Variation and evolution

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Variation

Variation is defined as the differences between individuals of the same species.
Phenotypic variation is the difference in features between individuals of the same species.
Phenotypic variation can be genetic (controlled entirely by genes), environmental (caused entirely by the environment), or a combination of both.
Examples of genetic variation in humans include blood group, eye colour, gender, ability to roll tongue, and free or fixed earlobes.
Environmental factors that cause variation include climate, diet, accidents, culture, and lifestyle.
An example of environmental variation is a plant in the shade of a big tree growing taller to reach more light.
Some features, such as height, are affected by both genes and the environment: tall parents pass on genes for height, but a poor diet can prevent the child from reaching their full height potential.

Genetic Variation and Mutation

There is usually extensive genetic variation within a population of a species.
All genetic variants arise from mutations, which are random genetic changes that occur continuously.
Most mutations have no effect on the phenotype because the mutated gene may still produce a working protein.
Rarely, mutations lead to the development of new alleles and so new phenotypes; most of these only have a small effect on the organism.
Occasionally, a new allele gives the individual a survival advantage over other members of the species.
If the new phenotype is suited to an environmental change, it can lead to a relatively rapid change in the species.
For example, a moth with a mutation for better camouflage against tree bark is less visible to predators, survives and breeds more, so the new colour quickly spreads through the species.

Evolution by Natural Selection

Evolution is defined as a change in the inherited characteristics of a population over time.
Evolution occurs by a process known as natural selection.
During natural selection, individuals with phenotypes best suited to their environment are more likely to survive and pass on their features to their offspring.
The theory of evolution by natural selection states that all species of living things have evolved from simple life forms that first developed more than three billion years ago.
Natural selection can lead to the development of new species by a process known as speciation.
Speciation is said to have occurred when two populations have phenotypes so different that they can no longer breed together to produce fertile offspring.
Remember: evolution refers to changes in species over time, while natural selection is the mechanism by which this change takes place.

Natural selection in peppered moths

Selective Breeding

Selective breeding (artificial selection) means to select individuals with desirable characteristics and breed them together.
Offspring that show the desired characteristics are selected and bred together, and this process is repeated for many successive generations before a new breed reliably shows those characteristics.
Animals are commonly selectively bred for characteristics such as cows, goats and sheep that produce lots of milk or meat, chickens that lay large eggs, domestic dogs with a gentle nature, sheep with good quality wool, and horses with fine features and a very fast pace.
Plants are selectively bred for characteristics such as disease resistance in food crops, increased crop yield, hardiness to weather conditions, better tasting fruits, and large or unusual flowers.
An example of selective breeding in plants is wild brassica, which has given rise to cauliflower, cabbage, broccoli, brussel sprouts, kale and kohlrabi.
An example of selective breeding in animals is the domestic dog, all breeds of which are descended from wolves.

Selective breeding of dog breeds from wolves

Problems with Selective Breeding

Selective breeding can lead to inbreeding, which occurs when only the 'best' animals or plants (which are closely related) are bred together.
Inbreeding results in a reduction in the gene pool – a reduction in the number of alleles in a population.
As inbreeding limits the size of the gene pool, there is an increased chance of organisms inheriting harmful genetic defects.
A reduced gene pool also makes organisms more vulnerable to new diseases because there is less chance of resistant alleles being present.

Genetic Engineering

Genetic engineering is changing the genetic material of an organism by removing or altering genes within that organism, or by inserting genes from another organism.
The organism receiving the genetic material is said to be genetically modified or is described as a transgenic organism.
The DNA of the organism that now contains DNA from another organism as well is known as recombinant DNA.
Examples of genetically modified organisms include bacteria that produce human insulin, crop plants resistant to insect pests, crop plants resistant to herbicides, and crops with additional vitamins such as golden rice.
Modern medical research is exploring gene therapy – inserting working versions of faulty genes into people with inherited disorders.

The Process of Genetic Engineering

The gene that is to be inserted is located in the original organism.
Restriction enzymes are used to isolate the required gene, leaving it with sticky ends (a short section of unpaired bases).
A bacterial plasmid is cut by the same restriction enzyme leaving it with corresponding sticky ends.
The plasmid and the isolated gene are joined together by DNA ligase enzyme.
The genetically engineered plasmid is inserted into a bacterial cell.
When the bacteria reproduce, the plasmids are copied as well, so the recombinant plasmid quickly spreads as the bacteria multiply and they all express the gene and make the human protein.
The genetically engineered bacteria can be placed in a fermenter to reproduce quickly in controlled conditions and make large quantities of the human protein.

Meeting Global Food Demands

Modern technology has increased food supply through agricultural machinery, chemical fertilisers, insecticides and herbicides, selective breeding, and more recently genetic engineering.
Fertilisers replace mineral ions in the soil and can make crops grow faster and bigger so that yields are increased.
Fertilisers can be organic (e.g. farmyard manure and compost) or chemical (often applied as dry granules or sprayed in liquid form).
Chemical fertilisers mainly provide crop plants with nitrogen, phosphorus and potassium.
A major disadvantage of fertilisers is that excess fertilisers not taken up by crops can get washed into lakes and rivers and cause problems such as eutrophication.
Biological control introduces other species to control pests; for example, ladybirds eat aphids, cane toads were introduced to eat crop-damaging beetles, and parasitic wasps can control whitefly in glasshouse tomato crops.
An advantage of biological control is that it can have longer-lasting effects than chemical pesticides and be less harmful to the environment.
However, biological control does not completely remove a pest but keeps it at lower levels, and in some cases the introduced organism can itself become a pest (e.g. cane toads in Australia).

GM Crops

GM crops are crop plants that have been genetically modified to have increased yields compared to normal crop plants.
Crop plants have been genetically modified to be resistant to pests, resistant to herbicides, and enriched in vitamins.
Crops such as maize (corn) and cotton have been genetically modified with a gene for a toxin that kills many insect larvae; the toxin is called Bt toxin as it was taken from the bacterium×Bacillus thuringiensis×.
The significance of genetically engineering crops to be insect resistant is that there is an increase in yield and fewer pesticides are used, which could have ecological benefits (e.g. non-targeted invertebrates are not harmed).
Crop plants have also been genetically modified to be resistant to certain herbicides, meaning that when the herbicide is sprayed it only kills weeds and does not affect the crop plant.
Some crops have been genetically modified to produce additional vitamins and improved nutritional value; for example, 'golden rice' contains genes from another plant and a bacterium which make the rice grains produce a chemical that is turned into vitamin A in the human body.
Some crops have been genetically modified to be drought-resistant (to grow better in very dry conditions), which can also improve crop yields in arid countries.
Concerns about GM crops include the effect on populations of wildflowers and insects, and some people feel the effects of eating GM crops on human health have not been fully explored.

The Human Genome Project

The entire set of genetic material of an organism is known as its genome.
The Human Genome Project (completed in 2003) was the international, collaborative research effort to determine the DNA sequence of the entire human genome and record every gene in human beings.
This was an important breakthrough for the prediction and prevention of diseases, the testing and treatment for inherited disorders, and the development of new and improved medicines.
A greater understanding of which genes predispose people to diseases such as cancers and heart disease enables doctors to provide more specific advice on lifestyle and diet to help avoid or delay the onset of these diseases.
The Human Genome Project has allowed doctors to identify faulty alleles (e.g. for cystic fibrosis) much more quickly, so people can be tested and treatments developed.
A greater understanding of how genetic variations make people more susceptible to certain diseases has allowed doctors to design new medicinal drugs specifically tailored to those with genetic variations, making drugs more effective and with fewer side-effects.
Potential drawbacks include increased anxiety and stress for someone told they have a high chance of developing a genetic disease, pressure not to have children, and discrimination by employers or insurers.

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1.Which of the following is a definition of variation?
Easy
- ADifferences between individuals of the same species
- BDifferences between individuals of different species
- CThe process by which organisms become better adapted to their environment
- DThe process by which humans breed organisms for particular characteristics
2.Which of the following is an example of genetic variation?
Medium
- AA plant grows taller because it is in the shade
- BA person has free or attached earlobes
- CA person gains weight because they eat too much
- DA person has a scar from an accident
3.A person has a scar on their skin after an accident. Which type of variation does this show?
Medium
- AGenetic variation
- BEnvironmental variation
- CA combination of genetic and environmental variation
- DNo variation
4.Which of the following are examples of genetic variation in humans? (Select all that apply)
Medium
- ABlood group
- BAbility to roll tongue
- CWeight gain due to diet
- DEye colour
- EScarring from an accident
5.Phenotypic variation can be caused by genes, the environment, or a combination of both.
Easy
True or false?
6.What is the name of the process by which humans breed plants and animals for particular genetic characteristics?
Medium
- ANatural selection
- BSelective breeding
- CGenetic engineering
- DEvolution
7.Which of the following are characteristics that plants are commonly selectively bred for? (Select all that apply)
Medium
- ADisease resistance in food crops
- BIncreased crop yield
- CGentle nature
- DLarge or unusual flowers
- EAbility to lay large eggs
8.Which of the following is a potential problem associated with selective breeding?
Medium
- AInbreeding leads to a reduction in the gene pool
- BIt always produces offspring that are genetically identical
- CIt introduces new alleles into a population
- DIt increases the number of alleles in a population

もっと問題

9.In genetic engineering, what is the role of a vector?
Medium
- AIt cuts the DNA at specific sequences
- BIt joins two pieces of DNA together
- CIt carries the desired gene into the target cell
- DIt provides nutrients for bacterial growth
10.Which of the following are examples of vectors used in genetic engineering? (Select all that apply)
Medium
- ABacterial plasmid
- BVirus
- CRestriction enzyme
- DDNA ligase
- EBacterial cell
11.Restriction enzymes are used to join two pieces of DNA together.
Easy
True or false?
12.Which of the following is the correct definition of a clone?
Medium
- AA genetically identical individual
- BAn individual with a new combination of alleles
- CAn organism that has been genetically modified
- DAn organism produced by sexual reproduction
13.In plant tissue culture, what are the small pieces of tissue that are scraped from the parent plant called?
Medium
- AExplants
- BCalluses
- CPlantlets
- DCuttings
14.Which of the following is the correct order of steps in adult cell cloning?
Medium
- ARemove nucleus from egg cell → insert adult body cell nucleus → electric shock to stimulate division → insert embryo into surrogate mother
- BInsert adult body cell nucleus → remove nucleus from egg cell → electric shock → insert embryo into surrogate mother
- CElectric shock to egg cell → remove nucleus → insert adult body cell nucleus → insert embryo into surrogate mother
- DRemove nucleus from egg cell → electric shock → insert adult body cell nucleus → insert embryo into surrogate mother
15.Mutations are random genetic changes that occur continuously.
Easy
True or false?
16.What is a mutation?
Medium
- AA random genetic change
- BA change in the environment
- CA type of selective breeding
- DA process that always changes the phenotype
17.Which of the following statements about mutations are correct? (Select all that apply)
Medium
- AMost mutations have no effect on the phenotype.
- BMutations are always harmful.
- CMutations can lead to new alleles.
- DMutations are caused by selective breeding.
- EMutations occur continuously.
18.Which of the following statements about the genetic engineering of human insulin are correct? (Select all that apply)
Medium
- ARestriction enzymes are used to cut the human insulin gene out of a human chromosome.
- BDNA ligase joins the insulin gene to a bacterial plasmid.
- CThe recombinant plasmid is inserted into a bacterial cell.
- DBacteria are genetically modified to produce human insulin.
- EThe insulin gene is inserted directly into human patients.
19.Match each stage of genetic engineering with its correct description.
Medium
- Restriction enzyme
- DNA ligase
- Vector
- Recombinant DNA
- Cuts DNA at specific sequences
- Joins two pieces of DNA together
- Carries a gene into a target cell
- DNA containing DNA from another organism
20.Place the steps in the production of human insulin by genetically engineered bacteria in the correct order.
Medium
- A plasmid is cut using restriction enzymes.
- The cut plasmids are mixed with copies of the human insulin gene.
- The plasmid and the human insulin gene are joined by DNA ligase.
- The recombinant plasmid is taken up by bacterial cells.
- The transgenic bacterial cells are grown in a fermenter.
21.Which of the following is an example of a vector used in genetic engineering?
Medium
- AA bacterial plasmid
- BA restriction enzyme
- CA DNA ligase enzyme
- DA fermenter
22.Which of the following are advantages of cloning plants by tissue culture? (Select all that apply)
Medium
- APlants can be produced cheaply.
- BA large number of plants can be produced quickly.
- CPlants can be produced at any time of the year.
- DThe plants produced are genetically identical to the parent.
- EThe plants produced are genetically different from the parent.
23.In tissue culture, the small pieces of plant tissue that are scraped from the parent plant are called explants.
Easy
True or false?
24.Match each selectively bred plant with the characteristic it has been bred for.
Medium
- Wheat
- Orchids
- Apple trees
- Wild brassica
- Increased crop yield
- Large or unusual flowers
- Better tasting fruits
- Disease resistance in food crops
25.Variation is defined as the differences between individuals of the same species.
Easy
True or false?
26.Which of the following best describes natural selection?
Medium
- AIndividuals with phenotypes best suited to their environment are more likely to survive and pass on their features.
- BHumans select individuals with desirable characteristics to breed together.
- CAll individuals in a population have an equal chance of surviving and reproducing.
- DOrganisms change their characteristics during their lifetime to suit the environment.
27.Which of the following statements about speciation are correct? (Select all that apply)
Hard
- ASpeciation occurs when two populations can no longer breed together to produce fertile offspring.
- BNatural selection can lead to speciation.
- CSpeciation is a change in the inherited characteristics of a population over time.
- DSpeciation requires two populations to be geographically separated.
- ESpeciation results in two populations that are genetically identical.
28.Place the stages of speciation in the correct order.
Medium
- A population becomes separated.
- Genetic variation exists within each population.
- Natural selection acts differently in each environment.
- Populations become so different they can no longer interbreed.
- Speciation has occurred.
29.A mutation in a moth population causes a change in colour that makes the moth blend in better with tree bark. Which of the following best explains why this new colour quickly spreads through the population?
Hard
- AThe moth has a survival advantage, so it breeds more frequently and passes on the mutated phenotype.
- BThe moth deliberately changes its colour to avoid predators.
- CThe mutation is always harmful, so the moth dies before reproducing.
- DThe new colour is caused by the environment, not by a mutation.
30.Most mutations have no effect on the phenotype.
Easy
True or false?
31.A graph shows insecticide use and the percentage of US cornfields growing GM corn between 1996 and 2013. In 1996 insecticide use was 30 million kg and the percentage of GM corn was 5%. By 2010 insecticide use had fallen to 10 million kg while GM corn had risen to 85%. Which statement best describes the relationship shown by the data?
Medium
- AAs the percentage of GM corn increased, insecticide use decreased
- BAs the percentage of GM corn increased, insecticide use also increased
- CThere is no relationship between GM corn and insecticide use
- DInsecticide use stayed constant while GM corn increased
32.A global study planted the most protein-rich seeds from each generation over 100 generations to produce high-protein maize. What is the name given to this process?
Medium
- ASelective breeding
- BGenetic engineering
- CNatural selection
- DMutation
33.High protein maize is considered to have superior nutritional value. Which of the following explains why?
Medium
- AProtein is required for growth and repair of tissues
- BProtein is an energy source
- CProtein provides roughage in a balanced diet
- DProtein provides insulation for key organs of the body
34.A farmer grows GM maize that contains the Bt toxin gene from Bacillus thuringiensis. The toxin is produced in the stems and leaves and kills insect larvae that feed on the crop. Which benefit to the farmer is most directly explained by this modification?
Hard
- ACrop yield increases and fewer chemical pesticides are needed
- BThe maize grains contain more vitamin A
- CThe maize can survive very dry conditions
- DThe maize is resistant to herbicides
35.A farmer is deciding whether to grow GM crops. Which of the following are reasons a farmer may wish to grow GM crops? (Select all that apply)
Medium
- AGM crops may be resistant to pests, increasing yield
- BGM crops may be resistant to herbicides, so weeds can be killed without harming the crop
- CGM crops may have improved nutritional value, such as golden rice producing vitamin A
- DGM crops always produce seeds that cannot be sold
- EGM crops are guaranteed to have no effect on wildflower populations
36.A farmer sows GM seeds that are resistant to a herbicide. The herbicide is sprayed on the field and only the weeds die. Which statement best explains why the crop plants survive?
Medium
- AThe crop plants have a gene that makes them resistant to the herbicide
- BThe herbicide only kills plants that are not crops
- CThe crop plants produce a poison that kills the herbicide
- DThe herbicide is absorbed only by weeds because of their leaf shape
37.Some people are concerned about the use of GM crops. Which of the following are concerns about GM crops? (Select all that apply)
Hard
- AThe effect on populations of wildflowers and insects
- BThe effects of eating GM crops on human health have not been fully explored
- CGM crops always cause the farmer to use more chemical pesticides
- DGM crops cannot be grown in dry conditions
- EGM crops have never been shown to increase yield
38.A farmer uses biological control by introducing ladybirds to eat aphids on a crop. Which statement best describes a limitation of this method?
Medium
- AIt does not completely remove the pest but keeps it at lower levels
- BIt kills all insects in the field, including beneficial ones
- CIt must be reapplied every week like a chemical pesticide
- DIt causes the crop plants to become resistant to the predator
39.A farmer applies excess fertiliser to a field. Some of the fertiliser is washed into a nearby lake. Which problem is most likely to result?
Medium
- AEutrophication of the lake
- BThe crop plants become resistant to herbicides
- CThe lake water becomes more acidic and kills all fish immediately
- DThe crop plants grow more slowly
40.A scientist grows human pancreatic tissue in the laboratory using tissue culture. The scientist then tests the effect of different glucose concentrations on the tissue. Which is the main advantage of using tissue culture for this experiment?
Medium
- AThe tissue can be studied in isolation without affecting a living organism
- BThe tissue will develop into a whole new organism
- CThe tissue will produce insulin that can be sold as a medicine
- DThe experiment can be done without any nutrients
41.Complete the sentence about evolution.
Easy
Evolution is defined as a change in the ____ characteristics of a population over time.
42.Complete the sentence about genetic engineering.
Medium
An organism that has received genetic material from another organism is described as a ____ organism.
43.Complete the sentence about selective breeding.
Medium
Selective breeding is the process by which humans breed plants and animals for particular ____ characteristics.
44.What is the name given to the process by which humans breed plants and animals for particular genetic characteristics?
Easy
45.Complete the sentence about mutation.
Medium
Mutations are ____ genetic changes that occur continuously.
46.A graph shows insecticide use in US cornfields was 30 million kg in 1996 and 10 million kg in 2010. Calculate the change in insecticide use between 1996 and 2010. Give your answer in million kg.
Medium
47.Complete the sentence about a genetically modified organism.
Medium
An organism that has had DNA from another organism inserted into its genome is described as being ____.
48.Complete the sentence about the DNA formed during genetic engineering.
Medium
DNA that contains DNA from another organism as well is known as ____ DNA.
49.Complete the sentence about the Human Genome Project.
Medium
The entire set of genetic material of an organism is known as its ____.
50.Complete the sentence about inherited disorders and the Human Genome Project.
Medium
Inherited disorders such as cystic fibrosis arise due to one or more faulty ____ in a person's genome.
51.Name the type of organism that is used as a vector in the genetic engineering of human insulin.
Medium
52.Explain how natural selection can lead to the development of a new species.
Hard
53.Explain why genetic engineering is said to change the genome of a species more extensively than selective breeding.
Hard
54.Name, and describe the roles of, the main enzymes used in genetic engineering.
Hard
55.Describe the process of adult cell cloning.
Medium
56.Explain one benefit of pest-resistant GM corn to a farmer.
Medium
57.A graph shows insecticide use in US cornfields was 30 million kg in 1996 and 10 million kg in 2010. Calculate the change in insecticide use between 1996 and 2010. Give your answer in million kg.
Medium
- A22 million kg
- B20 million kg
- C24 million kg
- D18 million kg

フラッシュカード

Define variation.

Variation is the differences between individuals of the same species.

What is phenotypic variation?

Phenotypic variation is the difference in features between individuals of the same species.

What are the two main causes of phenotypic variation?

Phenotypic variation can be caused by genetic factors (controlled entirely by genes) or environmental factors (caused entirely by the environment).

Give an example of genetic variation in humans.

Blood group, eye colour, gender, ability to roll tongue, or free or fixed earlobes.

What is environmental variation?

Environmental variation is caused entirely by the environment in which the organism lives, such as climate, diet, accidents, culture and lifestyle.

Give an example of a characteristic that is affected by both genetic and environmental factors.

Height: genes determine the potential height, but diet and other environmental factors affect how tall a person actually grows.

What are mutations?

Mutations are random genetic changes that occur continuously and are the source of all genetic variants.

Why do most mutations have no effect on the phenotype?

Because the protein produced by the mutated gene may work just as well as the protein from the non-mutated gene.

What is evolution?

Evolution is a change in the inherited characteristics of a population over time.

What is natural selection?

Natural selection is the process where individuals with phenotypes best suited to their environment are more likely to survive and pass on their features to their offspring.

What does the theory of evolution by natural selection state?

All species of living things have evolved from simple life forms that first developed more than three billion years ago.

What is speciation?

Speciation is the development of new species by natural selection, occurring when two populations have phenotypes so different that they can no longer breed together to produce fertile offspring.

What is selective breeding?

Selective breeding (artificial selection) is the process by which humans breed plants and animals for particular genetic characteristics by selecting individuals with desirable characteristics and breeding them together.

Why must selective breeding be repeated for many generations?

Because not all offspring will show the desired characteristics, so offspring that do are selected and bred together repeatedly until a new breed reliably shows those characteristics.

Give three characteristics for which animals are commonly selectively bred.

Cows, goats and sheep that produce lots of milk or meat; chickens that lay large eggs; domestic dogs with a gentle nature; sheep with good quality wool; horses with fine features and a very fast pace.

Give three characteristics for which plants are commonly selectively bred.

Disease resistance in food crops, increased crop yield, hardiness to weather conditions (e.g. drought tolerance), better tasting fruits, and large or unusual flowers.

What is inbreeding in selective breeding?

Inbreeding occurs when only the 'best' animals or plants (which are closely related to each other) are bred together.

What is the gene pool?

The gene pool is the number of alleles (different versions of genes) in a population.

What are the risks of inbreeding?

Inbreeding reduces the gene pool, increasing the chance of organisms inheriting harmful genetic defects and being vulnerable to new diseases.

What is genetic engineering?

Genetic engineering is changing the genetic material of an organism by removing or altering genes within that organism, or by inserting genes from another organism.

What is a transgenic organism?

A transgenic organism is an organism that has received genetic material from another organism.

What is recombinant DNA?

Recombinant DNA is DNA that contains DNA from another organism as well.

What is a vector in genetic engineering?

A vector is a structure used to insert a gene into the required cells of a target organism, usually a bacterial plasmid or a virus.

What is a plasmid?

A plasmid is a circle of DNA found inside bacterial cells.

What is the role of restriction enzymes in genetic engineering?

Restriction enzymes are used to isolate (cut out) the required gene, leaving it with 'sticky ends' (a short section of unpaired bases).

What is the role of DNA ligase in genetic engineering?

DNA ligase is used to join two separate pieces of DNA together, such as the plasmid and the isolated gene.

What are 'sticky ends'?

Sticky ends are short sections of unpaired bases left when restriction enzymes cut DNA strands at specific sequences.

What is the role of a fermenter in genetic engineering?

A fermenter allows genetically engineered bacteria to reproduce quickly in controlled conditions and make large quantities of the desired protein.

Give an example of a genetically modified organism used in medicine.

Bacteria have been genetically modified with the human insulin gene to produce human insulin for treating diabetes.

Give an example of a genetically modified crop that is resistant to pests.

Maize (corn) and cotton plants have been genetically modified with a gene from Bacillus thuringiensis to produce Bt toxin, which kills many insect larvae.

What is 'golden rice'?

Golden rice is a genetically modified crop that contains genes from another plant and a bacterium, making the rice grains produce a chemical that is turned into vitamin A in the human body.

What is gene therapy?

Gene therapy is the insertion of working versions of genes into people with a genetic disease to treat inherited disorders caused by faulty genes.

What is tissue culture?

Tissue culture is a process in which very small pieces of organisms ('tissues') are grown ('cultured') using nutrient media.

What are explants?

Explants are small pieces of tissue scraped from a parent plant and used in tissue culture.

What is the role of hormones in plant tissue culture?

Hormones (e.g. auxins) are added to encourage the cells of the explants to grow into small masses of tissue (callus tissue).

What is a clone?

A clone is a genetically identical individual.

What are the commercial uses of plant cloning?

It allows a variety of a plant with desirable characteristics to be produced cheaply, with a greater yield, quickly, at any time of the year, and in a small space.

What is embryo cloning?

Embryo cloning is a technique where an embryo from the best bull and cow is split apart many times before cells become specialised, forming many genetically identical embryos that are transplanted into host mothers.

What is adult cell cloning?

Adult cell cloning involves removing the nucleus from an unfertilised egg cell, inserting the nucleus from an adult body cell, stimulating division by electric shock, and inserting the embryo into a surrogate mother.

What was the first mammal to be cloned using adult cell cloning?

Dolly the sheep, cloned in 1996 by scientists in Scotland.

What is the Human Genome Project?

The Human Genome Project (completed in 2003) was an international, collaborative research effort to determine the DNA sequence of the entire human genome and record every gene in human beings.

What is a genome?

The genome is the entire set of genetic material of an organism.

What are the benefits of the Human Genome Project?

It allows prediction and prevention of diseases, testing and treatment for inherited disorders, and development of new and improved medicines.

What are the potential drawbacks of the Human Genome Project?

People may suffer increased anxiety and stress from knowing their genetic risks, be pressured into not having children, or face discrimination by employers or insurers.

What is biological control?

Biological control is the technique of controlling pests by introducing other species to the farmland to prey upon or parasitise the pest species.

What is an advantage of biological control over chemical pesticides?

Biological control can have longer-lasting effects than chemical pesticides and be less harmful to the environment (e.g. to non-target species).

What is a disadvantage of biological control?

It does not completely remove a pest but keeps it at lower levels, and in some cases the introduced organism can itself become a pest (e.g. cane toads in Australia).

Why are fertilisers needed in agriculture?

Fertilisers replace mineral ions taken up from the soil by crops, allowing crops to grow faster and bigger so that yields are increased.

What are the main mineral ions provided by fertilisers?

Nitrogen, phosphorus and potassium.

What is a disadvantage of using excess fertilisers?

Excess fertilisers not taken up by crops can get washed into lakes and rivers and cause problems such as eutrophication.

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