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Paper 2
6. Inheritance, variation and evolution
Genetics and Evolution
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Created by
Christelle Nacino
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Cards (23)
Outline the theory of evolution by natural selection
1. Individuals of a species show a wide range of
variation
for a
characteristic
2. Those with the characteristic most suited to the
environment
will survive
breed
most successfully
3. The
desirable
characteristic that has enabled the individuals to survive are passed onto their
offspring
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Lamarck's
theory of
inheritance
That changes during the lifetime of an organism can be
inherited
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Speciation
The formation of a new
species
, when two populations become so varied that they cannot interbreed to produce
fertile
offspring
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Species
A group of organisms with similar characteristics which are able to
interbreed
to produce
fertile
offspring
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Outline the process of speciation through geographic
isolation
1. Two populations of the same species are separated geographically
2. Geographic
isolation
prevents interbreeding and mixing of genes between the populations
3. Due to different selection pressures, different
mutations
occur producing different
phenotypes
in each population
4. Over time, the two populations may
evolve
so that they are not able to
interbreed
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Genetic variation
Important in speciation as it produces
phenotypic
variation, some of which are better suited to the
environment
and are selected for
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How did Mendel study inheritance
Through
carry breeding
experiments on plants and analysing the
ratio
of characteristics in offspring
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Why was Mendel's work not recognised until after his
death
?
He could not explain the mechanism of inheritance, as chromosomes were only discovered after his death.
It was not communicated well to other scientists and not published in a reputable scientific journal.
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He could not explain the mechanism of
inheritance
, as
chromosomes
were only discovered after his death
View source
It was not communicated well to other
scientists
and not published in a
reputable
scientific journal
View source
Evidence used to show evolution
Fossils
Antibiotic
resistance in
bacteria
View source
How are fossils formed
1. Parts of organisms that have not
decayed
due to conditions needed for decay being
absent
2. Parts of organisms that have been
replaced
by
minerals
as they decayed eg. bones
3. Traces of organisms are preserved, covered in
sediment
and becoming
rock
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Why are there few traces of early life-forms left behind?
Because they were mostly soft-bodied
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How fossils act as evidence for evolution
Scientists can identify the
ages
of the fossils and use them to show how
organisms
change over time
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Evolutionary trees
Branches
indicate where
speciation
has occurred
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Extinction
Where there are no individuals of a species still
alive
View source
Factors that may lead to extinctions
New disease
Predation
Competition
Changes
to the
environment
Catastrophic
events
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Why bacteria evolve quickly
The fast rate of their
reproduction
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Outline the process of antibiotic resistance bacteria evolving
1.
Mutations
occur in bacteria producing
genetic variation
2. Certain
strains
are resistant to antibiotics and are not killed when the
antibiotic
is applied
3.
Resistant
strains survive and
reproduce
4. Over time, the population of the
resistant
strains
increase
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Why resistant strains of bacteria are dangerous
People have no
immunity
to them and there is no
effective
treatment
View source
What can be done to reduce the rate of development of antibiotic resistant bacteria
Refrain
from
inappropriately prescribing
antibiotics eg. for viral diseases
Patients should complete the
prescribed course
of antibiotics
Restrict
agricultural
uses of antibiotics
View source
Why is it difficult to keep up with emerging
resistance
strains
View source
Why was
Darwin's theory of evolution
not accepted initially?
Most people believed that God made everything
Insufficient evidence to prove the theory
The
mechanism of variation and inheritance
was not known at the time
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