Topic 6- Genetics and evolution Flashcards
Outline the theory of evolution by natural selection
. Individuals of a species show a wide range of variation for a charachteristic
.Those with the charachteristic most suited to the environment will survive breed most successfully
.The desirable charachteristic that has enabled the individuals to survive are passed onto their offspring
Why was darwins theory of evolution not accepted initially
. The mechanism of variation and inheritance was not known at the time
what is speciation
The formation of new species , when two populations become so varied that they cannot interbreed to produce fertile offspring
What is a species
A group of organisms with similar charachteristics which are able to interbreed to produce fertile offsrping.
Why is genetic variation important in speciation
Genetic variation produces phenotypic variation, some of which are better suited to the environment and are selected for.
State two types of evidence used to show evolution
.Fossils
.Anitbiotic resistance in bacteria
How are fossils formed
.From parts of organisms that have not decayed . But replaced by mineral ions
. Fossils can be formed when traces of organisms is buried, in a soft material like clay hardens and leaves an impression
. When organisms do not decay because one or more of the conditions needed for decay is absent.
Why are there few traces of early-life forms left behind
They are mostly soft-bodied
How do fossils act as evidence for evolution
Scientists can identify the ages of the fossils and use them to show how organisms change over time
What do branches in evolutionary trees indicate
Where speciation has occurred
What is extinction
When there are no individuals of a species left
State the factors that may lead to extinction
.New disease
.predation
.competition
.Changes to the environment
What enables bacteria to evolve quickly
The fast rate of there reproduction
outline the process of anitbiotic resistance evolving
.Mutations occur in bacteria producing genetic variation
. Certain strains are resistant to antibiotics and are not killed when the antibiotic is applied
. Resistant strains survive and reproduce
. Over time , the population of the reisitant strains increase
WHy are resistant strains of bacteria dangerous
People have no immunity to them and there is no effective treatment
