B14&15 Variation And Genetics And Evolution Flashcards
1
Q
What is a ‘species’?
A
Organisms that are genetically similar enough to be able to breed and produce fertile offspring
2
Q
What are the 2 causes of variation within a species?
A
Genetics and environment
3
Q
What term is used to mean the physical expression of a pair of alleles?
A
Phenotype
4
Q
What are alleles?
A
Different forms of the same gene
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
6
Q
What do genes code for?
A
The amino acid sequence of a protein
7
Q
What is variation?
A
The existence of variety and difference within and between species
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
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
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
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
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
13
Q
What could cause genetically identical twins to have slight differences?
A
- Diet, exercise etc
- Exposure to sunlight
- Environmental factors
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
15
Q
what is environmental variation?
A
Differences between organisms caused by environmental factors e.g. language spoken, accent
16
Q
what is both inherited and environmental variation?
A
When the natural phenotype is affected by the environment e.g. height, weight
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
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
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
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
21
Q
What is a fossil?
A
The remains of a plant or animal from millions of years ago
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
23
Q
What do we think the earliest life forms were?
A
Simple cells
24
Q
What is cystic fibrosis a disorder of?
A
Cell membranes
25
Fossils
- 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
26
Fossils - the evidence for evolution
- 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
27
Fossil formation
- 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
28
Why is the fossil record incomplete?
- 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
29
Other evidence for evolution
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
30
Give three advantages of understanding the human genome
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
Name the two scientists that jointly proposed the theory of evolution by natural selection
Charles Darwin and Alfred Russel Wallace
32
What is the genome?
The entire set of genes for an organism
33
How do we decide whether two animals that look very alike are a different species?
- 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
How do new species arise?
- 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
Speciation
- There is always variation within a species, because of mutations and sexual reproduction
- New species arise because of isolation
36
Speciation answer framework
- 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
Porkfish speciation example answer
- 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
What do antibiotics treat?
Bacterial infections
39
Why can't antibiotics be used to treat HIV?
HIV is a viral infection and viruses live and reproduce inside our cells
40
How do bacteria reproduce?
Asexually (binary fission)
41
What is unique about bacterial DNA?
It is not contained inside a nucleus
42
What is antibiotic resistance?
When a bacteria that used to be killed by a drug isn't affected by it any more
43
How have antibiotic resistant bacteria evolved?
- 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
What are the problems with resistance?
- 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
What can be done about antibiotic resistance?
- 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
Antibiotics in agriculture
Animals are often given antibiotics to prevent infectious disease, particularly in farms where animals are kept in close contact with each other
47
What can we do to stop antibiotic resistance spreading?
Educating both professionals and patients that antibiotics are not always needed
48
What are the gametes in plants?
Pollen and egg
49
What does it mean to be heterozygous?
When the two alleles in a pair are the same
50
What do genes code for?
The amino acid code sequence for a protein
51
What is selective breeding?
- 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
Characteristics usually desired in selective breeding
- Disease resistance in food crops
- Animals which produce more meat to milk
- Domestic dogs with a gentle nature
- Large or unusual flower
53
How is selective breeding done?
- 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
Ensuring the selection in plants
- 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
Problems with selective breeding
- 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
What are the two plant cloning methods?
Taking cuttings, tissue culture
57
Explain the process of plant cloning by taking cuttings
- 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
Explain the process of plant cloning using tissue culture
- 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
Which twi scientists proposed the theory of evolution by natural selection?
Charles Darwin and Alfred Wallace
60
What is a fossil?
The remains of an organism from a long time ago
61
What are the causes of extinction?
- New predators
- New diseases
- Global warming
- Flooding, droughts, volcanic activity etc
- Competition for food and mates
- Lack of habitat or habitat change
62
Evidence of evolution
- Bacteria can become resistant to an antibiotic
- Older fossils are more simpler than more recent ones
63
Who developed the 'three-domain system' of classification?
Carl Woese
64
Suggest how scientists can estimate when the Siberian rhinoceros was alive
Compare with other fossils of a known age
65
Andrewsarchus was a carnivore and Brontotherium was a herbivore. Suggest how the extinction of Andrewsarchus could have resulted in the extinction of Brontotherium
- 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
Give three reasons why the fossil record is not clear for older species
- Fossils buried deeper so harder to find
- Oldest organisms were soft-bodied so most of the tissue decayed
- Dating older fossils is hard
67
Suggest uses of land after the trees have been removed
- Growing crops/biofuels
- Grazing animals
- Quarrying/mining
- Dumping waste
- Building houses
68
Why does the removal of trees cause an increase in carbon dioxide in the atmosphere? (2 marks)
- There is less photosynthesis
- The trees are burned
69
What effect would an increase in carbon dioxide in the atmosphere have on global air temperature? (1 mark)
Increase
70
What is a mutation? (1 mark)
A change in a gene
71
Describe the process of natural selection
- There is variation between members of a species
- Those better adapted survive
- Reproduce and pass on favourable genes
72
How can fossils form?
- 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
How could the extinction of plants have caused the extinction of some animals?
Less food and oxygen for animals
