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GCSE AQA biology > Topic 6- Inheritance, variation & evolution: > Flashcards

Topic 6- Inheritance, variation & evolution: Flashcards

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1
Q

Charles Darwin:

A
  • Scientist
  • Put forward the theory of evolution
  • Supported by experimentation and his knowledge of geology and fossils
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2
Q

Theory of evolution:

A
  • Variation exists within species as a result of mutations in DNA
  • Organisms most suited to the enviroment are more likely to survive and reproduce- SURVIVAL OF THE FITTEST.
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3
Q

What is variation?

A

Differences in characteristics of a population.

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4
Q

What are the causes of variation within a species?

A
  • Genetics
  • Enviroment
  • A mixture of the both
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5
Q

What is genetic variation?

A
  • Variation in the genotypes of organisms of the same species due to the presence of different alleles
  • Creates difference in phenotypes
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6
Q

What creates genetic variation in species?

A
  • Spontaneous mutations
  • Sexual reproduction
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7
Q

What is a mutation?

A

A random change to the base sequence in DNA which results in genetic variants. They occuur continouosly.

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8
Q

State the three types of gene mutation.

A
  • Insertion
  • Desertion
  • Substitution
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9
Q

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

A
  • Neutral mutation- does not change the sequence of amino acids. Protein structure and function same. No effect on phenotype.
  • Mutation may cause a 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-functional protein. Severe changes to phenotype.
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10
Q

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

A

There will be a RAPID change n the species.

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11
Q

What is evolution?

A
  • A gradual change in the inherited traits within a population over time.
  • Occuurs due to natural selection which may result in the formation of a new species.
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12
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 mutation
  2. Selection pressures (e.g. competition, disease) exist
  3. Random mutation give an organism selective advantage
  4. Organism is better adapted to the enviroment and it survives
  5. Organism reproduces, passing on it’s beneficial alleles
  6. Frequency of advantgaeous alleles increases.
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13
Q

How do two populations become different species?

A

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

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14
Q

What is selective breeding?

A

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

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15
Q

Outline the main steps involved in selective breeding?

A
  1. Identify a desired characteristics e.g. disease resistance.
  2. Selct parent organisms that show that desired traits and breed them together.
  3. Select offspring with desired traits and breed them together.
  4. Process is repetated until all offspring have the desired traits.
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16
Q

Give 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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17
Q

What is the main advantage of selective breeding?

A

Creates organisms with desireable features:
* Crops produce a higher yield of grain
* Cows produce greater supply of milk
* Plants produce larger fruit
* Domesticated animals

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18
Q

Other than agriculture, where is selective breeding useful?

A
  • In medical research
  • In sports, e.g. horse racing
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19
Q

Outline the disadvantages of selective breeding. (4)

A
  • Reduction in the gene pool (which becomes especially harmful if sudden enviromental change occurs.)
  • Inbreeding results in genteic disorders
  • Development in other physical problems e.g. respiartory problems in bulldogs
  • Potential to unkowingly select harmful recessive alleles.
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20
Q

What is genetic engineering?

A
  • The modification of the genome of an organism by the insertion of a desired gene from another organism- genes from chromosmes of humans and other organisms can be ‘cut out’ and transferred to cells of other organisms.
  • Enables the formation of an organism with beneficial characteristics.
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21
Q

Give an example of uses for genetically modified plants.

A
  • Disease resistant
  • Produce larger fruits
22
Q

What is a use for gm bacteria cells?

A

To produce human insulin to treat diabetes mellitus.

23
Q

Describe the benefits of genetic engeneering. (3)

A
  • Increased crop yields for growing population e.g. disease resistant
  • Useful in medicine e.g. insulin-producing bacteria, posibility to overcome some inheritted disrders
  • GM crops produce scare resources e.g. vitamin A from golden rice
24
Q

Describe the risks of genetic enegineering. (4)

A
  • Long term effects of GM crops are unknown
  • Negative enviromental impacts- reduction in biodiversity, impact on food chain
  • Late onset health problems in GM animals.
  • GM seeds are expensive
25
Q

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

A

Genetically modified crops e.g. those modified to insect attack and herbicides.

26
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.
27
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.
28
Q

What are the benefits of Bt crops?

A
  • Increased crop yields
  • Lessens the need for artificial insecticides
  • Bt toxin is specific to certain insect larvae so is not harmful to other organisms that ingest it.
29
Q

What are the risks of Bt crops? (3)

A
  • Long term effects of consumption of Bt crops are unkown
  • Insect larvae may become resistant to the Bt toxin
  • Killing insect larvae reduces biodiversity.
30
Q

Describe the process of genetic engeneering.

A
  1. Enzymes are used to isolate the required gene; the gene is inserted into a vector, usually a bacterial plasmid or a virus
  2. The vector is used to insert gene into the required cells.
  3. Genes are transferred to the cells of animals, plants or microorganisms at aan early stage in their development so that they develop with desired characteristics.
31
Q

What is a vector?

A

A structure that delivers the desired gene into the cell.

32
Q

How can plants be cloned. (2)

A
  • Taking plant cuttings
  • Tissue culture
33
Q

What is tissue culture?

A

Using small groups of cells from part of a plant to grow identical new plants.

34
Q

Describe how plants are grown using tissue culture.

A
  1. Select a plant that shows desired characteristics.
  2. Cut multiple small sample pieces fro meristem tissue.
  3. Grow in a petri dish containing growth medium.
  4. Transfer to compost for further grow.
35
Q

What must be ensured when preparing tissue cultures?

A

Ensure aseptic conditions to prevent contamination by microorganisms.

36
Q

What does the growth medium contain?

A

Nutrients and growth hormones.

37
Q

What are advantages of growing plants by tissue culture?

A
  • Fast and simple process
  • Requires little space
  • Enables the growth of many plant clones with the same desireable characteristics.
  • Useful in the preservation of endagered sspecies.
38
Q

What are the disadvantages of growing plants by tissue culture? (2)

A
  • Reduction in the gene pool
  • Plant clones often have a low survival rate
  • Could unkowingly increase the presence of harmful recessive alleles.
39
Q

Describe the plant cuttings method of plant cloning.

A
  • Older but simpler method than tissue culture
  • Gardeners use this method to produce many identical new plants from a parent plant.
40
Q

Detail the process of plant cuttings method of plant cloning.

A
  1. A branch is cut off from the parent plant.
  2. The lower leaves of the branch are removed and the stem is planted.
  3. Plant hormones are used to encourage new root development .
  4. A plastic bag is used to cover the new plant to keep it warm and moist.
  5. New roots and a new plant is formed after a few weeks.
41
Q

What does embryo transplanting invole?

A
  • Pre-specialised cells from a developing animal embryo are split apart.
  • The resulting seperate but identical embryos are transplanted into host mothers.
42
Q

Decribe how adult cell cloning is performed.

A
  1. The nucleus is removed from an unfertilised egg cell.
  2. The nucleus from an adult body cell, such as a skin cell, is inserted into the egg cell.
  3. An electric shock stimulates the nucleated egg cell to divide and it forms an embryo.
  4. The embryo cells contain the same genetic information as the adult body cell.
  5. When the embryo is a ball of cells, it’s inserted into the uterus of an adult female to continue developing.
43
Q

What are the classes of organisms as determined by Carl Linnaeus?

A
  • Kingdom (King)
  • Phylum (Phillip)
  • Class (Came)
  • Order (Over)
  • Family (For)
  • Genus (Good)
  • Species (Spaghetti)
44
Q

Which features are living creatures traditionally classified by?

A
  • Structure
  • Characteristics
45
Q

What is the binomial system of naming organisms.

A

Genus follwed by species name.

46
Q

Why were new classification models proposed?

A
  • Developments in microscopy- allowed better examination of internal structures.
  • Improvement in understanding of biochemical processes.
47
Q

State three domains.

A
  • Archaea
  • Eukarya
  • Bacteria
48
Q

Which organism lives in the domain archaea?

A

Bacteria- living in extreme environments.

49
Q

Which organism belongs to the domain Bacteria?

A

Bacteria

50
Q

Which kingdoms belong in domain Eukarya?

A
  • Plants
  • Animals
  • Fungi
  • Protists
51
Q

How are evolutionary trees created?

A

By examining the DNA of different species and analysing how similar the sequences are.

GCSE AQA biology (5 decks)

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