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A-Level Biology > Populations in Ecosystems 2.0 > Flashcards

Populations in Ecosystems 2.0 Flashcards

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1
Q

What is the purpose of the Hardy Weinberg Principle?

A

Mathematical equation used to predict the frequencies of alleles in a population

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2
Q

What is the equation for the Hardy Weinberg Principle?

A

p^2 + 2pq +q^2 = 1

p^2= no. of individuals that are homozygous dominant (AA)
2pq= no. of individuals that are heterozygous (Aa or aA)
q^2= no. of individuals that are homozygous recessive (aa)
1= all alleles present
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3
Q

What steps do you follow for Hard Weinberg Principle?

A 
Calculate q^2 = fraction
q = square root
p + q = 1
1 - q = p
2pq
Percentage
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4
Q

What assumptions should we make when using the Hardy Weinberg Principle?

A 
No selection
No mutations
No migration
Large population
Random mating
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5
Q

What MUST we assume when using the Hardy Weinberg Principle?

A

The proportion of dominant and recessive alleles of ANY gene in a population remains constant from one generation to the next

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6
Q

What is selection?

A

The process by which organisms better adapted to their environment tend to survive and breed at the expense of those less well adapted

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7
Q

What is phenotypic variation a result of?

A

Genetic factors

Environmental factors

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8
Q

Why does genetic variation occur?

A

Meiosis
Sexual reproduction
Mutations

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9
Q

Describe directional selection

A

Graph moves right/left
Change in environment
Change in mean
Extreme selected

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10
Q

An example of directional selection?

A

Moths

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11
Q

Describe stabilising selection

A

Graph squishes inwards
Both extremes
Phenotypic variation decreases
Environment remains stable

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12
Q

An example of stabilising selection?

A

Birth weight

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13
Q

Why does natural selection occur?

A

Random mutation in gene pool
Become advantageous trait in specific environment
Mutation = better adapted
Organisms survive at the expense of those less adapted
Reproduce
Allele frequency increases in gene pool
Evolution

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14
Q

Name some selection pressures

A

Predation
Natural disaster
Competition
Disease

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15
Q

What are selection pressures?

A

Environmental factors that limit population of a species

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16
Q

What do selection pressures determine?

A

The frequency of all alleles within the gene pool

17
Q

Evolution only occurs by natural selection if…

A

Organisms reproduce
Have sufficient resources
Genetic variation
Phenotypic variation

18
Q

In order for populations to survive + increase exponentially they must…

A

Have a suitable population size
Minimise intraspecific competition
Have high reproductive success

19
Q

What factors make populations survive + increase exponentially unlikely?

A

High death rates from predation
Low parental investment
Lack of resources

20
Q

Why is death rate not random?

A

Organisms better adapted survive

21
Q

What is variation essential for?

A

Chagrining environment
New disease
New predators
New competition

22
Q

Describe disruptive selection

A

Least common form
Opposite to stabilising
Favours extremes at the expense of intermediate phenotypes

23
Q

Examples of disruptive selection

A

Mean fur lengths

Coho salmon

24
Q

What is speciation?

A

The evolution of new species from existing species, that enables evolutionary change and diversity

25
Q

What is speciation due to?

A

Reproductive isolation
Genetic differences (mutations)
Geographical isolation

26
Q

What are the two forms of speciation?

A

Allopatric

Sympatric

27
Q

Describe allopatric speciation

A

Most common
Different location
Geographic separation

28
Q

Describe sympatric

A

Less common
Same location
Reproductive isolation

29
Q

How does allopatric speciation occur?

A 
Barrier occurs preventing migration between population
Environment of each new range may be different
Different mutations occur in each range
Different selection pressures
Selection favours advantageous allele
No gene mixing of alleles
Changes in allele frequency
Unable to interbreed
EVEN if barrier removed
30
Q

What is adaptive radiation?

A

The diversification of species into forms adapted to different ecological niches

31
Q

How do sympatric speciation occur?

A

eg. Apple maggot fly…
Only lay eggs inside Hawthorns Fruits
Apple trees introduced
Some flies lay eggs in apples
Mates are found by searching site they were raised
Raised in apples = mates wit flies raised in apples
Mutations may result in two new species

32
Q

What is genetic drift?

A

Genetic change due to CHANCE

33
Q

What will there be in smaller populations?

A

Smaller variety of alleles
Not equal chance of each allele being passed on
OR if a mutation passed on quickly
Speciation more likely

A-Level Biology (21 decks)

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