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a level biology > genetics year 13 > Flashcards

genetics year 13 Flashcards

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1
Q

what is phenotype

A

the expression of the genetic constitution and its interaction with the environment

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2
Q

what is genotype

A

the genetic constitution of an organism refering to the alleles that an organism has

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3
Q

what is the F1 generation

A

the first generation of the cross over between pure breeds

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4
Q

what is the F2 generation

A

the second generation of the cross over between the F1 parents

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5
Q

what is the law of segregation

A

phenotype is determined by alleles that occur in pairs and only one allele in the pair can be present in a single gamete

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6
Q

what is codominance

A

when both alleles are equally dominant so both are expressed in the phentype

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7
Q

what are sex linked chromosomes

A

any gene carried on the X or Y chromosome

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8
Q

why are recessive chromosomes on the X chromosomes more prevelent in males

A

males have no homologous dominant portion on the Y chromosome it would only be on the X chromosome but they are XY

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9
Q

what is dihybrid inheritance

A

how 2 characteristics determined by 2 different genes on different chromosomes are passed down and inherited

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10
Q

what does the crossing over of gametes from two heterozygous parents produce in crossing over

A

9:3:3:1

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11
Q

what is the inheritance ratio if you cross a heterozygous with homozygous recessive

A

1:1:1:1

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12
Q

what is epistasis

A

the interaction between different genes where the gene at one locus masks or suppresses the expression of another gene at a second locus

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13
Q

what happens in dominant epistasis

A

one dominant allele at the first gene locus masks the expression of an allele at the second gene locus

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14
Q

what happens in recessive epistasis

A

the two recessive alleles at one gene locus will mask the expression of alleles at the second gene locus

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15
Q

what is the resulting ratio for the recessive epistasis

A

9:4:3

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16
Q

what is autosomal linkage

A

when any two genes that occur on the same chromosome are said to be linked when it isn’t the X or Y chromosome

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17
Q

what is special about the crossover in autosomal linkage

A

almost all of the time there is no crossing over of the linked genes and they stay together to be passed on to the offspring

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18
Q

what is special about independent assortment in autosomal linkage

A

genes tend to be very close together and therefore most of the time there is no independent assortment as the chances of them being separated is very small

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19
Q

what are the conditions for the Hardy Weinberg equation

A

large population
no emigration
no natural selection
no mutations
random mating is essential

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20
Q

if the deviation probability is equal to or higher than 0.05 what does this mean

A

non-significant so the null hypothesis would be accepted

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21
Q

if the deviation probability is less than 0.05 what does this mean

A

significant and disregard the null hypothesis

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22
Q

define speciation

A

the development of a new species from existing ones when they become too distant to produce fertile offspring

23
Q

define species

A

group of individuals that have common ancestry and share the same genes are different alleles and can produce fertile offspring

24
Q

what is genetic drift

A

takes place in smaller populations that possess a small amount of alleles when there is an equal chance of alleles being passed on and the alleles are passed on due to chance not selection

25
Q

why may genetic differences occur

A

mutations occur introducing new alleles
selection pressures
genetic drift in a small population

26
Q

what are the two types of speciation

A

allopatric and sympatric

27
Q

what is allopatric speciation

A

population seperated by a geological barrier causing different selection pressures and a change in allele frequency leading to differences in the gene pool

28
Q

what is sympatric speciation

A

the formation of a new species where a mutation occurs that prevents the members of a population breeding with other members that don’t carry that gene

29
Q

what are the different types of sympatric speciation

A
  1. temporal
  2. behavioural
  3. mechanical
  4. gametic
30
Q

what is temporal speciation

A

seasonal mating does not coincide

31
Q

what is behavioural speciation

A

a mutation occurs affecting courtship

32
Q

what is mechanical speciation

A

anatomical differences that prevent mating

33
Q

what is gametic speciation

A

gametes prevented from fusing due to incompatibility

34
Q

what is an ecosystem

A

all the living and non living components of the area

35
Q

what is a community

A

all the populations of different species living and interacting in an area at the same time

36
Q

what is a population

A

a group of individuals of one species that occupy the same habitat at the same time and can potentially interbreed

37
Q

define carrying capacity

A

the size of a population an ecosystem can sustain

38
Q

define a habitat

A

a place where an organism normally lives and is characterised by physical conditions and the other organisms present

39
Q

what is an ecological niche

A

the role of a species within its habitat, what a species is like, where it occurs, how it behaves, its interactions with other species and its environment.

40
Q

what is the competitive exclusion principle

A

no two species can occupy the same niche at the same time

41
Q

how do you use random sampling to measure abundance of a species

A

Quadrats
1. lay out two long tape measures at right angles
2. obtains random coordinated by using random number generator
3. throw down the quadrat and work out the number of species in the quadrat and use it to find the estimation of the number of species in the whole area

42
Q

how do you use systematic sampling to measure abundance of species

A

belt transect or line transect

43
Q

how does mark ,release and recapture work

A
  1. known number of animals are caught, marked and then released back into the community
  2. sometime later collect a random sample of new ones
  3. number of previously marked in the new sample are recorded
  4. the size of the populations is then calculated using the equation :

total individuals in 2nd sample x toyal individuals in the 1st sample /number of marked in 2nd sample

44
Q

how do you make mark release and capture ethical

A
  1. treat them carefully
  2. handle as little as possible
  3. keep as short time as possible
  4. not painted with bright colours making them more vulnerable to predators
45
Q

what assumptions have to made for mark, release and capture

A
  1. mark isnt toxic
  2. mark or label isnt lost
  3. few deaths or births
  4. no migration
  5. the species distributes themselves evenly
  6. proportion of marked to unmarked is the same in the first sample compared to the second
46
Q

describe the steps to primary succession

A
  1. lichen pioneer a bare rock and cause it to weather and produce soil and sand and the lichen decomposes leaving nutrients
  2. moss and ferns follows continuing erosion of rock and increasing the amount of organic matter building a thicker layer of soil
  3. next come the small flowering plants such as grass, shrubs and then trees and these provide more sources of food and shelter leading to more food chains.
47
Q

what is secondary succession

A

when land has already sustained life but was suddenly altered as the result of land clearance for agriculture or forest fire and starts sustaining life again, occuring much quicker than primary sucession.

48
Q

compare and contrast primary and secondary succession

A
  1. primary begins with no life and secondary begins with existing biota
  2. primary there is no soil present whereas soil is already present in secondary
  3. primary succession is on a new area and secondary is on an old area
  4. primary succession lichen and moss come first and in secondary the seeds and roots are already present
  5. in primary succession the biomass is low and in secondary succession it is high
49
Q

what is conservation

A

management of the Earths natural resources by humans so we get maximum use out of them in future

50
Q

what does conservation involve

A
  1. active intervention by humans to maintain ecosystems and biodiversity
  2. careful management of existing resources and reclamation of those damaged by human activities
51
Q

what are the 4 main reasons for conservation

A

personal: to maintain our planet and therefore out life support system

ethical: other species have occupied earth much longer than us and we should respect that

economical: living organisms contain a big pool of genes with the capacity to make millions of substances many of which may prove valuable in the future. Long-term productivity is greater if ecosystems are maintained in their natural balance.

cultural and aesthetic: habitats and organisms enrich our lives. Their variety adds interest to everyday life and inspires people.

52
Q

what is a plagioclimax community

A

an area of habitat in which human influence has prevented the ecosystem from developing further.

53
Q

what happens to the earlier species in succession and why

A

many of the earlier species are no longer present as their habitats have disappeared because of succession or out competed

a level biology (6 decks)

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