviving. Reproduction – successful individuals with favourable characteristics reproduce with similar individuals and pass the genes for these

characteristics on to their offspring. This increases the number of favourable genes in the population this changing the gene frequency.

3. An example of natural selection is the change in the skin colour of a population over time. The original population has variation in skin colour from light to dark (variation). In a new environment with high levels of UV radiation, competition for survival takes place with skin colour being the selecting mechanism (competition). Dark-skinned individuals who are less likely to burn and are less likely to get skin cancer therefore have a greater chance of survival (selection). Dark-skinned individuals reproduce together increasing the number of dark-skinned individuals and genes in the population (reproduction).

4. The most common misconception about evolution is that an organism can change during its lifetime to suit its environment. When they are produced, organisms have a set genetic makeup and cannot change. What does happen is that when an organism reproduces, its offspring will show a range of variation and those that are best suited to the environment will have a greater chance of surviving.

5. In general, the gene frequencies of a large population do not change from one generation to the next unless natural selection favours or removes particular genes.

6. In small populations, a change in the gene frequencies may occur by chance (i.e. a random, non-directional change) due to the small size of the population (random genetic drift). An example is the Dunkers, a small German group that lived and bred in the USA in isolation from the general population. They show a statistical variation in characteristics such as blood group, ear lobes and L/R handedness.

7. Sometimes a small sample of a large population can become isolated, having migrated to a new area. On some occasions, due to the small initial gene pool, some gene frequencies become more prevalent in the population as it increases in size in comparison with the original population. This is called the ‘founder effect’.

8. There are many different pieces of evidence that support the theory of evolution. These can be classified into those that deal with gross morphology (e.g. the study of fossils, anatomy and embryology), and those that are based on a microscopic level (e.g. protein and DNA analysis).

9. Fossils of extinct organisms (particularly bones) enable scientists to follow the evolution of organisms by tracing structural similarities in organisms back to a common ancestor.

10. By determining the type and sequence of amino acids that make up proteins, scientists can compare various species for evolutionary relationships. Species that are more closely related have more similar proteins (type and sequence of amino acids) than those of distantly related species.

11. The study of DNA sequences can be used to compare evolutionary relationships. The more similar the DNA, the more closely related are the species under consideration.

12. By comparing homologous similarities in anatomy between different species of living organisms, scientists can work out evolutionary relationships. Species that have similar structures can be assumed to have a common ancestor. For example, the human hand, whale flipper, and the wing of a bat all have similar bone structure, suggesting a common ancestor/origin.

13. By comparing the development of organisms in the embryo stage, scientists can show that

many organisms, particularly vertebrates, have many structural similarities at the embryo level, which suggests that they share a common ancestor. For example, the cow, pig, human, fowl, and fish all look very similar in certain stages of embryo development.

HUMAN EVOLUTION – Fossilisation and dating methods1. A number of key ‘dates’ are important when studying human evolution:

Age of the earth – 4.6 billion years First life – 3.5 to 4 billion years First vertebrates – 470 million years First mammals – 200 million years First primates – 65 million years First hominids – 2 million years.

2. Palaeontology is the science of the study of fossils. A fossil is preserved trace or remains of past living organisms (bone, teeth, footprints, faeces). Archaeology is the study of the study of artefacts. An artefact is an object that was man made (e.g. pottery, tools, weapons). A kitchen midden is an accumulation of materials (e.g. fossils, artefacts, food wastes) that is evidence of hominid occupation of a particular site. Fossils, artefacts and kitchen middens help us to interpret the past lifestyles of hominids. Fossils give us an indication of hominid structure; artefacts provide information about tools used and lifestyle; kitchen middens give indications about foods eaten and behaviour.

3. Fossilisation is a process where the following steps usually occur. The organism dies and is quickly covered by sediments (alkaline soil with no oxygen). Minerals replace the organic matter in the bones (mineralisation). The bone is now fossilised. Most fossils are found in old lake, sea and river beds as suitable conditions for fossilisation are usually found in these areas.

4. The fossilisation of organic body tissue (e.g. skin/flesh) occurs in wet, acidic soils where there is little or no oxygen present. These particular conditions are not conductive to bacterial growth, as the bacteria that would normally decompose the tissues are not present. These conditions are very rare and most commonly occur in peat bogs.

5. Very few animal remains are fossilised, as the conditions required for fossilisation are rare. Very few fossils are found as very few fossils are produced in the first place. Many remain buried in sediment and those that are uncovered are very difficult to identify, especially to an untrained observer.

6. The dating of fossils is an important tool in the study of the evolution of humans. There are two general types of dating. Absolute dating gives an actual age in years with reference to the present. Relative dating compares the age of a specimen/sample to another which is older or younger.

7. Index fossils were only present on the earth for a short period of time and were widely distributed. Their appearance in rocks helps to correlate rock strata from different places. Once an index fossil has been identified in a particular layer of sediment, all other fossils in that layer can be inferred to the same age.

8. Stratigraphy is a dating method based on the principle of superposition. According to this theory, layers (strata) located below others are older in origin and layers that contain the same type of fossil (index fossil) are the same age. Stratigraphy involves studying strata either using core examples or investigating cliff faces. Fossils of unknown age below fossils of known age are said to be older. Strata can also be studied for index fossils of known age. Fossils associated with these must be the same age while fossils above are younger and those below are older.

9. Radiocarbon (carbon-14) is a dating method based on the theory that carbon-14 is continuously produced in the upper atmosphere by the action of cosmic rays on nitrogen. All living things contain radioactive carbon-14. When an organism dies, it no longer takes in radioactive carbon-14 but continues to decay at a fixed rate to nitrogen. Radiocarbon dating involves obtaining organic material contained in or around the fossil and assessing it for the ratio of carbon-14 to carbon-12 (normal carbon). With the known half-life of carbon-14 being 5730 years, the age of the fossil can be determined. Every 5730 years the amount of carbon-14 in a fossil will halve.

10. The table below compares stratigraphy and radiocarbon dating.Dating technique

Relative or absolute

Time limits

Material used

Source of material

Advantages/disadvantages

Stratigraphy Relative None Sedimentary rockRock strata

Core samplesCliff facesMine

Disadvantages – Folding/faulting of strata

Radiocarbon Absolute Up to Carbon Radioactive CO2 Disadvantages – Material must

(carbon-14) 70, 000 years

containing compounds

Incorporated during photosynthesis

contain carbon.Time limits.Advantages – Gives an absolute age

HUMAN EVOLUTION – Comparison of hominids and pongids1- 4. The table below outlines the differences between hominids and pongids with respect to the vertebral column, pelvis and femur carrying angle.

Characteristic Pongid Hominid Advantage to HominidVertebral column

C – shaped curve

Large processes on neck vertebrate

S-shaped curve

Small processes on neck vertebrate

Allows for the centre of gravity to pass through the knee and foot.Skull can balance on column with little muscle support.Allows for increased neck movement.

Pelvis Long and narrow and tilted forward

Short, broad, bowl-shaped and upright

Short and broad for muscle attachment of leg muscles. Bowl-shaped to support abdominal organs.

Femur/ carrying angle

Femurs come straight down from pelvis

Femurs angle in from pelvis

Creates a carrying angle and brings the knees closer together.Thus it is easier to transfer weight from one foot to another when walking.

5 – 9. The table below outlines the differences between hominids and pongids with respect to the hand and foot.

Characteristic

Pongid Hominid Advantage to Hominid

Hand Long finger and a short thumb.Limited mobility of thumb.

Shorter fingers.Larger thumb with increased mobility.

Allows for precision grip.

Foot Longitudinal arch

Opposable big toe

Small calcaneus

Longitudinal and transverse archLarge big toe alongside other toesLarge robust calcaneus

Produces a spring action and acts as a shock absorber when walking.Acts to give push off when walking as it transfers energy.Bears impact of body’s weight.

10 – 12. The table below outlines the differences between hominids and pongids with respect to their centre of gravity and stance.

Characteristic Pongid Hominid Advantage to Hominid

Centre of gravity Centre of gravity passes in front of the knee and feet

Centre of gravity passes through the knee and feet

Less effort required standing upright as the body is balanced over the knees and feet

Stance Semi-erect knuckle Fully erect bipedal Frees hands for carrying things and manipulating objects. Stands taller to see food and predators.

13 – 15. The table below outlines the differences between hominids and pongids with respect to the skull, jaw and teeth.

Characteristic

Pongid Hominid Advantage to Hominid

Skull Capacity 400 cm3 Capacity 1300 cm3 Larger brain capacity, higher brain functions. Increased learning and more complex behaviour.

Small foreheadLarge brow ridgeNo chinPrognatic faceForamen magnum at back of skull

Large foreheadSmall brow ridgeChinFlat faceForamen magnum at centre of base

Little muscle support required.Skull balances easier.Strengthens jaw.Balances skull.Allows skull to balance on the vertebral column without the need for large neck muscles.Allows for better vision.

Dentition/ Jaw U-shaped jawHeavy jawLarger canines with diastema

Simian shelf

Horseshoe jawLight jawSmaller canines with no diastema

No simian shelf

Better grinding action.Smaller muscles required and increased ability for speech.Increased mobility of jaw with better grinding action increased ability to eat a range of foods.Reinforces front of mandible in ape (not required in hominids).Helps reduce weight of skull.

HUMAN EVOLUTION – Evolution of humans1 – 3. Australopithecines

Alternative name - Southern ApeGeographical location - Southern AfricaTime period - 4 to 1 million years Before Present (BP)Cranial capacity - 400 cm3

Skull and jaw - Large brow ridges, low forehead, prognatic jaw and large molarsCulture - Loosely organised into groups

- May have used very simple tools but did not make themOther - Gracile and robust forms4 – 5. Homo habilis

Alternative name - Handy Man

Geographical location - AfricaTime period - 2 to 1.5 million years BPCranial capacity - 600 cm3 to 800 cm3; average 700 cm3

Skull and jaw - Larger brain and smaller jaw than AustralopithecinesCulture - Made and used simple stone tools (primary flakes)

- Used tools as cutters and scrapers - No cooperative hunting (were scavengers) - Increased meat in diet

- Larger family groups practised food sharing and division of labour- Temporary living shelters- Possible simple speech (large Broca’s area)

6 – 8. Homo erectus

Alternative name - Java Man, Peking Man, Upright ManGeographical location - Africa, Europe, AsiaTime period - 1.8 million to 300,000 years BPCranial capacity - 850 cm3 to 1150 cm3; average 1050 cm3

Skull and jaw - Heavy brow ridges, thick skull, low flat forehead, heavy chinless jaw, Prognatic upper jaw, small more modern teeth, occipital bun, central foramen magnum

Culture - First to use fire for cooking, warmth and protection- Made and used more complex pebble tools with secondary flaking

- Used stone hand axes - Cooperative hunting for larger animals which suggests complex

language (expansion of Broca’s area) for communication (tools found with bones at butchering sites)- Division of labour: women gathered food (nuts, fruits, roots and berries) while men hunted

- Constructed seasonal home sites and also lived in caves; increased use of home bases

Other - S-shaped spine/carrying angle

9 – 11. Homo sapiens neanderthalensis

Alternative name - Neanderthal ManGeographical location - Europe and Middle EastTime period - 125,000 to 30,000 years Before Present (BP)Cranial capacity - 1500 cm3 averageSkull and jaw - Long, low cranium, sloping forehead, reduced brow ridges and large occipital

bun, no chin and large noseCulture - Complex pebble tools with tertiary flaking

- Wood and stone tools (spears)

- Cooperative hunting of large game (mammoths/bison) with butchering and transfer of meat - Complex language- Division of labour- Wore simple clothing (animal skin) for protection against cold- Increased reliance on home base and fire for warmth and protection- Evidence of religious rituals and burials of dead (bear cult)- Care of sick and disabled

Other - Large nose moistened and heated cold air- Possessed all the adaptations required for bipedalism

12. Homo sapiens sapiens

Alternative name - HumansGeographical location - World-wideTime period - 100,000 years BP to present dayCranial capacity - 1350 cm3 averageSkull and jaw - Chin, high vertical forehead, no brow ridge, unspecialised small jaw,

rounded craniumCulture - Builds more complex, permanent shelters

- More elaborative clothing- More complex tools including use of bone, horn and ivory to make needles, hooks and harpoons - Very advanced stone tools- Visual art, cave paintings, bone carvings and clay statues, jewellery- Fishing with nets- Abstract thinking- Complex language

HUMAN EVOLUTION – Culture and lifestyle1. There has been a number of physical trends in the evolution of humans:

There was a progressive increase in size of the brain capacity from Australopithecines (375 to 530 cm3) to Homo sapiens sapiens 1360 cm3.

There was a reduction in the size and degree of specialisation of the teeth. The jaw became progressively smaller and more horseshoe-shaped. The foramen magnum moved progressively towards the base of the centre o the

skull. All hominids were thought to be bipedal and they became progressively more erect.

2. In any population, over an extended period of time changes occur in the lifestyle, customs and beliefs of the people in an area. There are usually gradual changes. This process is called cultural evolution.

3. A number of characteristics were prerequisites for the development of culture: Ability to communicate allowed transmission of customs, ideas and knowledge

within groups and between generations. Hand, precision grip allowed toolmaking excellence and the ability to record and

retain culture. Large cerebral cortex allowed abstract thought, logic, perception and

communication skills. Social organisation and division of labour, allowed time for some to indulge in

cultural pursuits (e.g. tools, technology and ideas).

4. A number of trends were evident in the evolution of culture in hominids: Tool type – simple to complex (e.g. pebble tools such as choppers/scrapers) → hand

axe → needles/spearheads → agricultural tools). Materials – stone → bone/antler/wood → metal. Use – casual → butchering → hunting → making other tools/agriculture. Lifestyle – nomadic hunter/gatherer → subsistence agriculture → small-scale

agriculture (bartering) → commercial agriculture (specialised) → towns (secondary sector) → urbanisation (tertiary sector) → general increase in specialisation.

Communication – oral/signs → simple speech → complex speech →art → written word.

Learning – personal experience → demonstration/copy → oral → written/recorded.5. Food gathering increased the availability of food which led to the more efficient use of time

(not everyone was needed for food gathering all of the time). This allowed more free time to develop aspects of culture like toolmaking. Food sharing also led to increased parental care and learning.

6. The agricultural revolution resulted in a great increase in food production and a relief from food gathering. This increased the time available for cultural development (inventing) and allowed for specialisation.

7. In addition to the physical and intellectual evolution of hominids, the evolution in culture can be classified into three main cultural periods. These are the Palaeolithic (Stone Age) period, the Mesolithic (transitional) period and the Neolithic (modern) period.

8. During the Palaeolithic period the culture was based on stone tools (Stone Age), which became increasingly sophisticated as it progressed. These hunter-gatherer-based societies became more and more reliant on the use of fire while art (cave paintings, carvings) became prevalent.

9. The Mesolithic period was the transitional period from the Stone Age to societies based on agriculture. Sophisticated stone tools were produced as well as tools make from antler/bone/wood. Shelters were semi-permanent and complex in design and clothes made from animal skins were introduced. Small communities of non-related individuals started to develop.

10. During the Neolithic period agricultural-based societies domesticated animals and plants. Metallurgy based on the use of copper, bronze and iron was developed. There was increased urbanisation, the development of organised trading and specialisation of labour. Increased leisure time resulted in the development of writing, music and drama.