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Biology > Topic 7 > Flashcards

Topic 7 Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

Monohybrid inheritance

A

> parents diploid
100% heterozygous for F1
F2 = 3:1

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2
Q

Dihybrid inheritance

A

> F1 generation = 100% heterozygous

> F2 generation phenotypic ration = 9:3:3:1

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3
Q

Codominance and multiple alleles

A

Example - ABO blood group, A and B are codminant and o is recessive

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4
Q

Epistasis

A

> when a phenotype is controlled by more than one gene - one gene can either mask or suppress the expression of another gene
recessive epistatic allele - 9:3:4 (recessive prevents the expression of another allele)
dominant epistatic allele - 12:3:1 (one gene completely masks the alleles)

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5
Q

Autosomal linkage

A

> genes on the same autosome are linked
they will stay together during independent assortment and will be inherited together
because linked genes are inherited together they behave like a monohybrid cross
means that more offspring will have the same phenotype and genotype as their parents

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6
Q

Autosomal linkage and crossing over

A

If crossing over occurs then the alleles are separated and there will be differing genotypes and phenotypes to the parents
> closer loci is to autosome - more closely linked

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7
Q

Haemophilia

A

blood los slowly and there may be slow and persistent internal bleeding
> females have two x chromosomes and you must be homozygous recessive to suffer
Males only have one x so only need one to suffer

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8
Q

Normal phenotypic ratios

A

Monohybrid crosses - 3:1
Dihybrid crosses - 9:3:3:1
Codominant crosses - 1:2:1

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9
Q

Epistatic phenotypic ratios

A

Recessive epistatic - 9:3:4

Dominant epistatic - 12:3:1

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10
Q

Sex linkage phenotypic ratio

A

Heterozygous dominant = 3:1

Heterozygous recessive = 1:1

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11
Q

The hardy weinburg principle

A

Predicts - the frequency of alleles of a gene will stay constant over generations
Assumptions - no mutations, no selection, random mating, large population, genetically isolated, no migration

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12
Q

Hardy-Weinberg equation

A

P+Q=1
P^2 + 2pq + q^2 = 1
P = dominant
Q = recessive

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13
Q

Causes of variation

A

> most variation is a result of both
Genetic - mutation, crossing over, independent assortment, random fertilisation, inherited
Environmental causes - changes the phenotype

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14
Q

Speciation

A

> variation exists in the population due to mutation
Different selection pressures cause directional selection of differnt phenotype
differental reproductive sucess causes a change in allele frequency over many generations

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15
Q

Genetic drift

A

> affects small populations much more than large population
changes the allele frequency , is a cause of evolution
is does not depend on the environment

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16
Q

Directional selection

A

> caused by a change in environmental conditions
only those with the desired allele will survive and reproduce
mean changes

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17
Q

Stabilising selection

A

> in a stable environment
both extremes of the phenotype are less likely to survive and reproduce
the mean remains the same

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18
Q

Disruptive selection

A

> both extremes of the phenotype are more likely to survive and reproduce than the means phenotype
environment select for two separate phenotypes
contributes to sympatric speciation

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19
Q

Abundance of organisms

A

> Intraspecific competition - species occupy the same niche and compete for everything
Interspecific competition - the abundance of one species will affect the other, species with a similar niche will compete for resources
abiotic factors - species can tolerate a range of conditions, where condition are optimal pop size is biggest

20
Q

Distribution of orgnaisms

A

Interspecific competition and predation will affect an organisms distribution
Organisms will only exist where they can survive

21
Q

Transects

A

> systematic sampling
record the distribution of species along the line
line transect - run a tape measure and record all that touches tape
belt transect - use quadrats along the length of transects
inherited transect - use quadrats at fixed intervals

22
Q

Quadrats

A

> random sampling
record the number of individuals in the quadrat
species frequency - how often a species is found in each square
percentage cover - if over 50% covered

23
Q

Sampling a population

A

> Random: avoids bias, divide into grid and use random generator to pick coordinates
non-ransom: systematic - samples are taken at fixed intervals
Data needs to be representative, large = more reliable, enough to carry out a stats test

24
Q

Mark-release-recapture

A

Used to estimate the abundance of a mobile species

1) capture organism
2) mark them in a way that doesn’t harm them
3) wait
4) take a 2nd sample
5) use equation

25
Q

Mark-release-recapture equation

A

Total pop = total caught in 1st sample x total caught in 2nd sample / no marked in 2nd sample

26
Q

Succession

A

> area is colonised by pioneer species - change the environmental conditions to make less hostile
allows other species to outcompete the preceding species
continues until climax community is reached

27
Q

What happens when succession takes place

A 
> soil depth increase
> H2O + nutrient availability increases
> biodiversity increase
> plant height increases
> niches increase
> light intensity on the ground decreases
28
Q

Primary succession

A

Starts from newly formed land
Harsh biotic conditions
Very slow

29
Q

Secondary succession

A

Starts from land where vegetation have been cleared
Less harsh abiotic conditions
Much faster
Pioneer species can be larger

30
Q

Deflected succession

A

Stops succession - tall plants cant grow because tips are continuously cut off
Cannot outcompete low growing grasses
Grassland becomes the climax community

31
Q

Climax community

A

Different ecosystems have different abiotic conditions - they develop into different climax communities

32
Q

Chi-squared

A

Sum of (O-E)^2/ E
> sample over 20
> find difference between observed and expected

33
Q

How is sex determined genetically

A

Sex is determined by the absence or presence of a y chromosome

34
Q

What do species compete for

A

Animals - food, water, space

Plants - light, water, minerals, root space

35
Q

How does predator - prey relationship affect the population size

A

> An increase in prey means more food for the predators so the predator population increases
more predators means less prey
less prey means less food for the predators so predator population decreases
less predation occurs so the prey population increases

36
Q

Factors to consider when using a quadrat

A

Size of the quadrat
The number of sample quadrats to record within the study area
The position of each quadrat within the study area
(What will be counted in the quadrat - eg partially in/ fully in)

37
Q

Measuring abundance of different species

A

Non moving - using a quadrat

Moving - mark-release-recapture

38
Q

Managing succession to help conserve habitats

A

Conservation can prevent succession in order to preserve the current ecosystem
Preventing succession keeps ecosystems intact
> eg animal grazing, managed fires

39
Q

Methods of conservation

A

Plants - using seedbanks which are stores of lots of seeds
Fishing quotas - limits the amount of certain fish species that fishermen can catch
National parks - protect habitats
Endangered species - breed in captivity

40
Q

Role of overproduction of offspring in natural selection

A

Most juveniles will not make it to adulthood
Means that those with desired characteristics survive
The parents genes have a higher chance of being passed on

41
Q

Effects of selection on evolution

A

Stabilising - mean survives
Directional - one extreme survives
Disruptive - both extremes survive
They dictate who will survive through evolution

42
Q

Selection affecting allelic frequency

A

Decreases the allele frequency - only a small and specific type of allele will survive

43
Q

Variation in natural selection

A

Allows for there to be an increase and decrease of frequency of alleles in the population

44
Q

How are new species formed

A

Through speciation - allopatric and sympatric speciation

45
Q

How do populations become geographically isolated

A

Movement of land masses, continental drift, mountain lines, etc

Biology (18 decks)

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