IGCSE Biology

A blog covering and explaining the Edexcel IGCSE Biology specification for the 2016 summer exams. If you are doing just double science, you do not need to learn the stuff for paper two, if you are doing triple you will need to learn all (GOOD LUCK!) I have separated the papers to make files easier to find. Hope it helps :)

Thursday, 20 April 2017

Hello again!!

Hi all, It's been so long! Long story short, sorta locked myself out of this account and thus...well...haven't been able to post h...

Monday, 16 May 2016

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

carbon monoxide - greenhouse gas sulfur dioxide - acid rain

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

Male Testis - produce sperm cells Sperm duct (vas difference) - carries sperm to the penis The prostate gland - adds fluid to the sperm, c...

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

nervous system - electrical impulses hormones - chemicals (nervous is much faster than hormonal)

1.2 describe the common features shared by organisms within the following main groups: plants, animals, fungi, bacteria, protoctists and viruses, and for each group describe examples and their features as follows (details of life cycle and economic importance are not required)

Plants - Are multicellular organisms - their cells contain chloroplasts - have cell walls made of cellulose - they sort carbohydrates as...

Saturday, 14 May 2016

Quick notice

Hi all! Hope all your revision is going well, I have now finished the spec for biology and am going through each point, editing and correc...

Friday, 13 May 2016

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

Diffusion in non-living - Make agar jelly by mixing phenolphthalein and dilute sodium hydroxide (NOTE: The jelly will be pink from the phen...

Wednesday, 11 May 2016

3.33 undersand that the incidence of mutations can be increased by exposure to ionising radiation (for exampe gamma raysX-rays and ultraviolet rays) and some chemical mutagens (for example chmicals in tobacco)

Ionising radiation can induce mutations. So can some chemicals in tobacco as this is why you can get cancer from smoking (as some cancers a...

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

When evaluating, you just need to go over the positives and negatives and weigh up which is more (more positives or more negatives) Positi...

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

Dolly is just used as an example as she was the first cloned mammal. The method is as follows... - Remove the nucleus of an egg cell. Thi...

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

If loads of plants are required, you can take cuttings from the explants to produce even more plants. It is also very quick so the farmer wi...

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

Micropropogation is a technique used to clone plants. Here's how it works... - A plant with desired characteristics is selected to be ...

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

Transgenic means the transfer of genetic material from one species to another. If something is said to be transgenic, it means they contain...

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

Crops can be genetically modified to increase yield. For example, making them resistant to insects/weed killers. Making them insect resist...

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

This is one of the uses of genetic engineering, here's how it works... - the DNA you want to insert (in this case, the gene for human ...

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

A vector is something that is used to transfer DNA into a cell. The two types of vectors are plasmids and viruses. Plasmids - small circul...

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

Ligase enzymes are used to join together two pieces/strands of DNA, alternatively, the restriction enzyme cuts DNA at a specific point by re...

5.11 understand that animals with desired characteristics can be develope by selevtive breeding

Selective breeding can ensure an animal produces the maximum yield of, for example, meat/milk, has good health/disease resistance, has good ...

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

Selective breeding can be used to combine the best characteristics to produce the best crops. For example, tall wheat plants have a very g...

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 waster products, quality and frequency of feeding and the use of selective breeding

Fish farming is a possible solution to the problem of overfishing. It is controlled and designed in a way to produce as many fish as possibl...

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

Okay so to start, here is a diagram... Conditions... The fermenter must be kept aseptic so only the desired microorganism grows. In...

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

Lactobacillus is the bacteria that ferments milk (into yoghurt) in yoghurt production. This is the process... - All equipment is sterilize...

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

When yeast respires aerobically, it produces carbon dioxide as a bi-product. Here is how to measure the effect of changing temperature on ca...

5.5 understand the role of yeast in the production of beer

When yeast respires anaerobically (without enough oxygen) it produces ethanol/alcohol as a bi-product. In beer production, yeast respires an...

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

Pesticides/pest control kills insects/microorganisms/mammals that feed on crops. they are useful as they are very effective. However, they a...

5.3 understand the use of fertiliser to increase crop yield

If plants don't get enough nitrogen, potassium or phosphorus, their growth and other life processes could be affected. These elements ...

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

Okay so, I mainly covered this, along with other factors, in point 5.1 , but here it is again... If carbon dioxide is increased, the rate ...

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

Glasshouses and polyethene tunnels/polytunnels help to create the ideal conditions for plants, thus increasing the yield (how much grows) of...

Tuesday, 10 May 2016

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

Leaching Trees leach nutrients when they are alive, but return nutrients to the soil when they die. When trees are cut down, nutrients get...

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

Like fertilisers, sewage also contains phosphates (from detergents) and nitrates (from faeces etc). If these are leaked into rivers, eutroph...

4.16 understand that eutropication can result from leached minrals from fertiliser

Nitrates and phosphates can leak from mineral fertilisers that are put on fields. If it rains, they are easily leached into rivers and lakes...

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

Heat from the sun is naturally radiated off the earth and into space. Greenhouse gases naturally keep in some of the heat (otherwise we woul...

4.13 understand how human activities contribute to greenhouse gases

Okay so basically... Contribution to carbon dioxide - Car exhausts, industrial processes (burning of fossil fuels etc), cutting down of tr...

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

NOTE: You may be asked where the greenhouses originate from. Well, its not in the spec but it was in the 2015 paper so just to be safe I hav...

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

Sulfur dioxide When fossil fuels are burnt, sulfur dioxide is released (from sulfur impurities in the fuel). When it mixes with rain cloud...

4.10 describe the stages in the nitrogen cycle, including the roles of nitrogen fixing bacteria, decomposers, nitrifying bacteria and denitryfying bacteria (specific names of bacteria are not required)

Firstly, here's a diagram... Okay so... nitrogen fixing bacteria - this turns atmospheric nitrogen into nitrogen compounds (in the...

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

To start, here is a diagram... Okay so... Respiration - breathing basically. this releases carbon dioxide back into the air. Photosy...

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

Firstly, here is a diagram... Okay, so... Evaporation - this is where water (from the ground) gets warmed (usually from sunlight). Whe...

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

This is mainly explained in point 4.6 , but I will cover the main points again... Much energy is lost so not all energy an organism takes ...

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

Food chain A food chain shows the flow of energy up the food chain. It can only show one organism at each trophic level, also you cannot ...

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

Plants use energy from the sun in photosynthesis, this energy makes its way through the food chain as animals eat the plants and each other....

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

Producers are the first trophic level because they are at the bottom of the food chain. They turn sunlight into usable energy, in other word...

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

This experiment is laid out along a line (known as a transect). - Mark out a line along the area you want to investigate - Using quad...

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

Firstly, this is a quadrat… They are usually 1m 2 and split up into 100 smaller squares. Just randomly place/throw it on the ground an...

4.1 understand the terms population, community, habitat and ecosystem

Population - All the organisms of one species in a habitat Community - All the different species in a habitat Habitat - The area/place i...

Monday, 9 May 2016

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

Bacteria can develop mutations too, this changes the characteristics and some bacteria become more resistant to particular antibiotics. This...

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

Most mutations are harmful. For example... - If a mutation occurs in reproductive cells, the offspring might develop abnormally or die - ...

3.30 describe the process of evolution by means of natural selection

- Living things show variation - The recourses living things need are limited. Individuals must compete for these resources to survive - on...

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

A mutation is a rare, random change in an organism's DNA (basically, a mutation in a gene). This can be inherited. Mutations are often h...

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

Genetic variation is just variation that you inherit, environmental variation is variation that is affected by your environment. That was a ...

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

Quite a simple one... in human cells, the diploid number of chromosomes is 46 and the haploid number is 23. NOTE: All human cells are dipl...

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

Gametes (sex cells) are produced by meiosis. Meiosis is when a cell reproduces by splitting itseld to form four haploid cells whose chromoso...

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

Mitosis is wen a cell reproduces itself by splitting to form two cells with identical sets of chromosomes. It is used for asexual reproducti...

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

Okay so mitosis is when a cell reproduces by splitting itself in two to form two cells with identical sets of chromosomes (this is the defi...

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

This is a very good diagram which basically has everything on... From this we can understand that there is a 50% chance of an offspring ...

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

Firstly, it is important to understand that there are 23 pairs of chromosomes in each human cell, resulting is 46 individual chromosomes. (N...

3.20 predict the probabilities of outcomes from monohybrid crosses

The each parent gives one allele to the offspring. There are two possible alleles it could give (for example, 'Bb' there is 'B...

3.19 understand hwo to interpret family pedigrees

A pedigree diagram enables someone to easily show a specific gene within a family. Here's how they work... - A square represents a mal...

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

Dominant - If an allele is dominant, the characteristic controlled by a dominant allele develops if the allele is present on one or both chr...

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

Different forms of a gene are known as alleles. For example, for the gene that codes for eye colour there are alleles that code for brown ey...

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