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A2 Biology > TOPIC 7: Genetics, populations, evolution and ecosystems > Flashcards

TOPIC 7: Genetics, populations, evolution and ecosystems Flashcards

1
Q

3.7.1 Inheritance

Define genotype.

A

The genetic consitution of an organism.
(Describes all the alleles an organism has.
Determines the limits within which the charactersitics of an individual may vary.)

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2
Q

3.7.1 Inheritance

Define phenotype.

A

The expression of the genes and its interaction with the environment.

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3
Q

3.7.1 Inheritance

Define gene.

A

A section of DNA that codes for a polypeptide that results in a characteristic

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4
Q

3.7.1 Inheritance

Define allele.

A

Different forms of the same gene.

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5
Q

3.7.1 Inheritance

Define diploid.

A

When an organism contains 2 copies of one chromosome = 2 alleles for the same gene.

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6
Q

3.7.1 Inheritance

Define haploid.

A

When an organism contains one copy of a chromosome = one allele for the same gene.

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7
Q

3.7.1 Inheritance

Define dominant alleles.

A

An allele that will always be expressed in the phenotype.

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8
Q

3.7.1 Inheritance

Define recessive alleles.

A

An allele only expressed if no dominant alleles is present.
Gg = dominant
gg = recessive homozygous.
There must be 2 recessive alleles for phenotype to be expressed.

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9
Q

3.7.1 Inheritance

Define monohybrid.

A

Genetic inheritance cross of characterisitcs determined by one gene

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10
Q

3.7.1 Inheritance

Genetic diagram coding of monohybrid.

A

Single letter
Capital or lower case letters.

example: G or g

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11
Q

3.7.1 Inheritance

What was Gregor Mendel’s study based on?

A

Study of the colour of pea pods.
Green or yellow.

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12
Q

3.7.1 Inheritance

Outline what pure breeding refers to in Gregor Mendel’s study of the colour of pea pods.

A

Green pods are bred with green pods continously for the character of green pods.

Give rise to plants with green pods.

Pods = homozygous

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13
Q

3.7.1 Inheritance

Outline what the first filial / F1 generation refers to in Gregor Mendel’s study on the colour of pea pods.

A

Pure bred Green pods + Pure bred yellow pods = allele for green pods (green pods are dominant)

Parental phenotype: Green pod Yellow pods
Parental genotype:
GP= GG
YP = gg
Gametes:
GP = G G
YP = g g
Offspring genotype:
punnet square using gametes to result in
4 x Gg
Offspring phenotype:
All plants have green pods (Gg)

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14
Q

3.7.1 Inheritance

Outline what the first filial / F1 generation refers to in Gregor Mendel’s study on the colour of pea pods.

A

Heterozygous plants (Gg) of F1 generation are crossed with another Gg = F1 intercross.
RATIO = G:Y = 3:1 plants.

F1 Offspring phenotype: Green pods Green pods.
F1 Offspring genotype:
GP = Gg
GP = Gg
Gametes:
GP = G g
GP = G g
Offspring F2 genotype:
Punnet square using gametes to result in
1 x GG
2 x Gg
1 x gg
Offspring F2 phenotype:
GREEN PODS ARE DOMINANT SO its a 3:1 ratio = GP:YP

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15
Q

3.7.1 Inheritance

What is the monohybrid genetic cross ratio?

A

3:1
G:Y

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16
Q

3.7.1 Inheritance

Why are the actual results of genetic crosses rarely the same as the predicted results?

A

Due to statistical error

Chance that determines which gametes fuses with each other.

Larger the sample = more likely actual results will come near to matching the theoritical one = 3:1

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17
Q

3.7.1 Inheritance

Define dihybrid.

A

Genetic inhertiance cross for a characteristic that is determined by 2 genes

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18
Q

3.7.1 Inheritance

What was Gregor Mendel’s study on for the dihybrid genetic cross?

A

Studied 2 characters of pea plants at the same time.
1. Seed shape:
round = dominant
wrinkled = recessive.

2. Seed colour:
yellow = dominant
green = recessive

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19
Q

3.7.1 Inheritance

Outline the genetic diagram coding of the dihybrid cross of Gregor Mendel’s study of the 2 characterisitcs of pea plants.

A

R = Round seeds
r = wrinkled seeds

G = Yellow seeds
g = green seeds

Roundyellow: RG (dominant,dominant)
Roundgreen: Rg (dominant,recessive)

Wrinkledyellow: rG (recessive,dominant)
Wrinkledgreen: rg (recessive,recessive)

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20
Q

3.7.1 Inheritance

Outline the genetic cross between purely bred round yellow seeds (dominant,dominant) and purely bred wrinkled green seeds (recessive,recessive).

A

Parental phenotype: Round yellow seeds, Wrinkled green seeds.
Parental genotype:
RY: RRGG
WG: rrgg
Gametes:
RY: RG
WG: rg
Offspring genotype:
RrGg

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21
Q

3.7.1 Inheritance

Genetic explanation of Mendel’s intercross between plants of F1 generation.

A

4 gametes produced from RrGg:
RG, Rg, rG, rg

Parental phenotype: round yellow, round yellow
Parental genotype:
RY: RrGg
RY: RrGg
Gametes:
RY: RG Rg rG rg
RY: RG Rg rG rg
Offspring (F2) genotype: heterozygous cross
punnet square of the gametes to result in
Offspring (F2) phenotype: heterozygous cross
9 x round yellow
3 x round green
3 x wrinkled yellow
1 x wrinkled green

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22
Q

3.7.1 Inheritance

State the theoritical ratio and the observed Mendel’s ratio.

A

Theoritical: 9:3:3:1
Observed Mendel’s 315:108:101:32

Theoritical is close enough to the observed results allowing for statistical error

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23
Q

3.7.1 Inheritance

What does the F1 generation produce?

A

4 gametes = RG, Rg, rG, rg
Gene for seed colour and shape are on seperate chromsomes
Fertilisation is random

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24
Q

3.7.1 Inheritance

Define codominance.

A

Both alleles are equally dominant and are expressed in the phenotype.

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25
Q

3.7.1 Inheritance

Genetic diagram coding of codominance.

A

Gene^allele

example: C^R C^W

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26
Q

3.7.1 Inheritance

A cross between a red and white-coated shorthorn cattle.

A

C^R = allele for red pigment production.
C^W = allele for white pigment production.

HOMOZYGOUS = C^R C^R and C^W C^W

Parental phenotype: Red coat White coat.
Parental genotype: C^R C^R and C^W C^W
Gametes:
C^RC^R = C^R C^R
C^WC^W = C^W C^W
Offspring genotypes:
punnet square of the gametes to result in
Offspring phenotype:
100% roan coat (C^RC^W)

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27
Q

3.7.1 Inheritance

A cross between the roan coated shorthorns. (C^RC^W)

A

HETEROZYGOUS = C^RC^W

Parental phenotype:roan coat & roan coat
Parental genotype: C^RC^W & C^RC^W
Gametes:
C^RC^W = C^R C^W
C^RC^W = C^R C^W
Offspring genotype:
punnet square of the gametes to result in
Offspring phenotype:
50% = roan coat = C^RC^W
25% = red coat = C^RC^R
25% = white coat = C^WC^W

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28
Q

3.7.1 Inheritance

Define mutliple alleles.

A

More than 2 alleles for a 1 gene.

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29
Q

3.7.1 Inheritance

Genetic diagram coding of multiple alleles.

A

Gene^allele

example: I^A I^O
I^B I^O

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30
Q

3.7.1 Inheritance

Outline the antibodies in the plasma and the antigens in the red blood cell of red blood cell group A.

A

AB in plasma = Anti-B
Antigen in RBC = Antigen A

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31
Q

3.7.1 Inheritance

Outline the antibodies in the plasma and the antigens in the red blood cell of red blood cell group B.

A

AB in plasma = Anti-A
Antigen in RBC = Antigen B

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32
Q

3.7.1 Inheritance

Outline the antibodies in the plasma and the antigens in the red blood cell of red blood cell group AB.

A

AB in plasma = none
Antigen in RBC = Antigen A and B

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33
Q

3.7.1 Inheritance

Outline the antibodies in the plasma and the antigens in the red blood cell of red blood cell group O.

A

AB in plasma = Anti-A and B
Antigen in RBC = none

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34
Q

3.7.1 Inheritance

Outline genotypes of the phenotypes:
Blood group A
Blood group B
Blood group AB
Blood group O

A

Blood group A = I^A I^O or I^A I^A
Blood group B = I^B I^O or I^B I^B
Blood group AB = I^A I^B
Blood group O = I^O I^O

A = dominant
B = dominant
AB = codominant
O = recessive.

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35
Q

3.7.1 Inheritance

Define autosomal linkages.

A

Two genes carried on / located on the same chromosome = autosome.
From the chromosome 1-23 the 23rd chromosome = sex chromosome ( X or Y)

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36
Q

3.7.1 Inheritance

What should you assume in autosomal linkages?

A

NO crossing over
All linked genes remian together in meiosis forming gametes then offspring.

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37
Q

3.7.1 Inheritance

Drosophila fruit fly example of autosomal linkage.

A

Two linked genes:
1. body colour =
grey = dominant = G
black = recessive = g
2. wing size
normal = dominant = N
vestigial = recessive = n

Grey normal = GN
Grey vestigial = Gn

Black normal = gN
Black vestigial = gn

Parental phenotype: Grey body & Grey body.
Parental genotype:
GB = Gg Nn
GB = Gg Nn
Gametes:
GB = GN & gn
GB = GN & gn
Offspring phenotype:
punnet square using the gametes to result in
Offspring genotype:
3 x fruit flies = grey body and normal wings
1x GGNN 2xGgNn
1 x fruit flies = black body and vestigial wings
1x ggnn

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38
Q

3.7.1 Inheritance

Desribe and explain the ratio of 3:1 in autosomal linkage using the Drosophila fruit fly.

A

3 fruit flies:
Linked
No crossing over
More common.
1 fruit fly:
Not linked
Crossing over occurs
More rare.

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39
Q

3.7.1 Inheritance

Define sex linkages.

A

A gene whose locus os on the X chromosome

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40
Q

3.7.1 Inheritance

Genetic diagram coding for sex linkages.

A

Chromsome^allele

example: X^R X^r

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41
Q

3.7.1 Inheritance

What is X-linked genetic disorder?

A

Disorder caused by a defective gene on the X chromosome.

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42
Q

3.7.1 Inheritance

What is Haemophillia?

A

Blood clots slowly.
Slow and persistent leading to internal bleeding.
Lethal if not treated.
Some selective removal of gene population = occurenece = rare = 1 in 20000 in europe

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43
Q

3.7.1 Inheritance

Outline one cause of Haemophillia.

A

Recessive allel with an altered sequence of DNA nucleotides which codes for a faulty protein = does not function.

Indivduals are unable to produce functional protein required for the clotting process

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44
Q

3.7.1 Inheritance

Inheritance of haemophillia from a female carrier.

A

H = dominant = allele for the production of clotting protein = rapid blood clot
h = recessive = allele for the non-production of clotting protein = slow blood clot.
} always attached to X chromosome = X^H X^h

Parental phenotype: Carrier female & normal male.
Parental genotype:
CF = X^H X^h
NM = X^H Y
Gametes:
CF = X^H & X^h
NM = X^H & Y
Offspring genotype:
punnet square using the gametes to result in
Offspring phenotype:
25% normal female = X^H X^H
25% normal male = X^H Y
25% carrier female = X^H X^h
25% haemophilliac male = X^h Y

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45
Q

3.7.1 Inheritance

Define epistasis.

A

One gene influences (affects / masks) the expression of another gene.

example = dihydrid = 2 genes = one masks the other one.
example = coat colour in mice, coat colour in Labradors, fruit colour of vegetables.

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46
Q

3.7.1 Inheritance

Epistasis = Coat colour in Labradors example.

A

Controlled by 2 genes
GENE 1 controls for expression of pigment
allele E = dominant = codes for pigment production.
allele e = recessive = does not code for pigment production so FUR IS YELLOW

GENE 2 controls which pigment is expressed.
allele B = dominant = black fur
allele b = recessive = brown fur

Parental phenotype: Black fur & black fur
Parental genotype: EeBb & EeBb
Gametes
EeBb = EB Eb eB eb
EeBb = EB Eb eB eb
Offspring genotype:
punnet square using gametes to result in
Offspring phenotype:
9 x black fur =
1x EEBB
2 x EEBb
2 x EeBB
4 x EeBb
3 x brown fur =
1 x EEbb
2 x Eebb
4 x no pigment produced =
1x eeBB
2 x eeBb
1 x eebb

47
Q

3.7.1 Inheritance

Define pedigree diagram.

A

Can be used to measure the inheritance of sex-linked characters such as haemophillia.

KEY SYMBOLS
Square = male
Circle = female
Shaded square or circle (affected male or female) = indicates prescence of character i.e. haemophillia in the phenotype.

48
Q

3.7.2 Populations

Define gene pool.

A

All the alleles of all the genes in a population at one time.

49
Q

3.7.2 Populations

Define population.

A

All the indivduals of one species in one area at one time that can be interbreeded.

50
Q

3.7.2 Populations

Define allele frequency.

A

proportion of an allele within a
the gene pool.
= how often an allele occurs in a population
= answer will be a decimal or a percentage

51
Q

3.7.2 Populations

Define species.

A

Exist as one or more populations.

52
Q

3.7.2 Populations

What is the Hardy Weinberg principle and what does it assume?

A

A mathematical model that makes assumptions which impedes (interferes with) the accuracy.

It assumes no change in allele frequency between generations within a population
} not accurate assumption.

53
Q

3.7.2 Populations

If the Hardy Weinberg principle assumptions are true under what conditions are they true?

A
  1. It must be a large population where there is NO immigration, emigration, mutation or natural selection.
  2. Random mating = all possible genotypes can breed with every other genotype and no in breeding.
54
Q

3.7.2 Populations

How can the frequency of the alleles, genotypes and phenotypes in a population be calculated using the Hardy Weinberg principle?

A

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

p^2 = frequency of homozygous dominant genotype
2pq = frequency of heterozygous dominant genotype = expresses dominant but carries a recessive allele.
q^2 = frequency of homozygous recessive allele.
1 = whole population.

SIMULATANEOUSLY USE THIS EQUATION TOO:

p + q = 1
P = frequency of dominant allele
q = frequency of reccesive allele.

55
Q

3.7.3 Evolution may lead to speciation

Why might indivduals within a population of a species may show a wide range of variation in the phenotype according to genetic factors?

A

Due to the genetic differences that occur as indivudals of a population will have different alleles of the same gene

Genetic variation arises because of:
1. Mutations: Sudden changes to genes and chromosomes could be passed onto next generation.
2. Meisosis: Nuclear divison = new combination of alleles before being passed into gametes.
3. Random fertilisation of gametes: sexual reproduction = gametes fusing is a random process = new combination of alleles are produced = offspring different from parent.

56
Q

3.7.3 Evolution may lead to speciation

What is the advantge for sexually reproducing organisms according to genetic variation?

A

Their variation is increased by all 3 methods = mutations, meisosis and random fertilisation of gametes.

Meisosis and RFG = sexual reproduction leads to further genetic variation

57
Q

3.7.3 Evolution may lead to speciation

Why might indivduals within a population of a species may show a wide range of variation in the phenotype according to environmental factors (highlight examples)?

A
  1. Climate conditions = temperature, rainfall, sunlight.
  2. Soil conditions
  3. pH
  4. Food availability.
58
Q

3.7.3 Evolution may lead to speciation

What happens if indivduals within a population of a species show a wide range of variation in the phenotype due to both genetic and environmental factors?

A

Natural selection occurs.

59
Q

3.7.3 Evolution may lead to speciation

What is the primary source of genetic variation?

A

Mutation.

Meisosis and RFG produces further genetic variation.

60
Q

3.7.3 Evolution may lead to speciation

What is natural selection?

A

Each organism is subjected to the process of selection based on its suitability for survival under conditions at that time.

61
Q

3.7.3 Evolution may lead to speciation

What is selection pressures?

A

Determine the frequency of alleles within the gene pool.
Environmental factors that can limit a population.
1. Predation
2. Disease
3. Competition

62
Q

3.7.3 Evolution may lead to speciation

What factors does evolution by a means of natural selection depend on?

A
  1. Organisms that produce more offsprings than the availability of food, light and space.
  2. Genetic variation within the populations of all species.
  3. Variety of phenotypes that selection will operate against.
63
Q

3.7.3 Evolution may lead to speciation

Over production + natural selection =

A

Too many offsprings for the available resources leading to competion between indivduals; intraspecific competition

More competition = more individuals will die but deaths are not random. Organisms with phenotypes that provide selective advantges are more likely to survive and reproduce

Pass on the favourable alleles to the next generation.

64
Q

3.7.3 Evolution may lead to speciation

What does predation, disease and competition result in?

A

Differential reproductive success.
= certain indivduals can reproduce and so the effect of differential reproductive success is that there is a change in the allele frequency within the gene pool.

65
Q

3.7.3 Evolution may lead to speciation

What are the 3 types of selection?

A
  1. Stabilising
  2. Directional
  3. Disruptive.
66
Q

3.7.3 Evolution may lead to speciation

What is the effect of stabilising selection?

A

It preserves the average phenotype (around the mean) of a population by favouring average indivduals

Selection against extremem phenotypes i.e. too low or too high.

Occurs when environmental conditions are constant over time.

67
Q

3.7.3 Evolution may lead to speciation

EXAMPLE: fur length and stabilising selection.

A

HOT TEMP: short fur mammals have an advantge as they can lose body heat more rapidly.

COLD TEMP: long fur mammals have an advantge as they can preserve more body heat.

CONSTANT TEMP: 10 degrees C indivduals at extreme ends i.e HOT & COLD will not survive.

68
Q

3.7.3 Evolution may lead to speciation

What is the effect of directional selection?

A

Within a population there is a range of genetically different indivduals of one phenotype.

If environmental conditions change so will the optimum value for survival.

DS results in one extreme of the range of variation being selected than the other or even the mean.

SELECTION PRESSURE: favours the combination of alleles that cause the mean moving right or left of its original position.

69
Q

3.7.3 Evolution may lead to speciation

EXAMPLE: Fur length and directional selection.

A

BELL SHAPED CURVE WITH FUR LENGTH INCREASING BY 0.5CM AND 1.5CM IS THE OPTIMUM

  1. OPTIMUM FUR LENGTH AT 10 degrees C = 1.5cm
  2. If temperature falls to 5 degrees C then the indivduals with 2.0 cm and more of fur length are better insulated; can survive and reproduce.
  3. Hence the selection pressure favours indivduals with the longest fur i.e. right side.
  4. The selection pressure causes a shift in mean towards the longer fur over generations. Selection pressure will continue.
  5. Selection pressure further shifts the mean fur length to the right until 2.0cm is reached.
    2.0cm is now the optimum length of fur for 5 degrees C. Selection pressure ceases.
70
Q

3.7.3 Evolution may lead to speciation

What is the effect disruptive selection?

A

Occurs when an environmental factors such as temperature take 2 distinct forms.

Indivduals that contain the extreme tratis are more likely to survive and reproduce and pass on their alleles.

Allele frequency will change as more wil begin to posses the allele for the extreme trait.

Middle trait will become less frequent

71
Q

3.7.3 Evolution may lead to speciation

EXAMPLE: Temperature and disruptive selection.

A

Temp that alters between 5 degrees in the winter and 15 degrees in the summer.

Can lead to 2 seperate species of the mammal
1. Long fur and active in the winter.
2. Short fur and active in the summer.

72
Q

3.7.3 Evolution may lead to speciation

What is speciation?

A

Evolution of new species from exisiting ones.

Occurs when an original population of the same species becomes reproductively isolated = they are 2 populations of the same species but they cannot breed together due to differences in their gene pool.

73
Q

3.7.3 Evolution may lead to speciation

Allopatric speciation.

A

Populations are Away / seperated geographically leading to reproductibe isolation such as moutain ranges, new water bodies.

Geographical sepearation may result in a physical barrier between the 2 populations preventing them from interbreeding.

They will both have different benefical mutations to help them survive in environments.

The accumulation of DNA differences over time will become so genetically different they would be unable to interbreed + reproduce.

74
Q

3.7.3 Evolution may lead to speciation

Sympatric speciation.

A

A population in the same area that leads them to become reproductively isolated due to differences in their behaviour.

Reproductively isolated because of random mutations that could impact reproductive behaviour. For example: performing different courtship rituals or indivduals being fertile at different times of the year.

Reproductive isolated populations will accumulate different mutations. DNA is different so unable to interbreed and reproduce because there is no gene flow between the 2 groups = 2 species.

75
Q

3.7.3 Evolution may lead to speciation

What is the importance of genetic drift in causing changes in the allele frequency in small populations?

A

When chance (not environmental selection pressures) lead to a change in the allele frequency then to speciation due to evolution via natural selection.

Will only impact small populations as there is a bigger impact of changes in the allele frequency that is passed onto the next generation.

Over time, some alleles can be lost or favoured by chance.

Evolution occurs more rapidly in smaller populations as in large populations as changes in the allele frequencies due to genetic drift will even out across the whole population.

76
Q

3.7.4 Populations in ecosystems

Define population.

A

All the indivduals of one species in one area at one time that can be interbreeded.

77
Q

3.7.4 Populations in ecosystems

Define community.

A

A population of different species in the same area at the same time.

78
Q

3.7.4 Populations in ecosystems

Define ecoystem.

A

A community and the non-living components of environment (biotic and abiotic factors).

Can range in size (small-large)

79
Q

3.7.4 Populations in ecosystems

Define habitat.

A

Part of an ecosystem where an organism lives and occupies a niche goverened by adaptations to biotic and abiotic conditions.

80
Q

3.7.4 Populations in ecosystems

Define a niche.

A

An organism’s role within an ecosystem = position in the food web and habitat.

81
Q

3.7.4 Populations in ecosystems

How many species can occupy the same niche?

A

NONE

1 species has it own niche which is governed by adaptations to biotic and abioitc conditions in order to survive and reproduce.

82
Q

3.7.4 Populations in ecosystems

Define biotic.

A

Impact of interactions between organisms

83
Q

3.7.4 Populations in ecosystems

Define abiotic.

A

non-living conditions of an ecosystem such as temperature, light, humidity.

84
Q

3.7.4 Populations in ecosystems

Define carrying capacity.

A

The size of population of species that an ecosystem can support.

85
Q

3.7.4 Populations in ecosystems

How can the population size vary?

A
  1. The effect of abiotic factors.
  2. Interactions between organisms: intra and interspecific competition and predation.
86
Q

3.7.4 Populations in ecosystems

What effect does abiotic factors have on a population size?

A

TEMPERATURE
Each species has different optimum temperatures.
i.e. Cold blooded animals and plants: if there’s a decrease in temperature below the optimum then enzymes will begin to work slowly, metabolic rate is slower so the population has a small carrying capacity.

LIGHT
Increase in light intensity, increase photosythesis rate, increase plant growth, more seeds are produced, carrying capacity is larger = animals that feed on these plants have larger carrying capacity.

pH
Affects enzyme action. The population of organisms is larger when there is a suitable pH.

WATER AND HUMIDITY
Water: only well adapted species live in dry conditions.
Humidity: affects the transpiration rates in plants and evapouration of water from the bodies of animals.

87
Q

3.7.4 Populations in ecosystems

What effect does interspecific competition have on a population size?

A

Members of different species are in competition for the same resources (water,food,light) that is limited in supply.

One species has a competitive advantge due to its adaptation to the environment. So the population size of that species will increase and the other one will decrease , could cause them to become extinct if conditions are the same.

88
Q

3.7.4 Populations in ecosystems

In interspecific competition, what is the competitive exclusion principle?

A

No two species occupy the same niche.

89
Q

3.7.4 Populations in ecosystems

What effect does intraspecfic competition have on a population size?

A

Members of the same species that are in competition for resources and mates.

The greater the availability of resources = larger population.

i.e: robins that compete for breeding territory. Female birds are only attracted to males who established their territory allowing them to gain more food, interbreed, reproduce and pass on adaptations.

90
Q

3.7.4 Populations in ecosystems

What effect does predation have on a population size?

A

Predation = when an organism is consumed by another one.

  1. Predator eats prey = reduces population of prey.
  2. Fewer prey available = competiton between predators for the preys that are left behind.
  3. Predator population reduced = unable to ibtain prey for their survival and hence die so cannot reproduce.
  4. Fewer predators = increase in prey = survive, and reproduce
  5. Predator population will increase as the prey population increased.
91
Q

3.7.4 Populations in ecosystems

Why is the mark release and recapture method used?

A

To estimate the size of a population of motile animals.

92
Q

3.7.4 Populations in ecosystems

Outline a method for the mark release and recapture method.

A
  1. Intial sample of population is captured.
  2. Indivduals are marked then released back into the wild. Number of caught is recorded. Mark must be weather resistant.
  3. Left for a period of time to allow them to randomly disperse throughout habitat.
  4. Second sample is captured. Number of caught is recorded. The number of recaptured is also recorded.
  5. Equation to estimate the size of the population:
    Estimated total population = (Number of organisms intially caught X number of organisms in the second sample) / number of marked organism recaptured.
  6. Repeat test = more times repeated = more reliable.
93
Q

3.7.4 Populations in ecosystems

What are the ethics of the mark release and recapture method?

A

How you capture and how you mark must cause no permanent harm

Considerations for the mark:
1. Non-toxic
2. Must not increase chance of predation.
3. Must not increase chance of reproduction (courtship rituals)
4. Must not interrupt with a bird’s ability to fly.

94
Q

3.7.4 Populations in ecosystems

Why is the estimated value not accurate and what assumptions are made to “show” it is accurate?

A
  1. The population size is constant = no birth, no death, no immigration or emigration.
    } These things will definately happen
  2. Animals will always redistribute evenly
    } Animals may huddle in a particular area because of food, water or shelter from weather conditions or predators.
95
Q

3.7.4 Populations in ecosystems

Why do we sample?

A

Sampling is more time efficient and can be accurate if implemented correctly.

96
Q

3.7.4 Populations in ecosystems

How is it ensured that a sample accurately represent a population?

A
  1. Random sampling: in uniform areas to avoid bias.
  2. Line transect to examine a change over distance.
  3. Large sample (+30)
97
Q

3.7.4 Populations in ecosystems

When estimating the population size of a slow organisms or a non-motile organism what type of sampling methods would you use?

A

sample using a quadrat.

Random sampling = uniform distribution.
Line transect = uneven distribution.

98
Q

3.7.4 Populations in ecosystems

Outline a method for random sampling.

A
  1. Lie 2 tapes measures at a right angle to create a gridded area.
  2. Use a random number generator to generate 2 coordinates
  3. Place quadrat and collect data (density/percentage cover or frequency).
  4. Repeat test at least 30 times and calculate a mean.
99
Q

3.7.4 Populations in ecosystems

Line transects

A

Used to estimate a population size when they are unevenly distrubted e:g: populations which change over distance.

Gives you a sample of different sections.

examples: Sandy/ rocky shores. Across a path or river.

100
Q

3.7.4 Populations in ecosystems

Types of transects.

A

Belt transects = quadrat is placed at every position along the tape measure.
} for slow or non-motile organisms.

Interrupted belt transects = quadrat placed a uniform intervals along tape measure i.e: every 5 metres = can see quicker difference.

101
Q

3.7.4 Populations in ecosystems

Outline a line transect method.

A
  1. Place a tape measure at a right angle to the shore line.
  2. Place quadrat at every 5 metres for interrupted belt transects or at every position for belt transect.
  3. Collect the data (density/ percentage cover/ frequency)
  4. Repeat by placing another 30 transects along the beach at a right angle to shore line.
102
Q

3.7.4 Populations in ecosystems

Local frequency

A

% of squares in a quadrat with the species present. (there are 100 squares)

Pros:
Quick method to sample a large area.
Useful if too difficult to identifty organism such as moss or too many to count such as grass.

Cons: Poor accuracy = doesn’t consider overlapping of plants (might be more underneath) or the size of plants (one plant = big = occupy entire quadrat)

103
Q

3.7.4 Populations in ecosystems

Density:

A

Number of one whole species in a given area = open quadrat is used.
i.e 11 daisies in quadrat in 0.5m x 0.5m = 0.25m2
whole field = 280m2

(280/0.25) x 11 = 12320 species in entire field.

Pros:
More accurate = easily distinguish indivdual plant and not too many to count.
Can be used to estimate species richness = count number of different species present.

Cons: time consuming.

104
Q

3.7.4 Populations in ecosystems

Percentage cover:

A

Proporation of ground occupied by the species = how many full squares are occupied by species.

Pros:
Quicker method than density.
Useful if too difficult to identify = moss or too many to count = grass.

Cons:
Subjective = limits accuracy.
Doesn’t consider overlapping plant (more underneath) or size of plants (one plant = big = occupy entire quadrat)

105
Q

3.7.4 Populations in ecosystems

Define succession.

A

Changes over time in the species that occupy a particular area.

106
Q

3.7.4 Populations in ecosystems

Example of succession:

A

When bare rock or other barren land is first colonised which can arise as a result of
1. Sand piled into dunes by wind or sea
2. Volcanoes erupting and deposing lava.

107
Q

3.7.4 Populations in ecosystems

Define ecosystem according to succession.

A

Dynamic systems.
Changes day to day as populations fluctuate, slowly or rapidly.

108
Q

3.7.4 Populations in ecosystems

Primary succession:

A

Colonisation by pioneer species to climax community.

Pioneer species colonise bare rock or bare sand } has high conc. of salt from the ocean.

109
Q

3.7.4 Populations in ecosystems

Primary succession: what type of pioneer species colonise bare rock or bare sand.

A

Lichen = they are adapted to survive harsh abiotic factors

Lichen exists as 2 species algae and fungus = symbiotic relationship.
Algae can photosynthesise to make glucose.
Fungus can absorb water and release enzymes outside the cell (extracellular breakdown) onto the rocks and release mineral ions which are absorbed by the algae and fungi

110
Q

3.7.4 Populations in ecosystems

Primary succession: When lichen die, decay and reproduce what type of layer is formed?

A

Thin layer of soil is formed = humus which provides nutrients to support the community of small plants i.e. mosses + more smaller plants

As the abiotic factors now become less harsh the larger plants can now survive and change environment, making it less suitable for the previous species hence they are outcompeted

Results in a less hostile environment and an increase in biodiversity i.e. shrubs = climax community.

111
Q

3.7.4 Populations in ecosystems

Secondary succession

A

When land that has already sustained life i.e. had trees growing has been altered / disrupted or the plants have been destroyed due to human activity such as land clearance for agriculture or a forest fire.

Succession will start again from soil and not bare rock.
Soil already exisiting = spores and seeds often remain alive in the soil and there’s an influx of animal and plants through dispersal and migration from surrounding area.
Soil already exisiting = allows some plants to grow and flourish whereas before they couldn’t due to large plants surrounding them.

112
Q

3.7.4 Populations in ecosystems

Conservation:

A

Mangement of earths natural resources by humans that maximises the use of them in the future.
Conservation of habitats involves managing succession.

113
Q

3.7.4 Populations in ecosystems

What are the reasons for conservation?

A

1.PERSONAL: to maintain our planet and life support system.
2.ETHICAL: other species occupying earth longer than us.
3.ECONOMIC: living organisms contain large amounts of genes to make millions of substances.
4.CULTURAL: habitats and organisms enrich our lives. Add interests to life and inspires poets, writers and artists.

114
Q

3.7.4 Populations in ecosystems

How does maintaining earlier stages in succession increase biodiversity?

A

Prevents climax community.
Greater variety of habitats are conserved which increases biodiversity.

Management between the conflict between human needs and conservation to maintain sustainability of natural resources such as forest being coppiced = trees (climax community) are not completely pulled out of the ground but are cut down to the base.
Wood is produced which can be used for timber = used for builiding products.

There is also now an area where different species can thrive whereas in the climax community they were outcompeted.

A2 Biology (4 decks)

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