Saturday, 23 February 2013

4.4 explain the names given to different trophic levels to include producers, primary, secondary and tertiary consumers and decomposers

Different trophic levels= different feeding levels

Producer (turns light energy into chemical energy)
v
Primary consumer (eats the producer and gains its energy)
v
Secondary consumers
v
Tertiary consumers

When these organism die they are broken down by decomposers- fungi and bacteria.

4.3 explain how quadrats can be used to sample the distribution of organisms in their habitats.

A sample square is taken at random. The number of a population in that square is taken. This is repeated in different areas and compared to show where populations are dense and not.

4.2 explain how quadrats can be used to estimate the population size of an organism in two different areas

A square of around a meter takes a sample from a area and the populations are counted. This can be repeated many times before being multiplyed out as if it were the complete area of the land. Two different samples can be put in two separate areas and the sampling done for both will estimate population for both areas.

4.1 understand the terms population, community, habitat and ecosystem

Population
Number of individuals in a particular species.

Community
Populations of different species interacting.

Habitat
The area where a population lives.

Ecosystem
A community in a particular habitat made up of different populations interacting with in the habitat.

3.12 understand the roles of oestrogen and testosterone in the development of secondary sexual characteristics.

Secondary sexual characteristics develop during puberty

Oestrogen- females
The beginning of the menstrual cycle
Body mass increases and redistributed- to hips and breasts
Body hair- pubic
Voice deepens slowly
Development of sexual organs

Testosterone- males
Production of sperm
Growth of sexual organs
Body hair- pubic, arms and face
Body mass will increase, including muscle mass
Voice breaks (becomes deeper)
Development of a sexual drive

3.11 understand how the developing embryo is protected by amniotic fluid

The fluid (mainly water) cannot be compressed- it absorbs pressure- so any force on the uterus wall will not harm the embryo.

3.10 describe the role of the placenta in the nutrition of the developing embryo

The embryo can't breath, digest or excrete.
Blood vessels inside the placenta can absorb the digested food molecules and oxygen that the embryo needs to survive. Waste products will be taken out of the embryo and put back into the mothers blood stream for her to excrete.

3.9 understand the roles of oestrogen and progesterone in the menstrual cycle

The menstrual cycle
Oestrogen and progesterone are both hormones which effect the menstrual cycle.
Oestrogen: produced in the ovaries; thickens the womb lining; prompts the release of LH.
Progesterone: produced in the corpus lutiem; maintains the lining of the womb

3.8 describe the structure and explain the function of the male and female reproductive systems

Male reproductive system
Testis- produce sperm cells, they are stored in the epididymus
Vas deference- carries sperm to the penis
The prostate- adds fluid to the sperm, creating semen (as does the seminal vesicles)
The urethra- carries sperm to the end of, and out of the penis.

Female reproductive system
Ovaries- produce eggs
Oviducts- carry the eggs to the uterus, is the site of fertilisation
Uterus- develops the fertilised egg on the placenta
Cervix- entrance to uterus


3.7 understand that plants can reproduce asexually by natural methods (illustrated by runners) and by artificial methods (illustrated by cuttings)

Asexual reproduction only involves one parent, this can be achieved in two ways by plants:
Runners- eg strawberries- a second stem extend, when it reaches the ground cells specialise into root cells and a new plant develops.
Cuttings: a clipping is put in to plant hormones, encouraging the ends to become roots, when placed in soil it will then create another plant.

3.6 understand how germinating seeds utilise food reserves until the seedling can carry out photosynthesis

Food reserves are in the cotyledons, sustain the plant growth until leaves are able to photosynthesis to support the plant.

3.5 understand the conditions needed for seed germination

Water, warm temperatures (enzymes eg to break down starch in to maltose) and oxygen for respiration

3.4 understand that the growth of the pollen tube followed by fertilisation leads to seed and fruit formation

A pollen will travel down the stigma through a pollen tube, in to the ovule in the carpel. Here the pollen will fertilise the ovule, forming a zygote (the seed). The carpel (reproductive organ) becomes a fruit.

3.3 describe the structures of an insect-pollinated and a wind-pollinated flower and explain how each is adapted for pollination

Insect
Brightly coloured, larger petals
Nectar
Scents

Wind
Anthers stick out- past other parts of the flower
Stamen will have large surface area.

3.2 understand that fertilisation involves the fusion of a male and female gamete to produce a zygote that undergoes cell division and develops into an embryo

Gametes are sex cells: the male one being sperm; the female one being an egg.
When they join together it is know as fertilisation. At this point the fused gametes become a zygote.
A the zygot then divides repeatedly, at this stage it becomes an embryo.

3.1 understand the differences between sexual and asexual reproduction

In sexual reproduction two parents create non-identical offspring, inheriting characteristics from both parents.
In asexual reproduction a single parent creates genetically identical offspring.

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

Sweating- when too hot, glands under the skin secrete sweat, this increases heat loss by evaporation.
Vasoconstriction- blood vessels by the skin shrink, this reduces the blood which runs by the surface meaning less heat can be lost to the air.
Vasodilation- blood vessels by the skin grow, this means that more blood, and so more heat, is travelling near the surface of your body, in this way heat will be lost as it is conducted by the air.

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

In response to increased light you pupil will shrink, in dim light your pupil will dilate (grow bigger). This happens because you iris will contract to make the pupil smaller or relax to make it bigger. Radial muscles also make the pupil bigger by contracting.
To focus at different distances the lens in your eye adapts its shape:
If an object is near, ciliary muscles will contract which relaxes the suspensory ligaments so that the lens is fat;
If an object is far, ciliary muscles will relax making the suspensory ligaments tight so they pull the lens thin.

Recomend a look at this page:
http://www.bbc.co.uk/schools/gcsebitesize/science/edexcel_pre_2011/electrical/thenervoussystemrev4.shtml

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

The eye is a receptor of light, it has light receptor cells in its retina. These cells turn stimuli into electrical impulses.

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

A reflex is an automatic reaction, for example removing your hand from extreme heat. A reflex arch is the path of the reaction.
It starts at a sense organ e.g a finger;
receptors pick up stimuli e.g heat;
Sensory neurones carry an electrical impulse to the CNS;
A relay neuron carries the impulse through the CNS where a response is decided;
The new impulse is sent through a motor neurone;
This makes an effector carry out a response e.g muscle contracts to bring finger away from heat.

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

Receptors send a electrical impulse through nerves when stimulate by a stimulus. This message goes to the CNS, here a response is decided and then sent strait back out in electrical impulses through nerves to the effector. The impulses are very fast, as is the reaction time.

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 is the centre of the nervous system which decides a response for a stimulus. Receptors in sense organs (eg eyes or skin) send messages through nerves to the CNS- either to you brain or spinal chord- it creates a response which it will send in electrical impulses down nerves to effectors to carry out the response.

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

The nervous system and hormones both coordinate responses with in the body. The nervous does this by electrical impulses so it is very fast. Hormones do this with chemicals which travel, a little slower, at the speed of the blood stream they are travelling in.

2.82 describe positive phototropism of stems

Stems experience positive photo-tropism, this means they always grow towards light.
In a place where light shines there will be fewer auxins (growth hormones) this encourages the stem to bend towards the source of light.

2.81 describe the geotropic responses of roots and stems

Geo-tropism is when a plant grows in response to gravity.
Roots always carry out posotive geo-tropism, towards gravity/ down.
Shoots always carry out negative geo-tropism, away from gravity/ up.

2.80 understand that plants respond to stimuli

Plants respond to stimuli. They will react to changes in the environment, like temperature and light, as they have receptors which can detect a change and effectors to carry out the response. Usually the response is plant hormones- commonly auxin- which stimulate plant growth, stimuli for this are often light (photo-tropism), water (hydro-tropism) or gravity (geo-tropism).

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

To be able to carry out a response several things are needed:
A stimulus- a change in the internal or external environment- is needed to prevoke a response.
A receptor is needed to detect a stimulus, so that it can send messages to a coordinator to coordinate a response,
An effector is needed to carry out the response to the stimulus.

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

Homeostasis is the regulation of conditions inside the body. For example osmoregulation is the control of water levels in the body. Temperature regulation also needs to take place (as body process work best at 37 degrees) it is called thermoregulation. An example is when you are hot you sweat- so the heat is absorbed from your skin- and when you are cold you body hairs stick out- to trap air as a layer of insulation.

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

Sensitivity is one of the life processes (mrs gren); it is responding to the environment around. Living things must have receptors to be able to detect the change and effectors to be able to carry out a response.

2.76 understand that urine contains water, urea and salts.

Urine is made up of waste products in the body that can be harmful if not excreted  Among other things this includes water, urea and salts.

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

Excess or lack of water is detected by the hypothalamus in the brain, it causes the pituitary gland to produce Anti-diuretic hormone, or ADH. This hormone then travels through the blood stream to the kidneys, when it reaches them the kidneys lower the amount of water that is excreted by the body, and increase the amount of water that is reabsorbed into the blood stream. The urine is then more concentrated with a lower volume.
If there is too much water the levels of ADH are lowered and the opposite effects happen, resulting with a more dilute urine and less water in the blood.

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

Glucose is a component of golmerula filtrate. Some of the glucose in this filtrate is reabsorbed into the blood stream as it is needed by the body. The first section of convoluted tubules (before the henle loop) is the proximal convoluted tubule, in this area glucose is removed from the nephron and taken back into the blood.

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

As components travel through the nephron some are reabsorbed into the blood- as they are needed by the body. Much water of reabsorbed to avoid dehydration. This happens in the collecting duct.

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

Blood arrives in Bowman's casual under the high pressure of an artery, it travels it to the glomerulus where the pressure is further increased (as the tubes are smaller). Components of the blood are forced out of the blood vessel into the glomerulus due to the high pressure, creating glomerulas filtrate (water, slats ect.)

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

Nephrons are tubular structures within the kidneys which carry out filtration.
The blood enters into the glomerulus in the Bowman’s capsule, this is where the blood is filtered to create a filtrate of water, glucose, salts and urea (among other things). This then travels through convoluted tubules, here some components are reabsorbed into the blood stream. The loop of HenlĂ© s where water is where water and sodium chloride and reabsorbed into the blood stream. The filtrate then travels down the collecting duct which transports it to the 'renal pelvis' after which it goes down the ureters to the bladder.

This video is very useful: http://www.youtube.com/watch?feature=player_embedded&v=vNvZaGcLzEo#!

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

Waste or excess products are filtered from the blood stream by the kidneys, ureters carries urine to the bladder, the urine then leaves the body through the urethra.

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

Excretion
amino acids contain nitrogen- which is toxic to the body- the liver converts it into urea. The kidneys filter urea from the blood stream and combine it with water to create urine which then moves into the bladder.

Osmoregulation
The kidneys react to ADH hormone released by the pituitary gland. If there is too little water ADH will be released and the kidneys will reabsorb water so that it can stay in the body. If there is too much water then less ADH is released and the kidneys reabsorb less water, so it is lost in urine.

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

The metabolic processes are respiration and photosynthesis.
Photosynthesis is CO2 + H2O > C6H12O6 + O2 thats carbon dioxide plus water becomes glucose and oxygen- the glucose is used for energy and oxygen is a waste product, it leaves the leaf through the stomata.
Respiration is C6H12O6 + O2 > H2O + CO2 + atp thats glucose + oxygen > water + carbon dioxide + energy- carbon dioxide is a waste product and is excreted from the leaf through the stomata.

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

Lungs
Carbon dioxide- a waster product from respiring cells- is diffused into the lungs and then breathed out.

Kidneys
Excess water, urea (amino acids) and salts are diffused into the kidneys.

Skin
Water and salts are excreted through the skin.

Friday, 22 February 2013

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.

Vein- to the heart
Artery- away from heart
Lung- pulmonary
Liver- hepatic
Kidney- renal
Stomach- gastric
Between the gut and liver is the hepatic portal vein.

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

Arteries
Take blood away from the heart
Blood in them is under high pressure
They are delivering blood to an organ
Thick, muscle wall; small lumen (to give high blood pressure)

Veins
Take blood to the heart
Blood is under low pressure
Their blood is returning from an organ
Relatively thin wall; large lumen (to give ow blood pressure)
Valves stop blood flowing back in the wrong direction

Capillaries
Exchange is taken place
Very thin cell walls (one cell thick) so that substances can diffuse easily

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

During exercise muscles require more energy which is created by respiration, that requires more oxygen to be brought to cells and more carbon dioxide to be taken away, this means the heart needs to increase its speed so that more blood is sent to muscles.
Adrenalin- produced in the adrenal glands in top of the kidneys- stimulates adrenegic receptors in the heart which increase the rate that your heart cells work at.

This is a good source:
http://www.livestrong.com/article/355672-why-adrenaline-speeds-up-heart-rate/

2.63 describe the structure of the heart and how it functions

The heart can be thought of in four sections: the right atrium; the right ventricle; the left atrium; the left ventricle. A description of the workings of the heart:
The right atrium fills with blood (from the vena cava) and the valve is closed; This area is squeezed forcing the blood through an atrio-ventricular valve into the right ventricle; This area contracts forcing the blood through the pulmonary artery where it is oxygenated at the lungs; the pulmonary vein fills the left atrium with blood; This contracts forcing the blood into the left ventricle; when the left ventricle contracts the blood is forced out through the aorta.

Things to remember:
Veins lead to the heart; arteries lead away.
Atrium means entrance hall in Latin; hence the atrium is where blood enters the heart.
The left side is bigger than the right as it has to pump blood through the whole body.
You talk about the heart from right to left, as if you were examining someone's heart and using their own left and right.

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

When you have a wound you are at risk of loosing blood and
Platelets are produced in the bone marrow- they are fragments of cells. The chemicals in platelets turn fibrigen in the blood into a solid called fiberin. A network of fibrin creates inherits red blood cells and platlets; it will then dry over to form a scab, beneath which the tissue can begin to repair.

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

Vaccination is when a harmless or inactive form of a pathogen is injected into the body. It stimulates a response from the immune system with out putting the body at risk.
The pathogen will meet the lymphocyte that has the ability to get rid of it, it will be disposed of. The key thing is, though, that when the lymphocyte divides it will create memory cells. If the same pathogen is ever in the blood stream again (in the case of a real harmful infection) the memory cells will meet it and produce the appropriate anti-bodies making the immune reaction occur sooner and faster meaning a greater quantiy of anti-bodies will be produced from when the pathogen enters the body.

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

White blood cells are specialised cells which can stop pathogens in your body.

Phagocytes
They can detect the presence of pathogens because of chemicals they give off.
The cell then engulfs the pathogen. It then destroys the cell with digestive enzymes.

Lymphocytes
They release anti-bodies that are specific to the pathogen.
When a lymphocyte meets its specific pathogen it divides: one cells it creates being a memory cell; the other being the cell which will create anti-bodies.
One type of anti-body will attach to the pathogen to attract phagocytes. The other type will disable the cell. A third type will group the pathogens together so that phagocytes can engulf them all.
If the memory cells every meet the pathogen again they will create the anti-bodies very quickly.

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 carry oxygen around the body. In order to do this they have haemoglobin- which is made from iron- that can bond to oxygen. Red blood cells are enucleate (they have no nucleus) to make room for the haemoglobin. There are no mitochondria as the cells respire anaerobically so the cells don't use any oxygen.
They are biconcave; they are a flat disk with a dip in the middle. The shape of a flat disk enables them to pass through narrow capillaries  They have a dip in the middle to increase the surface area and decrease the distance for diffusion meaning that diffusion of oxygen happens quickly.

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

Water- which is the main component of plasma- is a solvent and a liquid; so plasma carries these different things around the body disolved in water:
Carbon- Hydrogen carbonate
Digested food- soluble sugars and amino acids
Urea
Hormones.

Water also carries heat, which is important in the regulation of body temperature.

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

The blood has several different components.
55% of the blood is plasma: yellow liquid containing water with different things dissolved in it.
There are many red blood cells (Erythroeytes.)
There are less white cells: Phagosytes; lymphosytes.
Platelets (dead red blood cells) which play an important role in clotting.

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

Support a plant in a tray filled with a  given amount of water. Place in different conditions and record the time taken for all the water in the way to be taken up by the plant.

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

Humidity
Increased humidity decreases transpiration. This is because high water content outside the leaf will mean there is little difference in concentration, so the water will not be able to move- as it naturally does- from an area of high concontrartion to an area of low concentration.
Wind speed
Increased wind speed will increase transpiration. Because if the wind blows away the water vapour being produced their will be a greater difference in water concentration, meaning water will be able to continue leaving the leaf.
Temperature
Increased temperature increases transpiration, as increased heat makes evaporating easyer.
Light intensity
Increased light intensity increases transpiration, as more heat is absorbed by the leaf meaning more water will be evaporated, also there is more photosynthesis meaning more water is being transported through the leaf (so more will need to leave the leaf.)

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

Transpiration is the name given to the process by which water is evaporated from the surface of a plant.
Heat- from sunlight- is absorbed into the leaf which turns liquid water into gas, the gas then leaves the leaf through the stomata.

2.53 explain how water is absorbed by root hair cells

Roots branch to increase the surface area and to increase the chances of finding a water source. Root hairs are epidermal cells on the surface of the root: they also increase the surface area for absorption. They absorb  minerals by active transport and water by osmosis. These substances then move to the xylem.

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

Xylem transport nitrates, phosphates, water and other mineral salts from the roots to other parts of the plants, like the leafs, flowers and buds.
Xylem consists of columns of hollow, dead cells. Substances are carried up the tube dissolved in water.

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

Phloem tissue has tube like cells which carry dissolved substances like sucrose and amino acids around the plant. The phloem is made up of columns of living cells.

http://www.youtube.com/watch?v=nKE81wy_6y4

2.50 understand the need for a transport system in multicellular organisms

Multicellular organisms have a small surface area to volume ratio and the distance for diffusion would be very large and so very slow. This wouldn't support the organism; so they have developed transport systems, like the ventilation system and the circulatory system which speed up the process of getting necessary molecules in and out of the body enough to support themselves.

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

Unicellular organisms- including fungi and bacteria- have a large surface area to volume ratio and they are small and so the diffusion distance is short, meaning diffusion happens very quickly.

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

During exercise cells respire more quickly (to provide more energy for movement) this means oxygen has to be delivered more quickly and carbon dioxide taken away more quickly. As a result of this the lung muscles contract and relax more rapidly and the heart beats faster.

Measure a persons breaths per 10 seconds when stationary.
Then after one minute after running at 5mph then at two minutes and so on.
You will find a linear relationship as described above between the two.

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

Tar can cause cancerous mutations in the lungs.
Smoke removes the cilia- tiny hairs- which keep the lungs clean.
Smoking also hardens the arteries, constricting the blood flow and putting strain on the heart, resulting in coronary heart disease.

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

The alveoli have are thin, this allows gasses to diffuse through them easily.
They are small and there are many of them meaning there is a large surface area through which much gas can diffuse at once. It also means there is a lot of surface in contact with the blood stream for gasses to diffuse into.
Alveoli have a moist lining for gasses to dissolve into.

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

Breathing in
The intercostal muscles contract
The ribs move up and out
The diaphragm contracts and moves down
The trachea carries air towards the lungs; it splits into two bronchi- one leading to the left lung, and one o the right- which then split into even smaller tubes, called bronchiles; these end in alveoli where gas exchange takes place.
The pleural membranes prevent friction.

Breathing out
The intercostal muscles relax
The ribs drop down
The diaphragm also relaxes and moves upward
These things reduce the space inside the lungs, pushing the air out.

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

Once air is breathed in through the mouth or nose it travels down the trachea. The trachea splits into two- one going into the left lung and one going into the right lung- these pipes are called bronchi. Each bronchus will then divide further into many bronchioles: each ending in a sac called an alveoli.

The trachea and bronchi have walls of muscle that are supported by cartilage. The cartilage is in partial rings so that the tubes can be moved in any direction. Cilia on the walls move mucus out of the breathing system and into the stomach.

wikibooks

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

hydrogen-carbonate indicator is an indicator for carbon dioxide: under normal levels (atmospheric) of carbon it is orange; an increase turns it yellow; a decrease turns it purple.
Fill a test tube quarter full with HCIS, attach a leaf to a bung and put in the test tube; observe the indicator colour in different light intensities.

2.42 describe the role of stomata in gas exchange

Stomata are minute wholes in the lower epidermis of the leaf. Guard cells regulate the opening and closing of the stomata; allowing carbon dioxide and oxygen to be exchanged between the leaf and the atmosphere. The guard cells absorb water and become turgid- opening the stomata- during the day. At night the guard cells are flaccid and so close the stomata.

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

Leaves are thin which allows gasses to diffuse quickly through them. In addition the stomata at the bottom of the leaf allow the diffusion of gasses in to the leaf- when a guard cell is shrunk gasses can enter the leaf.

Wednesday, 20 February 2013

2.38 understand the role of diffusion in gas exchange

Diffusion is the movement of particles from an area of high density to an area of low density. In this way gasses will move from an area dense with gas to an area of low density.

In the circulatory system oxygen enters the blood and carbon dioxide leaves the blood via gaseous exchange. Gasses move across the walls of alveoli to an area of lower density than they are in: Oxygen moves into the blood as there is a low density of oxygen in the blood; Carbon dioxide moves into the lungs as it is an area of lower density.

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

Glucose > Lactic acid + Energy

C6H12O6 > 2C3H6O3 + energy

Glucose > ethanol + carbon dioxide + energy

C6H12O6 > 2C2H5OH + 2CO2

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

Glucose + Oxygen > Carbon dioxide + Water + Energy

C6H12O6 + 6O2    →    6CO2 + 6H2O (+ energy)

2.34 describe the differences between aerobic and anaerobic respiration

Aerobic respiration

Glucose + oxygen > carbon dioxide + water + energy

In this form of respiration all of the energy is released from the glucose as it is fully broken down. It is used for day to day life processes- like movement and reproduction- and keeping warm.

Anaerobic respiration

Glucose > lactic acid + energy

Anaerobic respiration takes place when the heart and lungs cannot work fast enough to provide to oxygen needed for aerobic respiration: for example when exercising  The energy released is less in anaerobic respiration because the glucose cannot be fully broken down.
The lactic acid produced accumulates in muscles; often making them feel soar. After this process 'excess post-exercise oxygen consumption' takes place. This process involves heavy breathing and fast heart rate to transport oxygen around the body so it can help break down lactic acid into carbon dioxide and water. Note that the time taken for the lactic acid to be removed and for the breathing and heart rate to return to normal is called the recovery period.

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

Respiration is a reaction that occurs in living things to create energy. It breaks down glucose to release energy.

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

The most common experiment for this is using pond weed, which is placed under water then factors are varied:
A lamp is moved further from the plant;
Baking powder is added to the water (increasing CO2);
A white leaved plant is tested against a green leaved plant (green has more chlorophyll).

The gas it gives off- being the products of photosynthesis- is counted as bubbles or measured by downwards displacement. This shows the speed of photosynthesis under different conditions.
Iodine can be used to test the production of starch.

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

As a young person a lot of energy is used because: activity levels tend to be high; energy is being used for growth. As a person ages they no longer use energy for growth and tend to have a less active lifestyle: thus having lower energy requirements.

Having a less or more active lifestyle has an effect because the more you do- the more energy you use- the more you need- the higher energy requirements. For example, an athlete has a more active lifestyle so has to eat more.

When pregnant a woman is not only supporting her own body but also that of her baby, this mean she requires the energy for both of them, increasing her energy requirements.

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


Carbohydrate
immediate energy
bananas, brown rice, wholemeal foods and potatoes.

Proteine
Growth; repair
sea food, eggs, pork and soy.

Lipids
long term energy store; insulation; protection
fish, eggs, milk and beef.

Vitamin A
maintaining normal reproductiongood visionformation and maintenance of healthy skin, teeth and soft tissues of the bodyimmune function (has anti-oxidant properties).
Milk, cheese, eggs, fatty fish, yellow-orange vegetables and fruits such as carrots, pumpkin, mango, apricots, and other vegetables such as spinach, broccoli.

Vitamin C
aiding absorption of iron and copper; helps fight infection.
Blackcurrants, orange, grapefruit, guava, kiwi fruit, raspberries, sweet peppers (Capsicum), broccoli, sprouts

Vitamin D
Aids absorption of calcium.
Sunlight on skin allows the body to produce Vitamin D. Few foods contain significant amounts however main dietary sources are fortified margarine, salmon, herring, mackerel, and eggs.

Calcium
development and maintenance of bones and teethgood functioning muscles and nervesheart function
Milk, cheese, yoghurt, bony fish, legumes, fortified soy beverages and fortified breakfast cereals.

Iron
Haemoglobin in red blood cells (important for transport of oxygen to tissues)component of myoglobin (muscle protein).
Red meats – beef, lamb, veal, pork, fish, chicken and wholegrain cereals

Dietary fibre
Keeping the bowels functioning well; reduces the risk of bowl cancer
Cereals, bread, rice, beans and nuts.

Water
Chemical reactions in cells need water; respiration
water.

Some information (© Commonwealth of Australia 2005)

Wednesday, 13 February 2013

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

The villi are in the small intestine. The are like lumps on this inside of the small intestine. They are the surface through which food diffuses into the blood stream.

They have very thin walls, only one cell thick, this enables molecules to pass through easily.

They also increase the surface area of the small intestine wall meaning that there is a lot of surface for diffusion to happen through.

On the outside of villi there are capillaries which pick up the diffused food into the blood stream.

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 is produce by the liver and stored in the gall bladder.
Enzymes in the small intestine work best in alkaline conditions but the food is acidic after being in the stomach. Bile is alkaline and so when it is released into the small intestine it enables the enzymes to work.
Bile also emulsifies fat; this gives it a larger surface area, which means that it is easier for lipases to work.

digestive enzymes are produced in the pancreas, bile stored in the gall bladder, bile production in liver
BBC

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


Enzymes break down food into useful things that our boddies need. Different enzymes break down different components of our food. You should learn that:

amylase and maltase convert starch to glucose

proteases convert proteins to amino acids

lipases convert lipids to fatty acids and glycerol.

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

Food is moved through the gut by peristalsis.
Muscles move food because mechanical action is needed to get food through the system.

Here is a short clip:
http://www.bbc.co.uk/schools/gcsebitesize/science/add_edexcel/common_systems/digestionrev2.shtml

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

Digestion: process in which large insoluble molecules of food are broken down into smaller ones.


Absorption: the process by which soluble molecules produced by digestion are taken from the gut (occurs mostly in the small intestine.) The soluble products of digestion are then transported to the various tissues by the circulatory system.

Assimilation: the cells of the tissues absorb the molecules for use.

Egestion: removal of waste- undigested- products as faeces.

Excretion: removal of waste products that have been in the body.

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

The mouth
Mechanical digestion happens here- your jaw action.
A bolus is created; this is a ball of food covered in saliva. This is help full as the food is lubricated to enable swallowing and enzymes in the saliva can begin to break down the food. (amylase)

The oesophagus
this tube connects you mouth and stomach. It is next to the trachea which is covered by the epiglottis when you swallow so the food only enters the oesophagus.
Peristalsis- or muscular contractions- moves the food downward.

The stomach
Churning mechanically digests whilst enzymes do so chemically.
Chyme is the name for liquid food existing in the stomach.

The small intestine
This absorbs digested molecules into the blood stream.
Villi cover the inside giving it a large surface area which many molecules can diffuse through into the blood.

Large intestine
This absorbs water from undigested food, producing faeces.

Pancreas
This produces the enzymes lipase, amylase and protease.

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

All the different components of the diet have their own important job so it is important that the human diet contains all of them. It is, however, important to have them in proportion, this is usually represented in day to day life by the eat well plate.

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

As well as water and sunlight, plants require mineral ions to grow. Different mineral ions do different things, two key examples of this are that: magnesium ions are needed for chlorophyll; nitrate ions are needed for amino acids. You simply need to learn this.

Tuesday, 12 February 2013

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

In terms of the basic features leaves have a large surface area; this allows them to absorb more sunlight. They are also thin, meaning that carbon dioxide has a shorter way to travel. In addition the stomata allow the entrance of carbon dioxide.

The more complex adaptations are of the internal leaf structure. The epidermis is thin and its transparent this means that more light can reach the palisade cells underneath the upper epidermis. The palisade cells themselves are er to the top of the leaf so they can absorb more if the light; they contain chloroplasts so that they can absorb the light. The spongy layer has air spaces in: these allow for carbon dioxide to diffuse through the leaf, and they increase the surface area. The wax cuticle is thin and made out of wax so it doesn't stop the sunlight from getting through.
Shows the waxy cuticle on top of the upper epidermis.Under this is the palisade mesophyll layer and spongy mesophyll layer, which has air spaces in it. At the bottom, is the lower epidermis and wax cuticle. Gases are exchanged through the stoma. On each side of the stoma there is a guard cell with chloroplasts.

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

Carbon dioxide
If there is insufficient carbon dioxide a plant will not be able to photosynthesis to its full potential. Because there is less carbon dioxide- less reactant- there has to be less product being made.

Light intensity
If the light is at a low intensity the rate of photosynthesis is lowered because the energy that the light provides is less, so the reaction is slowed down. A higher light intensity will enable photosynthesis to happen faster.

Temperature
In colder temperatures the rate of photosynthesis will decrease. If the temperature is too high however, the plant will not be able to photosynthesise.

This page has good graphs and explains in a different way: http://www.bbc.co.uk/schools/gcsebitesize/science/add_aqa/photosynthesis/photosynthesisrev2.shtml

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

Carbon dioxide + water > glucose + oxygen

6CO2 + 6H2O = C6H12O6 + 6O2

(You should learn these for your exam!)

2.17 describe the process of photosynthesis and understand its importance in the conservation of light energy to chemical energy

Photosynthesis is the process in which energy- from the sunlight- is used to create glucose.

Light energy is absorbed by chlorophyll in plants leaves. It is then used to convert carbon dioxide (from the air) and water (from the ground) into glucose; which is used for respiration. Oxygen is a by-product of this process.

This is using light energy, from the sun, to create chemical energy (glucose); which conserves the energy from the sun. This energy is then passed through the food chain, which is why plants are called the producer (producing the chemical energy in the chain from the sun light.)

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

Diffusion
Put a coloured substance (like food colouring) into a clear one (like water)
Time how long it takes for all the liquid to be the same colour.
Change the temperature of the liquid and make observations.
The higher the heat, the more kinetic energy meaning the colour moves through the liquid faster.

Osmosis
Cut two roughly equal pieces of potato and weigh them.
Put one in distilled water and one in salt water.
After a given amount of time weigh them.
The one in salt water will have lost mass as the water in the potato moves to the more highly concentrated salt water. Where as in the pure water the potato will have gained mass as it was less dens with water.