Natural Selection And Genetic Modification Flashcards
What is natural selection?
The process by which the advantageous traits are passed on in genes gradually increasing a population over time.
Which scientist came up with the idea of natural selection?
Alfred Russel Wallace
What is evolution?
A gradual change in species over time.
Which scientist developed the theory of evolution by natural selection?
Charles Darwin
What does it mean when bacteria are labelled as resistant?
This is when they are not killed by antibiotics that were previously effective against them.
How do bacteria reproduce?
Bacteria reproduce at a fast rate.
How do mutations during bacterial reproduction contribute to antibiotic resistance?
Mutations during reproduction can result in new genes, such as the gene for antibiotic resistance, leading to the creation of a new strain.
What is selection pressure in the context of antibiotic resistance?
Exposure to antibiotics creates a selection pressure, as bacteria with antibiotic-resistant genes survive while those without die.
How does the presence of antibiotic resistant bacteria support Darwin’s theory of natural selection?
Antibiotic-resistant bacteria survive and reproduce, passing on the advantageous gene to their offspring, which supports Darwin theory of natural selection.
Why does the population of antibiotic increase rapidly?
People are not immune to these new resistant bacteria and there is no treatment for it.
Describe the evidence for human evolution based on fossils.
Ardi from 4.4 million years ago
Lucy from 3.2 million years ago
Leakey’s discovery of fossils from 1.6 million years ago
What types of tools did Homo Habilis use in the early stone age?
1.5 millions years ago
Used basic tools created by smashing rocks together, used for simple uses such as cracking nuts.
What types of tools were used in the late stone age by modern Homo Sapiens?
40,000 years ago
Used pointed arrowheads, spears and hooks, enabling more advanced tasks like catching fish.
How can the age of these tools be determined? (2)
- Radiometric carbon dating - by looking at the natural radioactive decay of an isotope of Carbon we can estimate how long age an organism lived.
- Stratifying rock layers - looking at the layer of sediment where the rock was found. Each layer of sediment must have been formed at the same time. Therefore we can date once-living fossils in this layer and use this to estimate when the tools were formed.
Describe how the anatomy of the pentadactyl limb provides scientists with evidence for evolution
A pentadactyl limb is a limb with five digits, which can be seen in a number of organisms, implying that they all come from a common ancestor.
This could have been due to different selection pressures within different environments.
Name the five kingdoms in the Five Kingdoms classification old system
Animals
Plants
Fungi
Prokaryotes
Protists (e.g. algae)
Each kingdom is then subdivided into a phylum, class, genus, order and species.
What led to the change to the Three-domain system instead?
The improvement of the microscope and increased knowledge of biochemistry (e.g. RNA sequence analysis) found that some species were more distantly related than the first thought.
Name the Three-domain system groups
Archaea: primitive bacteria which live in extreme environments
Bacteria: true bacteria
Eukaryota: organisms who have a nucleus
What is selective breeding?
When humans choose which organisms to breed in order to produce offsprings with certain desirable characteristics.
What is inbreeding?
Breeding those with similar desirable characteristics means it is likely you are breeding closely related individuals, reducing the gene pools and increasing the likelihood of genetic defects in the offspring.
What is tissue culture?
A method of culturing living tissue within a growth medium. This is especially useful for plants where farmers can produce an entire field of identical cloned crops using just a small cutting.
How is tissue culture performed? (4)
- Take the plant that you would like to clone - e.g one with desirable characteristics.
- Using tweezers, remove a piece of tissue from a fast-growing region of the plant- e.g the root or shoot tip.
- Using aseptic technique (maintaining sterile conditions), place the tissue on a special growth medium (containing hormones and nutrients).
- Once the tissue has developed enough, it can be transferred to compost for further growth.
Describe benefits of tissue culture (3)
- Produces lots of offspring with a specific desirable feature.
- Increasing the number of crops resistant to bad weather, for example can increase crop yields.
- Can help extremely endangered species, or even bring back species that have become extinct.
Describe risks of tissue culture (3)
- The gene pool is reduced through producing clones, meaning it is less likely that the population will survive if a disease arises with low diversity in the population.
- Clones have a low survival rate and tend to have some genetic problems.
- It may lead to human cloning.
What is genetic engineering?
Modifying the genome of an organism by introducing a gene from another organism to give a desired characteristic.
What are the stages of genetic engineering to create Insulin?(5)
- The human insulin gene is cut out using restriction enzymes. This leaves sticky ends.
- The plasmid DNA is removed from the bacterium and some restriction enzymes are used to cut it and leave sticky ends.
3.Ligase enzyme is used to join the insulin gene and plasmid DNA together as their sticky ends are complementary. It is now called recombinant plasmid (DNA). - The recombinant plasmid is inserted into a bacterium.
- The bacteria is multiplied (grown) and purified to extract in insulin.
What are some benefits of genetic engineering? (3)
- In medicine to mass produce certain hormones in microorganisms (bacteria and fungi).
- In agriculture it can be used to improve yields by: improving growth rates, allow the crops to grow in different conditions, introducing modifications that allow plants to make their own pesticide.
- Crops with extra vitamins can be produced in areas where they are difficult to obtain.
What are some risks of genetic engineering? (3)
- GM crops might have an effect on wild flowers and therefore insects - GM crops are infertile and these genes could spread into wild plants, leading to infertility in other species, which affects the entire environment. Also, growing with herbicides and pesticides can kill insects and other plants, which would reduce biodiversity.
- People are worried that we do not completely understand the effects of GM crop on human health. (no evidence for this).
- They pose a selection pressure, which could lead to increased resistance in other species, creating super weeds and pests.
What are Bt crops and how can their toxins be used?
Produces a toxin that is lethal to insects.
Can be sprayed onto crops or genetically engineered into crop plants.
What is a vector?
A carrier used to transfer a gene from one organism to another.
What are some agricultural solutions to cope with the demands of growing human population? (2)
- Fertilisers - they provide useful nutrients to plants making them more resistant to environmental conditions and able to grow faster and larger, resulting in increased crop yields. However, excess fertiliser can often run off into rivers, killing fish and other wildlife and affecting biodiversity.
- Biological control - this is the use of certain species to control population of other species. However this reduces biodiversity.
What are some benefits of selective breeding? (2)
- It is possible to greatly increase the yield of a particular crop by selectively breeding only individuals that produce higher quality or a larger mass of food.
- Individual plants or animals can be bred to be resistant to a particular disease which could increase crop yield.
What are some disadvantages of selective breeding? (3)
- Alleles that may be useful in the future can be lost.
- If organisms are genetically similar, all may be affected by a change in condition.
- Animal welfare
