B2 VARIATION AND EVOLUTION Flashcards
variation?
differences in the characteristics of individuals in a population.
what is genetic causes caused by?
mutations
mutations?
random changes of DNA
take place all the time.
have no effect on the phenotype
some mutations can influence the phenotype e.g alleles for tallness may lead to tallness if a persons diet is suitable
small number of mutations determine the phenotype e.g eye colour
beneficial phenotypes?
mutations can lead to a new phenotype.
it can be beneficial if the environment changes , this can lead to a rapid change in species
an example of beneficial phenotype?
in the 1950s , virus spread to the uk and killed over 99% of wild rabbits , howver a mutations occurred which made the surviving rabbits resistant to the virus , this mutations gave the rabbits a new phenotype
when did life first developed on earth?
3 billion years ago
evolution by natural selection?
all species of living things have evolved from these simple life forms
natural selection?
individuals within a species show variation because of differences in their genes.
individuals with the characteristics best suited to the environment are more likely to survive and reproduce.
the genes that have helped these individuals to survive are then passed onto the next generation.
who created the theory of evolution?
Charles Darwin
why did many people reject Charles’ Darwin theory?
we didn’t know about DNA.
how characteristics were inherited and his theory went against religious ideas.
what is evolution?
change in the inherited characteristics of a population over time through a process through natural selection
what is speciation?
population of organisms that can interbreed to produce fertile offspring
if two populations of one species become so different in phenotype that they can no longer interbreed to produce fertile offspring they have formed two new species, this can happen if the two populations are isolated geographically.
what are 4 examples of selective breeding (artificial selection) ?
disease resistance in food crops
animals which produce more meat or milk
domestic dogs with a gentle nature.
large or unusual flowers.
what is artificial selection? (selective breeding)
process by which humans breed plants and animals for particular genetic characteristics, it can lead defects due to inbreeding
stages of artificial selection?
parents are chosen with the desired characteristics from a mixed population.
they are bred together.
from the offspring those with the desired characteristics are bred together.
this continues over many years generations until all the offspring show the desired characteristics.
