b14 - variation and evolution Flashcards
give three reasons for variation
- differences in the genes they have inherited
- conditions in which they have developed
- combination of genetic and environmental causes
what controls appearance of an individual?
genes
how might plants be affected?
- lack of light
- nutrients
- space to grow
what happens if a plant is deprived of nutrients?
it cannot grow as well as other plants with same genes growing in better conditions
how would a pregnant mother smoking and drinking affect baby?
may have low birthweight
why would individual organisms show a wide range of variation?
due to differences in genes
what do organisms in a population compete for?
- food
- shelter
- predators
- mates
which organisms are more likey to survive?
- if they are more suited to a certain environemt
- more likely to breed successfully
define a mutation
when a gene changes and becomes a new form
where are mutations important?
give an example
- in natural selection if environment changes
- rabbit disease mxyomatosis killed most rabbits in UK
- some had a mutated disease that gave immunity so these ones survived then bred and rabbit population became immune to disease
how does a new species evolve through natural increase?
if a population changes so much so they can no longer breed with another population to produce fertile offspring.
- this takes millions of years
when could evolution of a population occur in a relatively short time?
e.g if bacerium has a mutation to make it resistant to antibiotics then this mutation can spread rapidly through population until all bacteria are resistant
give key steps of natural selection
mutation of gene -> advantage -> to survival -> breed -> pass on genes
give three examples of animals or plants with desired characteristics
- cows that produce the most milk to breed next generation of dairy cattle
- high yielding cows may be crossed with bulls of mis temperament
- seeds are selected from plants with the biggest grain to grow next crop
define selective breeding
farmers and breeders select animals or plants with desired characteristics
give some features that selective breeding is used to select for
- disease resistance in food crops or garden plants
- animals producing more meat or milk
- domestic dogs and farm animals with gentle nature
- large, unusual, brightly coloured or heavily scented flowers
why are some animals cross-bred?
- two desireable traits
- offspring that shows both of favourable features will be selected
give some limitations of selective breeding
- greatly reduces number of alleles in population
- less variation between individuals in population
- new disease or climate change could destroy whole population
- inbreeding of related organisms, such as breeds of dogs, led to inherited defects
define genetic engineering
involving change of genetic make up of an organism
define process of genetic engineering
1) desired gene ‘cut out’ of chromosome using an enzyme
2) then inserted into chromosome of another organism, vector transfers gene
what happens when human gene produces to produce insulin is inserted into bacteria?
bacteria produces large quantities of insulin to treat diabetes
how are genes cut out of chromosomes to make an insulin gene?
cut out of DNA by an enzyme
what is a crop with changed genes referred to?
- genetically modified, GM crop plants
what can a GM crop do?
make its own pesticide, or hebicide resistant, usually has increased yields
