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Biology GCSE > Topic 4: Variation and Evolution > Flashcards

Topic 4: Variation and Evolution Flashcards

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1
Q

What are the two types of variation?

A

Continuous and discontinuous.

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2
Q

What is continuous variation?

A

Variation that can’t be categorised. A characteristic that changes gradually over a range of values
(Height, weight)

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3
Q

What is discontinuous variation?

A

Variation that can be categories into distinct groups. A characteristic of any species with only a limited number of possible values.
(Eye colour, blood type)

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4
Q

What are the 2 causes of variation in a species?

A

Genetics and environment.

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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 differences in phenotypes
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6
Q

What is heritable variation?

A

Variation caused by genes.

Example: Shape of nose

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7
Q

What is environmental variation?

A

Variation caused by the environment an organism has developed in.
Example: Scars.

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8
Q

What is a gamete?

A

A sex cell (sperm/egg cells)

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9
Q

What is asexual reproduction and how many parents are needed?

A

Reproduction that does not involve the fusion of gametes and therefore only needs one parent.

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10
Q

Are the offspring produced by asexual reproduction genetically identical or different?

A

Identical. Asexual reproduction produces clones of the parent.

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11
Q

What are 3 examples of asexual reproduction?

A

Bacteria
Production of spores by fungi
Formation of tubers in potatoes

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12
Q

What are spores?

A

A unit of asexual reproduction in some organisms.

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13
Q

What is fungi?

A

A large group of eukaryotic organisms that contain single-celled yeasts, moulds and mushrooms.

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14
Q

What are tubers?

A

A swollen, fleshy underground stem of a plant.

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15
Q

What process is used for asexual reproduction?

A

Mitosis

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16
Q

What is a zygote?

A

A fertilised egg cell.

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17
Q

How many chromosomes are found in gametes?

A

23.

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18
Q

What is the process of sexual reproduction?

A

The nucleus of a sperm and egg cell fuse together.
The 2 sets of 23 chromosomes (from each gamete) produce a zygote with 46 chromosomes.
This zygote then matures into an embryo and the number of cells increase by mitosis as it develops.
The cells then differentiate.

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19
Q

What is mutation?

A

The random change in a gene or chromosome.

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20
Q

What 2 factors can increase mutation?

A

Ionising radiation or certain chemical mutagens.

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21
Q

What is a mutagen?

A

A physical or chemical agent that can increase the frequency of mutation (in an organism).

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22
Q

What is an example of a chemical mutagen?

A

Tar from cigarette smoke.

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23
Q

What are the effects of mutation?

A

It may be neutral and have no effect.
It may be beneficial.
It may be harmful.

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24
Q

What is cystic fibrosis?

A

An inherited disorder that creates a thick/sticky mucus that mainly affects the lungs and pancreas.

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25
Q

What is cystic fibrosis caused by?

A

A recessive allele.

26
Q

What is a genotype?

A

The collection of alleles that determine characteristics and can be expressed as a phenotype.

27
Q

What is a phenotype?

A

The visible characteristics of an organism which occur as a result of its genes.

28
Q

What is a recessive allele?

A

The faulty one.

29
Q

What is the dominant allele?

A

The healthy one.

30
Q

What are recessive and dominant alleles expressed as?

A

Recessive - lower case (eg: c)

Dominant - Capital (eg: C)

31
Q

What is an allele?

A

One of two or more versions of a gene.

32
Q

What is CC?

A

Homozygous (the same) dominant - healthy.

33
Q

What is Cc?

A

Heterozygous - healthy (carrier)

34
Q

What is cc?

A

Homozygous recessive - sufferer.

35
Q

Why can’t you be a carrier of a faulty dominant gene?

A

If you have a faulty dominant, you will always be a sufferer.

36
Q

What is a carrier of a gene?

A

They have the ability to pass on a disease to their offspring without being affected by the disease themselves.

37
Q

What is gene therapy?

A

A range of techniques that can be used to remove the effects of a harmful allele.

38
Q

What are the two main ways of gene therapy?

A

Introducing a ‘healthy’ allele into the person’s DNA.

‘Switching off’ the harmful allele.

39
Q

How is ‘introduction’ gene therapy done?

A

If the harmful allele is recessive, a healthy dominant allele will counteract it. The recessive allele does not have to be removed.

40
Q

How is ‘switching off’ gene therapy done?

A

Can be done in various ways. An example is introducing a completely new gene into the body.

41
Q

What are 2 ethical issues surrounding gene therapy?

A

Some religious groups believe that humans should never alter the genes of living organisms.
The process is very expensive and funds could go to other types of health care that may help a larger group of people.

42
Q

Why can’t you tell if someone is a carrier of a disease?

A

Carriers don’t show symptoms of the disease, they can just pass it on.

43
Q

What is the basic process of gene therapy?

A

Cutting out the normal allele (done by special enzymes)
Making lots of copies of the allele
Putting copies of the normal allele into the cells of a person with the disorder.

44
Q

What are the potential problems of gene therapy?

A

The alleles may not go into every target cell
The alleles may join with the chromosomes in random places, so they don’t work properly
Treated cells may be replaced naturally by the patient’s untreated cells

45
Q

What is evolution?

A

The process by which living species have gradually changed and developed from earlier forms over a long period of time.

46
Q

What does evolution result in?

A

Organisms being better adapted to their environment.

47
Q

Who are Alfred Russel Wallace and Charles Darwin?

A

The men who proposed the theory of evolution by natural selection.

48
Q

What is natural selection?

A

The natural process whereby the best-adapted individual survive longer, have more offspring and thereby spread their characteristics.
(Also known as survival of the fittest).

49
Q

Why do all populations vary?

A

Due to past random mutations that can be inherited.

50
Q

When organisms over-produce, what happens?

A

There are more offspring that can possibly survive, leading to competition for survival.

51
Q

If an organisms characteristics are more suited to their environment, what will happen?

A

They are more likely to survive and reproduce.

52
Q

If an organisms characteristics are poorly suited to their environment, what will happen?

A

They are less likely to survive and reproduce. Their genes are less likely to be passed onto the next generation.

53
Q

Why is the next generation more likely to have more of the beneficial variations in comparison to the previous generation?

A

This is because the genes that are more suited to the environment are more likely to be passed on.

54
Q

What can result if two populations of one species become increasingly different in phenotype that they can no longer interbreed?

A

Can result in the formation of two species.

55
Q

What is an example of a model of natural selection?

A

Green card as background.
Randomly place 20 green and white pieces of string on card.
See how many you can take away in 10 seconds.
Count the amount of each colour left. (then repeat)
This should show how camouflage is helpful in the wild.

56
Q

What are the main steps in developing resistance in bacteria? (to antibiotics for example)

A

Random mutations
Mutations may protect bacterial cells from effects of antibiotic
bacteria die without mutation/ cannot reproduce when antibiotic is present
Resistant bacteria can reproduce with less competition from normal bacterial strains.

57
Q

Why does extinction occur?

A

The organism may:
Not adapt quick enough.
not adapt as well as other organisms.
adapt well, but environment changes suddenly.

58
Q

What is a superbug?

A

Bacteria that have become resistant to the antibiotics normally used to treat the infections.

59
Q

What is the genome?

A

All the genetic information in an organism.

Its: genes, sequence of chromosomes and DNA base pairs.

60
Q

What is the human genome project?

A

An international scientific research project that worked out the sequence of chemical base pairs in human DNA, identified all the genes in humans and their location in the chromosomes.

61
Q

What did knowing the existence of genes and their location on the human chromosomes allow for?

A

Allowed for the possibility of altering them or counteracting their effects.
Allowed for the possibility of creating targeted drugs or viruses that would only (for example) attack cells containing a mutated cancer-causing gene.

Biology GCSE (9 decks)

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