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) Summary

In plants, excretion happens primarily through gas exchange. Oxygen and carbon dioxide are excreted from photosynthesis and respiration respectively. Toxins within the plant will collect within a dying leaf so it can be removed from the plant.

In humans however, it is more complicated.
We excrete through our skin: sweat contains water, salts and urea. This is also important for osmoregulation and homeostasis.
We excrete through our lungs: we breathe out carbon dioxide and water vapour, which again aids osmoregulation.
And finally, we excrete through urination. Urine contains water, salts and urea.

Urine is excreted through this system. It is important to not get confused between the urethra and the ureter.

Urea, the key part of urine, is made in the liver. Excess amino acids are broken down in a process called deamination. The urea then enters the blood, which must now be cleaned as urea is a toxic chemical containing nitrogen. The blood is cleaned in the kidneys

The most important part is the nephron, the filtration unit. There are about 1.25 million units in each kidney. In the nephron, blood is passed through the glomerulus at a high pressure, forcing out smaller molecules: Urea, water, salt, and glucose.

The solution created is known as glomerular filtrate. It enters the Bowman's capsule, then the proximal convoluted tubule. This is where glucose is selectively reabsorbed using active transport. Water and mineral salts are also reabsorbed. The filtrate then enters the loop of Henle. In the first hald, just water is reabsorbed, and in the second just mineral salts. The distal convoluted tubule continues to reabsorb water and mineral salts. This is now urine, which is about 95% water and 2% urea, the rest being excess salts and nutrients. The urine travels down the collecting duct and ureter into the bladder, where it is stored until excreted.

Osmoregulation
The amount of water in the body is regulated by the hypothalamus which causes the pituitary gland to release ADH, anti-diuretic hormone.

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

Section 2 i) Key Words

ADH: Anti-diuretic hormone causes the tubules of the nephron to become more permeable and thus reabsorb more water.

Bladder: The organ where urine is stored before being expelled from the body through the urethra.

Bowman's capsule: The capsule encasing the glomerulus, receives the glomerular filtrate through ultrafiltration.

Convoluted tubule: The two convoluted tubules (proximal being the closer one to the glomerulus, distal being the further one) are where water, glucose, and salts are reabsorbed into the blood.

Glomerular filtrate: The substance created by ultrfiltration. Made of glucose, urea, water and salts.

Glomerulus: A series of capillaries under high pressure that forces small molecules through the walls.

Homeostasis: Maintaining constant internal conditions, e.g. temperature, water content, etc.

Hypothalamus: The part of the brain that detects water content and stimulates the pituitary gland.

Loop of Henle: A loop of tubule within the nephron where salts and water are reabsorbed. Separates the two convoluted tubules.

Nephron: The filtration unit within the kidney that removes waste products and cleans the blood.

Osmoregulation: Regulation of water content. The skin sweats, the kidneys remove and reabsorb water, and the lungs exhale water vapour. These all regulate how much water is in our bodies.

Pituitary gland: The gland that releases ADH.

Selective reabsorption: The reabsorption of some chemicals but not others, e.g. all glucose is reabsorbed, but only a certain amount of water and salt is, and no urea.

Ultrafiltration: The process of filtering the blood to separate large particles such as cells from small molecules such as glucose. Produces glomerular filtrate.

Urea: Substance created by breaking down amino acids. Toxic to the body, and excreted in urine.

Ureter: The tube that transports urine from the kidneys to the bladder.

Urethra: The tube that excretes urine from the bladder.

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) Summary

Multicellular organisms require transport systems, because their surface area to volume ratio makes it impractical for just diffusion osmosis and active transport. Unicellular organisms are able to function on these transport processes alone because they're so small.

Flowering Plants

In flowering plants, the transport system is made of the xylem and phloem vessels, arranged in vascular bundles as so:

Xylem vessels are made of dead cells, with the cell walls at either end broken down. Their walls are thick and function secondarily as support. Primarily, though, they transport water and mineral ions throughout the plant. 

Phloem vessels are made of living cells, but their top and bottom cell walls contain holes, and are called sieve plates. These vessels carry glucose and amino acids around the plant for use by cells. The process is know as translocation.

These nutrients are only able to get to the plant via absorption, which the root hair cells do via osmosis and diffusion. Their long, hair like structure increases the rate of diffusion and makes it ideal for absorbing water and nutrients. 

Inside the plant, water is transported up the stem by the transpiration stream. Water molecules are cohesive (they stick together), so when water is evaporated from the leaves it causes the root hair cells to take in more in. The water is removed from the leaves via evapotranspiration, where the water first evaporates, then the vapour diffuses into the environment. This creates a sort of tension pull in the xylem, causing more molecules to take the place of the evaporated ones. This makes a larger water potential gradient about the roots, and causes more water to be sucked in.

The rate of transpiration is affected by the following factors:

These variables can be investigated using a potometer.

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
Transport in humans happens through the circulatory system. 

It is a double circulation system, involving the pulmonary system and the larger circulation system.

Zooming in, the circulatory system is made of the blood vessels, the heart and the blood.

Blood:
55% Plasma, 45% Red blood cells, and a very tiny amount phagocytes, lymphocytes and platelets. The blood carries nutrients and fights off infection.

The white blood cells are responsible for the immune response.
Phagocytes engulf foreign cells, while lymphocytes detect antigens on pathogens and produce antibodies that mark them for destruction by other white blood cells. The lymphocytes keep a memory of how to make certain antibodies, so upon second infection many antibodies are produced quickly.

Vaccinations play this to our advantage; by injecting inactive or dead pathogens, the lymphocytes are able to detect the antigens and produce antibodies and 'remember' how to for the next infection.

Red blood cells are biconcave to maximise surface area, and have no nucleus. They contain haemoglobin which allows them to carry oxygen around the body.

Platelets are small cell fragments that bond together in fibrin to form clots and scabs. This prevents blood loss and infection.

Plasma carries digested nutrients (sugar, amino acids, etc.), carbon dioxide, urea, hormones and heat energy to where it needs to be in the body.


Blood vessels:
There are three kinds of blood vessels: arteries, veins, and capillaries.

Arteries have small lumen, thick walls, and high pressure. They carry blood away from the heart, and are far under the skin. The largest is the aorta.

Veins have large lumens, thin walls and low pressure. The contain valves to control the direction of flow. Some are quite close to the surface, so these are favourable for injections. (also their thin walls are easier to penetrate and their large lumen allow more space more error)

Capillaries are very tiny. They have very thing walls (one cell thick) for easy diffusion. They carry nutrients to all of the cells and their lumen are tiny.

Heart:
The heart is made up of muscle and fat. The left side is more muscular than the right, because the left must pump blood around the entire body and the right only to the lungs (which must be low pressure as it has to squeeze through tiny capillaries). It is made up of four chambers, the left and right atriums and ventricles.

The atriums receive blood and the ventricles pump it out. In diagrams, the left side of the heart is usually on the right, because of how it lays in the body, it's as if you're facing the person and using their left and right. The right side of the heart deals with deoxygenated blood, and the left with oxygenated blood.

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.


Circulation is affected by adrenaline and exercise:

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)

Section 2 h) Key Words

Antibodies: Produced by lymphocytes, they latch onto pathogens and mark them as a target for other white blood cells to engulf or destroy.

Antigens: Chemical markers on pathogens that make them identifiable.

Aorta: The largest artery, that carries oxygenated blood away from the heart. Connected to the left ventricle.

Artery: A vessel carrying blood away from the heart. Thick walls, small lumen and high pressure.

Atrium: The two smaller chambers of the heart are the atria. They take in blood from the vena cava and the pulmonary vein.

Blood: The fluid found in the circulatory system that carries nutrients and waste to and from cells. Most importantly, it carries oxygen and glucose.

Capillary: The smallest type of blood vessel. Walls are one cell thick, and the lumen are very tiny.

Circulatory system: The system in the body that transports blood (containing nutrients etc.) around the body.

Haemoglobin: A red, iron-containing protein found in red blood cells. Bonds with oxygen to allow it to be carried around the body.

Hepatic: To do with the liver.

Lumen: The hollow inside blood vessels.

Lymphocytes: White blood cells that detect antigens and produce antibodies. Responsible for immune responses.

Mesenteric: To do with the gut.

Oxyhaemoglobin: The compound formed when oxygen bonds with haemoglobin.

Pathogens: Microorganisms or viruses that cause illness or disease.

Phagocytes: White blood cells that engulf foreign materials in the blood.

Phloem: The vessel in a plant that transports mineral glucose and amino acids to all of the cells.

Plasma: Makes up 55% of the blood, and is mostly water. Contains salts and mineral ions, and is pale yellow.

Platelets: Small fragments of cells that aid with clotting.

Pulmonary: To do with the lungs.

Red blood cells: Biconcave, red cells with no nucleus. Make up 45% of the blood, and contain haemoglobin to carry oxygen.

Renal: To do with the kidneys.

Sieve plate: The plate of cellulose containing holes in the phloem vessels.

Translocation: The process by which glucose and amino acids are moved through the phloem.

Transpiration: The process of evaporation and diffusion of water from the leaf. Cohesion between molecules mean more water is pulled up, creating a transpiration stream.

Vein: Vessels in the circulatory system that carry blood towards the heart. Large lumen and thin walls.

Vena cava: The largest vein. It carries deoxygenated blood back into the heart, connected to the right atrium.

Ventricle: The two larger chambers of the heart. Pump blood out of the heart, connected to the pulmonary artery and the aorta.

White blood cells: Lymphocytes and phagocytes are both white blood cells. They are responsible for the immune response.

Xylem: The tube in plants that is responsible for transporting water and mineral ions throughout the plant.

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.