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Biology 2 > B6 Inheritance variation and evolution > Flashcards

B6 Inheritance variation and evolution Flashcards

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1
Q

Explain how two different species of squirrel could have developed from a common ancestor

A
  • ancestral population isolated (ie geographically by mountains)
  • genetic variation due to mutations
  • different environmental conditions (selection pressures) in the separate gene pools
  • individuals better adapted to environment survive (natural selection occurs) and they breed, passing favourable alleles on (in each population) to offspring
  • repeated over many generations, favourable allele frequency increases and so if two populations are brought together they cannot interbreed successfully to produce fertile offspring so have become genetically different
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2
Q

Suggest why two species not have become more different over a long period of time

A

Still live in similar environments with similar conditions so will have similar adaptations

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3
Q

Suggest how fossils of a bird was formed.

A

Animal buried in sediment, soft tissue decayed and bones did not decay, mineralisation occurred where bones are replaced by minerals

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4
Q

Explain why reproducing asexually means there is no variation

A

No fusion of gametes so the offspring are genetically identical (genetic material does not mix)

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5
Q

Suggest two ways embryo screening can help people with a family history of a genetic disorder

A
  • Inform parents to consider having an abortion
  • prevent future child from suffering
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6
Q

Suggest three reasons why there are gaps in fossil record for older species

A
  • Geological activity destroyed many fossils
  • Conditions not right for fossilisation as many early life forms were soft bodied
  • Buried deeper so not yet discovered
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7
Q

Suggest one advantage of having DNA analysis

A

Help with treatment and understanding of inherited disorders

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8
Q

Why is DNA described as a polymer?

A

Many nucleotides that are monomers in a chain

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9
Q

Describe the structure of a nucleotide.

A
  • Phosphate attached to a sugar
  • Sugar has one of four bases (which have a complementary pairing)
  • Bases are A, T, G, C
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10
Q

Describe how non-coding parts of DNA can affect the expression of genes

A

Can switch genes on/off - controlling gene expression

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11
Q

Give three differences between meiosis and mitosis

A
  1. mitosis has one cell division whereas meiosis has two
  2. mitosis produces two daughter cells whereas meiosis produces four cells
  3. mitosis produces genetically identical cells whereas meiosis produces non genetically identical cells
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12
Q

Describe one similarity between the processes of mitosis and meiosis

A

Both involve DNA replicating

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13
Q

A woman has three children, aged 4, 6 and 9 years.
Give two reasons why the children are not genetically identical.

A
  • From different egg/sperm
  • Each gamete has different genes, multiple genes determine appearance
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14
Q

14b) Suggest two advantages of asexual reproduction for bluebells.

A
  • Many offspring produced in less time (than sexual)
  • More energy efficient
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15
Q

Explain why sexual reproduction is an advantage for bluebells

A

Genetic variatio/n in offspring so the better adapted survive (natural selection). This means bluebells more likely to colonise new areas by seed dispersal (breed), as seeds are sexually produced. There will be many offspring so higher probability of survival.

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16
Q

Explain how a mutation could cause an enzyme not to work

A
  • Change in the three (triplet) bases - three bases code for one amino acid
  • Changes order of amino acids, may have different amino acids in the chain
  • Different protein made meaning active site may have changed shape
  • Enzyme can no longer bind to substrate shape as they are no longer complementary
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17
Q

What are stem cells?

A

Undifferentiated cells which can become specialised

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18
Q

Why would it not be possible to treat a genetic disorder in a child using his own umbilical cord stem cells?

A

stem cells have same faulty gene/allele

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19
Q

What is a fossil?

A

Remains of an organism from a long time ago

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20
Q

Give four possible reasons for extinction

A
  1. catastrophic event eg asteroid
  2. new disease/pathogens
  3. new predators
  4. competition for food
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21
Q

How can scientists use fossils to determine age?

A

By the age of the rocks where the fossils were found/ how deep they were buried in sediment

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22
Q

Give one disadvantage and one advantage of mass extinction events.
Answer in terms of evolution.

A

D: reduction in range of (favourable) alleles (gene pool)
A: allows evolution of new species (which may be more complex)

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23
Q

Describe the process of natural selection

A
  • Variation (due to mutations)
  • Selection pressure (biotic/abiotic)
  • Organisms better adapted to environment survive
  • Survivors breed and pass down favourable alleles to offspring and this favourable allele frequency eventually increases
  • This occurs over many generations (a long time)
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24
Q

Suggest how scientists could prove individuals belong to the same species.

A

Interbreed to see if they successfully produce fertile offspring

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25
Q

State the (modern) classification order

A

Domain
Kingdom
Phylum
Class
Order
Family
Genus
Species

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26
Q

Explain why birds of the same species may have a greater range in beak depth on one island compared to another

A
  • Variation of beak depth ranges due to mutations
  • One island may have less food available so there is more competition so the birds have a greater range in beak depth to increase likelihood of survival as can all get enough food and then breed
  • Survivors pass down favourable alleles to offspring
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27
Q

Why may an area be able to have different species living in the same area

A

Bigger area with more food so there is enough food for both species

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28
Q

How can you prove an offspring is heterozygous?

A

Not all of its offspring produce a dominant allele characteristic

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29
Q

Describe how the scientists would produce a type of cattle producing large volumes of low fat milk

A
  • Select female producing a large yield of low fat milk
  • Select a male who’s female offspring have highest yield of low fat milk and mother produced highest yield of low fat milk
  • Breed and select offspring which matches both features and breed them
  • Repeat this over many generations
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30
Q

Describe the type of evidence used for developing the theory of migration

A
  • Fossil record
  • DNA analysis of living species (the genome studied)
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31
Q

In GE explain why all the GM bacteria in this clone are able to produce a growth hormone

A

Clones produced by asexual reproduction. All genes are copied so each bacteria receives the gene.

32
Q

Give two reasons for selective breeding in domestic animals

A
  • So they do not have specific genetic defects
  • Produce docile animals
33
Q

Give one problem caused by inbreeding

A

More susceptible to diseases

34
Q

For tissue culture give a reason why several cells are scraped off

A

To make a large number of clones

35
Q

For tissue culture give a reason why nutrients are added to agar

A

To make amino acids(to make proteins, for growth)

36
Q

For tissue culture give a reason why hormones are added to agar

A

To stimulate cell division

37
Q

For tissue culture give a reason why it is done in sterile conditions

A

To prevent microorganisms entering/forming like bacteria

38
Q

For tissue culture give a reason why they are incubated at 20 degrees

A

Optimum for growth

39
Q

Explain why using tissue culture produces the same type of plant

A

All have been produced by asexual reproduction (mitosis) so the clones formed all have the same genes (genetically identical)

40
Q

What causes cells to be genetically identical?

A

DNA/chromosomes are replicated and equally split (like in mitosis) with no fusion of gametes

41
Q

Describe how embryos can be screened for the alleles that cause genetic disorders.

A
  • DNA isolated from embryo
  • (fluorescent) probe mixed with embryo DNA probe (then) binds with embryo DNA
  • (UV light) to show alleles / gene for disorder
42
Q

What is the importance of bases?

A

Three bases code for a particular amino acid and so base order code for a particular amino acid sequence which code for a specific protein

43
Q

How are organisms fossilised in amber

A

Trapped in amber and conditions for decay are absent (so decay is prevented)

44
Q

Describe three ways fossils can be formed

A
  • mineralisation (hard bones replaced by minerals)
  • conditions for decay are absent
  • preserved traces/ imprints of organisms
45
Q

Why may people disagree with cloning children? (2)

A
  • Unethical
  • Illegal in the UK with a low survival rate
46
Q

Give two reasons why some farmers are in favour of growing GM crops

A
  • Less use of pesticides
  • Increases yield (and so profits)
47
Q

Give two reasons why many people are against the growing of GM crops

A
  • reduction in gene pool and biodiversity
  • long term health risks unknown
48
Q

Explain why the dark moth population increased during industrial revolution (trees turned dark)

A

Dark moth less easily seen by predators
Dark moth less likely to be eaten and more likely to survive and so breeds and passes down favourable alleles to offspring

49
Q

Define a gene

A

A small section of DNA/chromosome that controls characteristics as its bases code for a particular protein

50
Q

Explain how Lamarcks theory works and why it couldn’t be true

A

Organism keeps on using characteristic during their lifetime so it becomes more complex. Survives and reproduces, passing down this characteristic to offspring.
-> could not be true as mutations occur continuously and randomly, not because of a characteristic use

51
Q

In the 1800s, many scientists could not decide whether Lamarck’s theory or Darwin’s theory was the right one.
Give two reasons why

A
  1. insufficient evidence
  2. DNA not yet discovered
52
Q

Explain why its difficult for scientists to be certain about what early life forms were like

A

Many early life forms were soft bodied and so decayed, meaning there was a lack of fossils (insufficient evidence) to show

53
Q

Explain why each chromosome must become two strands before the cell divides

A

one copy of each chromosome to each offspring cell
each offspring cell receives a complete set of / the same genetic material

54
Q

Give one advantage and disadvantage of embryo screening

A

+ prevent future suffering (for inherited disorders)
- promote ‘designer babies’ and prejudices against genetic disorders

55
Q

How do mitochondria and ribosomes make enzymes?

A

Mitochondria releases energy which is used by ribosomes for protein synthesis, which uses amino acids to make the protein enzymes

56
Q

Define evolution

A

Change in inherited characteristics over time (due to natural selection) and is a continuous process

57
Q

How can doctors reduce the number of bacteria that become resistant to antibiotics?

A

Don’t overprescribe antibiotics by reducing use of them for mild infections and viruses. If antibiotics are given, ensure patient finishes full course

58
Q

Describe the structure of a DNA molecule

A

Two stranded polymer in a double helix structure made from monomers called nucleotides

59
Q

Describe the type of cell division that produces gametes

A

Meiosis. DNA replicates and parent cells divide twice to produce 4 non genetically identical gametes.

60
Q

Suggest two disadvantages for garden centres growing plants only by asexual reproduction

A
  1. no variation (genetically identical) so all offspring susceptible to same diseases
  2. no variation meaning customers have less choice + range
61
Q

Describe the steps scientists would have taken to produce rice with short stems

A
  • select two rice plants with the shortest stems and breed them
  • choose plant offspring with desired characteristics (short stem) and breed them
  • repeat over many generations until all plants have the desired characteristic
62
Q

Explain two reasons why people will agree and disagree with GM plants

A
  • Less pests so increased yield of crops
  • Larger grains so greater profit for farmers
  • LT health risks unknown as insufficient research
  • Reduces biodiversity as less varieties are now grown
63
Q

Explain why herbicide resistant plants have a higher yield

A

Not killed by spraying herbicides, only weeds are killed. Survivors get more light and so photosynthesise more.

64
Q

Explain advice doctors should give to prevent the spread of new strains (3)

A
  • Don’t give antibiotics to patients with viruses as antibiotics only kill bacteria, not viruses
  • Do not overprescribe antibiotics for mild infections as patients will feel better due to their immune system
  • Ensure patient finishes full course so no bacteria left to develop resistance, survive and reproduce rapidly
65
Q

What are extreme conditions?

A

Conditions most organisms couldn’t be able to survive eg high salt concentrations

66
Q

Describe the ‘three domain’ system

A

Based on biochemistry advances
- Archaea: primitive bacteria
- Bacteria/prokaryota: ‘true’ bacteria
- Eukaryota: including protists, fungi, animals and plants

67
Q

How can you prove a characteristic is inherited?

A

Offspring characteristic will be similar to their parents

68
Q

Explain why a particular disease may not be found on the Y chromosome

A

The Y chromosome is only found on males, if females also have inherited the disease it will not be on the Y chromosome as females don’t have a Y chromosome (they have XX)

69
Q

How can fossils be used to show evidence for evolution?

A

Older fossils can be compared with current species, showing change over time

70
Q

Why are scientists unsure of how life on Earth began?

A

Insufficient evidence (many fossils destroyed by volcanic activity)

71
Q

What was insulin initially made from before it was genetically engineered?

A

Pigs and cattle (moral ethic objection)

72
Q

Explain how genetic engineering is used to make insulin

A
  • Cut vector (plamid) with a restriction enzyme
  • Cut insulin producing gene with same restriction enzyme (from pancreas cells)
  • Complementary sticky ends on gene and plasmid, allowing them to bind perfectly
  • Insert plasmid into bacteria cell so and incubate so it divides rapidly
  • Collect and purify the insulin from the bacteria cells
73
Q

What did Mendel study

A

Inheritance in pea plants when they breed, said determined by ‘hereditary units’ which can be dominant/recessive (units now known as genes)
-> investigated colour of the flowers and peas

74
Q

What are the two kingdoms in the Linnaean system?

A

Plant and animal

75
Q

Which system is used traditionally to classify organisms?

A

Linnaean classification system

76
Q

What is the advantage of a Linnaean system being used?

A

Each species has its own unique name so it allows scientists to discuss individual species without confusion

77
Q

Genus vs species

A

A genus is a group of species that are very similar and most likely have a common ancestor. In contrast, a species is just one type of animal.

Biology 2 (3 decks)

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