B14 - variation and evolution fact test Flashcards
what is variation
the differences in phenotypes in a population
what differences can variation be due to
- the genes they have inherited (genetic causes)
- conditions in which they have developed (environmental)
- combination of genes and the environment
what do all variants arise from
mutations
most have no effect on the phenotype but some influence the phenotype and very few determine phenotype
what is evolution
evolution is a change in the inherited characteristics of a population over time through a process of natural selection which may result in the formation of a new species
how does evolution by natural selection happen
- there is variation between organisms
- the best adapted have an advantage
- these organisms are more likely to survive and reproduce
- they pass on useful alleles to offspring
- the useful characteristics becomes more common in the population
what is natural selection described as
survival of the fittest because if you have an advantage, you are more likely to survive and reproduce, passing on your advantageous alleles to your offspring
when are 2 organisms from the same ancestor become classed as different species
when they become so different in phenotype that they can no longer interbreed to produce fertile offspring
what is selective breeding
(artificial selecting) is the process by which humans breed plants and animals for particular genetic characteristics
what are the steps involved in selective breeding
- decide desirable characteristics
- choose parents with desirable characteristics and breed them together
- select best offspring and breed them together
- repeat the process continuously over many generations until all of the offspring show desired characteristics
what are some characteristics desired in animals
- produce more meat or milk
- animals with gentle temperaments
- aesthetic
- without specific genetic defects
what are some characteristics desired in food crops
- disease resistant
- bigger yield of fruit
what are the characteristics desired in plants
big or unusual coloured flowers
what can selective breeding lead to
‘inbreeding’ where some breeds are particularly prone to disease or inherited defects
what is genetic engineering (genetic modification)
modifying the genome of an organism by introducing a gene from another organism to give a desired characteristic
what have plant cells been engineered for
- resistant to diseases, pests and herbicides
- produce bigger better fruits/increased yield of fruit
- have more nutritional value e.g golden rice
what have bacterial cells been engineered to produce
useful substances such as human insulin to treat diabetes
what is the process of genetic engineering
- genes from chromosomes are cut out using restriction enzymes leaving sticky ends (short sections of exposed, unpaired bases)
- a virus or bacterial plasmid is cut using the same restriction enzyme to also create sticky ends. this also creates an antibiotic marker gene
- the loop and gene sticky ends are joined together by DNA ligase enzymes
- the combined loop is placed in a vector, such as a bacterial cell and then allowed to multiply as it will now contain the modified gene
in plants, where is the vector placed into
meristematic cells which can then produce identical copies of the modified plant
what are concerns about genetically modified crops
- effect on populations of wildflower and insects
- some people feel the effects of eating GM crops on human health have not been fully explored
how is genetic modification used in medicine
- may be possible to cure genetic disorders
- this is called gene therapy and involves transferring normal genes into patients so the correct proteins are produced
what are the benefits of genetic modification
- faster and more efficient way of getting the same results as selective breeding
- improve crop yields or crop quality, which is important in developing countries. this may help reduce hunger around the world
- introduce herbicide resistance, which results in less herbicides being used as weeds are quickly and selectively killed
- insect and pest resistance can be developed and inserted into the plant . the plant produces toxins which would discourage insects from eating the crop
- sterile insects could be created such as a mosquito. they would breed, leading to infertile offspring. this may help with the spread of diseases, such as malaria, dengue fever and the zika virus
what are the risks of genetic modification
- transfer of the selected gene into other species, what benefits one plant could harm another
- some believe it’s not ethical to interfere with nature in this way
- GM crop seeds are often more expensive and so people in developing countries can’t afford them
- GM crops could be harmful e.g. toxins from the crops have been detected in some people’s blood
- pollen produced by the plants could be toxic and harm insects that transfer it between plants
what are the 4 types of cloning methods
cuttings, tissue culture, adult cell cloning and embryo transfers
what are cuttings
cuttings from a plant can be used to make identical new plants
