B7 Flashcards
Variation?
Differences in the characteristics of individuals in a population
3 causes of variation?
alleles - genetic e.g. hair and eye colour
Environment - language
a mix of both - height
Mutation?
random changes in dna
What can very rarely happen due to mutation?
a new phenotype leading to a change in species
what have all species of living things evolved from?
Simple life forms e.g. single cells
Called natural selection
what is the process of natural selection?
for example, rabbits that have inherited the allure for thicker are more likely to survive in the cold temperature than rabbits with thinner fur which means they are more likely to go on to reproduce and they’re offspring could inherit the alleles for thicker fur and they are more likely to survive and reproduce
How do two separate species occur?
Sometimes two populations of one species can become so different in a phenotype that they can no longer into breed to produce fertile offspring
How did dogs occur and why?
thousands of years ago humans realise that wolves actually very useful animals as they provide protection, warmth and company. so humans took wolves and using the process of selective breeding over thousands of years created dogs. 
why have certain plants been selectively bred?
To produce large and unusual flowers
Why have domestic dogs been selectively bred?
To have a gentle nature
Why have food crops such as wheat been selectively bred?
To be resistant to disease
why have animals such as cows been selectively bred?
To produce more meat or milk
how is selective breeding carried out?
For example, if scientist wanted to breed large cows for meat, first we select the largest male and female, we then breed these together to produce offspring. We continue doing this over many generations until all the offspring are large.
what is a problem with selective breeding?
If we breed together closely related animals or plants, then we can get inbreeding
What could inbreeding lead to?
Disease or inherited defects
Evolution?
the change in the inherited characteristics of a population over time through natural selection
what happens in genetic engineering?
genes from one organism, e.g. humans I’ll cut out and transferred to cells of a different organism e.g. bacteria
The genome of the bacteria is modified and now includes a human gene
what is an example of genetic engineering?
For example insulin, which is a hormone involved in blood glucose regulation in humans. bacteria have been genetically modified to contain the human insulin gene and now these bacteria produce human insulin 
Another example of genetic engineering for plants?
we can also transfer genes into plants to produce genetically modified crops, which produce a greater yield than normal crops. we can also make them resistant to disease or insect attack.
2 possible problems with genetically modified crops?
could they be harmful to insects or wild flowers?
could they be unsafe to eat?
gene therapy?
genetic modification is currently being explored as a way to treat inherited disorders in humans
steps of genetic engineering?
1) identify the gene that we want to transfer
2) then use ends arms to isolate the gene
3) transfer the gene into a plasmid or virus
4) the desired gene is transferred into the cells of the target organism
why do we always transfer the gene at an early stage in the organisms development?
to make sure that all of the cells receive the transferred gene so that the organism develops with the characteristic that we want
how do fossils provide really good evidence for evolution?
because they are the remains of organisms from millions of years ago which are found in rocks
