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Topic Four: Biodiversity and Natural Resources
Variety of Life
Natural Selection
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What was Darwin's theory of natural selection?
If an
organism changes
during it's
life
in order to
adapt
to it's
environment
, those changes are passed onto it's
offspring
What happens during natural selection?
A population has
genetic variation
and
mutations
lead to
new alleles.
A
change
in the
environment
leads to a
change
in the
selection pressures
on the
population
An
allele
that was of no
advantage
becomes
favourable
Organisms with the
allele
are more likely to
survive
,
reproduce
and pass on the
advantageous
allele to their
offspring
The
offspring
are more likely to have the
advantageous
allele so its
frequency increases
in the population
Which main words need to be included in an answer on Natural Selection?
mutation
/ variation
advantage
(selection pressure)
survival
reproduction
greater
allele frequency
What is selection pressure?
Environmental
factors that influence the
survival
of individuals, leading to certain
traits
becoming more or less
common
in a
population
over time.
What causes speciation?
Natural selection-
leads to the
formation
of a new
species
How can speciation occur?
Through species
isolation
What does speciation provide evidence for?
Natural selection
Which factors lead to sexual reproduction of fertile offspring?
Looks ie
colourful
feathers
Behaviour
ie
bird
songs
Time
/
seasonality
ie pollination season
Anatomy
Gamete
compatibility
Hybrid
inviability
Hybrid
being
fertile
What can cause speciation?
Reproductive
isolation due to
geographical
barriers/
changes
How did the experiment result in
speciation
(EQ)?
The population was
split
up and
geographically
separated, leading to no
gene
flow between the two groups.
Mutations
/
gene
variation led to a change in the
allele
frequencies between the populations
The species became reproductively
isolated
and their
offspring
could no longer
breed
to make
fertile
offspring
Why may populations not be able to breed together?
Mechanical
changes/ Physical
incompatibility
Seasonal
changes
Behavioural
changes
What
is a species?
A group of
organisms
that can breed to produce
fertile
offspring
What
is the heterozygozity index?
A measure of
genetic diversity
within a population.
What
is species richness?
The different
number
of species in a
habitat