The linnaean system of classification groups living organisms into small yet specialised groups, based on their structure and characteristics.
The five kingdoms are:
However through genetic analysis of DNA sequences in the recent years, the current classification system has suggested that organisms should be classified under three domains, rather than five kingdoms.
Through looking at DNA sequences, scientists have found that the closer the species are in relation, the fewer differences can be found within the DNA sequence.
Carl Woese is one of main scientists has updated the classification system, and has divided organisms in the following groups:
- Archaea (primitive bacteria - cells that live in extreme environments, has no nucleus and has an unused section of genes)
- Bacteria (true bacteria - bacteria cells with no nucleus and no unused section of genes)
- Eukaryota__ __(including protists, fungi, plants and animals - they have a nucleus and have an unused section of genes)
Selective breeding is _a method used to improve crop and livestock yield _that is becoming increasingly popular, as it allows people to create species with desirable characteristics.
People need to decide which is the desirable characteristic. Then they would choose parents that display these desirable characteristics, and they would use them to produce the next generation. This process will be repeated.
Tissue culture is a way to__ clone__ plants. Scientists would take small pieces of plants, and are grown in vitro using sterile agar jelly. The jelly would contain plant hormones and nutrients that would allow the plant to grow.
Bacillus thuringiensis is a bacteria that produces a toxin that is poisonous to many insects.
Some crop plants have had the gene inserted into them, to produce the toxin, meaning that they are resistant to insects that may eat the plant. This means that less insecticide has to be used, and there would be a higher yield of crops.
There are, however, also disadvantages. The toxin may also kill harmless insects that were near the plant. The gene may also be transferred into other wild plants, which would then affect the wider community. And, some insects will evolve so that they are resistant to the toxin - eventually, all insects will be, and the gene is useless.
Genetic engineering is the process where scientists modify the genome of an organism in order to introduce desirable characteristics.
This diagram explains the main stages of genetic engineering:
- Restriction enzymes are used to cut open DNA at particular places to leave ‘sticky ends’
- Ligase enzymes are then used to rejoin DNA strands at the ‘sticky ends’
- Plasmids are the loops of DNA that can be found in the cytoplasm of bacteria. They can pass from one bacterial to another - therefore scientists tend to use them as vectors, as they carry DNA into the bacterium.
Benefits and Risks
As the human population increases, we are in demand of agricultural solutions in order to create more crops and animals.
In order to meet food demands,__ __intensive farming methods are commonly used in order to grow more crops. Fertilisers and pesticides are used to encourage more crops to grow.
However, pesticides can harm the environment. The use of herbicides can remove competing plants from the area that the crop is being grown, but it may reduce biodiversity. Farmers can consider using nutrient rich solution rather than soil in order to encourage growth.
Some insecticides that are used do not get broken down. For example, DDT is a chemical that will pass on through the food chain as it passes from insects to birds, then to birds of prey. This would have negative effects on the consumers as they suffer from the bioaccumulation of DDT.
Biological control such as releasing a natural predator into the crop growing area can be used instead of pesticides. However, this affects the natural food web, and the predator itself may cause more issues than the pests that it was sent in to destroy.
- What is genetic engineering?
- Your answer should include: Scientists / Modify / Modification / Genome / Desirable / Characteristics
Explanation: Genetic engineering is a process where scientists modify the genome of an organism in order to introduce desirable characteristics.
- Why is selective breeding becoming increasingly popular?
- Your answer should include: Improve / Improves / Crop / Livestock / Yield / Desirable / Characteristics
Explanation: It improves crop and livestock yield that have desirable characteristics.
Benefits & Risks
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