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Biology > 7. Genetics, populations, evolution and ecosystems > Flashcards

7. Genetics, populations, evolution and ecosystems Flashcards

1
Q

What is a dominant allele?

A

An allele which is always expressed in the phenotype even when there is only one copy of it

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2
Q

What is a recessive allele?

A

An allele that can only appear in the phenotype if two copies are present.

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3
Q

What are codominant alleles

A

Alleles that are both expressed in the phenotype because neither one is recessive.

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4
Q

If an organism carries two copies of the same allele it is said to be……….

A

homozygous at the locus.

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5
Q

If an organism carries two different alleles it is said to be…….

A

heterozygous at the locus.

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6
Q

What is monohybrid inheritance?

A

Inheritance of a characteristic controlled by a single gene.

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7
Q

What do monohybrid crosses show?

A

The likelihood of the different alleles of that gene being inherited by the offspring of certain parents.

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8
Q

What type of offspring would a monohybrid cross with two homozygous parents produce?

A

It will always produce all heterozygous offspring.

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9
Q

What is a phenotypic ratio?

A

The ratio of different phenotypes in the offspring.

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10
Q

What is the usual phenotypic ratio you would get if you did a monohybrid cross with two heterozygous parents?

A

3:1 ratio of dominant:recessive characteristics.

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11
Q

What ratio would you expect to see if you did a monohybrid cross with two heterozygous parents involving codominant alleles?

A

1:2:1

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12
Q

What is dihybrid inheritance?

A

The inheritance of two characteristics which are controlled by different genes.

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13
Q

What can dihybrid crosses show?

A

The likelihood of offspring inheriting certain combinations of two characteristics from particular parents.

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14
Q

What phenotypic ratio would you expect to see if you did a dihybrid cross with 2 heterozygous parents?

A

9:3:3:1 dominant both : dominant first, recessive second : recessive first, dominant second : recessive both

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15
Q

What does sex-linked mean?

A

The alleles that code for them are located on a sex chromosome.

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16
Q

Which sex chromosome carries most genes?

A

X chromosome

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17
Q

Which gender is more likely to express the characteristic of sex linked genes? Why?

A

Males - they have one X chromosome so they only have one copy of the allele, they express it even if it is recessive.

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18
Q

What are two X linked disorders?

A

Colour blindness and haemophilia

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19
Q

Why can’t males be carriers of X-linked disorders?

A

Because they only have one copy of each chromosome so if they have the allele they have the disease whether it is recessive or not.

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20
Q

What is an autosome?

A

Any chromosome that is not a sex chromosome.

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21
Q

What are genes on the same autosome said to be? Why?

A

Linked - they will stay together during the independent segregation of chromosomes in meiosis 1 and their alleles will be passed on to their offspring together.

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22
Q

What can cause autosomal genes not to stay together during independent segregation?

A

If crossing over splits them up first.

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23
Q

What is independent segregation?

A

The random division of homologous chromosomes into separate daughter cells during meiosis.

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24
Q

If two genes are autosomally linked, what ratio would you expect to see and why?

A

3:1 because the two autosomally linked alleles are inherited together.

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25
What is epistasis?
A phenomenon when the genotype of one gene can mask the effects of a separate gene.
26
What happens if the epistatic allele is recessive?
Two copies of it will mask the expression of the other gene.
27
In recessive epistasis alleles, if you cross a homozygous recessive parent with a homozygous dominant parents, what phenotypic ratio would you get in the F2 generation?
9:3:4 dominant both : dominant epistatic, recessive other : recessive epistatic
28
What happens when the epistatic allele is dominant?
Having at least one copy will block the expression of the other.
29
What is the chi-squared test?
Statistical test that is used to see if the results of an experiment support a theory.
30
What are the 5 steps in the chi-squared test?
Theory Expected results Observed results Null hypothesis Chi-squared test
31
What is the null hypothesis?
Is always "there is no significant difference between the observed and expected results."
32
What is the formula for the chi-squared value?
The sum of = (O-E)2 / E O = observed result E = expected result
33
If the chi-squared value is larger or equal to the critical value then..... the null hypothesis.
reject
34
If the chi-squared value is less than the critical value then..... the null hypothesis.
fail to reject the null hypothesis
35
What is a species?
A group of organisms that can interbreed and produce fertile offspring in nature.
36
What is a population?
A group of individuals of the same species living in the same area at the same time.
37
What is a gene pool?
Is the complete range of alleles present in a population.
38
What is the Hardy-Weinberg principle?
Mathematical model that predicts the frequencies of alleles in a population won't change from one generation to the next.
39
What is the allele frequency and what is the equation?
The total frequency of all possible alleles for a characteristic in a certain population. It is always 100% or 1.0 p+q = 1 p = the frequency of one allele q = the frequency of the other allele
40
What is the genotype frequency and the equation?
The total frequency of all possible genotypes for one characteristic in a certain population is 1.0 or 100% p^2 + 2pq + q^2 = 1 p^2 = frequency of homozygous dominant genotype q^2 = frequency of homozygous recessive genotype
41
What conditions need to be met for the Hardy-Weinberg principle to be true?
Large population with no immigration, emigration, mutations or natural selection. Random mating.
42
What is intraspecific variation?
Any difference between individuals of the same species.
43
What factors can cause variation?
Genetic or environmental factors.
44
Which two things can evolution occur by?
Genetic drift, natural selection.
45
What are selection pressures?
Pressures that affect an organism's chance of survival such as predation, disease and competition.
46
What are the three types of natural selection?
Stabilising selection Directional selection Disruptive selection
47
What is stabilising selection?
Selection against the extremes (for the averages).
47
What is disruptive selection?
Favours individuals at both extremes of the phenotypic range.
47
What is directional selection?
Extreme phenotype is more likely to survive.
48
What is speciation?
The formation of a new species from an existing species.
49
When does speciation occur?
When geographic or reproductive isolation prevents members of two populations from interbreeding.
50
What is geographical isolation?
Individuals in a species become separated because of a physical barrier such as earthquakes or floods.
51
What is allopatric speciation?
The formation of a new species in populations that are geographically isolated from one another and have slightly different climate.
52
What is sympatric speciation?
The formation of a new species without the presence of a geographic barrier, occur when random mutations prevent individuals from breeding.
53
Which three changes cause reproductive isolation?
Seasonal changes Mechanical changes Behavioural changes
54
What is genetic drift?
A change in allele frequencies caused by random events.
55
Why can genetic drift be a problem for small populations?
Because it may cause species to be less able to adapt to future environmental changes.
56
What is an ecosystem?
All the living and non-living things interacting in an area.
57
What are biotic conditions?
Living features of an ecosystem.
58
What are abiotic conditions?
Non-living features of an ecosystem.
59
What is a habitat?
The place where an organism lives.
60
What is a niche?
It is the role of a species within it's habitat; what it eats, where and when it feeds.
61
What happens if two species try to occupy the same niche?
They will compete with each other and one will be more successful.
62
What is an adaptation?
A trait that helps an organism survive and reproduce.
63
What is the population size?
The total number of organisms of one species in a habitat.
64
What is the carrying capacity?
Maximum stable population size of a species that an ecosystem can support.
65
What happens if abiotic conditions aren't ideal?
More energy will be needed to maintain
66
What is interspecific competition?
When organisms of different species compete with each other for the same resources.
67
What is intraspecific competition?
When organisms of the same species compete with each other for the same resources.
68
Explain how intraspecific competition can cause cyclical change in population size around an ecosystems carrying capacity.
Because a population of species grows when resources are plentiful which leads to more organisms competing so, eventually, the resources become limited again. If the population grows beyond the carrying capacity there won't be enough resources so the population decreases.
69
What is predation?
An interaction in which one organism kills another for food.
70
What is a broth culture?
A liquid broth containing bacteria.
71
A broth culture with a high absorbable value has a........ number of bacteria present.
high
72
What is a spectrophotometer?
Measures amount of light passing through a sample.
73
What does an exponential graph show?
Doubling in number at regular intervals.
74
What does abundance of species mean and how is it calculated?
The number of individuals of one species in a particular area, estimated by counting the number of individuals in samples taken.
75
What are the two methods of measuring abundance?
Frequency - the number of samples a species is recorded in Percentage cover - how much of the area you're investigating is covered by a species.
76
What is distribution?
Where a particular species is within the area you're investigating.
77
What are the methods for investigating populations and what are they used for?
Quadrats and transects - non-motile organisms Nets and traps - motile organisms
78
What is a quadrat?
A square frame enclosing a known area divided into grids of 100.
79
What are the advantages and disadvantages of using quadrats?
Advantage - useful for quickly investigating areas with plant species that fit within it Disadvantage - areas with larger plants and tree would need very large quadrats
80
What is a belt transect?
Quadrats are placed next to each other along the transect (line) to work out species frequency and percentage cover along it.
81
What is an interrupted belt transect?
Quadrat placed at regular intervals.
82
What is the mark-release-recapture method?
Used to measure abundance of motile species by capturing a small sample, marking them, releasing them and take a second sample a week later to see how many marked are caught.
83
What equation would you use to work out the total population size in the mark-release-recapture method?
(No. caught in 1st sample x No. caught in 2nd sample) / No. marked in 2nd sample
84
Which three assumptions does the accuracy of mark-release-recapture count on?
- the marked sample has had enough time and opportunity to mix back in - the marking hasn't affected the individuals chance of survival - there are no changes in population size due to births, deaths, migration
85
What does dynamic mean?
Constantly changing.
86
What is succession?
When one community completely replaces another over time in a given area.
87
What is primary succession?
Succession that occurs on surfaces where no soil exists.
88
What are pioneer species?
Species such as lichens that are the first to colonise the new area.
89
How does primary succession work?
Pioneer species grow and die, changing the environment so it is better for the next species until a more complex ecosystem is built.
90
What is a climax community?
A relatively stable community that results from a long period of plant and animal succession.
91
What is secondary succession?
After a major disturbance in an area that already has soil and once had living organisms.
92
What does phlagioclimax mean?
While succession is stopped artificially by human activities.
93
What is a climax community
A stable group of plants and animals for a particular climate.
94
What is conservation?
The protection of natural resources.
95
What does sustainable mean?
Enough resources are taken to meet the needs of people today without reducing the ability of people in the future to meet their own needs.
96
What are the five main conservation methods?
Management of succession Seed banks Captive breeding Fishing quotas Protected areas

Biology (3 decks)

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