Monday, 20 May 2013

3.33 understand that the incidence of mutations can be increased by exposure to ionising radiation (for example gamma rays, X-rays and ultraviolet rays) and some chemical mutagens (for example chemicals in tobacco).

There are things that make you more likely to have a mutated gene, these include: ionising radiation and chemical mutagens like some chemicals in tobacco.

3.32 understand that resistance to antibiotics can increase in bacterial populations, and appreciate how such an increase can lead to infections being difficult to control

Bacteria experience mutations (the reproduce very frequently so it is not rare.) These mutations can mean that they are no longer affected by a certain antibiotic, this makes it easier for them to survive. If bacteria evolve to be resistant to drugs we are treating them with then they are difficult to control; sometimes they can be stopped using a different antibiotic, but some are becoming resistant to all the drugs that we know of...

3.31 understand that many mutations are harmful but some are neutral and a few are beneficial

A lot of mutations are harmful, like genetic diseases; cystic fibrosis.
Some don't change the chances of survival: like having a different colour hair.
There are a few mutations which are beneficial, for example a insect pollinated plant becoming brighter.

3.30 describe the process of evolution by means of natural selection

Evolution is a change in species over a very long time (sometimes into different species.)
Natural selection is survival of the fittest.
What happens is:

  • A mutation occurs
  • If the mutation is beneficial, the animal will survive longer and reproduce more
  • Some of its offspring will inherit the mutation
  • These offspring will also have better chance of survival, meaning they live longer and reproduce more
  • Over a long period of time this process is repeated and gradually the mutation becomes a common gene in a species and those with the mutation become the only ones, as those without cannot compete with those expressing the mutated gene

3.29 understand that mutation is a rare, random change in genetic material that can be inherited

A mutation is when a gene is copied incorrectly, this gene can be passed down. It doesn't happen very often or on purpose.

3.28 understand that variation within a species can be genetic, environmental, or a combination of both

Variation in a species is the differences between the members of a species.
Genetic is caused by what genes are inhereted.
Environmental is caused by some action after birth (e.g the sun giving you a tan.)
Some variation is a bit of both...

3.27 know that in human cells the diploid number of chromosomes is 46 and the haploid number is 23

The diploid number is how many chromosomes each cell is meant to have: 46 in humans (23 pairs).
The haploid number is half of the diploid number: so 23.

3.26 understand that random fertilisation produces genetic variation of offspring

Because gametes contain a random selection of genetic information from each parent, the fertilised egg will be a mix of different genotypes which is why offspring are genetically different to their parents.

3.25 understand that division of a cell by meiosis produces four cells, each with half the number of chromosomes, and that this results in the formation of genetically different haploid gametes

Meiosis is when a cell splits in half, creating two copies, and then splits in half again to create four cells each with half the genetic information of a normal cell (haploid 23 chromosomes.)
This is how gametes are made.

3.24 understand that mitosis occurs during growth, repair, cloning and asexual reproduction

Mitosis cell division is the type that occurs in growth, repair cloning and asexual reproduction.

3.23 understand that division of a diploid cell by mitosis produces two cells which contain identical sets of chromosomes

Mitosis is when a cell replicates it self to make an identical copy.
A diploid cell is one with 23 pairs of chromosomes.
(you don't need to know the stage names, but its useful to know how mitosis happens.)


3.22 describe the determination of the sex of offspring at fertilisation, using a genetic diagram

Genetic diagrams work the same as mono-hybrid inheritance diagrams: showing the mothers and fathers and then the different out comes. The only difference is, they will always be the same because one parent is always male and one parent is always female:
Gender determination

3.21 understand that the sex of a person is controlled by one pair of chromosomes, XX in a female and XY in a male

One pair of chromosomes (out of 23 pairs) controls the gender of a person. XX is female; XY is male.

3.20 predict probabilities of outcomes from monohybrid crosses

From mono-hybrid cross diagrams there are four outcomes, some times some of the out comes are the same.
To work out the probability of a child inheriting a genotype, you see how many times it comes up and divide it by 4 then times by 100 for a percent.
To work out phenotype probability you work out how many times they will express a characteristic and divide it by four then times by 100 for a percent.

If we say in this diagram the B represents brown hair and b represents red hair
(The capital letter is always dominant)


The likely hood of the chlid carrying one allele for brown and one for red (Bb) is two out of four:
2/4= 0.5
x100= 50%
The likely hood of the child having red hair (red hair is recessive so they both have to be red (bb)) is two out of four: also 50%

3.19 understand how to interpret family pedigrees

A pedigree diagram shows a specific gene in a family. It will have a key but most often: a circle represents a female and a square represents a male; often coloured in represents one allele and blank another (but sometimes they are different colours.)

In this diagram, the mother and two sons have a different genes to the others:


3.18 describe patterns of monohybrid inheritance using a genetic diagram

Monohybrid inheritance is the inheritance of one gene.
A genetic diagram consists of the parents gamets (according to their genotype) and their possible offspring:
(B and b represent an allele for a gene)

3.17 understand the meaning of the terms: dominant, recessive, homozygous, heterozygous, phenotype, genotype and codominance

Dominant: a dominant allele is the one that will be made
Recessive: a recessive allele will be masked by a dominant one and not visible
Homozygous: if you have two of the same alleles for a gene in one persons DNA
Heterozygous: if you have two different alleles for a gene in in someones DNA
Phenotype: what allele is expressed as a protein
Genotype: what alleles you have in your DNA for a gene
Codominance: when two alleles have equal dominance (they will both be expressed)

By expressed I mean shown as in having brown hair is brown hair allele being expressed; and by masked I mean not expressed.

3.16 understand that genes exist in alternative forms called alleles which give rise to differences in inherited characteristics

Genes (sections of DNA coding for different proteins) come in a variety of forms: for example the gene that codes for hair can come in many different colours. These different forms are different alleles, having these differences is where you vary in inherited characteristics (If there was only one allele for hair we would all have exactly the same hair.)

3.15 describe a DNA molecule as two strands coiled to form a double helix, the strands being linked by a series of paired bases: adenine (A) with thymine (T), and cytosine (C) with guanine (G)

DNA resembles a ladder (that has been twisted,) on either side of each rung will be a base- they are a base pair: either adenine (A) with thymine (T) or cytosine (C) with guanine (G).

3.14 understand that a gene is a section of a molecule of DNA and that a gene codes for a specific protein

Different genes code different proteins. Genes are sections of your DNA.

3.13 understand that the nucleus of a cell contains chromosomes on which genes are located

In the nucleus of a cell there are chromosomes; these are long sections of tangled DNA, sections of which are different genes.

Friday, 17 May 2013


Finished. I have now posted notes on every point on the spec!
Hope it helps,
Good luck!!!

5.20 evaluate the potential for using cloned transgenic animals, for example to produce commercial quantities of human antibodies or organs for transplantation.

Transgenic animals are ones that have had genes from other animals put in their DNA.
Animals can be given the gene to make human antibodies. These can then be injected into humans to help them face an infection- instead of waiting a long time for their body to find the correct antibody and then replicate it.
Sheep and goats have been made to produce human proteins in their milk: this makes milk more beneficial to humans.
Animals could be made with organs that are similar enough to humans that they could be transplanted: this would mean there was never a shortage; it would also mean less moral questions are asked (then using human organs.)

4.15 understand the biological consequences of pollution of water by sewage, including increases in the number of micro-organisms causing depletion of oxygen

Sewage contains nutrient which enable algae to flourish. They take up sunlight and oxygen. Many fish die and other organisms die. Decomposers thrive on there dead bodies; meaning even more oxygen is taken up by microorganisms.

Basically its the same process as eutrophication.

5.13 describe how plasmids and viruses can act as vectors, which take up pieces of DNA, then insert this recombinant DNA into other cells

When a virus or plasmid is inside a host cell it may pick up DNA, it may then carry this into another host cell. The foreign DNA is known as recombinant DNA.

Wednesday, 15 May 2013

5.19 describe the stages in the production of cloned mammals involving the introduction of a diploid nucleus from a mature cell into an enucleated egg cell, illustrated by Dolly the sheep

A egg cell with the nucleus removed has the DNA of another cell put in (this will be have a complete set of chromosones (diploid number of)). The embryo that forms will then have DNA from only one parent: the one the DNA was taken from. This means it will be a clone! for example dolly the sheep.

Inline images 1

5.18 understand how micropropagation can be used to produce commercial quantities of identical plants (clones) with desirable characteristics

In micropropagation, plant clippings are taken and put in a growth medium. They will develop into a new plant with the same DNA. This means that every plant made from the clippings of one plant will be clones with exactly the same characteristics. If many clippings are taken then you will have many clones.

5.17 describe the process of micropropagation (tissue culture) in which small pieces of plants (explants) are grown in vitro using nutrient media

Plant clippings are taken and placed in a sterile growth medium. Roots will develop from the clipping (and shoots) making a whole new plant. The plant will then be transferred into compost and grown as a normal plant.
The plant is a clone of the one is was taken from because it has the same DNA. This means that there will be no variation, so you can have the same plant every time.

5.16 understand that the term ‘transgenic’ means the transfer of genetic material from one species to a different species

transgenic material is genetic material that is taken from one species and put into another.

5.15 evaluate the potential for using genetically modified plants to improve food production (illustrated by plants with improved resistance to pests)

Genetically modified plants are ones with desired characteristics which are meant to enhance a crop.

They may have DNA which gives them more nutritional value: like golden rice which is rice with carotene in. This will benefit a population which eats a lot of rice by giving them a better diet.

Plants may also have DNA which makes them more resistant: for example genetically modified soya plants. This means that a broad spectrum herbicide that kills many different types of plant can be spread on the crops to kill weeds; where as before many different types of herbicides would have to be spread to avoid killing the crop (time consuming/ expensive.)

Although GM plants appear to be only of benefit, there are people who claim side effects observed in lab animals such as: sterility; infant mortality; allergies; stunted growth. Another disadvantage would be that a broad spectrum herbicide that can be spread on GM crops will kill many plants in the wild not just the weeds  threatening the crops.

5.14 understand that large amounts of human insulin can be manufactured from genetically modified bacteria that are grown in a fermenter

The gene that causes human insulin production is taken from a cell and put into a bacteria's DNA. This bacteria is then put into a fermenter where the conditions are optimum for it to replicate many times. These bacteria then produce human insulin which can be harvested and given to humans with diabetes.

This is a very helpful animation:

5.12 describe the use of restriction enzymes to cut DNA at specific sites and ligase enzymes to join pieces of DNA together

Restriction enzymes effectively cut through DNA strands so that a section of DNA can be taken from a cell.

Ligase enzymes can be used to join together different sections of DNA.

These processes are done to create new DNA.

Something like this:


5.6 describe a simple experiment to investigate carbon dioxide production by yeast, in different conditions

Have a test tube of yeast in glucose solution. Put a layer of oil on top if you want the yeast to respire anaerobically (as it will prevent oxygen entering the solution.)

Put the test tube in a water bath, heat the water to vary the temperature.

Collect gas coming off in a tube then: count the bubbles; use downwards displacement.

5.11 understand that animals with desired characteristics can be developed by selective breeding

Farmers can choose to make sure animals with characteristics they desire reproduce, their offspring will inherit the genes of the characteristic.

5.10 understand that plants with desired characteristics can be developed by selective breeding

Farmers can breed plants selectively  choosing plants with characteristics they desire (eg colour, size of fruit) to pollinate.

Sunday, 28 April 2013

5.9 explain the methods which are used to farm large numbers of fish to provide a source of protein, including maintenance of water quality, control of intraspecific and interspecific predation, control of disease, removal of waste products, quality and frequency of feeding and the use of selective breeding.

Fish are a source of protein in many diets, humans consume a lot of fish for this reason. Fish farms are used to supply fish because: the fish's food safety standard is monitored; fresh water fish are declining; the deman for fish is increasing.

Fresh water fish may have come into contact with unclean water; containing sewage, waste, chemicals. In fish farming the water is filtered to make sure the fish don't come into contact with anything it would be unsafe to digest. Also if the water is cleaned regularly the spread of disease is minimised and the oxygen levels are high enough to maintain the respiration of the fish.

Intraspecific predation is the fish being bred eating each other, this can be stopped by: separating fish of different ages; separating fish of different genders; feeding fish regularly; giving fish adequate room.

Interspecific predation is the farmed fish being prayed on by other species, this can be prevented by: fencing the area the fish are in; putting nets around the area the fish are in; keeping the fish in inside tanks.

To minimise spread of disease, the water the fish are in should be changed regularly and their surroundings sterilised often. Also if small amounts of fish are kept together then disease can only contaminate a few fish.

Waste can be removed by changing the water in a tank, or changing the nets and location of fish kept outside.

Fish need to be fed often in small amounts, this is so they don't starve but they wont be able to over eat. It is important to feed fish food with nutrients in for growth.

Selective breeding can ensure that farmers produce fish with desired characteristics  by letting only the fish with the right characteristics breed and pass on the gene.

A useful source is:

5.8 interpret and label a diagram of an industrial fermenter and explain the need to provide suitable conditions in the fermenter, including aseptic precautions, nutrients, optimum temperature and pH, oxygenation and agitation, for the growth of micro-organisms

Here is a diagram of a fermenter, the key parts are labelled:
The motor (labelled here as stirrer) turns the blades, this evens out the mixture: making sure the temperature and concentration is the same through out; and increasing the contact between the micro-organisms and other components.

The cooling jacket (labelled here as water column) controls the temperature as the cool water conducts heat from within. The temperature and PH both need to be monitored so that they can be kept at the optimum level for the enzymes. If the enzymes are in their optimum conditions then they will react faster.

Inoculum is the starter culture; basically it helps the fermentation start.

The air inlet gets oxygen into the fermenter. Oxygen is needed for the micro-organisms to respire. A sparger/agitator makes the air into very small bubbles; this means they have a larger surface area and can dissolve easily, so there is better access to oxygen for micro-organisms.

Aseptic conditions are needed as if there were other microbes in the fermenter; firstly they would contaminate the product; secondly they would use up nutrients and oxygen.

Nutrients are needed in the fermenter so the micro-organism can grow.

Thursday, 25 April 2013

5.7 understand the role of bacteria (Lactobacillus) in the production of yoghurt

When Lactobacillus respire anaerobically, they make lactic acid: this acid clumps milk proteins together making yoghurt.

5.5 understand the role of yeast in the production of beer

Yeast converts sugar to ethanol and CO2 whe it respires anaerobically.
ethanol is alcohol...

5.4 understand the reasons for pest control and the advantages and disadvantages of using pesticides and biological control with crop plants Micro-organisms

Pests can eat crops or damage them so they can't be sold.

Pesticides are used to kill pests that reduce crop yield.
The assure that crops won't be damaged. Fast and accurate to apply. Instant results.
They can harm other wildlife.
Killing the pest may affect biodiversity.
Pesticides can leech into the soil and possibly pollute rivers or surrounding habitats.
Pests can become immune.

Biological control is introducing a predator into the environment with the crops to kill the pests.
Cheep. Self regulating.
The predator may enter the wild and effect the biodiversity.

5.3 understand the use of fertiliser to increase crop yield

Fertilisers contain minerals that plants require to grow; most of them are called NPK fertilisers, this means they contain nitrates, phosphates and potassium.

Nitrates are needed to make proteins- proteins are what plant cells are made of. If there is a lot of nitrate in the soil then plants have the ability to grow as much as they can.

Phosphates are involved in respiration and growth- both things are needed to sustain a plant.

Potassium must be present for enzymes to work- with out it the plant wouldn't be able to carry out reactions and so would die or have very limited growth.

5.2 understand the effects on crop yield of increased carbon dioxide and increased temperature in glasshouses

Glass houses and polythene tunnels increase the heat in the environment that crops are growing in. Reactions happen faster when there is more heat, for example photosynthesis. Given photosynthesis produces energy that the plant needs to grow, if there is more heat there is more growth and so higher yield.

Carbon dioxide is a reactant in photosynthesis. If there is a more than enough carbon dioxide, then every plant will be able to photosynthesise as best as it can. The more photosynthesis the more glucose, the more glucose the more energy, the more energy the more growth. Hence crop yield is increased.

5.1 describe how glasshouses and polythene tunnels can be used to increase the yield of certain crops

In glasshouses and polythene tunnels conditions can be controlled. This control means that all the limiting factors for plant growth can be set to the optimum conditions; this will result in more growth, so higher yield.

Sunday, 21 April 2013

4.17 understand the effects of deforestation, including leaching, soil erosion, disturbance of the water cycle and of the balance in atmospheric oxygen and carbon dioxide.

Leeching is basically loss of nutrient from soil. Normally nutrient is rained into the soil; absorbed by plants; shed in their leaves/when they die; digested by decomposers so its back in the soil. If you take away the vegetation you remove nutrients from the cycle. In addition to this the soil is not protected by plants and so when it rains there will be a higher rate of surface run off, this will take the nutrients from the soil with it. Soil erosion is also caused by the fact that without plants to protect the soil there is more surface run off, because soil is taken with it.

Plants absorb water from the soil and lose water from their leaves (through transpiration) in to the atmosphere which goes on to make clouds. If there are less plants then less water is evaporated into the atmosphere, this means there are less clouds; less clouds means less rain, which can mean drought.

Plants also convert carbon dioxide into oxygen when they photosynthesise. Forests carbon sinks, they use more carbon than they release: this means they help to make sure there aren't too high levels of CO2 in the atmosphere. When forests are cut down this process is lost and additionally the trees are usually burnt which releases CO2 into the atmosphere.

This article is explains some of the effects of deforestation nicely:

4.16 understand that eutrophication can result from leached minerals from fertiliser

Eutrophication is when there are excessive amounts of nutrients in a lake. The effects of this are that algae will bloom (grow quickly). Having a lot of algae will mean that there is not enough oxygen for other organisms, they will also struggle to find enough light as algae covers the surface. More organisms will die then usual- more algae to die/ less oxygen and light so fish die- so decomposers will thrive; these decomposers will also use a lot of oxygen from the water. In the end there will not be enough oxygen for fish.

Nutrient get leached into rivers from soil as rain water runs off land into rivers and lakes taking nutrient with it. If fertiliser has been put in the soil then the soil will be rich in certain nutrient, especially nitrogen: so rain water runs off fertilised soil it will bring high amounts of nutrient into surrounding rivers or lakes causing eutrophication.

4.14 understand how an increase in greenhouse gases results in an enhanced greenhouse effect and that this may lead to global warming and its consequences

The sun heats up the earth with infra-red waves that it emits, these waves travel from the sun through the earth atmosphere and warm it up. The earth emits its own rays so that it maintains its heat instead of just warming up forever! Many of these rays escape the earth's atmosphere- revealing it of heat- but some are absorbed by certain gasses- Greenhouse gasses- this means the heat is trapped within the earth's atmosphere. On a large scale this heats the earth, which we call global warming, and this can lead to climate change: the expected weather patterns reverse or exaggerate: this is thought to result in natural disaster (drought, floods).

4.13 understand how human activities contribute to greenhouse gases

Many of the processes that we carry out in homes and factories produce or release gasses with the greenhouse effect. Many things release greenhouse gasses when they are burned; reactions can create greenhouse gasses; some plants and animals that we keep a lot of naturally release greenhouse gasses. Processes that produce greenhouse gasses include burning fossil fuels and keeping large amounts of live stock.

4.12 understand that water vapour, carbon dioxide, nitrous oxide, methane and CFCs are greenhouse gases

A green house gas is one that absorbs heat reflected by the earth, this heat is then trapped in the earth's atmosphere warming the earth. In large quantities these gasses can change the climate by keeping in too much heat. Gasses that do this include: water vapour, carbon dioxide, nitrous oxide, methane and CFCs.

A CFC is a compound that contains only carbonchlorinehydrogen and fluorine.

4.11 understand the biological consequences of pollution of air by sulfur dioxide and by carbon monoxide

Sulfur dioxide and carbon monoxide are created by many processes we use in factories and homes. When in the atmosphere they can dissolve in rain water to create rain the is acidic. Acid rain corrodes metals and rocks like limestone which can damage buildings and statues. Acid rain can also change the PH in soil or rivers, this can mean that some species can not survive in that area.

Monday, 15 April 2013

4.10 describe the stages in the nitrogen cycle, including the roles of nitrogen fixing bacteria, decomposers, nitrifying bacteria and denitrifying bacteria

Nitrogen fixing bacteria turn nitrogen from N2 into ammonia.
Decomposers break down dead animals, urea and egested materials which releases nitrogen into the soil as ammonia.
Nitrifying bacteria convert nitrates into nitrogen.
Denitrifying bacteria break down nitrates into nitrogen which is then released into the atmosphere.

Here is a diagram to help explain:
File:Nitrogen Cycle.svg

This animation is very helpful:

4.9 describe the stages in the carbon cycle, including respiration, photosynthesis, decomposition and combustion

Respiration is carried out by animals and plants to release energy from glucose, the equation is:
C6H12O6 + 6O2    →    6CO2 + 6H2O . This means carbon is produced.

Photosynthesis is what plants do to create glucose the equation is:
6 CO2 + 12 H2 C6H12O6 + 6 O2 + 6 H2O. This means carbon is used.

Decomposition is happens when an animal dies, it is then eaten by a decomposer which releases the carbon in it back into the atmosphere.

Combustion is burning, if something with carbon is burnt it will release it into the atmosphere, e.g. a tree, fossil fuel.

This is one of many useful diagrams:

4.8 describe the stages in the water cycle, including evaporation, transpiration, condensation and precipitation

Evaporation is when water turns into steam due to being heated
Transpiration is when water is evaporated from leaves
Condensation is when water vapour turns into water due to being cooled, this forms clouds
Precipitation is when water is released from a cloud, e.g. rain, snow, hail

The best way to understand this is with a diagram:

Saturday, 30 March 2013

4.7 explain why only about 10% of energy is transferred from one trophic level to the next.

The reason why not all of the energy will make it to the next tropic level is that some of it will be used up on the level it is at. The energy is used for the life processes of the animal that it is in.
e.g If a bunny rabbit eats a cabbage, it will use some of the energy to keep warm, some to move e.c.t so fox only gets some of the original energy from the cabbage.

4.6 understand the transfer of substances and of energy along a food chain

As one thing consumes another the energy and other things inside it- for example fat and vitamins- get transferred to the consumer. If you eat a fatty piece of beef you get the fat from the cow.

4.5 understand the concepts of food chains, food webs, pyramids of number, pyramids of biomass and pyramids of energy transfer

A food chain shows the transfer of energy up the food chain beginning with the producers then the primary consumers and so forth.

A food web links several animals within a habitat showing what consumes what and is consumed by what.
A pyramid of number progresses through the trophic levels of a food chain representing the number of each species by the area of the pyramid block.
A pyramid of biomass represents the mass of each consumer (and producer) by the area of a pyramid block.

diagram representing energy transfer in a food chain
A pyramid of energy shows the transfer of energy through the food chain.

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 a continuous process in living things, so won't stop at any time. But photosynthesis depends on light and so will stop in the dark. This means that in the night carbon dioxide will be being given out by respiration but not taken in for photosynthesis, so the net exchange of carbon has an increased out put. In the same way at night oxygen will not be being given out as there is no photosynthesis.

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

In photosynthesis: 6CO2 + 6H2O > C6H12O6 + 6O2 + 6H2O
So the plant takes up carbon dioxide and gives out oxygen

In respiration: C6H12O6 + 6O2 > 6CO2 + 6H2O
So the plant gives out carbon dioxide

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

Collect the gas coming off the seed and bubble through lime water to see if it turns cloudy. Place in a cool environment and measure the surrounding air heating up.

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

Hold a piece of food under a tube of water, burn the food. When it is fully burned compare the heat of the temperature before and after. The change in heat is the energy in degrees, convert if needed.

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)
Primary consumer (eats the producer and gains its energy)
Secondary consumers
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

Number of individuals in a particular species.

Populations of different species interacting.

The area where a population lives.

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

Brightly coloured, larger petals

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.

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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:!

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

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.

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

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

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

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

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)

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

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:

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.

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.

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

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

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.
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.

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.


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

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

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

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.

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.

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.

Chemical reactions in cells need water; respiration

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

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:

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.

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.

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:

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

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.

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.

Monday, 21 January 2013

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

Surface area
with a larger surface area- molecules have more surfaces through which to diffuse, this increases the rate of moment

Increased temperature means increased kinetic energy- this will mean molecules collide with the cell membrane more often making movement through it more likely

Concentration gradient
This is the difference between the concentration inside and outside of the cell. The bigger the difference is the more opportunity molecules have of diffusing.

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

A turgid cell is one that is, effectively, full of water; this increases the volume of the cytoplasm, which exerts pressure outwards. These cells are stronger so they support the plant- meaning that a plant grows upwards.

This is why a dehydrated plant will wilt.

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

These three processes (defined in 2.12) are the ways in which substances move in and out of cells.
This video explains how:

2.12 understand definitions of diffusion, osmosis and active transport

Diffusion is when molecules move from a area of high concentration to a area of low concentration

Osmosis is the movement of water, it follows the rule that water will move from a dilute solution to a concentrated solution.

Active transport is molecules being moved from an area of low concentration to an area of high concentration  energy is needed to make this happen hence 'active'

Thursday, 3 January 2013

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

  • Put starch into a test tube; either heat or cool it.
  • Add amylase
  • With this mixture on white tiles, add iodine
  • Time how long it takes for the iodine to stop being blue black
  • Repeat at different temperatures and compare
When the iodine stops being blue/black there is no starch present, so it must have been digested by the enzymes.

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

Change in PH can denature enzymes by breaking the bonds that  hold the structure in place. So the active site no longer fits with the the substrate it is meant to be breaking down. The PH at which this happens is different for different enzymes, but generally an extreme PH will denature any enzyme.

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

Enzymes lower the activation energy of a reaction- making it faster- and they are unchanged from begining to end of a reaction. These two things mean its a catalyst.

For information on enzymes this is a great source:

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

As heat increases kinetic energy increases, this means enzymes and substrates more around more so they are more likely to 'bump into' one another (collide) and bind. This means that as heat increases so does the amount of reactions an enzyme catalyses.

However if the temperatures are too high it will denature enzymes, so they can't function. Because the energy breaks the bonds that hold the shape of the enzyme: without these the structure will be distorted, which will mean the active site won't be able to bind with the substrate to break it down.

Note the active site is the area on an enzyme that binds with a substrate to break it down; it is the lock in the lock and key theory.

Optimum temperature is in between these two scenarios, where there is lots of energy from heat but not enough to denature the enzyme. It is different for different enzymes.

2.7 describe the tests for glucose and starch

Test for glucose
Heat object with Benedict’s or Fehling’s Reagent.
if it turns from blue to orange then glucose is present.

The starch test
Apply iodine to the object you are testing,
if it turns from red to blue/black then there is starch.
Note: in an exam you are safest saying blue/black instead of blue or black.

2.6 describe the structure of carbohydrates, proteins and lipids

as large molecules made up from smaller basic units

Simple sugars- monosaccharides-such as glucose are the basic carbohydrates
They join together to make more complex disaccharides and polysaccharides: 

are made up of amino acids
amino acids differ depending on what the 'r' (rest) is:
Lipids, Carbohydrates, and Proteins

are made from combining glycerol and three fatty acids:
Lipids, Carbohydrates, and Proteins

The following video is quite good to watch, but it has a lot of extra content: