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Biology PMT > 6.2 Variation and Evolution > Flashcards

6.2 Variation and Evolution Flashcards

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1
Q

What is variation?

A

Differences in the characteristics of individuals in a populations is called variations.

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2
Q

What are the two causes of variation within a species?

A
  • Genetics
  • Environments
  • A mixture of both
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3
Q

What is genetic variation?

A

Variations in the genotypes of organisms of the same species due to the presence of different alleles.

Creates differences in phenotypes

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4
Q

What creates genetic variation in a species?

A
  • Spontaneous Mutations
  • Sexual reproduction
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5
Q

What is a mutation?

A

A random change to the base sequence in DNA which results in genetic variants.
They occur continuously.

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6
Q

State the three types of gene mutation

A
  • Insertion
  • Deletion
  • Substitution
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7
Q

How may a gene mutation affect an organism’s phenotype? (3)

A
  • Neutral Mutation does not change the sequence of amino acids. Protein structure and function same .No effect on phenotype
  • Mutation may cause a minor change in an organism’s phenotype e.g. change in eye colour.
  • Mutation may completely change the sequence of amino acids. This may result in a non-fictional protein. Severe changes to phenotype.
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8
Q

What is the consequence of a new phenotype caused by a mutation being suited to an environmental change?

A

There will a rapid change in the species.

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9
Q

What is evolution?

A
  • A gradual change in the inherited traits within a population overtime.
  • Occurs due to natural selection which may result in the formation of a new species.
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10
Q

Outline the theory of natural selection.

A

All species of living things have evolved from simple life forms that first developed more than 3 billion years ago.

  1. Genetic Variation exists due to spontaneous mutations.
  2. Selection pressures (e.g. competition, disease) exist
  3. Random mutation gives an organism a selective advantage.
  4. Organism is better adapted to the environment and survives.
  5. Organism reproduces, passing on its beneficial alleles.
  6. Frequency of advantageous alleles increase
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11
Q

How do two populations become different species?

A

When their phenotypes become different to the extent that they no longer interbreed to produce fertile offspring.

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12
Q

What is selective breeding?

A

The process by which humans artificially select organisms with desirable characteristics and breed them to produce offspring with similar phenotypes.

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13
Q

Outline the main steps involve in selective breeding.

A
  1. Identify a desired characteristic e.g. disease resistance.
  2. Select parent organisms that show the desired traits and breed them together.
  3. Select offspring with the desired traits and breed them together.
  4. Process repeated until all offspring until all offspring have the desired traits
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14
Q

Examples of characteristics selected for in selective breeding

A
  • Disease resistance in crops
  • Higher milk or meat production in animals
    -Gentle nature in domestic dogs
    -Large flowers
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15
Q

What is the main advantage of selective breeding?

A

Creates organisms with desirable features:

  • Crops produce a higher yield of grain
  • Cows produce a greater supply of milk
  • Plants produce larger fruit
  • Domesticated animals
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16
Q

Other than in agriculture, where else is selective breeding useful?

A
  • In medical research
  • In sports e.g. horse racing
17
Q

Outline the disadvantage of selective breeding (4)

A
  • Reduction in the gene pool (which becomes especially harmful if sudden environment change occurs).
  • Inbreeding results in genetic disorders
  • Development of other physical problems e.g. respiratory problems in bulldogs.
  • Potential to unknowingly select harmful recessive alleles
18
Q

What is genetic engineering?

A
  • The modification of the genome of an organism by the insertion of a desired gene from one organism - genes from chromosomes of human and other organisms can be ‘cut out’ and transferred to cells of other organisms.
  • Enables the formation of an organism with beneficial characteristics
19
Q

Give an example of uses for genetically modified plants

A
  • Disease resistance
  • Produce larger fruits
20
Q

What is a use for genetically modified bacteria cells?

A

To produce human insulin to treat diabetes mellitus.

21
Q

What are the positives of genetic engineering (3)

A
  • Increased crop-yields for growing population e.g. herbicide-resistance, disease-resistance.
  • Useful in medicine e.g. insulin-producing bacteria, anti-thrombin in goat milk, possibly to overcome some inherited disorders
  • GM crops produce scarce resources e.g. GM golden rice produces beta-carotene
22
Q

Describe the risks of genetic engineering (4)

A
  • Long-term effects of consumption of GM crops unknown.
  • Negative environmental impacts e.g. reduction in biodiversity, impact on food chain, contamination of non-GM crops forming ‘superweeds’
  • Late-onset health problems in GM animals.
  • GM seeds are expensive. LEDCs may be unable to afford them or may become dependent on businesses that sell them.
23
Q

What is the name for crops that have had their genes modified?

A

Genetically modified (GM) crops e.g those modified to be resistant to insect attacks and herbicides

24
Q

What is Bacillus thuringiensis (Bt)?

A
  • Insect larvae are harmful to crops
  • Bt is a bacterium which secretes a toxin that kills insect larvae
25
Q

How is genetic engineering used to protect crops against insects?

A
  • The gene for toxin production in Bt can be isolated and inserted into the DNA of crops
  • Bt crops now secrete the toxin which kills any insect larvae that feed on it.
26
Q

What are the benefits of Bt crops? (3)

A
  • Increased crop yields (fewer crops damaged).
  • Lessens the need for artifical insecticides
  • Bt toxin is specific to certain insect larvae so is not harmful to other organisms that ingest it.
27
Q

What are the risks of Bt crops? (3)

A
  • Long term effects of consumption of Bt crops unknown.
  • Insect larvae may become resistant to the Bt toxin
  • Killing insect larvae reduces biodiversity

Biology PMT (24 decks)

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