Section 2 j) Specification

2.77 understand that organisms are able to respond to changes in their environment

Organisms have receptors to detect changes in the environment, that sends a signal through the body to create the appropriate response.

2.78 understand that homeostasis is the maintenance of a constant internal environment and that body water content and body temperature are both examples of homeostasis

Humans are homeostatic organisms; their internal conditions don't change. This requires constant maintenance, as we are constantly using and removing water from our bodies, and the external environment is constantly changing in temperature. Thermoregulation is the regulation of body temperature, and osmoregulation is the regulation of water content.

2.79 understand that a coordinated response requires a stimulus, a receptor and an effector

One of the criteria for life is sensitivity. This means that an organism can detect a change in environment, a stimulus, using a receptor, which will then send a signal to an effector which will respond to the change.


Flowering plants:

2.80 understand that plants respond to stimuli

Plants are living organisms, and can therefore respond to stimuli, such as changes in light intensity (phototropism), water (hydrotropism) and gravity (geotropism). The response is usually in plant hormones, auxins being the hormones that are most important.
A positive tropism is when the plant grows towards the stimulus, and a negative tropism is when the plant grows away from the stimulus.
Auxin causes cells in stems to grow more, and cells in roots to grow less:

As depicted above, the auxin gathering on one side of the stem stimulates growth of cells, causing that side of the stem to elongate more than the other side, and the stem to curve. The opposite is true for roots: auxin gathering in the bottom stunts growth, causing that side to grow less than the other side and the root to bend downwards.

2.81 describe the geotropic responses of roots and stems

Roots are positively geotropic, they respond to gravity by growing in the direction of it, whereas stems are negatively geotropic, they respond to gravity by growing in the opposite direction. Auxin collects in the bottom of the plant due to gravity, causing the growth of cells to be uneven (stunted on one side of the root and increased on the same side of the stem), meaning the roots will bend down and the stem will bend up.

2.82 describe positive phototropism of stems

Stems are positively phototropic, auxin collects on the side that receives less light, which causes the cells there to grow more and the plant to then bend towards the light.


Humans:

2.83 describe how responses can be controlled by nervous or by hormonal communication and understand the differences between the two systems

In the human body, there are two systems that respond to stimuli: The endocrine system, which releases hormones, and the nervous system, which releases electrical impulses.
These two systems have a number of similarities and differences.

2.84 understand that the central nervous system consists of the brain and spinal cord and is linked to sense organs by nerves

The CNS or central nervous system consists of the brain and a bundle of neurones called the spinal cord. It is connected to the rest of the body by neurones, which make up the peripheral nervous system or PNS. The neurones are connected to sensory organs, such as the eyes and skin, which detect stimuli and cause an electrical impulse through the body, to create a response.

2.85 understand that stimulation of receptors in the sense organs sends electrical impulses along nerves into and out of the central nervous system, resulting in rapid responses

When a receptor is stimulated, it sends an electrical impulse to the sensory neurone, which can be identified by the cell body in the middle of the axon. The sensory neurone carries the impulse to the relay neurone, which then carries the impulse to the motor neurone.
The motor neurone carries the impulse from the relay neurone to the effector and causes the response. This all happens in a fraction of a second.

Sensory neurone: it has the cell body poking out, like it's an eye looking around to SENSE what's going on.
Relay neurone: Shorter, can transmit signals both ways because it's versatile like that. symmetrical(ish??) so the cell body is central.
Motor neurone: it causes the effect, so it thinks it's important that's why it has a big head.

2.86 describe the structure and functioning of a simple reflex arc illustrated by the withdrawal of a finger from a hot object

1. Receptor in the finger detects that the object is hot.
2. Sensory neurone sends an electrical impulse from the finger to a relay neurone in the CNS.
3. Relay neurone transmits the signal to a motor neurone.
4. The impulse is carried along the motor neurone to an effector in the arm muscle, causing it to contract and the finger to be moved away from the hot object.
This prevents the tissue from being damaged in the finger and is an involuntary (reflex) action.
A synapse is the gap between two neurones, and this is where impulses are transmitted from one to another.

2.87 describe the structure and function of the eye as a receptor

The eye is protected by the conjunctiva, which is a membrane at the front of the eye, over the cornea. The cornea is the outer layer of the eye, which can develop cloudiness with age. It contains the aqueous humour, a clear fluid that refracts light. The light is let in through the pupil, which is enlarged or shrunk by the iris to let in more or less light (iris is controlled by circular and radial muscles). The light passes through the pupil to the lens, which is a flexible fluid-filled sac, suspended by suspensory ligaments and ciliary muscles. The ciliary muscles relax to make the lens more disc-like, and they contract to make the lens more round. The lens focuses the light through refraction, allowing it to then pass through the vitreous humour to the retina, focusing specifically on a point known as the fovea, where more rods and cones are found (the actual receptors) and they send an impulse to the optic nerve, which sends electrical impulses through the nervous system to send the information around the body. The whole eye is encased by the choroid (which is black to prevent internal reflection) and the sclera, which is hard to protect the eye.

2.88 understand the function of the eye in focusing near and distant objects, and in responding to changes in light intensity

Accommodation is how the eye focuses on objects that are near and far.
If an object is far away, the ciliary muscles will relax, pulling the suspensory ligaments tight and making the lens more disc-like and flat. This decreases refraction so the light focuses on the fovea.
If an object is closer, the ciliary muscles contract, releasing the suspensory ligaments. This causes the lens to become more round and refraction of light to increase.

Iris reflex is how the eye responds to changes in light intensity.
If the light is brighter, the eye will detect it, sending an impulse to the optic nerve and through the CNS, and then back to the eye and to the radial and circular muscles to cause the radial muscles to relax and the circular muscles to contract, making the pupil smaller so less light is let in to protect the retina from damage from intense light.
If the light is dimmer, the eye will send a message through the nervous system so it reaches the radial and circular muscles, and will cause the radial muscles to contract and the circular muscles to relax, increasing the size of the pupil to let more light in so you can see better.

2.89 describe the role of the skin in temperature regulation, with reference to sweating, vasoconstriction and vasodilation

Upon entering a hot environment, the body will attempt to cool itself to maintain its temperature. This is called thermoregulation. The skin releases heat by sweating. It releases water, which will then evaporate from the skin, taking heat energy with it and thereby cooling the surface of the skin. Blood vessels close to the surface of the skin will become wider to increase the blood flow near the surface so heat can be lost through radiation; this is called vasodilation.
Upon entering a cooler environment, the hairs on the surface of the skin prickle up to trap air and insulate the body (although this is virtually useless now, it would have been more useful before we evolved into fairly hairless humans), and the blood vessels close to the surface constrict to limit blood flow and therefore limit heat loss. This is called vasoconstriction.

2.90 understand the sources, roles and effects of the following hormones: ADH, adrenaline, insulin, testosterone, progesterone and oestrogen.

ADH: Produced in the pituitary gland in the brain, makes the tubules in the nephrons more permeable so more water is reabsorbed.

Adrenaline: Produced in the adrenal glands, creates a fight or flight response (increases heart rate, blood flow and breathing so more glucose and oxygen reaches the muscles for respiration)

Insulin: Produced in the pancreas, controls the blood sugar levels (stimulates the liver to store glucose as glycogen)

Testosterone: Produced in the testes, it is the main male sex hormone. and promotes secondary sex characteristics such as facial hair, body hair and the Adam's apple.

Progesterone: Produced in the ovaries, it maintains the uterine wall lining for pregnancy.

Oestrogen: Produced in the ovaries, it is the main female sex hormone and controls the menstrual cycle and promotes secondary sex characteristics such as widening hips, growth of breasts and body hair.

Section 2 i) Specification

Flowering plants:
2.67 understand the origin of carbon dioxide and oxygen as waste products of metabolism and their loss from the stomata of a leaf

Plants excrete carbon dioxide as it is produced as a waste product of respiration, as well as oxygen as it is a waste product of photosynthesis. They both leave the leaf through the stomata by diffusion in gas exchange.


Humans:
2.68 recall that the lungs, kidneys and skin are organs of excretion

The lungs excrete carbon dioxide, the kidneys excrete urea and other waste products in the blood to be passed through the urinary tract, and the skin excretes urea and salts in sweat.

2.69 understand how the kidney carries out its roles of excretion and osmoregulation

Excretion
Urea is a chemical produced in the liver from excess amino acids (deamination), and is toxic to the body. It is released from the liver into the blood, and the blood then flows through the renal artery into the kidneys. Inside the kidneys, there are many nephrons (filtration units within the kidney). The blood flows through capillaries into the glomerulus, where high pressure forces water, urea, salts and glucose into the bowmans capsule and through the proximal convoluted tubule. Here, glucose is selectively reabsorbed into the bloodstream from the glomerular filtrate by active transport. Salts are reabsorbed, but only just enough, no excess. Once the glomerular filtrate has travelled through the proixmal convoluted tubule, the loop of Henle, and the distal convoluted tubule, it enters the collecting duct as urine and is transported to the bladder, where it is held until it is excreted.

Osmoregulation
ADH (anti-diuretic hormone) is released from the pituitary gland, as stimulated by the hypothalamus in the brain. If the hypothalamus detects a rise in water content, the pituitary gland will release less ADH, but if it detects a fall in water content, the pituitary gland will release more ADH. More ADH makes the tubules more permeable, so more water is reabsorbed, and the opposite is also true.

2.70 describe the structure of the urinary system, including the kidneys, ureters, bladder and urethra

Blood is filtered to remove waste products in the kidneys, and leaves through the collecting duct into the ureter, which transports urine to the bladder. Urine is expelled through the urethra.

2.71 describe the structure of a nephron, to include Bowman’s capsule and glomerulus, convoluted tubules, loop of Henlé and collecting duct

The nephron is a series of tubules and blood vessels. The glomerulus is inside the bowman's capsule, and this is where ultrafiltration occurs. The filtrate travels through the proximal convoluted tubule, then the loop of Henle, then the collecting duct.

2.72 describe ultrafiltration in the Bowman’s capsule and the composition of the glomerular filtrate

Blood is pushed through the glomerulus at a high pressure, causing smaller molecules to be forced through into the bowman's capsule. Larger particles (cells etc.) remain in the blood as they are too large to fit through. Glomerular filtrate is therefore made up of water, glucose, urea and salts.

2.73 understand that water is reabsorbed into the blood from the collecting duct

Water is reabsorbed from the glomerular filtrate throughout the whole series of tubules, including the collecting duct, except for the second half of the loop of Henle, where only salts are reabsorbed.

2.74 understand that selective reabsorption of glucose occurs at the proximal convoluted tubule

Glucose is a very valuable nutrient required for respiration, so is selectively reabsorbed in the proximal convoluted tubule. This happens through active transport, because while this requires respiration to occur, the glucose saved means that it is worth it.

2.75 describe the role of ADH in regulating the water content of the blood

Excess of water detected by hypothalamus > Pituitary gland stimulated to produce less ADH > less ADH travels through the blood into the nephron > Tubules become less permeable > Less water is reabsorbed > Normal water content level achieved
Deficit of water detected by hypothalamus > Pituitary gland stimulated to produce more ADH > more ADH travels through the blood to the nephron > Tubules become more permeable > More water is reabsorbed > Normal water content level achieved

2.76 understand that urine contains water, urea and salts.

Urine is the substance excreted by the kidneys. It contains urea, a toxic substance from broken down amino acids, excess salts, and excess water. It should not contain glucose or proteins, which are indications of illness.

Section 2 h) Specification

2.49 understand why simple, unicellular organisms can rely on diffusion for movement of substances in and out of the cell

Unicellular organisms have a small volume to surface area ratio, and are small, meaning they have a short diffusion distance. This makes them ideal for diffusion, active transport and osmosis without a transport system.

2.50 understand the need for a transport system in multicellular organisms

Larger, multicellular organisms, need a transport system to move necessary substances (e.g. mineral ions, water, oxygen, sugars) around the organism. If they didn't have transport systems, because the volume to surface area ratio is large, it would take a long time for all of the nutrients to reach all the cells. Without transport systems, multicellular organisms would not be able to live, they wouldn't have enough nutrients to work.


Flowering plants:

2.51 describe the role of phloem in transporting sucrose and amino acids between the leaves and other parts of the plant

Phloem tubes are columns of living cells. Their cell walls at either end form small holes to allow substances to pass through (sieve plates). The tubes allow dissolved sugars and amino acids to be transported through the plant. This movement is known as translocation.

2.52 describe the role of xylem in transporting water and mineral salts from the roots to other parts of the plant

Xylem tubes are made up of hollow, dead cells. There are no cell walls at either end, allowing water and dissolvedd mineral ions to flow through the plant freely. The tube has thick, reinforced cell walls, that have a secondary function of support.

2.53 explain how water is absorbed by root hair cells

Water in drawn into the root hair cells by osmosis. The cells have long 'hairs', hence the name. This increases the surface area, making them specialised for absorbing water and mineral ions.

2.54 understand that transpiration is the evaporation of water from the surface of a plant

Transpiration is the evaporation and diffusion from leaves, the vapour escaping from the stomata. Water molecules are cohesive (they stick together), so a tension pull is produced, causing more water to travel up to the leaf, creating a transpiration stream.

2.55 explain how the rate of transpiration is affected by changes in humidity, wind speed, temperature and light intensity

More humid = Less transpiration. This is because there is a less steep concentration gradient so the water vapour doesn't diffuse away.
More windy = More transpiration. The water vapour is blown away from the leaf more quickly so diffusion is sped up.
More heat = More transpiration. Higher temperatures mean more evaporation, and the particles move more quickly so diffusion is faster.
More light = More transpiration. More light means more photosynthesis, so the stomata open wide. When it begins to get darker, the stomata begin to close. Open stomata allow water to escape.

2.56 describe experiments to investigate the role of environmental factors in determining the rate of transpiration from a leafy shoot

A potometer can be used to measure the rate of transpiration.

Different environmental factors can be changed (Placing in a warmer environment, near a fan, increasing humidity or light, etc.) and the following experiment carried out:

1. Set up apparatus so it is watertight, allowing a bubble to form in the capillary tube. The shoot should be cut diagonally to maximise surface area. Take note of where the bubble starts. 
2. Start a stopwatch and record the distance moved by the bubble per unit of time (e.g. cm/h)
3. Record on a graph, and see how it changes with different variables. 

All of the variables should cause it to change proportionally. 

Humans:

2.57 describe the composition of the blood: red blood cells, white blood cells, platelets and plasma

The blood is made up of four main components: Plasma (54.3%), red blood cells (45%), white blood cells and platelets (0.7%).

2.58 understand the role of plasma in the transport of carbon dioxide, digested food, urea, hormones and heat energy

Plasma is about 93% water, and 7% proteins. It is a pale yellow liquid, and is the medium in which most substances are transported around the body. It transports white blood cells and platelets, as well as red blood cells which transport oxygen around the body, it transports amino acids and glucose absorbed from the gut to bodily cells, urea from liver to kidneys where it is removed, then excreted, hormones from different glands around the body to send chemical messages around the body, and heat energy.

2.59 explain how adaptations of red blood cells, including shape, structure and the presence of haemoglobin, make them suitable for the transport of oxygen

Red blood cells have a bi-concave shape, and are small. This means they have a high surface area to volume ratio, ideal for absorbing and releasing oxygen. Haemoglobin is the chemical contained in red blood cells that bonds with oxygen in the lungs to form oxyhaemoglobin, allowing them to carry oxygen around the body. They also have no nucleus to decrease volume.

2.60 describe how the immune system responds to disease using white blood cells, illustrated by phagocytes ingesting pathogens and lymphocytes releasing antibodies specific to the pathogen

Phagocytes are able to detect foreign substances and objects in the body, and engulf them. They are non-specific, so they attack anything. This is why people with organ transplants must take immunosuppressants; the phagocytes would otherwise attack the foreign cells and reject the organ.
Lymphocytes detect the antigens found on the surface of pathogens, and release the corresponding antibody: a specific protein that will attack the pathogens, and mark them for destruction by other white blood cells. Once the infection has been fought off, some antibodies remain in the blood so they are easily able to detect and reproduce the same antibody when in contact with the disease.

2.61 understand that vaccination results in the manufacture of memory cells, which enable future antibody production to the pathogen to occur sooner, faster and in greater quantity

In a vaccine, dead or inactive pathogens, or a harmless part of a pathogen or even just the genetic material is injected into the bloodstream. This sample contains antigens, which creates an immune response that allows the lymphocytes to produce antibodies to attack the antigens. Once this harmless 'infection' is fought off, these lymphocytes contain a 'memory' of how to produce the particular antibody, and are able to fight off real infection later on, with quick and large-scale production of antibodies.

Some people have weaker immune systems, so vaccines can cause problems. If they have an immune condition, are taking immunosuppressants, or are too young or too old, they cannot have an immunisation and thus are unprotected. This is why it is so important for the vast majority to be vaccinated, so vulnerable people are protected too.

2.62 understand that platelets are involved in blood clotting, which prevents blood loss and the entry of micro-organisms

Platelets are small fragments of cells that clump together, held in a web-like structure of proteins, called fibrin, over damaged areas. This is known as blood clotting, and prevents blood from escaping from the damaged vessels, as well as stopping potentially harmful microorganisms from getting in.

2.63 describe the structure of the heart and how it functions

The heart is made up of four chambers; the left atrium, the left ventricle, the right atrium and the right ventricle. These chambers are each attached to their own blood vessel.

The right atrium is connected to the vena cava. It takes in deoxygenated blood from the body and passes it through the tricuspid valve to the right ventricle.
The right ventricle pumps deoxygenated blood at a low pressure to the lungs (through the semi-lunar valve to the pulmonary artery). This must be low pressure to fit through the tiny capillaries in the lungs without bursting them.
The left atrium receives oxygenated blood from the pulmonary vein, after it has passed through the lungs. The blood is then passed through the biscuspid valve into the left ventricle.
The left ventricle has a thick muscular wall that allows blood to be pumped around the body at high pressure. It squeezes strongly so the oxygenated blood passes through the semi lunar valve into the aorta.

2.64 explain how the heart rate changes during exercise and under the influence of adrenaline

More exercise means more respiration, meaning there is more carbon dioxide being released into the bloodstream, and a higher demand for oxygen. This causes the heart to pump faster so more oxygen can reach the muscles.

Adrenal glands are hormonal glands that release a chemical called adrenaline. This is released when the organism is threatened. It sends a signal to the brain to make the heart pump faster in order to get more oxygen to the bodily tissues for action (fight or flight)

2.65 describe the structure of arteries, veins and capillaries and understand their roles

Arteries are the blood vessels that carry blood away from the heart. This is usually oxygenated, but not in the case of the pulmonary artery. Arteries are under high pressure, as it has come directly from the heart. The walls are strong and elastic (with thick layers of muscle), and they are thick compared to the size of the lumen, and no valves. This allows them to withstand and maintain high blood pressure.

Veins carry blood back to the heart. They usually contain deoxygenated blood, but again the pulmonary vein is an exception. They have thin walls and low pressure, but contain valves to prevent the blood travelling backwards. They have large lumen to help the blood flow despite the low pressure.

Capillaries are really tiny blood vessels. Their walls are just one cell thick, making them ideal for diffusion. They carry blood close to every cell to provide them with the necessary nutrients. They have very small lumen.

2.66 understand the general structure of the circulation system to include the blood vessels to and from the heart, the lungs, the liver and the kidneys.

In humans, the blood circulates in two systems. This is called double circulation.

The two systems work together in oxygenating the blood and pumping it around the body.

Section 2 g) Specification

2.38 understand the role of diffusion in gas exchange

Oxygen must diffuse into the organism and carbon dioxide out during gas exchange. Because of this, the organs designed for gas exchange, such as leaves and alveoli have a large surface area and a thin lining to increase the rate of diffusion.

Flowering plants:

2.39 understand gas exchange (of carbon dioxide and oxygen) in relation to respiration and photosynthesis

Photosynthesis is the conversion of carbon dioxide and water into glucose and oxygen, taking in energy from the sun:
6CO2 + 6H2O --> C6H12O6 + 6O2
Gas exchange is the conversion of glucose and oxygen into water and carbon dioxide, releasing energy:
C6H12O6 + 6O2 --> 6CO2 + 6H2O

As you can see, gas exchange is the reverse of photosynthesis, and vise versa.

2.40 understand that respiration continues during the day and night, but that the net exchange of carbon dioxide and oxygen depends on the intensity of light

Respiration is not limited by the energy absorbed by the plant (sunlight), so it can continue during day and night. Photosynthesis is affected by the intensity of light it receives, it can only occur during the day. However, in plants, the exchange of gas is controlled by the opening and closing of the stomata. To prevent water loss, the guard cells become flaccid and close the stomata at night. This decreases the rate of respiration as well, and the net gas exchange decreases significantly

2.41 explain how the structure of the leaf is adapted for gas exchange

It has stomata and spongy mesophyll with air pockets that increase the surface area for gas exchange. Leaves are thin to decrease the diffusion distance, as well as wide and flat to increase surface area

2.42 describe the role of stomata in gas exchange

Stomata can open and close due to the turgidity of the guard cells, which become flaccid and close at night, preventing water loss when photosynthesis is not possible. The stomata allow gas to travel inside the plant, where there are air pockets that further increase the leaf's surface area and allow gas to be exchanged between the leaf and the atmosphere.

2.43 describe experiments to investigate the effect of light on net gas exchange from a leaf, using hydrogen-carbonate indicator

1. Choose 3 leaves of similar sizes from the same plant, and suspend in a sealed boiling tube containing hydrogen carbonate indicator.
2. Leave one tube in the light, cover another tube in foil so it is in total darkness, cover another in gauze so it receives dim light, then leave a control without a leaf in the light. 
3. The hydrogen carbonate indicator will start off red in all, but each will end up with different results. The one in darkness will be yellow, the one in dim light will stay orange/red, the one in light will become yellow, and the control will not change in colour. 

These results are caused by the ratio of the rate of photosynthesis compared to the rate of respiration. 

Humans:

2.44 describe the structure of the thorax, including the ribs, intercostal muscles, diaphragm, trachea, bronchi, bronchioles, alveoli and pleural membranes

The thorax is enclosed by the rib cage, which is made up of rows of ribs connected by intercostal muscles that contract and relax which breathing. Inside the rib cage are the lungs, which is where gas exchange takes place. The lungs are surrounded by pleural membrane, holding them in place, and pleural fluid, which allows the lungs to move easily. Air rushes in through the mouth, down the trachea or windpipe, then through the two bronchi and many bronchioles (muscular tubes held open by rings of cartilage). The air reaches the alveoli, tiny sacs of air surrounded by capillaries, where gas exchange takes place, and the oxygen diffuses into the bloodstream, and carbon dioxide out.

2.45 understand the role of the intercostal muscles and the diaphragm in ventilation

In humans, breathing happens in the thorax. In inhaling, the intercostal muscles between the ribs contract, the rib cage moves up, the diaphragm contracts and lowers, increasing the volume of the chest and decreasing the pressure. This causes air from the atmosphere to rush into the lungs and fill them up. In exhaling, the intercostal muscles relax and the ribcage moves downwards. The diaphragm relaxes and raises, decreasing the volume of the chest and increasing the pressure, causing air to rush out into the atmosphere

2.46 explain how alveoli are adapted for gas exchange by diffusion between air in the lungs and blood in capillaries

Alveoli have a wet surface for dissolving oxygen, large surface area, thin lining for easy diffusion, and a lot of capillaries surrounding them.

2.47 understand the biological consequences of smoking in relation to the lungs and the circulatory system, including coronary heart disease

In the trachea and bronchi, there are ciliated epithelial cells, which are specialised cells that move mucus to clean the lungs of pathogens.

Tar from cigarettes coats and paralyses the cilia of these cells, preventing them from moving the mucus. This increases risk of bacterial infection and is known as chronic bronchitis, or commonly smoker's cough.
Tar also damages the alveoli - they are fused together by the sticky substance and their surface area is decreased, limiting gas exchange and making breathing difficult. This is called emphysema.

Cigarettes, when smoked, release carbon monoxide. This is a dangerous and highly toxic substance as it binds with haemoglobin in the bloodstream, as oxygen does, but is not released, it causes the red blood cell to be useless as it can no longer carry the less reactive oxygen. This leads to an increased heart rate, as not enough oxygen is able to reach the body's cells.

Nicotine, the addictive substance in cigarettes, affects the central nervous system, increasing heart rate and narrowing the blood vessels. This causes high blood pressure, which can lead to coronary heart disease.

2.48 describe experiments to investigate the effect of exercise on breathing in humans

Measure the rate of breathing while stationary (breaths per minute) by counting the number of breaths in fifteen seconds, then multiplying by four.
Exercise at a sustained and measured level for 1 minute (perhaps by running on a treadmill, which allows you to control your speed), then measure the rate of breathing again. Repeat after two minutes of exercise, then three, then four, and so on.
Draw a graph based of the length of time exercised (on the x-axis) and the breathing rate (on the y-axis), and you will see that the breathing rate is proportional to the time exercised.

This can also be done by using a spirometer to measure the depth of breath. 

Section 2 f) Specification

2.33 understand that the process of respiration releases energy in living organisms

Respiration is the process by which living organisms release energy from sugar.

2.34 describe the differences between aerobic and anaerobic respiration

Aerobic respiration is respiration that occurs with oxygen, and anaerobic is without. Anaerobic respiration produces significantly less energy than aerobic respiration, and usually has a toxic by-product (lactic acid in humans, alcohol in yeast or plants, etc.)

2.35 write the word equation and the balanced chemical symbol equation for aerobic respiration in living organisms

C6H12O6 + 6O2 --> 6CO2 + 6H2O (+energy)
Glucose + Oxygen --> Carbon dioxide + Water (+energy)

2.36 write the word equation for anaerobic respiration in plants and in animals

Plants: Glucose --> Carbon dioxide + Ethanol (+some energy)
Animals: Glucose --> Carbon dioxide + Lactic acid (+some energy)

2.37 describe experiments to investigate the evolution of carbon dioxide and heat from respiring seeds or other suitable living organisms.

Rising dough (yeast):

1. Place dough into oiled measuring cylinders, and record their height. 
2. Place each measuring cylinder into a water bath (regular intervals of 10℃), with three cylinders in each bath so an average for each can be found.
3. Measure the height of the dough every 10 minutes, for 30 minutes.
4. Record the average heights in a table, then find the average percentage change in height. 

Seeds:

1. Fill one vacuum flask with living seeds, and thee other with surface-sterilised seeds. Place a thermometer in each and seal the top with cotton wool.
2. Record starting temp, then wait 30 minutes. 
3. The flask containing the living seeds will have increased in temperature, and the one with dead seeds will not. 

Heat is a by-product of the use of the energy for respiration. 

Humans: 

You can see that we produce carbon dioxide by blowing into a straw in a boiling tube containing lime water - it goes cloudy - or hydrogen carbonate indicator - it goes from red to yellow. 

Section 2 e) Specification

Flowering plants:
2.17 describe the process of photosynthesis and understand its importance in the conversion of light energy to chemical energy

Photosynthesis is the process in which plants create glucose and oxygen for respiration from carbon dioxide and water.

2.18 write the word equation and the balanced chemical symbol equation for photosynthesis

6 CO2 + 6 H2O --> C6H12O6 + 6 O2
Carbon dioxide + Water --> Glucose + Oxygen

2.19 understand how varying carbon dioxide concentration, light intensity and temperature affect the rate of photosynthesis

Carbon dioxide concentration: Increased CO2 concentration increases rate of photosynthesis as this increases the amount of reactants for this reaction. It will plateau after a while due to limited stomata and chlorophyll.

Light intensity: More intense light increases rate of photosynthesis. Limited by number of chloroplasts.

Temperature: Increases rate of photosynthesis with increased temperature as temp. increases kinetic energy of the particles, leading to more collisions and a faster rate of reaction. The rate of reaction will steadily increase, up until optimum temperature, after which it will drop steeply as it causes enzymes to denature.

2.20 describe the structure of the leaf and explain how it is adapted for photosynthesis

The leaf is structured in 5 layers:

• Waxy Cuticle: Prevents water loss, protects the plant from damage 
• Upper epidermis: Thin, transparent layer that lets sunlight through to the chloroplasts beneath.
• Palisade mesophyll: Cells are packed full of chloroplasts to absorb as much sunlight as possible. 
• Spongy mesophyll: Contains air spaces that allow gas exchange to occur, maximises surface area for diffusion.
• Lower epidermis: protects the underside of the leaf, has stomata and guard cells that control gas exchange, preventing water loss at night. 

2.21 understand that plants require mineral ions for growth and that magnesium ions are needed for chlorophyll and nitrate ions are needed for amino acids

Plants require mineral ions for growth, and deficiency can cause a variety of problems:

2.22 describe experiments to investigate photosynthesis, showing the evolution of oxygen from a water plant, the production of starch and the requirements of light, carbon dioxide and chlorophyll

Experiment 1: Oxygen and water plants

1. Choose the variable you wish to change (temp, light intensity, etc.) 
2. Place containers of water and water plants of about the same size in the different conditions. 
3. Count the bubbles that are formed in a certain length of time. 

Experiment 2: Starch and light intensity

1. Put 3 leaves from the same plant of similar sizes in different light conditions: One in a dark room, one in direct sunlight, and one in shaded light. Leave for 48 hours.
2. Test leaves for starch by boiling each in water for 1 minute, then placing in ethanol, then returning it to the water and finally spreading on a petri dish. Add iodine solution to see which leaves test positive for starch 

Experiment 3: Chlorophyll
Test variagated leaves for starch. You can see the green parts test positive for starch while the white parts do not.

Experiment 4: Carbon dioxide
Place a plant in a sealed plastic bag with a container of sodalime (which removes CO2), then test for starch.

Experiment 5: Carbon dioxide
Place water plants in different light levels for 12 hours, with hydrogencarbonate indicator. At the start, indicator should be red, then change to purple for low levels of CO2 (In sunlight) and change to yellow for high levels of CO2 (In darkness)



Humans:
2.23 understand that a balanced diet should include appropriate proportions of carbohydrate, protein, lipid, vitamins, minerals, water and dietary fibre

A human diet must contain a variety of different nutrients in order to be able to carry out necessary functions. The proportions of each group of nutrients is represented by the eatwell plate:

2.24 identify sources and describe functions of carbohydrate, protein, lipid (fats and oils), vitamins A, C and D, and the mineral ions calcium and iron, water and dietary fibre as components of the diet

2.25 understand that energy requirements vary with activity levels, age and pregnancy

Generally, the greater a person's mass, the more energy they require. Men are generally larger than women, so they require more energy. Adults require more energy than children because they are much larger. Mid- to late- teens usually require more energy than adults as they are growing, and generally after puberty people will gradually require less and less food as they age. Athletes and people who do more exercise require more energy than people who are less active. Pregnant women require more food, due to growth and increase in mass.

2.26 describe the structures of the human alimentary canal and describe the functions of the mouth, oesophagus, stomach, small intestine, large intestine and pancreas

When food enters the body, it first is mechanically and chemically digested in the mouth. The teeth break up the food to increase its surface area (aiding chemical digestion later on) and to make it easier to swallow, in food bolus. Salivary amylase begins to break down carbohydrates into glucose.
The food is then swallowed, (the epiglottus closes over the trachea to avoid food from falling into the lung) and it travels down the oesophagus through peristalsis: the waves of contraction and relaxation of circular and longitudinal muscles. Peristalsis pushes the bolus of food into the stomach.
The stomach is a large muscular bag that contracts and relaxes to churn the food. The food is held here for 2-4 hours, during this time mixing with gastric juice (a combination of HCl and pepsin, a form of protease), which breaks down protein in the food. The stomach is lined with mucus-producing goblet cells, which helps to prevent the highly acidic HCl from damaging the stomach. Food then passes through into the duodenum.
The duodenum is the first part of the small intestine, it is where digestion is completed. Digestive enzymes (Carbohydrases, proteases and lipases) are secreted in pancreatic juice, from the pancreas. Bile is also released after being made in the liver and stored in the gall bladder. It emulsifies lipids to increase their surface area. The fully digested nutrients are then transported to the ileum.
The ileum is where absorption, or assimilation takes place. The surface of the intestine is folded into tiny villi, which increase the surface area for maximum absorption. It can take place passively, through diffusion, or via active transport. The villi contain capillaries and lacteals (lymph vessels) which absorb digested lipids, amino acids and glucose.
The remaining material is now passed on to the large intestines, the colon. Here, water and mineral ions are reabsorbed. The leftover undigested food, bacteria, etc. (faeces) is stored in the rectum, then egested via the anus.

2.27 understand the processes of ingestion, digestion, absorption, assimilation and egestion

Ingestion: Taking food into the body, eating it.
Digestion: Breaking the food down into nutrients that can be absorbed by the body.
Absorption: Absorbing digested food molecules.
Assimilation: When the absorbed molecules become part of the body, they are used or stored.
Egestion: Discharge of undigested material from the digestive tract.

2.28 explain how and why food is moved through the gut by peristalsis

Peristalsis occurs throughout the entirety of the digestive tract. It works using a series of circular and longitudinal muscles that contract and relax to push the material through.
For example in the oesophagus, when the food enters, the circular muscles contract behind it and the longitudinal muscles relax, pushing the food down. The longitudinal muscles then contract and the circular muscles relax, pushing the bolus further along. This is repeated: the circular muscles contract and the longitudinal muscles relax to move it down, etc. This occurs in waves.

2.29 understand the role of digestive enzymes, to include the digestion of starch to glucose by amylase and maltase, the digestion of proteins to amino acids by proteases and the digestion of lipids to fatty acids and glycerol by lipases

2.30 understand that bile is produced by the liver and stored in the gall bladder, and understand the role of bile in neutralising stomach acid and emulsifying lipids

Bile emulsifies fat, which provides a bigger surface area on which lipase can act. It is an alkali, therefore neutralises acidic stomach acid. Bile is produced in the liver, stored in the gall bladder, and released into the duodenum.

2.31 describe the structure of a villus and explain how this helps absorption of the products of digestion in the small intestine

Villi are small, hair-like protrusions in the lining of the small intestine. Their shape increases the surface area, helping to absorb nutrients more quickly. Each villus is covered in micro-villi, which further increase the surface area.
The walls of the villi are just one cell thick to decrease the distance and increase the rate of absorption.
Villi each contain a lacteal, a vessel connected to the lymphatic system. This absorbs fatty acids and glycerol, then transports them away from the small intestine.
Each villus contains a network of capillaries connected to blood vessels. Glucose and amino acids are absorbed into the bloodstream through them.

2.32 describe an experiment to investigate the energy content in a food sample.

1. Take a food sample, and light it on fire. Hold beneath a quantity of water with a thermometer in it. 
2. If the sample goes out, quickly relight it. 
3. Note down the temperature rise

Use this equation to calculate the energy content:

energy transferred (J) = mass of water (g) × 4.2 (J/g°C) × temperature increase (°C)

Section 2 d) Specification

2.12 understand definitions of diffusion, osmosis and active transport

Diffusion: The net movement of particles from an area of high concentration to an area of low concentration in a fluid. Goes with the concentration gradient (passive), so doesn't require energy.

Osmosis: The net movement of water particles through a semi-permeable membrane from an area of high water potential to an area of low water potential, (an area with higher concentration of water particles to an area of low concentration of water particles) Goes with the concentration gradient (passive), so doesn't require energy.

Active Transport: The movement of particles from an area of low concentration to an area of high concentration, absorption against a concentration gradient. Requires energy from respiration.

2.13 understand that movement of substances into and out of cells can be by diffusion, osmosis and active transport

Diffusion: gas exchange in the alveoli

Osmosis: Water moves around plant cells, making them turgid for support

Active transport: Root hair cells absorb mineral ions from the soil

2.14 understand the importance in plants of turgid cells as a means of support

Plants don't have bones or an exoskeleton, so their means of support is turgid cells, which, with their cellulose cell walls, are strong and support the plant's shape. Without turgidity, the plant wilts and dies.

2.15 understand the factors that affect the rate of movement of substances into and out of cells, to include the effects of surface area to volume ratio, temperature and concentration gradient

Diffusion and osmosis are affected by the following factors:

• Temperature. The particles move more quickly as they have more kinetic energy with increased temperature, meaning they move along the concentration gradient more quickly. 
• Concentration gradient. A greater difference in concentration means a steeper concentration gradient. (Fick's Law)
• Distance. Further distances mean slower diffusion, for obvious reasons. It takes longer for particles to travel a further distance. 
• Particle size. Larger particles in diffusion are heavier, and therefore move more slowly.
• Surface area to volume ratio. If the surface area is proportionally larger, there is more surface for passive transport to occur through. 

2.16 describe experiments to investigate diffusion and osmosis using living and non-living systems.

Osmosis can be investigated using Visking tubing, sugar solution and water. (Model cell)
1. Place sugar solution in one sealed Visking tube, and water in another. Weigh each.
2. Place the sugar tube in a beaker full of water, and the water tube in a beaker full of sugar solution.
3. Remove the tubes after 30 minutes and weigh again. Note the changes.
You can see that the sugar tube has increased in mass, because osmosis has caused water to enter the tube. The water tube has lost mass, as osmosis has caused water to leave the Visking tubing.

Osmosis can also be investigated using potato cylinders.
1. Using a cork borer, create a potato cylinder and cut into equal lengths of 3cm.
2. Weigh each cylinder, then place each into different concentrations of sugar solution, making sure to keep track of which is which.
3. After 30 minutes, remove and dry the potato cylinders, then reweigh and note the change in mass for each of them. ( percentage change in mass = (final mass - initial mass) x 100 / initial mass )
These results can be graphed to find the water potential of the potato, as this is the point at which the mass should not change.

Diffusion can be investigated by placing food colouring into water. Then by timing how long it takes for the water to become entirely one colour at different temperatures will tell us how temperature affects diffusion.

Section 2 c) Specfication

2.5 identify the chemical elements present in carbohydrates, proteins and lipids (fats and oils)

In carbohydrates and lipids, there are CHO: Carbon, Hydrogen and Oxygen.
In proteins, there are CHON: Carbon, Hydrogen, Oxygen and Nitrogen.

2.6 describe the structure of carbohydrates, proteins and lipids as large molecules made up from smaller basic units: starch and glycogen from simple sugar; protein from amino acids; lipid from fatty acids and glycerol

Starch and glycogen are carbohydrates that are polymers, their monomers being simple sugars (monosaccharides) such as glucose: C6H12O6

Proteins are made of amino acids, which join together to form unique shapes and combinations, important for each protein to have its own properties.

Lipids are made up of fatty acids and glycerol, in this structure:

2.7 describe the tests for glucose and starch

Starch: Test using iodine solution. If it changes from brown-orange to blue-black, there is starch present.

Glucose: heat with Benedict's solution. It will turn red if positive.

2.8 understand the role of enzymes as biological catalysts in metabolic reactions

Enzymes work with the lock and key model. They are a certain shape that allows substrates to fit in, then bond together or break apart in the active site. It speeds up the reaction. They are useful in digestion, enzymes such as protease break up proteins, amylase breaks up starch into glucose,

2.9 understand how the functioning of enzymes can be affected by changes in temperature, including changes due to change in active site

The active site of the enzyme is the most important part of it. It allows the enzyme to take part in metabolic reactions, however if it is put in conditions that are too far from the optimum it can be damaged. In high temperatures, the shape of the active site can be changed, rendering the enzyme useless. The enzyme is denatured.

This curve depicts the way temperature affects enzymes:

Beyond the optimum temperature, the enzyme is denatured. Leading up to the optimum temperature, the enzyme activity increases due to increasing kinetic energy of the particles which increases the rate of collisions.

2.10 understand how the functioning of enzymes can be affected by changes in active site caused by changes in pH

Extreme change in pH can also cause the enzyme to be denatured. This varies depending on the optimum pH of the enzyme, but a very extreme pH will denature any enzyme. 

2.11 describe experiments to investigate how enzyme activity can be affected by changes in temperature.

1. Place test tubes containing the same mixture of amylase and starch in water baths of different temperatures with regular temperature intervals (e.g. 20℃, 30℃, 40℃, 50℃, 60℃, 70℃)
2. Take a sample from each at regular time intervals (every 30 seconds) and test for starch with iodine
3. Record which sample was the first to not test positive for starch.
From this, you can see how long it took for the enzyme to break down the starch. It can be graphed to determine the optimum temperature.

Section 2 b) Specification

2.2 describe cell structures, including the nucleus, cytoplasm, cell membrane, cell wall, chloroplast and vacuole
AND
2.3 describe the functions of the nucleus, cytoplasm, cell membrane, cell wall, chloroplast and vacuole 

The nucleus is, simply put, the "brain" of the cell. It contains DNA with instructions of what the cell should do and controls the cell.
Cytoplasm is the medium in which all of the chemical reactions within the cell take place.
The cell membrane is a thin, semi-permeable layer that holds the whole cell together.
The cell wall is not found in animal cells, but in plant cells it is made of cellulose and functions as support for the cell.
Chloroplasts contain chlorophyll, which is necessary for photosynthesis. They allow glucose to be created with just sunlight.
The vacuole contains water and stores of glucose and minerals, and supports the structure of the cells too.

2.4 compare the structures of plant and animal cells.

Animal and plant cells both have cytoplasm, nuclei, and cell membranes, however they are differently shaped and plant cells have additional structures, such as chloroplasts, cellulose cell walls and sap vacuoles. 

Section 2: Structures and Functions in Living Organisms Specification

a) Levels of organisation 

2.1 describe the levels of organisation within organisms: organelles, cells, tissues, organs and systems.


b) Cell structure

2.2 describe cell structures, including the nucleus, cytoplasm, cell membrane, cell wall, chloroplast and vacuole

2.3 describe the functions of the nucleus, cytoplasm, cell membrane, cell wall, chloroplast and vacuole 2.4 compare the structures of plant and animal cells.


c) Biological molecules

2.5 identify the chemical elements present in carbohydrates, proteins and lipids (fats and oils)

2.6 describe the structure of carbohydrates, proteins and lipids as large molecules made up from smaller basic units: starch and glycogen from simple sugar; protein from amino acids; lipid from fatty acids and glycerol

2.7 describe the tests for glucose and starch

2.8 understand the role of enzymes as biological catalysts in metabolic reactions

2.9 understand how the functioning of enzymes can be affected by changes in temperature, including changes due to change in active site

2.10 understand how the functioning of enzymes can be affected by changes in active site caused by changes in pH

2.11 describe experiments to investigate how enzyme activity can be affected by changes in temperature.


d) Movement of substances into and out of cells 

2.12 understand definitions of diffusion, osmosis and active transport

2.13 understand that movement of substances into and out of cells can be by diffusion, osmosis and active transport

2.14 understand the importance in plants of turgid cells as a means of support

2.15 understand the factors that affect the rate of movement of substances into and out of cells, to include the effects of surface area to volume ratio, temperature and concentration gradient

2.16 describe experiments to investigate diffusion and osmosis using living and non-living systems.


e) Nutrition

Flowering plants:
2.17 describe the process of photosynthesis and understand its importance in the conversion of light energy to chemical energy

2.18 write the word equation and the balanced chemical symbol equation for photosynthesis

2.19 understand how varying carbon dioxide concentration, light intensity and temperature affect the rate of photosynthesis

2.20 describe the structure of the leaf and explain how it is adapted for photosynthesis

2.21 understand that plants require mineral ions for growth and that magnesium ions are needed for chlorophyll and nitrate ions are needed for amino acids

2.22 describe experiments to investigate photosynthesis, showing the evolution of oxygen from a water plant, the production of starch and the requirements of light, carbon dioxide and chlorophyll

Humans:
2.23 understand that a balanced diet should include appropriate proportions of carbohydrate, protein, lipid, vitamins, minerals, water and dietary fibre

2.24 identify sources and describe functions of carbohydrate, protein, lipid (fats and oils), vitamins A, C and D, and the mineral ions calcium and iron, water and dietary fibre as components of the diet

2.25 understand that energy requirements vary with activity levels, age and pregnancy

2.26 describe the structures of the human alimentary canal and describe the functions of the mouth, oesophagus, stomach, small intestine, large intestine and pancreas

2.27 understand the processes of ingestion, digestion, absorption, assimilation and egestion

2.28 explain how and why food is moved through the gut by peristalsis

2.29 understand the role of digestive enzymes, to include the digestion of starch to glucose by amylase and maltase, the digestion of proteins to amino acids by proteases and the digestion of lipids to fatty acids and glycerol by lipases

2.30 understand that bile is produced by the liver and stored in the gall bladder, and understand the role of bile in neutralising stomach acid and emulsifying lipids

2.31 describe the structure of a villus and explain how this helps absorption of the products of digestion in the small intestine

2.32 describe an experiment to investigate the energy content in a food sample.


f) Respiration

2.33 understand that the process of respiration releases energy in living organisms

2.34 describe the differences between aerobic and anaerobic respiration

2.35 write the word equation and the balanced chemical symbol equation for aerobic respiration in living organisms

2.36 write the word equation for anaerobic respiration in plants and in animals

2.37 describe experiments to investigate the evolution of carbon dioxide and heat from respiring seeds or other suitable living organisms.


g) Gas exchange

2.38 understand the role of diffusion in gas exchange

Flowering plants:
2.39 understand gas exchange (of carbon dioxide and oxygen) in relation to respiration and photosynthesis

2.40 understand that respiration continues during the day and night, but that the net exchange of carbon dioxide and oxygen depends on the intensity of light

2.41 explain how the structure of the leaf is adapted for gas exchange

2.42 describe the role of stomata in gas exchange

2.43 describe experiments to investigate the effect of light on net gas exchange from a leaf, using hydrogen-carbonate indicator

Humans:
2.44 describe the structure of the thorax, including the ribs, intercostal muscles, diaphragm, trachea, bronchi, bronchioles, alveoli and pleural membranes

2.45 understand the role of the intercostal muscles and the diaphragm in ventilation

2.46 explain how alveoli are adapted for gas exchange by diffusion between air in the lungs and blood in capillaries

2.47 understand the biological consequences of smoking in relation to the lungs and the circulatory system, including coronary heart disease

2.48 describe experiments to investigate the effect of exercise on breathing in humans


h) Transport 

2.49 understand why simple, unicellular organisms can rely on diffusion for movement of substances in and out of the cell

2.50 understand the need for a transport system in multicellular organisms

Flowering plants:
2.51 describe the role of phloem in transporting sucrose and amino acids between the leaves and other parts of the plant

2.52 describe the role of xylem in transporting water and mineral salts from the roots to other parts of the plant

2.53 explain how water is absorbed by root hair cells

2.54 understand that transpiration is the evaporation of water from the surface of a plant

2.55 explain how the rate of transpiration is affected by changes in humidity, wind speed, temperature and light intensity

2.56 describe experiments to investigate the role of environmental factors in determining the rate of transpiration from a leafy shoot

Humans:
2.57 describe the composition of the blood: red blood cells, white blood cells, platelets and plasma

2.58 understand the role of plasma in the transport of carbon dioxide, digested food, urea, hormones and heat energy

2.59 explain how adaptations of red blood cells, including shape, structure and the presence of haemoglobin, make them suitable for the transport of oxygen

2.60 describe how the immune system responds to disease using white blood cells, illustrated by phagocytes ingesting pathogens and lymphocytes releasing antibodies specific to the pathogen

2.61 understand that vaccination results in the manufacture of memory cells, which enable future antibody production to the pathogen to occur sooner, faster and in greater quantity

2.62 understand that platelets are involved in blood clotting, which prevents blood loss and the entry of micro-organisms

2.63 describe the structure of the heart and how it functions

2.64 explain how the heart rate changes during exercise and under the influence of adrenaline

2.65 describe the structure of arteries, veins and capillaries and understand their roles

2.66 understand the general structure of the circulation system to include the blood vessels to and from the heart, the lungs, the liver and the kidneys.


i) Excretion

Flowering plants:
2.67 understand the origin of carbon dioxide and oxygen as waste products of metabolism and their loss from the stomata of a leaf

Humans:
2.68 recall that the lungs, kidneys and skin are organs of excretion

2.69 understand how the kidney carries out its roles of excretion and osmoregulation

2.70 describe the structure of the urinary system, including the kidneys, ureters, bladder and urethra

2.71 describe the structure of a nephron, to include Bowman’s capsule and glomerulus, convoluted tubules, loop of Henlé and collecting duct

2.72 describe ultrafiltration in the Bowman’s capsule and the composition of the glomerular filtrate

2.73 understand that water is reabsorbed into the blood from the collecting duct

2.74 understand that selective reabsorption of glucose occurs at the proximal convoluted tubule

2.75 describe the role of ADH in regulating the water content of the blood

2.76 understand that urine contains water, urea and salts.


j) Coordination and response

2.77 understand that organisms are able to respond to changes in their environment

2.78 understand that homeostasis is the maintenance of a constant internal environment and that body water content and body temperature are both examples of homeostasis

2.79 understand that a coordinated response requires a stimulus, a receptor and an effector

Flowering plants:
2.80 understand that plants respond to stimuli

2.81 describe the geotropic responses of roots and stems

2.82 describe positive phototropism of stems

Humans:
2.83 describe how responses can be controlled by nervous or by hormonal communication and understand the differences between the two systems

2.84 understand that the central nervous system consists of the brain and spinal cord and is linked to sense organs by nerves

2.85 understand that stimulation of receptors in the sense organs sends electrical impulses along nerves into and out of the central nervous system, resulting in rapid responses

2.86 describe the structure and functioning of a simple reflex arc illustrated by the withdrawal of a finger from a hot object

2.87 describe the structure and function of the eye as a receptor

2.88 understand the function of the eye in focusing near and distant objects, and in responding to changes in light intensity

2.89 describe the role of the skin in temperature regulation, with reference to sweating, vasoconstriction and vasodilation

2.90 understand the sources, roles and effects of the following hormones: ADH, adrenaline, insulin, testosterone, progesterone and oestrogen.

Section 2 a) Specification

2.1 describe the levels of organisation within organisms: organelles, cells, tissues, organs and systems.

Organelles are the specialised structures within a cell that carry out a specific function, e.g. the nucleus, vacuole, etc. They are the smallest level of organisation within an organism.

Cells are made up of organelles and are the smallest unit of life, the "building blocks", if you will, e.g. nerve cells, muscle cells, etc.

Tissues are made up of the lots of the same type of cell working together to carry out a specific function, e.g. palisade mesophyll, nervous tissue, etc.

Organs are groups of tissues working together to carry out a specific function in an organism, e.g. the brain, a leaf, etc.

Organ systems are a group of organs that work together to perform one or more functions, e.g. the nervous system, circulatory system, etc.

Organisms are entire living things that carry out the functions of MRS GREN, e.g. human, cactus

Section 1 b) Specification

1.2 describe the common features shared by organisms within the following main
groups: plants, animals, fungi, bacteria, protoctists and viruses, and for each
group describe examples and their features

The five kingdoms of classification are plants, animals, fungi, bacteria and protoctists. Viruses are not classified as living organisms, but they are a special case (they can carry out all of the functions of living organisms within a living cell)

Animals (Animalia) are multi-cellular organisms that need to feed off other living organisms as they do not contain chloroplasts for photosynthesis. Animal cells have no cell walls and are able to move freely. Animals are able to move their entire body due to their nervous system. They store carbohydrates as glycogen in their muscles.
Examples include: Humans, Fish, Bumble Bees, Chicken, Tortoises, etc.

Plants (Plantae) are multi-cellular organisms that contain chloroplasts to produce food through photosynthesis. They have cellulose cell walls, that provide the plant with structure and support, and they store carbohydrates as starch or sucrose. Carnivorous plants such as the venus flytrap are able to catch and digest small animals in order to obtain nutrients in poor soil.
Examples include: Rice, Sunflowers, Bananas, Beans, Roses, Wheat, etc.

Protoctists (Protoctista), also known as the 'dustbin kingdom', are a kingdom of greatly varied uni-cellular organisms. Some have characteristics of animal cells, some photosynthesize like plant cells, and some are pathogenic.
Examples include: Chlorella, Amoeba, Plasmodium, Euglena, Paramecium, etc.

Fungi (Fungus) can be multi- or uni-cellular. They cannot photosynthesize, so they must feed off other organisms. They do this through saprotrophic nutrition, the secretion of digestive enzymes into the surrounding environment to break down nutrients the fungus will then absorb the broken-down organic matter (this is also known as extracellular digestion, it happens outside the cell). Their bodies are organised in a fungal hyphal structure: they look like threads called 'hyphae', which are organised in mycelium. They have chitin cell walls and store carbohydrates as glycogen.
Examples include: Yeast (uni-cellular), Mucor, Basidiomycota, etc.

Bacteria (Prokaryotes) are uni-cellular organisms without a nucleus, instead containing a loop of DNA and a plasmid, which can move between cells. They have polysaccharide or protein cell walls, glycogen or lipid food stores and mesosomes for respiration. Some have flagellum to allow them to move, or chlorophyll to carry out photosynthesis (however most feed off other living organisms)
Examples include: Pneumococcus, Lactobacillus bulgaricus (used to make yoghurt), E.Coli, etc.

Viruses are much smaller than bacteria, and all are parasitic. They can only reproduce inside living cells, and don't carry out all of the seven life processes. Viruses are made up of genetic material and a protein coat. All viruses are pathogenic, disease-causing.
Examples include: Influenza, Human Immunodeficiency Virus (HIV), Tobacco Mosaic Virus, etc.

1.3 recall the term ‘pathogen’ and know that pathogens may be fungi, bacteria,
protoctists or viruses.

A pathogen is a disease-causing micro-organism. Pathogens include bacteria, viruses, fungi and protoctists.
Examples of pathogens:

• E.Coli (Bacterium)
• Influenza (Virus)
• Candida (Fungus)
• Pneumococcus (Bacterium)
• HIV (Virus)
• Cryptococcus (Fungus that causes meningitis)

Section 1 a) Specification

1.1 Understand that living organisms share the following characteristics:
– they require nutrition
– they respire
– they excrete their waste
– they respond to their surroundings
– they move
– they control their internal conditions
– they reproduce
– they grow and develop. 

All species of living organisms follow the 7 life processes: MRS GREN:

M- Movement
All living organisms can move or change position. Animals have total mobility; we can walk around, lift things up, turn our heads, etc. Plants move in less obvious ways. They can turn their leaves to face the sun and open and close their flowers.

R- Respiration
All living things release energy through chemical reactions. They break down nutrients such as glucose in order to release energy and allow the organism to perform all of the other life processes.

S- Sensitivity
All living things have the ability to sense a change in their environment and react to it. E.g. A person will move their hand away from a very hot object, a plant will turn to face the sun to maximise photosynthesis.

G- Growth
All living things increase in size or cell number as the organism matures, involving chemical reactions and increase in dry mass. Animals stop growing after reaching a certain maturity, but plants continue growing until they die.

R- Reproduction
All living things have the ability to produce live offspring through sexual or asexual reproduction. Sexual reproduction involves two parents, resulting in an offspring sharing both parents' DNA and characteristics, whereas asexual reproduction involves one parent and will result in an exact copy.

E- Excretion
All living things excrete harmful or toxic chemicals within the organism, e.g carbon dioxide through gas exchange in plants and animals, and urination in animals remove urea from the body. Plants can concentrate toxins into leaves when they drop them.

N- Nutrition
All living things require nutrients for energy, growth and repair. Plants can photosynthesize to create glucose for respiration, but animals and fungi must absorb or eat other organisms to gain energy and nutrients.

Section 1: The Nature and Variety of Living Organisms Specification

a) Characteristics of living organisms

1.1 Understand that living organisms share the following characteristics:
– they require nutrition
– they respire
– they excrete their waste
– they respond to their surroundings
– they move
– they control their internal conditions
– they reproduce
– they grow and develop.

b) Variety of living organisms

1.2 describe the common features shared by organisms within the following main
groups: plants, animals, fungi, bacteria, protoctists and viruses, and for each
group describe examples and their features

1.3 recall the term ‘pathogen’ and know that pathogens may be fungi, bacteria,
protoctists or viruses.