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Biology AQA Triple > Inheritance, Variation and Evolution > Flashcards

Inheritance, Variation and Evolution Flashcards

Paper 2 - B6

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1
Q

What is the purpose of meiosis?

A

Production of gametes (sex cells)

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2
Q

How is mitosis different from meiosis?

A

Meiosis leads to production of 4 non-identical cells, mitosis leads to production of 2 identical cells

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3
Q

Name the gametes (sex cells) in a) flowering plants b) animals

A

a) pollen and egg cells b) sperm and egg

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4
Q

Why is sexual reproduction important?

A

It involves mixing of gametes which leads to variation

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5
Q

What is asexual reproduction?

A

Reproduction involving only one parent and no fusion of gametes

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6
Q

What type of offspring are produced in asexual reproduction?

A

Genetically identical organisms (clones)

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7
Q

What does meiosis do to the number of chromosomes in gametes?

A

It halves the number

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8
Q

Gametes have half the number of chromosomes as body cells. In what process is the full number restored?

A

Fertilisation

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9
Q

What happens in the nucleus of a cell before meiosis?

A

Copies of the genetic information (DNA, chromosomes) are made

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10
Q

How many gametes are produced in meiosis?

A

Four

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11
Q

What type of cell division occurs AFTER fertilisation to lead to an embryo?

A

Mitosis

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12
Q

What happens to the cells in an embryo to eventually cause organs etc. to develop?

A

Cells continue to multiply by mitosis and then they DIFFERENTIATE

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13
Q

(Triple only) What is the advantage of sexual reproduction

A

Produces variation in offspring giving an advantage if the environment changes

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14
Q

(Triple only) Give 4 advantages of asexual reproduction

A

Only 1 parent needed; more time/energy efficient as don’t need to find a mate; faster than sexual reproduction; many identical offspring produced when conditions are
favourable

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15
Q

(Triple only) Why is genetic variation an advantage?

A

Natural selection can occur if the environment changes

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16
Q

(Triple only) Name 3 organisms that can reproduce by both sexual and asexual reproduction

A

Malarial parasites; fungi; plants e.g. daffodils, strawberry plants

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17
Q

(Triple only) Which type of reproduction (asexual or sexual) of malarial parasites occurs in the human host and which occurs in the mosquito?

A

Asexual in human host, sexual in mosquito

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18
Q

What is the structure of DNA?

A

Double helix

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19
Q

What is the genome?

A

The entire genetic material of an organism

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20
Q

What is DNA?

A

A polymer made up of two strands in a double helix

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21
Q

What structures contain DNA?

A

Chromosomes

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22
Q

What is a gene?

A

A small section of DNA on a chromosome

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23
Q

What does a gene code for?

A

A particular sequence of amino acids to make a specific protein

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24
Q

Give 3 reasons why understanding the human genome is important

A

Search for genes linked to different diseases; understanding & treatment of inherited disorders; use in tracing human migration patterns from the past

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25
Q

(Triple only) What units make up DNA?

A

Nucleotides

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26
Q

(Triple only) What are the 3 components of a nucleotide in DNA?

A

Sugar, phosphate group, one of 4 bases

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27
Q

(Triple only) Name the 4 bases in DNA and say how they pair up

A

A, T, C, G; A pairs with T; C pairs with G

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28
Q

(Triple only) How many bases are the code for one amino acid?

A

Three

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29
Q

(Triple only) In DNA, what does the order of bases control?

A

The order in which amino acids are assembled to make a particular protein

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30
Q

(Triple only) Where are proteins synthesised?

A

On ribosomes

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31
Q

(Triple only) What happens in protein synthesis?

A

A copy of the DNA (a template called mRNA) attaches to a ribosome which reads the bases in threes. Carrier molecules (tRNA) bring the correct amino acids to add to the growing protein chain

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32
Q

(Triple only) What is a mutation and how might it affect a protein?

A

A change in DNA structure (different bases) which changes the shape/function of the protein produced

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33
Q

(Triple only) What happens to a protein to give it a unique function?

A

It folds up into a unique shape

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34
Q

(Triple only) List three types of proteins

A

Enzymes, hormones, structural

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35
Q

(Triple only) How might a mutation affect an enzyme?

A

It alters the shape of the active site so the substrate cannot bind

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36
Q

(Triple only) Give one role of the non-coding parts of DNA

A

Switch genes on and off

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37
Q

(Triple only) What effect might a mutation have to a non-coding part of DNA

A

It might affect how genes are expressed

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38
Q

What is the effect of most mutations?

A

Most have no effect, some may be harmful or beneficial

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39
Q

What are alleles?

A

Different forms of a gene

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40
Q

In genetics, what does dominant mean?

A

Only one copy of an allele is needed to produce a characteristic (always expressed)

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41
Q

In genetics, what does recessive mean?

A

Two copies of an allele are needed to produce a characteristic (only expressed if no dominant allele is present)

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42
Q

What is the genotype?

A

Pair of alleles for a characteristic

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43
Q

What is the phenotype?

A

The characteristic caused by a particular
pair of alleles

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44
Q

What does homozygous mean?

A

Two alleles of the same type for a characteristic (i.e. both dominant or both recessive)

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45
Q

What does heterozygous mean?

A

A genotype with one dominant and one recessive allele

46
Q

Give an example of a characteristic in humans controlled by a single gene

A

Red-green colour blindness

47
Q

Name the grid used to show the results of a genetic cross

A

Punnett square

48
Q

Why do most characteristics have many different possible phenotypes (e.g. lots of different hair colours and types)?

A

They are caused by multiple genes, not just one

49
Q

Name an inherited condition caused by a recessive allele

A

Cystic fibrosis

50
Q

Name an inherited condition caused by a dominant allele and affecting the hands and feet

A

Polydactyly

51
Q

How can embryo screening be used to prevent genetic disorders

A

Following IVF, embryos can be tested for genetic disorders before being implanted back into the mother

52
Q

What is the ethical issue relating to embryo screening?

A

Deciding what counts as a ‘genetic disorder’ (level of severity etc.) and fact that embryo may then be destroyed

53
Q

How many pairs of chromosomes are in ordinary body cells?

A

23 pairs

54
Q

What pair of sex chromosomes are found in the nucleus of male body cells?

A

XY

55
Q

What pair of sex chromosomes are found in the nucleus of female body cells?

A

XX

56
Q

Aside from genes, what else can affect the overall phenotype of an organism?

A

Interaction with the environment

57
Q

How does new genetic variation arise?

A

Mutations

58
Q

What is evolution?

A

A change in the inherited characteristics of a population over time through natural selection

59
Q

When did the first life forms on earth develop?

A

Over 3 billion years ago

60
Q

What is natural selection?

A

When organisms with the most favourable genetic variants survive, reproduce and pass on their alleles, meaning that these increase in the population

61
Q

When is a new species formed?

A

When two populations of one species become so different in phenotype that they can no longer interbreed to produce fertile offspring

62
Q

What is a species?

A

Organisms with similar characteristics that can interbreed to produce fertile offspring

63
Q

What is selective breeding?

A

When humans breed plants or animals for particular genetic characteristics

64
Q

How is selective breeding carried out?

A

Choose parents with desired characteristics, breed together, select offspring and repeat over many generations

65
Q

List 4 characteristics which might be chosen for selective breeding

A

Disease resistance in food crops; more meat or milk in animals; domestic dogs with gentle nature; large or unusual flowers

66
Q

What is the main disadvantage of selective breeding

A

Inbreeding where some breeds are particularly prone to disease or inherited defects

67
Q

What is genetic engineering?

A

Modifying the genome of an organism by introducing a gene from another organism to give a desired characteristic

68
Q

Give two characteristics produced by genetic engineering in plants

A

Disease resistance; bigger, better fruits

69
Q

What useful product is now produced by certain bacteria as a result of genetic engineering

A

Human insulin

70
Q

Give three characteristics of genetically modified crops

A

Resistance to insect attack; resistance to herbicides; increased yield

71
Q

Give two concerns relating to GM crops

A

Effects of wild populations of flowers and insects; effects on human health haven’t been fully explored

72
Q

How could genetic modification be used in humans?

A

To overcome certain inherited disorders (gene therapy)

73
Q

In genetic engineering, what is used to isolate and remove the required gene?

A

Enzymes

74
Q

In genetic engineering, what is usually used as a vector to transfer the gene into the new organism?

A

A plasmid or a virus

75
Q

In genetic engineering, what is the purpose of the vector?

A

To transfer the gene into the required cells

76
Q

Why is genetic engineering usually done during an early stage of the organism’s development?

A

So that the organism develops with the desired characteristic

77
Q

(Triple only) What is tissue culture?

A

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

78
Q

(Triple only) Give two methods of cloning plants

A

Tissue culture; taking cuttings

79
Q

(Triple only) How is cloning carried out in animals?

A

Embryo transplants; nuclear transfer (adult cell cloning)

80
Q

(Triple only) How are embryo transplants carried out in order to clone an animal?

A

Cells in an embryo are split apart before they become specialised, then the embryos are transplanted into host mothers.

81
Q

(Triple only) How can cloning be carried out using adult cells?

A

Nucleus removed from unfertilised egg cell and replaced with nucleus from adult body cell. Electric shock given, so cell divides to form an embryo, then inserted back into womb of adult female

82
Q

(Triple only) Who came up with the theory of natural selection and how?

A

Charles Darwin, on a round the world expedition and based on observations of fossils, geology and experimentation

83
Q

(Triple only) Describe the stages in evolution by natural selection

A

Genetic variation, survival of the fittest, breeding and passing on characteristics

84
Q

(Triple only) Name Darwin’s book and the date of publication

A

On the Origin of Species, 1859

85
Q

(Triple only) Give 3 reasons why Darwin’s theory was only gradually accepted

A

It challenged ideas about God making all the animals/plants; insufficient evidence at the time; mechanism of inheritance (genes) was not known for another 50 years after publication

86
Q

(Triple only) Who came up with an alternative theory to Charles Darwin?

A

Jean-Baptiste Lamarck

87
Q

(Triple only) How did Lamarck’s theory differ from Darwin’s?

A

He proposed that characteristics developed during an organism’s lifetime could be passed on (Darwin said only characteristics you were born with)

88
Q

(Triple only) Who proposed natural selection independently to Darwin but also published papers with him?

A

Alfred Russell Wallace

89
Q

(Triple only) Aside from evolutionary theory, what else did Alfred Russell Wallace work on?

A

Warning colouration in animals

90
Q

(Triple only) What is speciation?

A

Development of a new species through natural selection occurring differently in isolated populations

91
Q

(Triple only) What did Mendel do, and how did it influence the theory of evolution?

A

Experiments on plant breeding; Basic ideas about ‘units’ of inheritance (later known as genes)

92
Q

Give two pieces of evidence for evolution

A

Fossils; antibiotic resistance in bacteria

93
Q

How do fossils provide evidence of evolution?

A

Show gradual changes in organisms over time

94
Q

How does antibiotic resistance provide evidence for evolution?

A

It shows how an organism can change when the environment changes

95
Q

What are fossils?

A

Remains of organisms from millions of years ago which are found in rocks

96
Q

How do fossils form (three ways)?

A

Parts of organisms don’t decay; parts of organisms are replaced with minerals as they decay; preserved footprints etc.

97
Q

Why don’t all organisms form fossils?

A

Many organisms are soft bodied and don’t form fossils easily; some are destroyed by geological activity

98
Q

What is extinction?

A

When there are no individuals of a species left on earth

99
Q

List some factors that may contribute to extinction of a species

A

Climate change; hunting; disease; new predators etc.

100
Q

What is MRSA?

A

A particular microorganism that is resistant to antibiotics

101
Q

How can we reduce antibiotic resistance?

A

Only prescribe antibiotics when necessary; patients must complete the course; reduce agricultural use of antibiotics

102
Q

Why is antibiotic resistance a concern?

A

People are not immune to the bacteria but it cannot be treated with antibiotics; Development of new antibiotics is costly and slow - can’t keep up with emergence of resistant strains

103
Q

Who developed the first system for classification of organisms?

A

Carl Linnaeus

104
Q

List the levels in the classification system proposed by Carl Linnaeus

A

Kingdom, phylum, class, order, family, genus, species
(King Philip Came Over For Good Soup)

105
Q

What are the two parts of an organism’s binomial name?

A

Genus and species

106
Q

Give two reasons why our ideas about classification have changed since Carl Linnaeus first proposed his system

A

Development of microscopes advances knowledge of structures inside cells; understanding of biochemical processes progressed

107
Q

Who proposed the ‘Three Domain system’ of classification?

A

Carl Woese

108
Q

What are the three groups of the ‘three domain system’ of classification?

A

Archaea, bacteria, eukaryota

109
Q

What are the archaea (in the ‘three domains system’ of classification)?

A

Primitive bacteria usually living in extreme environments

110
Q

How can we show in a visual way how organisms are related?

A

Evolutionary trees

111
Q

What information is needed to construct an evolutionary tree?

A

Classification data for living organisms and fossil data for extinct organisms

Biology AQA Triple (16 decks)

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