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AQA A Level Biology > 4-9/10 Genetics + Biodiversity > Flashcards

4-9/10 Genetics + Biodiversity Flashcards

1
Q

What is base substitution mutation?

A

when a nucleotide in the DNA sequence is replaced by another, a quick mutation

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2
Q

What is base deletion mutation?

A

a nucleotide is lost, more harmful, causes frameshift

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3
Q

What is a mutagenic agent?

A

factors increase the rate of gene mutation: x-rays, UV light

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4
Q

What are chromosome mutations?

A

when an individual has 3 or more sets of chromosomes instead of two

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5
Q

What is meiosis?

A

a form of cell division that produces four genetically different haploid cells

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6
Q

What happens during meiosis 1?

A

homologous chromosomes pair to form bivalents
crossing over occurs at chiasmata
the cell divides in two, separate randomly
each cell contains either a maternal or paternal copy

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7
Q

What happens during meiosis 2?

A

independent segregation of sister chromatids, the cell divides again to create 4 haploid cells

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8
Q

How does meiosis create a genetic variation?

A

crossing over, the independent assortment of chromosomes, resulting in new alleles

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9
Q

What is the importance of meiosis?

A

if gametes are haploid, chromosome number would double indefinitely

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10
Q

What is genetic combination?

A

exchange of genetic material between organisms resulting in reshuffling

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11
Q

What is genetic diversity?

A

the total number of different alleles in a population

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12
Q

What is the advantage of a high genetic diversity?

A

the ability to adapt to change in the environment allows natural selection

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13
Q

How does natural selection affect evolution?

A

random mutations result in new alleles, some more advantageous so they will survive and reproduce

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14
Q

What is directional selection?

A

when environmental conditions change, individuals with phenotypes suited to new conditions will survive to pass on genes, over time population will move towards those characteristics

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15
Q

What is stabilising selection?

A

when environmental conditions stay the same, individuals closest to the mean are favoured, any new characteristics are selected aginst

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16
Q

What are the three types of adaptation?

A

behavioural, physiological, anatomical

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17
Q

What is a species?

A

a group of organisms that can interbreed to produce fertile offspring

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18
Q

What is courtship behaviour?

A

identifying sexually mature members of their own species of the opposite sex, synchronise mating, form a pair bond and breed

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19
Q

How do you name species?

A

the binomial system

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20
Q

What are the principles of classification?

A

artificial
- observable characteristics
phylogenic
- evolutionary relationships + characteristics

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21
Q

How do you organise groups of species?

A 
Domain
Kingdom
Phylum
Class
Order
Family
Genus
Species
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22
Q

What is phylogeny?

A

arranging organisms into groups based on evolutionary relationships and origins

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23
Q

What is biodiversity?

A

the variety of living organisms measured in species diversity ecosystem and genetic diversity

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24
Q

What is the species diversity index?

A

D = Σ(n / N)2

∑ = n(n-1)
N(N-1)

n = the total number of organisms of a particular species
N = the total number of organisms of all species
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25
What is the impact of agriculture?
decreases species richness, pesticides, loss of habitat
26
How is the balance between conservation and farming maintained?
hedges > fences, rotate crops, limit pesticides
27
How do you compare DNA base sequences?
using gene technology + computers to read sequences, species have similar DNA
28
How do you compare mRNA sequences?
mRNA is reliant on DNA, the two will show the same results
29
How do you compare by amino acid sequence?
the amino acid sequence is determined by mRNA, which comes from DNA
30
How do you carry out random sampling?
randomly generated coordinates for a quadrant until sufficient data collected
31
How do you calculate standard deviation?
``` √∑ (x-x_)2 n-1 x = measured value x_ = mean value n = total values in samples ```
32
What is the process of prophase 1?
Chromosomes condense and become visible Nuclear envelope breaks down Contains 4n genetic material
33
What is the process of metaphase 1?
Homologous pairs of chromosomes line up next to each other Spindle fibres connect to the centrioles Contains 4n genetic material
34
What is the process of anaphase 1?
Homologous pairs are pulled apart to opposite poles of the cell Contains 4n genetic material
35
What is the process of telophase 1?
Nuclei reform Cytokinesis Forms two cells with 2n genetic material each
36
What is the process of prophase 2?
Nuclei break down | Contains 2n genetic material
37
What is the process of metaphase 2?
Chromosomes lime up on the equator of the cell Spindle fibres attach to the centromeres Contains 2n genetic material
38
What is the process of anaphase 2?
Chromatids are separated by the contraction of the spindle fibres They're pulled apart to opposite poles Contains 2n genetic material
39
What is the process of telophase 2?
Nuclei reform Cell divides Produces n genetic material per cell
40
What are the two forms of variation during meiosis?
Independent segregation | Crossing over
41
What is the process of independent segregation?
The homologous chromosomes randomly line up in meiosis 1 along the equator so the chromosomes at the poles are randomly selected
42
What is the process of crossing over?
During meiosis 1, the chromatids become twisted round each other The twisting creates tension where portions are broken off
43
What is the aim of meiosis?
To create gametes (haploid cells) with half the number of normal chromosomes To create sperm and ovum To introduce variation
44
What is a substitution reaction?
A nucleotide in a DNA molecule is replaced by another nucleotide that has a different base This changes the amino acid and disrupts the primary structure This could mess up the whole chain because the R groups affect the secondary and tertiary structure A mutation could give you exactly the same amino acid and have little or no effect It can change an enzyme's active site so that it doesn't work
45
What is a deletion mutation?
DNA bases shift to the left which completely changes the sequence, stops the polypeptide from functioning
46
What is meant by random fertilisation?
Any egg can be fertilised by any sperm which increases variation
47
What is crossing over?
When portions of DNA are swapped between non-sister chromatids
48
What is the role of the centromere during mitosis?
Centromere attaches to the spindle fibres | It allows separation in anaphase as centromere splits
49
What are the steps of variation on a larger scale?
There is an initial gene pool A random mutation occurs- mostly harmful If it is advantageous, the organism is better adapted and more likely to live and breed The offspring is also likely to have a new allele Over time the allele frequency increases
50
How do the conditions an organism lives in affect a mutation?
Happens no matter what conditions it lives in | The benefits of a mutation are determined by the environment
51
What is a species?
A group of organisms that can interbreed to produce fertile offspring
52
What is a population?
A group of organisms of the same species living in the same area
53
What is directional selection?
When the normal distribution shifts to the left or right due to an environmental charge (selection pressure) or an advantageous mutation occurs Graph shifts in favour of the advantageous allele
54
What is stabilising selection?
Environmental conditions are stable Individuals with phenotypes closest to the mean are favoured These individuals are more likely to breed It tends to eliminate phenotypes at the extremes Graph: peak is higher and spread is narrower
55
How does a mutation affect a protein receptor?
Change in DNA nucleotide sequence Change in amino acid sequence Alters position of hydrogen/ionic/disulfide bonds Change in tertiary structure of receptor
56
What is taxonomy?
The practise of grouping organism
57
What is the binomial system?
Two names per organism | Only works for physical characteristics
58
What are the subgroups of the binomial system?
Kingdoms - five levels Phylum ``` Class Order Family Genus Species ```
59
How are animals named?
Genus species E.g. Homo* sapien, H.* sapien*, (Homo sapien) * = italics, () = underlined
60
What are the three types of traits in animals?
Anatomical: where the different components are Physiological: how an organism works Behavioural: how the organism reacts to its environment and other organisms
61
What is a species?
Organisms that can interbreed together and produce fertile offspring
62
What is a phylogenetic group?
A group linked by evolution/genetic relationships/common ancestry
63
How can information on amino acid sequences help to construct a phylogenetic tree?
Those with similar groups are closely related | The larger the differences between sequences, the longer ago the groups diverged
64
What are the stages of courtship?
Recognition: recognising a member of the same species, scent can aid this Capability: is the organism capable of mating, sometimes communicated Forming a bond: being in close proximity, fighting over territory or offspring, protective bond Synchronisation: takes place when there is a maximum probability of the sperm and egg meeting, oestrus is the time in which they are fertile and can conceive Breeding
65
How are phylogenetic relationships of different species represented?
Shows genetic links, not observable traits All taxons have evolved from a common ancestor Branch node represents a speciation event (can be an event which doen not remove the common ancestor) Sister taxa are taxa which come from the most recent branch node, this means they are more genetically similar X axis represents time Variation can occur within a taxon
66
What do farmers do that reduces the genetic variety of alleles?
They select species for particular qualities that make them more productive Most of a farmers area is taken up by desirable species which means that other species have to compete for remaining resources which will reduce their numbers or cause them to go extinct
67
Why do pesticides reduce the diversity index?
They exclude those species that compete with the farmed species for food, light, mineral ions and water This reduces the diversity index
68
What practises reduce biodiversity?
Removal of hedgerows and woodland Creating monocultures e.g replacing a field with one crop Filling in ponds and draining marsh/wetland Over-grazing of land e.g upland areas by sheep which prevents regeneration Use of pesticides and inorganic fertilisers
69
What are the main conservation techniques?
Use hedges over fences as field boundaries Maintain existing ponds and create new ones Plant native trees on land with a low species diversity Reduce pesticide use Use organic fertilisers Introduce conservation headlands- free of pesticides to aid wildlife
70
How has the government encouraged conservation efforts?
Conservation methods make food more expensive so financial incentives have been put in place
71
How do you calculate the means of grouped or tallied data?
Sum of fx -------------------------------- Number of data values f = frequency, x = data value When x is a range, use the midpoint
72
What is the individual?
One member of the population
73
What is a population?
Members of the same species living in the same area
74
What is a community?
Populations that live together in a defined area
75
What is an ecosystem?
A community plus it's non-living surroundings
76
What is a biosphere?
All of the ecosystems on Earth
77
What is a habitat?
The place where an organism lives
78
What is the equation for the diversity index?
N(N - 1) ------------------- Sum of n(n - 1) N = total number of all organisms n = total number of each different species
79
What are the limiting factors in aquatic environments?
Salinity Dissolved oxygen content Light Temperature
80
How can genetic diversity be compared?
The frequency of measurable or observable characteristics The base sequence of DNA The base sequence of mRNA The amino acid sequence of the proteins encoded by DNA and mRNA
81
In which types of sampling are quadrats and transects used?
Random- quadrat | Systematic- quadrat and transect
82
What is the difference between species richness and diversity index?
The species index is the number of different species | The diversity index looks at the species richness as well as the abundance of each
83
What is an abiotic factor?
A non-living factor
84
What is a transect?
Sampling at regular intervals | Needs an abiotic factor to study e.g light intensty
85
What is the general population curve?
Exponential curve then levels off once it reaches the carrying capacity

AQA A Level Biology (19 decks)

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