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biology paper 2
variation and evolution
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Cards (138)
Variation
All the
differences
in the characteristics of individuals in a
population
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Causes of variation
Alleles
inherited
Environmental
factors
Combination
of genes and environment
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Genetic variation
Examples: hair color, eye color
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Environmental variation
Examples: flower color,
language
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Variation from
genes
and
environment
Example:
height
in humans
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Mutation
Random changes to
DNA
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Most mutations have no effect on the
phenotype
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Some mutations can influence the
phenotype
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A small number of
mutations
determine the
phenotype
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Beneficial
mutation
A mutation that leads to a new
phenotype
that is
advantageous
in a changed environment
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Evolution
The change in the inherited characteristics of a population over time through a process of
natural selection
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Natural selection
1.
Genetic
variation within a population
2.
Differential
survival and
reproduction
3. Passing on of
beneficial
traits to offspring
4.
Change
in population over
generations
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Only about
1%
of the total species that have ever lived on Earth are still alive today, the rest are
extinct
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Life first developed on Earth more than
3 billion years ago
, starting with
simple single-celled organisms
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All
species
of living things have evolved from these
simple life forms
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Genetic variation within a population
Rabbits have different
alleles
for
traits
like fur thickness, eyesight, and hearing
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Environment gets colder
Rabbits
with thicker fur are more likely to
survive
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Predator moves into the area
Rabbits
with better eyesight or hearing are more likely to
survive
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Speciation
When two populations of the same
species
become so different that they can no longer interbreed to produce
fertile
offspring, they are considered separate species
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Speciation in rabbits
Normal-sized
rabbits
Pygmy
rabbits
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Selective
breeding
Also called
artificial selection
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Selective
breeding
Humans take
wild
animals and through selective breeding over many generations produce
domesticated
animals with desired traits
Humans take
wild
plants and through selective breeding over many generations produce
domesticated
crops with desired traits
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Humans took wolves
Through
selective breeding
over thousands of years produced the
dogs
that we see today
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Examples of selective breeding
Domestic
dogs selectively bred to have a
gentle
nature
Food crops
such as
wheat
selectively bred to be resistant to disease
Animals such as
cows
selectively bred to produce more
meat
or milk
Certain plants selectively bred to produce
large
or
unusual
flowers
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Selective breeding process
1. Take a
mixed
population
2. Select the
largest
male and female
3.
Breed
these together
4. Select the
largest
offspring
5. Breed the
largest
offspring together
6.
Repeat
over many generations
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Inbreeding
can cause some breeds to be prone to disease or
inherited defects
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Many
dog breeds develop
inherited disorders such as joint problems, heart disease or epilepsy due to selective breeding over hundreds of generations
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Genetic engineering
The process of modifying the
genome
of an organism by cutting out
genes
from one organism and transferring them to cells of a different organism
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Genetic engineering
1. Identify the
gene
to
transfer
2. Use
enzymes
to
isolate
the gene
3. Transfer the gene into a
plasmid
or
virus
(vector)
4. Transfer the vector into the
cells
of the
target
organism
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Genetic engineering in medicine
Used to produce human
insulin
in bacteria for treating type 1
diabetes
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Genetic engineering in agriculture
Used to create
genetically modified
(GM) crops that have higher yields, resistance to disease/insects, or tolerance to
herbicides
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Spraying herbicides on GM crops
Does not
harm
the GM crop
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Some people question the
safety
of GM crops, such as potential harm to insects or wildflowers, and want more research on
health effects
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Gene therapy
The use of
genetic
engineering to treat
inherited
disorders in humans
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The long-term effects of gene therapy are
not
known, such as the
potential
effects on other genes
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Genetic engineering
is done at an early stage of an organism's development, such as the embryo stage, to ensure all cells receive the
transferred gene
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Cloning
Producing
genetically identical
organisms
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Humans have been
cloning plants
for many
years
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Advantage of cloning plants
The clone is
genetically identical
to the original plant, so we know exactly what the clone's characteristics will be
Offspring from
sexual reproduction
would be different
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Cloning plants by cuttings
1. Take a small piece of the
plant
2. Dip the end in
rooting
powder (contains plant
hormones
)
3. Roots develop, producing a
genetically identical clone
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