Natural Selection, Speciation & Evolution Flashcards
(47 cards)
evolution
Evolution is the change is species over time. It is usually very gradual, but in the correct circumstances, can be reasonably rapid.
what does evolution lead to:
one species forming 2 (or more) new species
OR
a change in a species without the formation of a new species
how does evolution occur
Evolution occurs in a species NOT in an individual
it what two ways does evolution occur
convergent evolution
divergent evolution
convergent evolution
(unrelated species become more similar)
occurs when different species
change in a very similar way
due to the species experiencing
the same selection pressures.
divergent evolution
(one species changes into two species)
occurs when different adaptations occur (and are selected for) in separate populations of the same species. This normally occurs when the populations live in areas with different environments
How do we know that evolution occurred?
a) we can see progressive change through fossils
b) many species have vestigial structures.
what does Charles Darwin say about evolution
- proposed that evolution
occurs through the process of
Natural Selection. - this theory relies on naturally
occurring variation within
populations that provides
some of the organisms with a
survival advantage.
why is charles darwin important in this topic
his theory of evolution is most accepted
what did his theory rely on and how was it veiwed?
- relied on favourable traits being inherited (his theory was
formed long before knowledge of DNA/inheritence) - was viewed as radically “anti-church”
do adaptations occur because a species needs them, why?
It is important to realise that adaptations don’t occur because a species needs them. They arise through chance mutations and they help the individuals of that species survive.
what is a reason that some species go extinct
Plenty of species have gone extinct though - largely due to the fact that the DNA didn’t mutate in a way that provided a benefit (or because the environment changed too quickly for the allele frequency for the beneficial adaptation to increase).
Natural Selection
Natural Selection is a theory used to explain how the frequency of alleles changes within a popuation.
what is needed for natural selection to occur
For natural selection to occur, there must be variation within the population. This variation occurs by chance through mutation which creates new alleles.
what happens when an mutation gives an advantage in its habitat
If the mutation gives an organism an advantage in its habitat, it is more likely to survive, reproduce and pass the beneficial gene on to its offspring
what happens when a trait continues to be beneficial
If the trait continues to be beneficial, its presence in the population will increase over generations
what does the process of natural selection result in
The process of natural selection results in some individuals having more offspring than others.
what is a selection agent + egs
The factor that acts on the population and favours some individuals more than others is known as the selection agent. It can include climate, predators, food availability or disease.
how is Charles Darwins’ theory described
Although he did not come up with the phrase, the term “survival of the fittest” is often used to describe Charles’ Darwin’s theory of natural selection.
what does the survival of the fittest phrase mean
The “fittest” organisms in this sense are the ones that are best adapted to their environment and are most likely to survive and reproduce
why did Alfred Wallace receive no credit for the same theory?
Darwin was actually lucky to be credited
with this theory because Alfred Wallace
came up with the same theory at the
same time but Darwin’s book was
published first so he got all of the glory.
what leads to the formation of a new species
an important process in evolution is speciation which can lead to the formation of a new species
Whether two individuals are from the same species used to be determined by the following rule:
if they could breed together under natural conditions as produce a fertile offspring, then they are of the same species.
how does DNA tell us if two individuals are the same species
Now they also use DNA to test whether two individuals are the same species. >1% difference is usually regarded as different species.
