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AQA Biology GCSE > Inheritance, Variation and Evolution > Flashcards

Inheritance, Variation and Evolution Flashcards

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1
Q

What are chromosomes?

A

long molecules of DNA

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2
Q

What does DNA stand for?

A

DeoxyriboNucleic Acid

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3
Q

What is DNA?

A

A polymer of nucleotides and the chemical that all genetic material in a cell is made up of

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4
Q

What does DNA contain?

A

coded information

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5
Q

What does DNA determine?

A

inherited characteristics

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6
Q

Where is DNA found in animal and plant cells?

A

The nucleus

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7
Q

True or false: Chromosomes normally come in threes.

A

False- they come in pairs.

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8
Q

What shape is DNA?

A

A double helix

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9
Q

What is a gene?

A

A small section of DNA found on a chromosome.

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10
Q

What does each gene code for?

A

a particular sequence of amino acids that are put together to make proteins

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11
Q

How many types of amino acids are there?

A

20

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12
Q

What do proteins determine?

A

what type of cell it is

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13
Q

What is a genome?

A

The entire set of genetic material in an organism

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14
Q

What are the repeating units of DNA strands called?

A

nucleotides

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15
Q

What does each nucleotide consist of?

A

One sugar molecule
One phosphate molecule
One ‘base’

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16
Q

What do sugar and phosphate molecules in nucleotides form?

A

the ‘backbone’ to DNA strands

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17
Q

Why is it important that scientists understand the human genome?

A
  1. so that they can identify genes that are linked to diseases
  2. allows them to develop better treatments to inherited diseases
  3. allows them to trace the migration patterns of certain populations of people around the world
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18
Q

True or false: The sugar and phosphate molecules alternate.

A

True

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19
Q

One of how many bases joins to each sugar molecule in DNA?

A

one of four

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20
Q

What are the base pairs?

A

A and T
C and G

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21
Q

What is complimentary base pairing?

A

How base A and T or C and G always pair in a strand of DNA

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22
Q

What does the order of bases in a gene determine?

A

the order of amino acids for a protein

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23
Q

How many bases code for one amino acid?

A

three

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24
Q

What do non-coding parts of DNA do?

A

Control whether or not a gene is expressed to make a protein

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25
Q

What carries the code of DNA to the ribosomes?

A

mRNA

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26
Q

Where are proteins made?

A

Ribosomes

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27
Q

How do ribosomes make proteins?

A

They use the DNA code from the mRNA to form amino acids in the correct order to produce a specific protein

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28
Q

What are three types of protein?

A
  1. Enzymes
  2. Hormones
  3. Structural proteins - physically strong, strengthens tissue
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29
Q

What are mutations?

A

random changes to the genetic code of an organism

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30
Q

True or false: Mutations can be inherited.

A

True

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31
Q

Give an example of how a mutation can occur spontaneously.

A

when a chromosome isn’t replicated properly

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32
Q

What is the chance of mutation increased by?

A

exposure to certain substances or radiation

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33
Q

What do mutations change?

A

the sequence of the DNA bases to produce a genetic variant and can lead to changes in the protein that the amino acid codes for

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34
Q

What will happen to enzymes and structural proteins if a mutation was to occur?

A
  1. The shape of an enzymes active site is changed so its substrate may no longer bind to it
  2. Structural proteins could lose their strength so cannot support or structure the tissue effectively
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35
Q

What would happen if there was a mutation in non-coding DNA?

A

It can alter how genes are expressed

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36
Q

What are the three different types of mutation?

A
  1. Insertions
  2. Deletions
  3. Substitutions
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37
Q

What are insertion mutations?

A
  1. When a new base is inserted into the DNA base sequence where it shouldn’t be
  2. Changes the way that the groups if three bases are read resulting in a different amino acid formed
  3. They can change more than one amino acid and have a knock-on effect
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38
Q

What are deletion mutations?

A
  1. When a random base is deleted from the DNA base sequence
  2. Changes the way that the groups if three bases are read resulting in a different amino acid formed
  3. They can change more than one amino acid and have a knock-on effect
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39
Q

What are substition mutations?

A
  1. When a random base is replaced by a different base
  2. Changes the amino acid made
  3. Doesn’t have a knock-on effect
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40
Q

What is sexual reproduction?

A

The fusion of male and female gametes (produced by meiosis) to produce genetically different offspring

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41
Q

What is asexual reproduction?

A

One parent dividing by mitosis to produce two identical offspring/ clones

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42
Q

Give an example of something that reproduces asexually.

A

Bacteria
Some plants
Some animals

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43
Q

Why are the offspring from sexual reproduction genetically different to the parents?

A

They contain a mixture of chromosomes from the mum and dad

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44
Q

What type of plants can reproduce sexually?

A

flowering plants

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45
Q

How many chromosomes does a gamete have in humans?

A

23

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46
Q

How many cell divisions does meiosis have?

A

two

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47
Q

Where does meiosis happen in humans?

A

Ovaries (female)
Testes (male)

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48
Q

True or false: Meiosis produces cells which have the same amount as the normal number of chromosomes.

A

False - They have half the amount of the normal number

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49
Q

Describe the stages of meiosis.

A

1- DNA replication
2- Chromosome pairs line up in the centre
3- The pairs are pulled apart so each new cell only has one copy of each chromosome
4- Second division, chromosomes line up and the arms are pulled apart
5- Four gametes are produced with only a single set of chromosomes, each gamete is genetically different

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50
Q

After two gametes have fused, what does the new cell divide by?

A

mitosis

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51
Q

What are the advantages of sexual reproduction?

A
  • Offspring have a mixture of chromosomes from each parent, resulting in variation
  • Variation increases the chance of a species surviving in a changing environment
  • Some organisms will be better adapted so have a better chance of survival (natural selection)
  • Selective breeding can be done to increase the number of organisms with desirable characteristics
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52
Q

What are the advantages of asexual reproduction?

A
  • Only one parent needed
  • less energy wasted as organisms don’t have to find a mate
  • Faster than sexual reproduction
  • identical offspring can be produced in favourable conditions
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53
Q

In malarial parasites, where do they reproduce sexually and asexually?

A

sexually - in the mosquito
asexually - in the human host

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54
Q

What type of species releases spores?

A

fungi

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55
Q

What do asexually-produced spores form?

A

genetically identical fungi

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56
Q

What do sexually-produced spores form?

A

a variation of fungi that can survive change in the environment

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57
Q

What type of plant produces ‘runners’?

A

strawberry plants

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58
Q

What are runners?

A

Stems that grow horizontally in the surface of the soil away from the plant that produce new genetically identical plants

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59
Q

What chromosome causes male characteristics?

A

Y

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60
Q

True or false: Females have XX chromosomes.

A

True

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61
Q

Draw a punnet square to show the probability of a child being male or female.

A

X X
X XX XX
Y XY XY

50% or 1/2 chance

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62
Q

What are versions of genes called?

A

Alleles

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63
Q

What are alleles represented by?

A

Letters

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64
Q

How many alleles do you have of each gene in your body?

A

two, one on each chromosome in a pair

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65
Q

What is the term for two alleles for a particular gene that are the same?

A

homozygous

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66
Q

What is the term for two alleles for a particular gene that is different?

A

heterozygous

67
Q

If the two alleles are different, which one determines the characteristic present?

A

Dominant allele

68
Q

What do the alleles have to be for a recessive characteristic to be displayed?

A

they both must be recessive

69
Q

What is your genotype?

A

the combination of alleles that you have

70
Q

What are phenotypes?

A

The characteristic that an allele determines

71
Q

What type of allele do carriers of a characteristic have?

A

heterozygous

72
Q

What type of allele is cystic fibrosis caused by?

A

recessive

73
Q

If both parents are carriers of a recessive disease what is the probability that their offspring will inherit it?

A

1 in 4 chance (25%)

74
Q

What type of allele is polydactyly caused by?

A

a dominant allele

75
Q

If one parents has the dominant disease and the other doesn’t, what is the probability that their offspring will inherit it?

A

1 in 2 chance (50%)

76
Q

What is embryonic screening?

A

checking for genetic disorders in an embryo

77
Q

Why are people for embryonic screening?

A
  • it will help to stop people suffering
  • treating disorders would cost money
  • there are laws to stop it going to far
78
Q

Why are people against embryonic screening?

A
  • implies that genetic disorders are ‘undesirable’
  • could encourage others to want to screen their embryos to pick the most desirable
  • Screening is expensive
  • wasted embryos are discarded and believed to be forms of potential human life
79
Q

What did Mendel discover?

A
  • how characteristics of plants are determined by hereditary units
  • hereditary units are passed on to offspring unchanged from both parents, one unit from each parent
  • Hereditary units can be dominant or recessive
80
Q

What are the two types of variation?

A

genetic variation and environmental variation

81
Q

What is genetic variation?

A

How plants and animals inherit different characteristics from each parent making them genetically different from one individual parent.

82
Q

Give three examples of characteristics only determined by genes.

A
  • eye colour
  • blood group
  • inherited disorders
83
Q

What is environmental variation?

A

How the environment can cause differences between members of the same species.

84
Q

What characteristics are due to genes and the environment?

A

body weight
height
skin colour
teeth condition
academic or athletic prowess

85
Q

What is the theory of evolution?

A

All of today’s species have evolved from simple life forms that first started to develop over three billion years ago.

86
Q

What is the theory of evolution by natural selection?

A
  1. Organisms in a species have phenotypic variation.
  2. Individual with the most suitable characteristic for the environment are more successful competitors and more likely to survive.
  3. If an organism is more likely to survive, it is more likely to reproduce and pass on the genes for the beneficial
    characteristics to their offspring.
  4. Organisms that are less well adapted would be less likely to survive and reproduce so less likely to pass on their genes.
  5. Over time, the beneficial characteristics become more common and the species changes.
87
Q

What is the development of a new species called?

A

Speciation

88
Q

What is a species?

A

A species is a group of similar organisms that can reproduce to give fertile offspring.

89
Q

What is extinction?

A

When no individuals of a species remains.

90
Q

What is a reason for why species become extinct?

A
  • The environment changes too quickly
  • A new predator kills them all
  • A new disease kills them all
  • The can’t compete either another new species for food
  • A catastrophic event happens that kills them all (volcanic eruption)
91
Q

Why were Darwin’s theories controversial?

A
  • Went against religious beliefs at the time
  • He couldn’t explain why these characteristics appeared or how they were passed on
  • There wasn’t enough evidence to support them
92
Q

What was Lamarck’s theory about evolution?

A
  • Changes that an organism acquires during its lifetime will be passed on to its offspring
  • If a characteristic was used a lot by an organism then it would become more developed
93
Q

Why do scientists hypotheses differ?

A

they have different beliefs or have been influenced by others

94
Q

Why was Lamarck’s hypothesis rejected?

A

Experiments did not support it

95
Q

What evidence supported Darwin’s theory of evolution?

A

The discovery of genetics
The fossil record

96
Q

What is selective breeding?

A

When humans artificially select the plants or animals that will breed so that the genes for a particular characteristic remain in the population.

97
Q

Give an example of selective breeding.

A
  • animals that produce more meat or milk
  • crops with disease resistance
  • dogs with good, gentle temperament
  • decorative plants with big flowers
98
Q

Describe the basic process of selective breeding.

A
  1. From your existing stock, select the ones which have the desired characteristics.
  2. Breed them with each other.
  3. Select the best offspring and breed them together.
  4. Continue this process over several generations so that the desired trait gets stronger and stronger.
99
Q

What is selective breeding used for in agriculture?

A

To improve yields

100
Q

What is the main problem with selective breeding?

A

It reduces the gene pool

101
Q

What is a gene pool?

A

the number of different alleles in a population

102
Q

How does selective breeding in farming cause a reduce in the gene pool of a species?

A

Farmers keep breeding from the best animals or plants which are all closely related. Also known as inbreeding.

103
Q

What can inbreeding cause?

A

Health problems - organisms inherit harmful genetic defects when the gene pool is limited

Problems if new diseases occur - there is a lack of variation in the population so less chance of resistant alleles

104
Q

What is genetic engineering?

A

transferring a gene responsible for a desired characteristic from one organism’s genome into another organism.

105
Q

Describe the process of genetic engineering.

A
  1. A useful gene is extracted from one organism’s genome using enzymes and is inserted into a vector (usually virus or bacterial plasmid)
  2. When the vector is introduced to the target organism, the useful gene is inserted into its cells.
106
Q

What has been genetically modified to produce human insulin?

A

bacteria

107
Q

Why have GM crops had their genes modified?

A

to improve size, quality of their fruit or make them resistant to disease, insects and herbicides

108
Q

How have sheep been genetically modified?

A

Their milk can provide drugs to treat human diseases

109
Q

What is gene therapy?

A

inserting working genes into people with an inherited disease

110
Q

What are the advantages of GM Crops?

A
  • Characteristics can increase yield, making more food
  • Can be engineered to contain more nutrients for people in developing countries that don’t have them
  • they are already being grown without problems
111
Q

What are the disadvantages of GM Crops?

A
  • could affect the number of wild flowers that live around the crops, reducing biodiversity
  • some people don’t believe that they are safe and don’t fully understand the effects of eating them
  • transplanted genes may escape into the environment e.g. creating ‘super weeds’ that are also resistant to herbicides
112
Q

What are the two ways that plants can be cloned?

A

Tissue culture and cuttings

113
Q

How can plants be cloned by tissue culture?

A

A few plant cells are put into a growth medium with hormones and they grow into clones of the parent plant.

114
Q

What are the advantages of tissue culture?

A

Plants can be made very quickly and can be grown all year round.
They can be used to preserve rare plants that are hard to reproduce naturally.

115
Q

How can plant clones be made from cuttings?

A

Gardeners can take cuttings from good parent plants and replant them to produce genetically identical copies of the parent plant.

116
Q

What is the advantage of producing plant clones from cuttings?

A

can be produced quickly and cheaply
simpler method than tissue culture

117
Q

How can animal clones be made?

A

Embryo transplants

118
Q

Describe how embryo transplants produce animal clones.

A
  1. Sperm cells from a good animal is used to fertilise an egg from another good animal in a lab.
  2. The embryo develops and splits many times to form clones.
  3. Before the cells specialise, the cloned embryos are implanted into lots of individuals to grow into genetically identical offspring.
119
Q

What is adult cell cloning?

A

Taking an unfertilised egg cell and removing its nucleus.
The nucleus is then replaced with one from an adult body cell (e.g. skin cell).
The egg cell is stimulated by an electric shock causing it to divide like a normal embryo.
Once the embryo has formed, it is implanted into the womb of an adult female where it grows into a clone of the original adult.

120
Q

What are the issues surrounding cloning?

A
  • can cause a reduced gene pool
  • cloned animals may not be as healthy
  • some people worry that humans would be cloned in the future
121
Q

What is the advantage of cloning?

A

Can help to preserve endangered species and lead to a greater understanding of the development of embryos

122
Q

What are fossils?

A

The remains of organisms from many thousands of years ago, which are found in rocks

123
Q

What are fossils?

A

The remains of organisms from many thousands of years ago, which are found in rocks.

124
Q

What do fossils tell us?

A

How much or how little organisms have evolved over time

125
Q

What are the three ways that fossils form in rocks?

A
  1. Gradual replacement by materials
  2. From casts and impressions
  3. From preservation in places where no decay happens
126
Q

Explain how fossils form from gradual replacement by materials.

A

As materials decay they form a rock-like substance shaped like the original hard part.
The surrounding sediment also turn to rock, but the fossil stays distinct inside the rock.

127
Q

What type of materials don’t decay easily?

A

teeth, bones, shells

128
Q

Explain how fossils are formed from casts and impressions.

A

When an organism is buried in a soft material like clay, the material around it hardens and the organism decays. This creates a cast of the organism.

129
Q

Explain how fossils are formed from preservation in places where no decay happens.

A
  • In amber and tar pits, there’s no oxygen or moisture so microbes can’t survive.
  • In glaciers it’s too cold for the decay microbes to work
  • Peat bogs are too acidic for decay microbes
130
Q

Where did the first living thing come from?

A

It is unknown

131
Q

Why is how life began unknown?

A

There are many hypotheses suggesting how life first came into being.
There is a lack of valid evidence.
Many early forms of life were soft-bodied so the fossil record is incomplete.
Fossils formed millions of years ago have been destroyed by geological activity.

132
Q

What is isolation?

A

where populations of a species are seperated

133
Q

When does speciation occur?

A

when populations of the same species become so different that they can no longer reproduce to give fertile offspring

134
Q

What two things lead to speciation?

A

Isolation and natural selection

135
Q

Describe the process of speciation.

A
  • There are two populations of the same species
  • They become geographically separated
  • The climate in each location differs
  • The two populations adapt to their environment by natural selection
  • Over time the populations become so different that they no longer reproduce to give fertile offspring
136
Q

Who was a pioneer of the theory of speciation?

A

Alfred Russel Wallace

137
Q

What did Wallace discover?

A

He realised that warning colours are used by some species (butterflies) to deter predators from eating them. Therefore it is a beneficial characteristic that had evolved by natural selection.

138
Q

What lead to antibiotic-resistant strains of bacteria?

A

Random mutations occur causing changes in the bacteria’s characteristics. This gene then becomes more common in the population due to natural selection.

139
Q

Why do bacteria evolve quickly?

A

They are rapid at reproducing

140
Q

Why is being antibiotic resistant a beneficial characteristic for bacteria?

A

It makes them better able to survive, so it lives for longer and reproduces many more times

141
Q

What is MRSA?

A

a common ‘superbug’ that is very resistant to antibiotics, so difficult to get rid of

142
Q

Why is antibiotic resistance getting worse?

A

Due to overuse and inappropriate use of antibiotics

143
Q

Why is it important that a patient takes all of the antibiotics prescribed?

A

It makes sure that all of the bacteria are destroyed, so that none mutate and develop into antibiotic resistant strains.

144
Q

How are antibiotics used in farming?

A

To prevent animals from becoming ill and to help them grow faster.

145
Q

Why are antibiotics in farming creating an issue?

A

By overusing antibiotics in agriculture, antibiotic resistant strains develop in animals which then can spread to humans - e.g. during meat preparation and consumption.

146
Q

Why are companies unlikely to meet the demand for new antibiotics?

A

the rate of development is slow and the antibiotic resistant strains are developing rapidly, it is also costly

147
Q

What is classification?

A

Organising living organisms into groups

148
Q

Since when have organisms been classified?

A

1700s

149
Q

What is the system of classification called?

A

the Linnaean system

150
Q

What is the order of classification?

A

Domain
Kindom
Phylum
Class
Order
Family
Genus
Species

151
Q

What has helped to develop new models of classification?

A
  • knowledge of the biochemical processes inside organisms
  • microscopes improving
152
Q

When was the three-domain system proposed?

A

1990

153
Q

What is the three-domain system?

A

How organisms are split into three groups (Archaea, Bacteria and Eukaryota)

154
Q

What is the Archaea domain?

A

Primitive bacteria often found in extreme places, such as hot springs and salt lakes

155
Q

What is the Bacteria domain?

A

True bacteria

156
Q

What is the Eukaryota domain?

A

a broad range of organisms including fungi, animals, plants and protists

157
Q

How are organisms named?

A

According to the Binomial System

158
Q

How many parts are in the latin binomial name of an organism?

A

two parts (Genus and species)

159
Q

What is the first part of the latin binomial name of an organism?

A

the Genus (Capital letter)

160
Q

What is the second part of the latin binomial name of an organism?

A

The species (lowercase)

161
Q

What do evolutionary trees show?

A

Evolutionary Relationships

162
Q

True or false: The more recent the common ancestor, the more characteristics they are likely to share.

A

True

163
Q

How do scientists work out evolutionary relationships?

A

Living organisms - current classification data (DNA analysis/ structure)

Extinct species - fossil records

AQA Biology GCSE (5 decks)

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