Paper 2: Topic 6 Inheritance, variation & evolution - Variation & evolution Flashcards

1
Q

Define the term variation

A

Differences in the characteristics of individuals within a population

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2
Q

State 3 causes of variation within a population

A
  1. Genetics
  2. Environment
  3. Combination of genetics and the environment
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3
Q

Explain how genetics can lead to variation in a population

A
  • Different individuals will inherit different combinations of alleles
  • The different combination of alleles will cause differences in the proteins that are or are not produced
  • This will cause differences in the characteristics in the different individuals
  • E.g. eye colour, blood group, genetic disorders such as cystic fibrosis
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4
Q

Explain how the environment can lead to variation within a population

A

Different environmental factors can affect certain characteristics in individuals

e.g.

  • Road accident → loss of a limb
  • Exposure to UV light → affects melanin content of the skin
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5
Q

Explain how genetics and the environment can lead to variation in a population

A

Individuals who possess certain genes and are exposed to certain environmental factors can have different characteristics e.g.

  • skin colour (affected by UV light and gene for melanin production)
  • body mass (affected by quality and quantity of diet and the genes for muscle development and growth)
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6
Q

State what factors influence most physical characteristics

A

Genetics AND the environment

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7
Q

State what causes variation within a population

A

Mutations

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8
Q

Describe the range of variation observed in most populations

A
  • Extensive
  • This means there is a wide range of variants for most characteristics within a population
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9
Q

Define the term ‘evolution’ Hint: 3 key parts to this definition

A
  • A change in the inherited characteristics of a population over time
  • Through a process of natural selection
  • Which result in the formation of a new species
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10
Q

Explain the theory of natural selection

A
  • A mutation occurs within an individual in a population
  • This causes variation to develop within a population
  • Some individuals are more suited to their environment (due to the characteristics they possess)
  • The individuals who are more suited to the environment are more successful
  • These individuals are more likely to survive and breed
  • These individuals will pass on the alleles for the beneficial characteristics to the their offspring
  • Over a LONG period of time and MANY generations the beneficial alleles will become more common in the population
  • Over time the variants that posses the best phenotypes are selected for and increase in number
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11
Q

Define the term ‘selective breeding’

A

Selective breeding (artificial selection) is the process by which humans breed plants and animals for particular genetic characteristics

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12
Q

State 2 examples of how Humans have used selective breeding for centuries

A

Humans have been doing this for thousands of years.

They have used it to:
* produce food crops from wild plants and
* bred domesticated animals.

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13
Q

State the 4 key steps in artificial selection/selective breeding

A
  • Selective breeding involves choosing parents with the desired characteristic from a mixed population
  • They are bred together
  • From the offspring those with the desired characteristic are bred together
  • This continues over many generations until all the offspring show the desired characteristic
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14
Q

Give 4 features that have been selected for in selective breeding

A
  1. Disease resistance in food crops
  2. Animals which produce more meat or milk
  3. Domestic dogs with a gentle nature
  4. Large or unusual flowers
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15
Q

State 3 disadvantages of using artificial selection / selective breeding

A
  1. Inbreeding can result in a reduced gene pool
  2. Inbreeding can result in health problems
  3. Inbreeding results in reduced variation within the population
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16
Q

Explain what is meant by the expression ‘reduced gene pool’

A

The number of different alleles in a population decreases

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17
Q

Explain how artificial selection can result in health problems in the population

A
  • Selective breeding can lead to ‘inbreeding’ where some breeds are particularly prone to disease or inherited defects
  • This is because of a reduced gene pool
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18
Q

Explain how artificial selection can reduce the gene pool

A

The number of alleles in the population can be decreased over time
This is because some alleles are selected AGAINST so their frequency in the population decreases
Over time this reduces the total number of alleles present in the population

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19
Q

Explain how artificial selection can cause problems if a new disease occurs

A
  • As a result of selective breeding there is less variation in a population
  • So all the individuals in the population have very similar characteristics
  • This means that if one individual is likely to be killed by the new disease then all the individuals in the population are also likely to die from the new disease
  • This is because there is less chance of any resistant alleles being in a population
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20
Q

Give 3 reasons why a gardener/farmer may use selective breeding

A
  1. To produce a crop with higher yield
  2. To produce a crop with more fruits
  3. To produce a crop with larger fruits
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21
Q

Describe the process of genetic engineering

A

A process which involves modifying the genome of an organism by introducing a gene from another organism to give a desired characteristic

22
Q

Give 2 characteristics that have been genetically engineered in plants

A
  1. Resistant to diseases
  2. To produce bigger better fruits
23
Q

Describe an example of where bacteria have been used in genetic engineering

A

Bacterial cells have been genetically engineered to produce useful substances such as human insulin to treat diabetes

24
Q

Describe the 10 key steps in genetic engineering

A
  1. The desired gene is identified
  2. The gene for the desired protein is isolated (cut) from the DNA of one organisms genome using a restriction enzyme
  3. Plasmids are isolated from bacteria
  4. The same restriction enzyme is used to cut the plasmids
  5. The cut plasmids and the desired gene are mixed together in the presence of DNA ligase
  6. The DNA ligase joins the plasmid and desired gene together to form a recombinant (hybrid) plasmid
  7. The recombinant/hybrid plasmid is inserted back into the bacteria
  8. The bacteria are grown in large scale fermenters
  9. The bacteria produce the required protein
  10. The protein is extracted, purified and packaged for use
25
Q

Explain why plasmids used in genetic engineering are called vectors

A

A vector transfers something from one place to another

In this case it transfers the DNA from one organism to another

26
Q

State the 2 types of vectors that are usually used in genetic engineering

A
  1. Bacterial plasmids
  2. Viruses
27
Q

Give 3 examples of genetic engineering

A
  1. Production of human insulin (Humulin) to treat type I diabetics
  2. Production of GM crops
  3. Production of specific drugs in sheep’s milk to treat disease
28
Q

Give 4 reasons scientists may want to use genetic engineering in plants

A
  1. To produce a herbicide or insecticide resistant crops
  2. To produce plants with larger fruits
  3. To produce plants which are disease resistant
  4. To produce crops with greater yield
29
Q

Define a insecticide

A

A chemical that selectively kills insects

30
Q

Define a herbicide

A

A chemical that selectively kills plants e.g. broad leaved plants

31
Q

Define a pesticide

A

A chemical that selectively kills pests e.g. aphids

32
Q

Give one example of genetic engineering in embryos

A

To insert a corrected gene into the ovum or early embryo to prevent certain genetic diseases

33
Q

Give 7 concerns some people have with GM crops

A
  1. We do not yet know the long-term effect of consuming GM food i.e. they may have negative impacts on human health
  2. Consumption of GM food may trigger allergies in some people
  3. The modified crops may susceptible to changes in the environment in the future as they have a reduced gene pool
  4. The gene may be passed between different plant species and ‘escape’ into wild plants and other crops
  5. GM crops will reduce the biodiversity in the areas where they are grown
  6. The long term effect on other organisms in the food chain is unknown e.g. effect on insects that feed on the GM plants
  7. Transplanted herbicide resistant genes may spread to other plants and lead a new ‘super weed’ variety
34
Q

Give 3 reasons why some people are in favour of GM crops

A
  1. It can be used to produce food that is rich in certain nutrients e.g. high vitamin A content. These nutrient rich foods can then be made available to people in countries with poor diets to prevent malnutrition
  2. There are no studies to date that indicate ther are long-term side effects of consuming GM foods
  3. It can help provide food security for a growing human population
35
Q

Give an example where a GM crop has been used to help reduced disease

A
  • The use of GM rice called ‘golden rice’
  • Which is rich in Vitamin A
  • To prevent a specific form of blindness In developing countries which have poor diet and rely heavily on rice
36
Q

State the two methods that can be used to clone plants

A
  1. Tissue culture
  2. Cuttings
37
Q

Define the term ‘tissue culture’

A

The process of using small groups of cells from part of a plant to grow identical new plants

38
Q

Give 2 uses of tissue culture

A

This is important for

  • preserving rare plant species
  • producing large numbers of genetically identical plants commercially in nurseries
39
Q

Describe how tissue cultures are carried out

A
  • A few plant cells are selected from the plant with the desirable characteristics
  • The cells are placed in a growth medium which contains nutrients and growth hormones
  • The cells grow into plantlets
  • Which are genetically identical i.e. clones
40
Q

Give 4 advantages of using tissue culture

A
  1. Only a few cells are needed
  2. Many (100s) genetically identical plants can be produced from one parent plant
  3. The technique only requires a small amount of space to produce many plants
  4. The technique can be used throughout the year
41
Q

Give 4 disadvantages of using tissue culture

A
  1. The procedure requires specific skills and equipment
  2. The cloned plants will all be susceptible to the same diseases
  3. There will be a reduced gene pool in the plants
  4. The technique is slower (than cuttings) as the cells need time to divide and differentiate to become established plants
42
Q

Define the term ‘clone’

A
  • Individuals which have the same genetic information (DNA)
  • And therefore have the same characteristics
43
Q

Explain why gardeners may use cuttings

A
  • Simple method
  • Which is used to produce many identical new plants from a sinlge parent plant
44
Q

Give 4 advantages of using cuttings

A
  1. It is a simple procedure
  2. No technical apparatus is required
  3. It is a cheap technique
  4. It is a quick process (as plants form roots quickly to give an independent plant)
45
Q

Give 4 disadvantages of using cuttings

A
  1. Only a limited number of cuttings can be taken from any one parent plant
  2. So cuttings produces a lot less plants than tissue culture (10s compared to 100s)
  3. The cloned plants will all be susceptible to the same diseases
  4. There will be a reduced gene pool in the plants
46
Q

State the 2 techniques that can be used to clone animals

A
  1. Embryo transplants
  2. Adult cell cloning
47
Q

Define the term ‘embryo transplants’

A

A process which splits apart cells from a developing animal embryo before they become specialised, then transplanting the identical embryos into host mothers

48
Q

Describe the 7 main steps when carrying out embryo transplants

A
  1. Sperm cells from a male with the desirable characteristics are collected
  2. Ova from a female with the desirable characteristics are collected
  3. The sperm are then used to fertilise the ova to form a zygote
  4. The zygote divides by mitosis and develops into an embryo
  5. The embryo is then split into many smaller groups of cells (clones)
  6. The clones are then implanted into the uterus of other females (surrogate mothers)
  7. The cloned embryos then develop into new individuals which are all genetically identical
49
Q

State the advantage of using embryo transplants

A

Hundreds of genetically identical offspring can be produced each year from one prize male and one prize female e.g. bull and cow

50
Q

Describe the 5 main steps in adult cell cloning

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 egg cell to divide to form an embryo
  4. These embryo cells contain the same genetic information as the adult skin cell
  5. When the embryo has developed into a ball of cells, it is inserted into the womb of an adult female to continue its development
51
Q

State 3 concerns some people have with the use of animal cloning techniques Applies to both adult cell cloning and embryo transplants

A

Any 3 from:
1. The production of clones reduces the gene pool
2. The variation within the population decreases
3. If a new disease occurs then the entire population may be wiped out (killed) as there is less chance of having an allele that provides resistance to the disease
4. Clones may be less healthy and may be more prone to disorders related to old age
5. Concerns exist that the technique could be applied to Humans in the future

52
Q

State 2 reasons why some people are in favour of using animal cloning techniques

A
  1. The study of animal clones can mean scientists can gain a greater understanding of embryo development, ageing and age-related disorders
  2. Can be used to produce more individuals of an endangered species and hence prevent extinction.