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Biology Paper 2 > B14&15 Variation And Genetics And Evolution > Flashcards

B14&15 Variation And Genetics And Evolution Flashcards

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1
Q

What is a ‘species’?

A

Organisms that are genetically similar enough to be able to breed and produce fertile offspring

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2
Q

What are the 2 causes of variation within a species?

A

Genetics and environment

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3
Q

What term is used to mean the physical expression of a pair of alleles?

A

Phenotype

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4
Q

What are alleles?

A

Different forms of the same gene

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5
Q

What is a recessive allele?

A

One that is only expressed if both alleles are recessive/if a dominant one is not present

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6
Q

What do genes code for?

A

The amino acid sequence of a protein

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7
Q

What is variation?

A

The existence of variety and difference within and between species

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8
Q

Types of variation - discontinuous

A
  • Also known as Discrete variables
  • Variables are assigned to clearly defined categories or distinct groups
  • Examples include: blood group, sex
  • Data usually presented as a bar graph
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9
Q

Variation within species

A
  • This relies upon mutations within a species
  • This variation is acted upon by selection pressures, something that makes an individual more or less likely to survive
  • Only the fittest individuals will survive to breed
  • This is the way that Evolution via Natural Selection operates
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10
Q

Types of variation - continuous

A
  • The full range of variables between 2 extreme values
  • Examples in nature include: height weight, length
  • Normally presented in a Normal Distribution bell-shaped curve
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11
Q

Genetic variation

A
  • Every person on Earth has their own unique genetic makeup (unless they are an identical twin)
  • Most of our genes are controlled by more than 1 allele
  • A few traits are determined by a single allele e.g. blood group and some inherited disease
  • Caused by miscopying of the DNA of gametes resulting in changes in (or loss of) proteins
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12
Q

What could cause genetically identical hydrangeas to have different coloured flowers?

A
  • Soil pH
  • Mineral ion intake, magnesium and nitrate
  • Temperature
  • Water uptake
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13
Q

What could cause genetically identical twins to have slight differences?

A
  • Diet, exercise etc
  • Exposure to sunlight
  • Environmental factors
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14
Q

what is inherited variation?

A

Differences between organisms passed to offspring by their parents in reproduction e.g. eye colour, natural hair colour, blood type

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15
Q

what is environmental variation?

A

Differences between organisms caused by environmental factors e.g. language spoken, accent

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16
Q

what is both inherited and environmental variation?

A

When the natural phenotype is affected by the environment e.g. height, weight

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17
Q

Mutations

A
  • Inherited variation is all due to mutations in genes
  • A mutation is a change in the genetic code, a mistake when DNA is being copied during cell division
  • Mutations happen all the time and most have no impact on the protein being made
  • However, sometimes, a mutation can lead to a change in the phenotype and this can affect the survival of the organism
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18
Q

Lamarck’s theory of evolution

A
  • His idea was that every type of animal evolved from primitive worms
  • The change from worms to other organisms was caused by the inheritance of acquired characteristics
  • Proposed that the way organisms behaved affected the features of their body
  • Any useful changes that took place in an organism during its lifetime would be passed from a parent to its offspring
  • Animals adapted and changed their phenotype to their surroundings
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19
Q

Darwin’s theory of evolution by natural selection

A
  • Individual organisms in a particular species tend to show a wide variation for each characteristic
  • Reproduction always gives more offspring than the environment can support. The organisms with the inherited characteristic most suited are more likely to survive and breed (Survival of the fittest)
  • When they breed they pass on the genes that have enabled them to survive onto their offspring
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20
Q

Why was Darwin’s theory of natural selection not widely accepted at first?

A
  • The relevant scientific knowledge and evidence was not available at the time e.g. no understanding of genes and inheritance
  • It conflicts with the accepted religious beliefs about divine creation
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21
Q

What is a fossil?

A

The remains of a plant or animal from millions of years ago

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22
Q

What is the theory of evolution?

A

That all living things have evolved from simples cells that evolved over 3 billion years ago

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23
Q

What do we think the earliest life forms were?

A

Simple cells

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24
Q

What is cystic fibrosis a disorder of?

A

Cell membranes

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25
Q

Fossils

A
  • A fossil is the preserved parts or traces of an animal or plant that once lived on earth
  • They provide evidence that animals and plants were once much simpler than they are today
  • They also show how species may have arisen from common ancestors
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26
Q

Fossils - the evidence for evolution

A
  • Fossils of the simplest organisms are found in the oldest rocks, and fossils of more complex organisms in the newest rocks
  • This supports the theory of evolution, which states that simple life forms gradually evolved into more complex ones
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27
Q

Fossil formation

A
  • As preserved traces e.g. footprints, burrows or rootlet traces
  • When parts/all of the organism doesn’t decay because one or more of the conditions for decay are absent
  • When parts of the organism are replaced by minerals as decay happens
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28
Q

Why is the fossil record incomplete?

A
  • Whilst the fossil record gives lots of evidence for evolution, it does not provide evidence for how life first evolved, or what the first life forms looked like
  • This is because these were soft bodied organisms and would not have left traces or had bones to be replaced by minerals
  • Many fossils remain undiscovered, and many would have been destroyed by geological activity
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29
Q

Other evidence for evolution

A

Other evidence for common ancestors and change over time includes:
- looking at the anatomy of animals
- how animals develop
- all cells have a very similar chemistry e.g. enzymes, DNA, ribosomes etc
- some organisms can be observed evolving e.g. bacteria

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30
Q

Give three advantages of understanding the human genome

A

It enables us to:
- search for genes linked to different types of diseases
- understand inherited disorders and their treatment
- trace human migration and evolution

31
Q

Name the two scientists that jointly proposed the theory of evolution by natural selection

A

Charles Darwin and Alfred Russel Wallace

32
Q

What is the genome?

A

The entire set of genes for an organism

33
Q

How do we decide whether two animals that look very alike are a different species?

A
  • DNA sequencing
  • Interbreeding and identifying if the offspring is fertile
  • If organisms are of different species, they are genetically different to the point that they are unable to breed successfully
  • Even if they can actually produce offspring, the young are infertile
34
Q

How do new species arise?

A
  • The population of organisms is separated by some sort of barrier
  • The conditions on each side of the barrier are different
  • Long periods of time elapse
  • Selection pressures exerted by the environment (biotic/abiotic factors)
  • For example, the earth’s tectonic plates are constantly moving, this causes continents to move apart, mountain ranges to form and new land areas to appear
35
Q

Speciation

A
  • There is always variation within a species, because of mutations and sexual reproduction
  • New species arise because of isolation
36
Q

Speciation answer framework

A
  • Geographical separation
  • Environmental differences
  • Random mutation/variation
  • Best adapted in each area to survive, breed and pass on alleles/genes
  • Eventually, the different populations can no longer successfully breed with each other
37
Q

Porkfish speciation example answer

A
  • The original species of pork fish were separated when the land rose, so some were on either side of the barrier and they could not breed with each other
  • Conditions on either side of the barrier could have been different e.g. different temperatures or different food available
  • Random mutation meant that there would be genetic variation within the populations
  • The fish best adapted to the conditions in each area survive and breed and pass on their genes
  • Eventually, the two groups are so genetically different that, even if they did meet, they would not be able to breed with each other to produce fertile offspring
38
Q

What do antibiotics treat?

A

Bacterial infections

39
Q

Why can’t antibiotics be used to treat HIV?

A

HIV is a viral infection and viruses live and reproduce inside our cells

40
Q

How do bacteria reproduce?

A

Asexually (binary fission)

41
Q

What is unique about bacterial DNA?

A

It is not contained inside a nucleus

42
Q

What is antibiotic resistance?

A

When a bacteria that used to be killed by a drug isn’t affected by it any more

43
Q

How have antibiotic resistant bacteria evolved?

A
  • A natural population of bacteria has variation and a mutation can lead to one or two bacteria being resistant to the antibiotic
  • The patient starts taking the antibiotic and the non-resistant bacteria die first
  • As the patient continues taking the antibiotic the non-resistant bacteria will continue to die
  • Until eventually only the resistant bacteria are left, the resistant bacteria now have no competition for nutrients or oxygen
  • The resistant bacteria reproduce rapidly, they use asexual reproduction so all the offspring will have the mutation for resistance
44
Q

What are the problems with resistance?

A
  • Having bacteria that are resistant to antibiotics is a real threat to us and increases the risk of becoming infected with bacterial illnesses
  • It makes surgery riskier as the threat of infection a person with a bacteria that cannot be killed is potentially fatal
  • The development of resistance is being driven by overuse of antibiotics
45
Q

What can be done about antibiotic resistance?

A
  • Not prescribing antibiotics unless absolutely needed
  • Educating patients to ensure they finish the course of any antibiotics they are prescribed
  • Antibiotics given to animals in agriculture should be limited
46
Q

Antibiotics in agriculture

A

Animals are often given antibiotics to prevent infectious disease, particularly in farms where animals are kept in close contact with each other

47
Q

What can we do to stop antibiotic resistance spreading?

A

Educating both professionals and patients that antibiotics are not always needed

48
Q

What are the gametes in plants?

A

Pollen and egg

49
Q

What does it mean to be heterozygous?

A

When the two alleles in a pair are the same

50
Q

What do genes code for?

A

The amino acid code sequence for a protein

51
Q

What is selective breeding?

A
  • Where animals or plants with specific traits that we want to see are deliberately used in breeding programmes
  • They are very often bred with organisms with other desirable feature so that, hopefully, the offspring show all of the desired characteristics
  • It very often has to be done over many generations though, meiosis and fertilisation are random
52
Q

Characteristics usually desired in selective breeding

A
  • Disease resistance in food crops
  • Animals which produce more meat to milk
  • Domestic dogs with a gentle nature
  • Large or unusual flower
53
Q

How is selective breeding done?

A
  • Parents with desired characteristics are chosen
  • They are bred together. In plants, this means ensuring that the pollen from one desired plant is transferred to the other plant and not allowed to self fertilise
  • The offspring are examined, and the ones with the best features are chosen for the next breeding round
  • This continues over many generations until the offspring show all of the desired characteristics
54
Q

Ensuring the selection in plants

A
  • Pollen is transferred from the flowers of one plant to the other
  • The plant is prevented from self-fertilising by removing the anthers or being cross-pollinated by another plant by bagging the plant
  • The process is repeated over several generations until the plants breed true for the required characteristics
55
Q

Problems with selective breeding

A
  • The process can be long as there are no guarantees the offspring will have the features needed
  • It is faster in organisms that produce lots of organisms in one go e.g. plants, IVF can be used to speed things up
  • Because a limited number of organisms are used for breeding, the variety in the gene pool becomes reduced, inbreeding is the result
  • Inbreeding can lead to an increased chance of inherited disorders
56
Q

What are the two plant cloning methods?

A

Taking cuttings, tissue culture

57
Q

Explain the process of plant cloning by taking cuttings

A
  • Cut off a growing side stem, and keep it in damp conditions until roots grow
  • It can then be planted as normal
  • Rooting powered can also be used to help promote root growth
58
Q

Explain the process of plant cloning using tissue culture

A
  • A few cells are taken and placed on nutrient agar with auxin to promote root and shoot development
  • They can then be planted normally
  • All the plants produced are genetically identical to the original plant
59
Q

Which twi scientists proposed the theory of evolution by natural selection?

A

Charles Darwin and Alfred Wallace

60
Q

What is a fossil?

A

The remains of an organism from a long time ago

61
Q

What are the causes of extinction?

A
  • New predators
  • New diseases
  • Global warming
  • Flooding, droughts, volcanic activity etc
  • Competition for food and mates
  • Lack of habitat or habitat change
62
Q

Evidence of evolution

A
  • Bacteria can become resistant to an antibiotic
  • Older fossils are more simpler than more recent ones
63
Q

Who developed the ‘three-domain system’ of classification?

A

Carl Woese

64
Q

Suggest how scientists can estimate when the Siberian rhinoceros was alive

A

Compare with other fossils of a known age

65
Q

Andrewsarchus was a carnivore and Brontotherium was a herbivore. Suggest how the extinction of Andrewsarchus could have resulted in the extinction of Brontotherium

A
  • The extinction of Andrewsarchus led to a population increase of another predator
  • Because Andrewsarchus is no longer competing for food
  • Other predator hunted more Brontotherium
66
Q

Give three reasons why the fossil record is not clear for older species

A
  • Fossils buried deeper so harder to find
  • Oldest organisms were soft-bodied so most of the tissue decayed
  • Dating older fossils is hard
67
Q

Suggest uses of land after the trees have been removed

A
  • Growing crops/biofuels
  • Grazing animals
  • Quarrying/mining
  • Dumping waste
  • Building houses
68
Q

Why does the removal of trees cause an increase in carbon dioxide in the atmosphere? (2 marks)

A
  • There is less photosynthesis
  • The trees are burned
69
Q

What effect would an increase in carbon dioxide in the atmosphere have on global air temperature? (1 mark)

A

Increase

70
Q

What is a mutation? (1 mark)

A

A change in a gene

71
Q

Describe the process of natural selection

A
  • There is variation between members of a species
  • Those better adapted survive
  • Reproduce and pass on favourable genes
72
Q

How can fossils form?

A
  • Animal or plant dies, body covered in sediment
  • Bones do not decay
  • Mineralisation, bones are replaced by other minerals
  • Preserved traces, footprints, burrows etc
73
Q

How could the extinction of plants have caused the extinction of some animals?

A

Less food and oxygen for animals

Biology Paper 2 (10 decks)

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