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 starch or sucrose
-have a nucleus
- they can photosynthesise

Animals
- are multicellular organisms
- cells do not contain chloroplasts
- have no cell walls
-store carbohydrates as glycogen
- have a nucleus

Fungi
- some are multicellular, some are single celled
-have cell walls made of chitin
- store carbohydrates as glycogen
- their body is organised into a mycelium made from thread-like structures called hyphae which may contain nuclei
- can not carry out photosynthesis (and therefore do not contain chloroplasts). Instead they feed by saprotrophic nutrition (extracellular secretion of digestive enzymes onto food material and absorption of the organic product


Bacteria
- all are single celled
-have a cell wall
- lack a nucleus but contain a circular chromosome of DNA (a plasmid)
- some can carry out photosynthesis, must most feed of living or dead organisms

Protoctists
- all are single celled
- some have chloroplasts (but some don't)
- some have features like animals (for example, no cell wall) whilst others have features like plants (for example, have a cell wall)

Viruses
- they have no cellular structure (so are not even single celled)
- they have a protein coat
- they contain one type of nucleic acid (either DNA or RNA)
- can not photosynthesise. They are parasitic and can reproduce only inside living cells. They infect every type of living organism.

Examples

Plants - maize
animal - human
fungi - Mucor (multicelled), yeast (single celled)
bacteria - lactobacillus
protoctists - amoeba (plant like) chlorella (animal like)
viruses - influenza, HIV

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 phenolphthalein, incase you were wondering)
- Fill a beaker with dilute hydrochloride acid
- Cut different sized cubes (e.g 1x1cm, 2x2cm, 3x3cm) and put them in the dilute hydrochloric acid
- Leave the cubes for a whole

you should observe that they go colourless because the acid diffuses into the agar jelly


Osmosis in living
- cut a potato into 5 even cuboids, measure their lengths
- obtain 4 beakers wit different sugar solutions in them, and 1 with just watr (this will be our control)
- put each potato strip into one of the 5 beakers
- leave for 1 hour
- remove potato and measure strips again

Conclusion - if water has entered the potato, the length will be greater, if it has left, the length will be shorter (than before).


Osmosis in non-living

- tie a piece of string/wire around one end of some visking tubing and put a glass tube in the other, fixing it in place with more wire.
- pour sugar solution down the glass tube into the visking tubeing
- put the visking tubing into a beaker, fill the beaker with pure water and make a note of how far up the beaker the waterline sits
- leave the experiment overnight
- return the next day and measure the amount of water in the beaker

Conclusion - the water should have been drawn into the Visking tubing by osmosis, this will force the liquid up the glass tube

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. This creates an enucleated egg cell (just a cell without a nucleus)

- Insert the nucleus of a diploid cell of the mammal you want to clone

- shock the new cell by electric shock to start division by mitosis. This creates an embryo

- Implant the embryo into the uterus of a surrogate mother (has to be the same species) to develop.

Now wait for the animal to be born

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 will not need to rely on the correct conditions like during natural growth - the commercial company can ensure they ill have stock (of plants).

NOTE: the process of micropropogation is explained in point 5.17.

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 cloned. Small pieces are cut from the tips of the stems and the side shoots of the plant (these cuttings are known as explants)

- The explants are sterilized to kill any microorganisms

- The explants are grown in vitro. All this means is that they're placed in a petri dish that contains a nutrient medium. This medium has all the stuff the plant needs to grow. It also contains growth hormones (auxins)

- The explant begins to grow and are taken out of the medium and planted in soil.


These plants develop into plants that are genetically identical to the original plant, meaning they will share the same characteristics.

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 resistant means farmers can spend less money on chemicals such as pesticides, this also increases yield.

making them resistant to weedkiller means farmers can kill weeds without killing the plant.

However, many people are against genetically modifying foods as there are no studies on long term effects on humans. There are also religious reasons. Also, if a weed gets the weedkiller resistance gene, there will be no way to kill it.

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 insulin) is cut out of a human cell using a restricton enzyme.

- The vector DNA (either a plasmid or virus, in this case, plasmid) is cut open with a restriction enzyme.

- the vector DNA and insulin DNA are combined with a mixture of ligase enzymes. The ligase enzymes join the two pieces of DNA together, producing recombinant DNA

- The recombinant DNA is inserted into  a bacterium

- The bacterium is grown in a fermenter


The bacteria cells now make insulin. This is useful to produce insulin on a mass scale for people with diabeties etc.

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 circular molecules of DNA that can be transferred between bacteria

Viruses - insert DNA into the organisms they infect

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 recognizing the specific sequences of DNA.

NOTE: Two different bits of DNA that have been stuck together is known as recombinant DNA

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 mothering skills, not a bad temper, is fast (good for racehorses etc) and has high fertility.

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 good yield but are easily damaged by the elements whereas dwarf wheat plants can resist the elements but have quite a low yield. The two plants can be bred together, ensuring the offspring can battle the elements and have a good crop yield.

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 possible.

NOTE: Everything specifically to do with fish farming in cages in the sea is in blue, everything specifically to do with fish farming in tanks is in green.

Maintenance of water quality
There is a current in the sea so water is naturally kept 'clean'.
The water can be removed, filtered and cleaned. Water can be monitored to ensure temperature, [H and oxygen level is at the best potential.

Control of intraspecific and interspecific predation

Firstly, interspecific predation is being eaten by other animals, intraspecific predation is cannibalism, basically.

Fish farming in cages stops interspecific predation as it means no animals/fish can eat the farmed fish. Big fish and baby fish are kept separate to keep intraspecific predation low.

Control of disease

Fish in cages are prone to diseases such as lice . Biological pest controls are used to control the lice as chemical pesticides can harm the fish.

Removal of waste products

The water can be removed and filtered, getting rid of waste.

Quality and frequency of feeding

A diet of food pellets is carefully controlled to maximize the amount of energy the fish get as more energy = more growth = bigger fish. Furthermore, the better the quality of food, the bigger the fish will grow.

It is easy to control how much food is given, as it doesn't wash away in the current of the sea.

Selective breeding

The fish can be selectively bred to produce fast growing, less aggressive fish, for example.

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 carbon dioxide production from yeast...

- mix together some suger, yeast aand distilled water. Add this mixture to a test tube

- attatch a bung with a delivery tube. Attatch the other end of the delivery tube to a test tube of water

- Put the tube containing the yeast/water/sugar solution in a water bath at 10°.

- leave to warm up for 5 minutes and then count how many bubbles are produced in one minute

- repeat with 4 other test tubes, one at 15°, one at 20°, one at 25° and one at 30°. You should also do one at room temperature as a control

- plot results in a graph and compare/find patterns/anomalies

should all go well, you should conclude that as temperature increases, the rate of respiration (and therefore amount of bubbles) should increase. However, if you have done a water bath past optimum temperature for the enzymes (as respiration is controlled by enzymes), then there will be very little/no data for this tube.

NOTE: You can use the same apparatus but measure the effect on different concentration of sugar, for example, by keeping the water bath the same temp but adding more/less sugar to each tube. the same can be done with volume of water and/or concentration of sugar solution etc

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 anaerobically. It is the ingredient in the production of beer that makes the alcohol, it ferments the sugars into alcohol.

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 are poisonous to humans so must be used carefully around foods etc (e.g. growing carrots) and some pesticides are harmful to other wildlife.

Biological control is an alternative to pesticides, it involves using other organisms to control pests (e.g. introducing hoverflies to an area to reduce the amount of aphids, as aphids kill hoverflies). This has a longer lasting effect on the crop/area than pesticides do and is less harmful to the ecosystem. However, it can cause problems. for example, the introduced species could become uncontrollable and their predator would have to be introduced to control them. It can also take longer (potentially).

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 are naturally found in the soil, however, they could be lacking due to previous crops using them up. All fertilisers do is replace them in the soil, so the plants can grow very well.

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 of photosynthesis will be increased. Meaning more photosynthesis will occur each day, meaning a bigger crop yield.

If temperature is increased, plants can grow throughout the winter and don't die of frost etc. This also lowers the rate of transpiration (as there is a lower concentration gradient inside vs outside the plant leaf so the rate of transpiration is lower).

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 a crop. Some ways they create the perfect conditions are...

- The plants are enclosed, meaning they are at no/a significantly lower rick of pests and diseases.

- Artificial light can be supplied which will increase the time per day a plant is photosynthesizing

- The suns heat can be trapped (particularly in glasshouses). This keeps the plant warm. In winter it can stop the plants from being damaged by frost etc

- As it is an enclosed space, farmers can increase the level of carbon dioxide in the glasshouse/polyethene tunnel. They can do this by burning a paraffin lamp etc (combustion fossil fuels gives carbon dioxide). This further increases the amount/rate of photosynthesis the plant endures.

All of the above increase the yield of a plant.

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 gets leached but not returned, resulting in infertile soil.

Soil erosion

When trees are removed, soil can be washed away by rain etc as tree roots hold soil together (but there will be no tree roots, as there will be no trees).

Disturbance of the water cycle

Trees take up water, when they are cut down, water runs straight into rivers, causing flooding. also, the local climate gets drier as there is much less transpiration occurring.

Disturbance of the balance of carbon dioxide and oxygen

When trees die, carbon dioxide is naturally released. When they are burnt, all the carbon dioxide is released at once. alternatively, if wood is used in furniture etc, the carbon is stored and not released, disrupting the carbon cycle.

Fewer trees means fewer photosynthesis means less oxygen.

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. this results in eutrophication. Basically...

- The extra nutrients causes algae to grow super fast. This blocks out the light
- Plants in the river (before the algae) can not photosynthesise due to low light. They die.
- With more food (dead plants) available, microorganisms living in the water rapidly increase in number and deplete/use up all of the oxygen in the water.
- Organisms, like fish for example, that need oxygen, die.