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AQA A-Level Biology > Y2: Population Genetics > Flashcards

Y2: Population Genetics Flashcards

1
Q

What is a gene pool?

A

All the alleles of the genes of all the organisms of a population at a given time

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2
Q

Define allele frequency

A

The proportion of a given allele in the gene pool

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3
Q

What is the Hardy-Weinberg Equilibrium/principle?

A

The assumption that allelic frequency will remain constant over time

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4
Q

What is the Hardy-Weinberg equation?
3

Describe
Actual equation
What each thing represents

A

Mathematical equation that allows us to calculate the expected frequencies of alleles in a population

p2 + q2 +2pq = 1.0

(p = frequency of homozygous dominant and q = frequency of homozygous recessive and pq = frequency of heterozygous)

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5
Q

What must be true for the Hardy-Weinberg principle to be true?

(What assumptions must be made?)

5

A
  1. No new mutations
  2. Population is isolated so no new alleles
  3. No selection
  4. Large population
  5. Mating is random
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6
Q 
What is a species?
1
And two characteristics of a species
-genes
2
A

A group of individuals that interbreed to produce fertile offspring

Each species is reproductively isolated

There is no gene flow as each species have a single gene pool

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7
Q

What is speciation?
1
And what does it require?
1

A

The evolution of a new species from existing ones

Requires populations to become reproductively isolated

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8
Q

What is allopatric speciation?

1

A

Relies on geographical barrier

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9
Q

What acronym is used for allopatric speciation?

8

A

GIMSPARI

Geographically 
Isolated
Mutations occur
Selection
Pressure
(Differs)
Allelic frequencies (change)
Reproductively 
Isolated
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10
Q

What is Allopatric speciation full answer?

6

A
  1. Population becomes geographically isolated
  2. Mutations occur in the two populations
  3. The populations will experience different selection pressures due to different environments
  4. The allelic frequencies of the two populations change to favour the beneficial alleles
  5. The populations change until they are reproductively isolated so can no longer interbreed to produce fertile offspring
  6. Two populations are now different species
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11
Q

What is sympathetic speciation?

1

A

Populations become isolated in SAME GEOGRAPHICAL AREA

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12
Q

What is the acronym for sympatric speciation?

9

A

NGIMSPARI

NOT Geographically 
Isolated
Mutations occur
Selection
Pressure
(Differs)
Allelic frequencies (change)
Reproductively 
Isolated
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13
Q

What are the different types of sympatric speciation?

4

A
  1. Temporal: different breeding seasons
  2. Mechanical: mismatch of reproductive parts
  3. Ecological: they inhabit different niches in the same habitat
  4. Genetic: (plants) become polyploid and are now incompatible with diploid
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14
Q

Define biotic factor

A

All of the living things in an ecosystem that affects an organisms survival

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15
Q

Define abiotic factor

A

All of the non-living things in an ecosystem that affects an organisms survival

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16
Q

Name 4 biotic factors

A
  1. Prey abundance
  2. Disease
  3. Predators
  4. Competitors
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17
Q

Name 4 abiotic factors

A
  1. Weather
  2. Oxygen and CO2
  3. Temperature
  4. pH
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18
Q

Define ecosystem

A

Self-contained dynamic interaction between all biotic and abiotic factors in an area

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19
Q

Define population

A

Group of individuals of the same species that occupy the same habitat at the same time

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20
Q

Define community

A

Interacting group of various species in a location

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21
Q

Define habitat

A

Place within an ecosystem where a population of organisms is found

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22
Q

Define niche
1
Extra
2-role, dependant on?

A

All the conditions and resources required for an organism to survive, reproduce and maintain a viable population

Functional role an organism plays in an ecosystem

Depends on the biotic and abiotic factors

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23
Q

What is interspecific competition?

1

A

Overlap between niches of two species in an ecosystem

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24
Q

What are the two results for interspecific competition?
And describe them
4

A
  1. Resource partitioning: species alter their niche and divide resources
  2. Competitive exclusion: one species uses resources more efficiently and drives the other to extinction
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25
Describe a population growth graph 4
1. Initially all populations have the capacity to grow exponentially (if no limiting factors) 2. Therefore growth rate increases 3. Growth rate decreases as resources become limiting and competition for resources increases S shaped curve that plateaus at carrying capacity
26
What is carrying capacity? | 1
Maximum population of an organism that can be sustained indefinitely without degrading the ecosystem
27
What is the population growth equation and what do the things stand for?
PG = (B+I) - (D+E) B: birth rate I: immigration rate D: death rate E: emigration rate
28
Why do we use logarithms for population growth? | 1
The set of numbers often have a very large range
29
What is a logarithmic graph? | 1
Scale increases between increments / as number increases scale increases to accommodate
30
What is intraspecific competition? | 1
Competition within a species
31
What is interspecific competition? | 1
Competition with a DIFFERENT species
32
What is strophic cascade?
The effect of the removal of things at the top of the food chain
33
What is rewilding? | 1
Restoring diversity in ecosystems by reintroducing species driven out
34
What is an example of rewilding?
Beavers in the UK | Wolves in Yellowstone
35
What is the founder effect? | 1
Large fluctuations in population that results in genetic variation
36
What is heterozygosity? 1 Adaptation? 1
Large number of organisms heterozygous for an allele More variability which results in a greater ability to adapt
37
What is homozygosity? 1 Adaptation? 1
Large number of organisms that are homozygous for alleles Less variability so less ability to adapt
38
Define ecological succession?
Process of change in the species structure of an ecological community over time
39
What does ecological succession result in? | 1
Increase in biomass and biodiversity
40
What are the 6 stages of ecological succession? | 6
1. Colonisation by a pioneer species 2. This causes a change in environment 3. This enables other species to colonise which outcompete the pioneer species 4. This results in a change in biodiversity 5. Stability increases / less hostile environment 6. Climax community
41
What is a climax community? | 2
An ecological community in which populations of plants or animals remain stable and exist in balance with each other and their environment. Organisms that make up the final stage in ecological succession
42
What is a pioneer species?
Pioneer species are hardy species which are the first to colonize barren environments or previously biodiverse steady-state ecosystems that have been disrupted.
43
What are some characteristics that make avoid pioneer species? 6
1. Asexual reproduction: multiply rapidly 2. Wind dispersed seeds/spores: allows far travel of species 3. Rapid germination with no dormancy: rapid increase in population 4. Ability to photosynthesise: not dependent on other species 5. Ability to fix nitrogen from the atmosphere: to use in proteins etc 6. Ability to tolerate harsh conditions
44
What does random sampling measure?
Abundance
45
What is a sample and what should it be? 3
Small selection from a population Should be representative so what is true of the sample should be true of the whole population Need to balance accuracy with logistical possibility
46
What are the three ways to measure abundance? And what type of species/pattern are they used for? 1 2 4
1. Counting: infrequent species where individuals are distinct 2. % cover: estimate of area within a quadrat that a plant species covers. Used for hard to count and abundant species 3. Frequency: measure of how likely it is for a species to appear. Used for hard to count species. Simple yes no if it is or isn’t there. Shows distribution but not abundance/density
47
What is the method for using a quadrat? | 6
1. Place two tape measures at right angles along the edges of the field to produce coordinates 2. Use a random number generator to select a coordinate 3. Place the quadrat at this coordinate and count the number of organisms 4. Repeat until running mean stabilises 5. Calculate the mean number of dandelions per quadrat, the area of quadrat and the area of field 6. Do mean x (area of field / area of quadrat)
48
What is the equation for population size for mark release recapture?
(Number in sample 1 x number in sample 2) / number marked in sample 2
49
What are the assumptions for mark release recapture? | 5
1. No large migration 2. No large numbers die or are born 3. Marking does not affect their survival 4. Marks are not removed 5. Population has a definite boundary
50
What is the method for mark release recapture? | 5
1. Capture sample for a set period of time 2. Mark all organisms in sample with appropriate safe method 3. Capture a second sample for the same set period of time 4. Count marked organisms in the second sample 5. Pop = no. S1 x no. S2 / no. M S2
51
What is an example of a marking method? | 3
1. Uv pens 2. Cutting wings or fins 3. Tagging
52
When is mark release recapture used? | And how accurate is it
For animals | Fairly inaccurate
53
What is conservation? 2 What does it involve? What is its goal?
Managing nature in order to protect species and their habitats. Maintain and restore biodiversity. Involves active management by humans End goal is to maximise biodiversity
54
What do you need for conservation? | 2
High birth rate Sizeable area
55
How do you achieve a high birth rate in conservation? 2 Why do you do these things? 2
1. Need more females than males 2. Need enough males so there is genetic diversity - otherwise all offspring would have similar alleles - so change in environment would affect all offspring
56
Why do you need a sizeable area for conservation? 1 Why should it not be too big or two small? 1&1
Higher maximum carrying capacity If too small area: 1. More competition for food, habitat and mate If too large: 1. Organisms can’t find mates
57
What is systematic sampling used for? | 1
Places where there is a clear environmental gradient
58
Systematic sampling method? 3 What is this method called/uses?
1. Stretch string or tape measures across the ground in a straight line 2. Lay a frame quadrat alongside the line and count the species against two of the lines of the quadrat to prevent double counting 3. Move the quadrat along the line and repeat Using belt transects
59
Define consumer
An organism that obtains energy by 'eating' another
60
Define producer
An organism that synthesises organic molecules from simple inorganic ones
61
Define biomass
Total mass of living materials in a specific area at a given time (Usually dry mass)

AQA A-Level Biology (11 decks)

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