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Biology Paper 2 > Ecology > Flashcards

Ecology Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

define ecology

A

study of an ecosystem, and interactions

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2
Q

define ecosystem

A

living and non-living organisms interacting in an area

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3
Q

define biotic factor

A

living factor

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4
Q

define abiotic factor

A

non-living factor

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5
Q

define habitat

A

where an organism lives

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6
Q

define population

A

all the same species in a place at the same time that are able to interbreed to produce fertile offspring

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7
Q

define community

A

total number of species in a population

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8
Q

define niche of species

A

specific rile the organisms plays in an ecosystem

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9
Q

what type of organisms are decomposers

A
  • bacteria
  • fungi
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10
Q

what affects population size

A
  • births
  • death
  • immigration
  • emmigration
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11
Q

linear vs log graphs

A
  • log offers the advantage where there a large range of values
  • allow all data points to be represented accurately and patterns to be observed
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12
Q

population growth curve stages

A

1) lag phase - slow change due to small numbers
2) log phase - rapid change due to increasing numbers
3) stationary phase - a stable population that fluctuates around the carrying capacity

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13
Q

what is carrying capacity

A

maximum population size that can be maintained in an environment. its dependent on the limiting factors present

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14
Q

what factor is density dependant?

A

biotic factors
abiotic actors are density independant

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15
Q

the two types of sampling?

A
  • random
  • systematic
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16
Q

what is random sampling

A

-eliminates bias and allows for statistical testing
- used to estimate size of a population

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17
Q

what is systematic sampling

A
  • used when there appears to be gradual change in the distribution of a species
  • used to determine the relationship between the distribution and an abiotic factor
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18
Q

how to carry out random sampling

A
  1. divide the area into aa grid
  2. generate pairs of numbers as coordinates
  3. use a large number of quadrats (>10) to improve reliability
  4. record abundance of species present in each quadrat (count individuals,% cover )
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19
Q

point quadrats

A
  • every plant on each pin hits is recorded. if the pin hits several overlapping plants all of them are recorded
  • quadrat is placed at regular intervals across the tape measure
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20
Q

‘in/out’ rule

A

top or right = IN
bottom or left = OUT

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21
Q

things to consider when using quadrats:

A

1) size of the quadrat - the smaller the quadrat the greater the accuracy
2) number of samples being taken in the area - more samples you take the more reliable the results are
3) placing quadrat at coordinates - i.e. bottom left corner on coordinates

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22
Q

drawing the graph

A
  • plot the cumulative number of species or mean density against the number of quadrats used
  • there is no need to use more quadrats once the line plateaus
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23
Q

equation for estimated mean density

A

total no. of individuals counted / (number of quadrats x area of quadrat)

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24
Q

equation for population total

A

mean per quadrat x no. of quadrats that fit into the sampled area

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25
Q

how to measure abundance

A
  • species frequency - no. of quadrats that contain the species
  • percentage cover - how much of the area in a quadrat is covered by a particular species. useful for species that are difficult to count e.g. grass
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26
Q

what are transects?
types?

A

systematic technique

  • line transect -all individual touching the line are required
  • continuous belt transect - all species within quadrats are recorded
  • interrupted blet transect - all species are counted at set intervals
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27
Q

how to sample animals

A

capture, mark, release (Lincoln index)

  1. a set of animals are caught and then marked in some way
  2. animals are then released back into the community
  3. after a specified length of time, several individuals are caught again
  4. the number of marked individuals are counted
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28
Q

population size calculation via Lincoln index

A

no in the first sample x no in the second sample/number of marked individuals recaptured

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29
Q

what is the assumption that has to be made

A
  • the proportion of marked to unmarked is the same in the sample as it is in the whole population
  • method of marking must not be toxic, overly conspicuous or rub off
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30
Q

for the assumption to be true, what has to happen

A
  • marked individuals need to be distributed evenly in the population
  • defined boundaries of the population
  • few deaths/births within the time frame
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31
Q

what is succession

A

a change in community over time

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32
Q

what is a community

A

a dynamic unit and passes through a number of stages from its origin to its climax

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33
Q

when do transitions take place

A

occur from one seral stage to the next as the abiotic and biotic factors change
as transitions occur the species present in the previous stage are outcompeted

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34
Q

the first species to colonise an area are called

A

pioneer species

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35
Q

features of pioneer species

A
  • small, grow and reproduce quickly
  • exploits sudden favourable change in conditions
  • short-lived as outcompete by more complex organism
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36
Q

what happens when pioneer species die

A

change the abiotic factors and makes them more favorable for later species e.g. organic matter

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37
Q

final set of species to colonise an area are?

A

climax community
community stability is the greatest once the climax community

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38
Q

what is primary succession

A

when a community develops on uncolonized ground (bare ground) which has never had any vegetation

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39
Q

secondary succession

A

occur in areas which have previously been colonsied by vegetation, but has been colonised
e.g. forest fire

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40
Q

what is a plagioclimax?
when does it occur

A

deflected climax community
occurs when the normal process of succession is prevented e.g. intensive grazing. by sheep, cutting grass

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41
Q

what is a gene

A

an inherited instruction which codes for a polypeptide

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42
Q

what is an allele

A

alternative forms of the same gene alleles arise because of mutation

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43
Q

what is a genotype

A

genetic constitution (make up) of an organism

44
Q

what is a phenotype

A

observable trait(s) of an organism

45
Q

monohybrid cross

A

across in which the alleles of only one gene are involved

46
Q

what is a test cross

A

type of genetic cross to determine the genotype of organisms expressing the dominant phenotype

47
Q

what is codominance

A

alleles of a gene have to share dominance of a characteristic.
both dominant alleles are present the phenotype shows a mixture of the two characteristics

48
Q

how to lay out a genetic cross

A
  • parents phenotype
  • parents genotype
  • gamete genotype
  • offspring genotype
  • offspring phenotype
  • ratio
49
Q

name the blood groups

A
  • A
  • B
  • AB
  • O
50
Q

blood group features

A
  • autosomal - not on the sex chromosome
  • multiple alleles - more than two alleles for the gene
51
Q

blood group formula

A

( I A = I B) > I O

IA & IB are codominant and both of these alleles are dominant to IO

52
Q

what is dihybrid inheritance

A

two genes, two alleles each
genes are on separate chromosomes (unlinked) they can be inherited in any combination
4 possible gametes can be prodcuted

53
Q

dihybrid inheritance
What are the results if the parents are both heterozygous

A

9 : 3 : 3 : 1

54
Q

dihybrid inheritance
results if one parent is homozygous recessive

A

1 : 1 : 1 : 1

55
Q

sex chromosomes for most species

A

normally female: XX
male: XY

56
Q

what is said when a gene is on a sex chromosome

A

every gene on the sex chromosomes is sex linked

57
Q

difference between the x and y chromosome

A
  • y chromosome is smaller so for many genes on the x chromosome there is no homologous pair present on the y
  • so characteristics caused by recessive alleles have a greater change appearing in males
58
Q

what do you have to write when talking about sex-linked characteristics?

A

you must show the sex chromosomes as well as the alleles

59
Q

competition occurs for limited resources such as

A
  • food
  • shelter
  • nesting sites
  • mates
  • light
  • territory
  • mineral ions
60
Q

intraspecific competition

A

competition in the same species living in the same habitat

61
Q

interspecific competition

A

competition between different species in the same community

62
Q

features of intraspecific competition

A
  • availability for resources will determine the size of the population
  • individuals best adapted will survive and pass on their alleles while others die out
63
Q

features of interspecific competition

A

the more similar the species are the more intense the competition is

64
Q

what is the competitive exclusion principle

A

two species will never occupy the same niche and both survive

65
Q

what is predation

A

when one species is caught and eaten by another species. The populations of the predator and prey will both affect one another. This is called a predator-prey relationship

66
Q

The predator-prey relationship and occurs as follows:

A
  1. When the predator eats the prey, the prey population falls.
  2. So predator population grows, so more prey is consumed.
  3. The population of prey reduces and there is increased competition for the prey between the predators.
  4. The lack of food for the predators means that the population falls meaning that less prey is eaten.
  5. This allows the population of the prey to recover and therefore the cycle occurs over
67
Q

what is conservation

A

human management of the Earth’s resources and involves managing succession.

68
Q

what are linked genes

A

linked genes are a set of genes at different loci on the same chromosome that except for crossing over will be inherited together

69
Q

when will crossing over occur

A

if genes are far apart they may be separated by crossing over

70
Q

what will happen if linked genes are close together

A

unlikely to be separated by crossing over, so will be inherited together

71
Q

what does it mean if you have offspring in intermediate categories in a test cross (linked genes)

A

there has been some crossing over - alleles are linked

72
Q

if there’s no crossing over in a test cross (linked genes) what will the ratio be

A

1 : 0: 0: 1

73
Q

forming a hypothesis for chi-squared test

A

There is no difference between the observed and expected results

74
Q

How to work out degrees of freedom

A

Classes - 1

75
Q

When would you accept the null hypothesis

A

if the calculated value is less than the critical value

76
Q

what is polygenic?

A

when characteristics are determined by more than one gene

77
Q

what is epistasis

A

when alleles of one gene mask the expression of the alleles of another gene

78
Q

what is dominant epistasis

A

dominant allele at one gene locus masks the expression of alleles at a second gene locus

79
Q

dominant epistasis
heterozygous cross ratio

A

12 : 3: 1

80
Q

what is recessive epistasis

A

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

81
Q

recessive epistasis
heterozygous cross with the same parents

A

9: 3: 4

82
Q

what is a gene pool

A

all of the alleles of all of the genes present in a population

83
Q

what is the allele frequency

A

number of times an allele appears within a gene pool

84
Q

what is the Hardy-Weinberg principle used for

A

calculate the frequencies of the different alleles of a gene in a population

85
Q

what does the hardy Weinberg principle assume

A

that frequencies of the alleles in a population remain constant between generations

86
Q

assumption of the hardy-Weinberg principle to be accurate

A
  1. no selection
  2. no mutation
  3. no migration
  4. population needs to be large enough
  5. random mating
87
Q

hardy Weinberg principle
reason for no selection

A

all alleles are likely to be passed on

88
Q

hardy Weinberg principle
reason for no mutation

A

no new alleles are created

89
Q

hardy Weinberg principle
reason for migration

A

no new alleles are introduced or lost

90
Q

hardy Weinberg principle
reason for the population being large enough

A

there are no genetic bottlenecks

91
Q

hardy Weinberg principle
reason for random mating

A

alleles are mixed randomly

92
Q

hardy Weinberg principle
allele equations

A

p + q = 1

p = frequency of dominant allele
q = frequency of recessive allele

93
Q

hardy Weinberg principle
genotypes equations

A

p2 + 2pq + q2 = 1

p2 = frequency of homozygous dominant
q2 = frequency of homozygous recessive
2pq = frequency of heterozygous

94
Q

Variation in phenotype

A
  1. Random fertilisation - different alleles will join randomly.
  2. Meiosis - nuclear division that creates gametes and the alleles will be assorted in the gametes randomly
  3. Mutation - creation of new allele that is passed to the next generation
95
Q

what is variation

A

the difference that exists between individual organisms

96
Q

two types of variation

A
  • interspecific - variation between species
  • intraspecific - variation between members of the same species
97
Q

how does variation occur

A

can be inherited or influenced by the environment

98
Q

continuous variation features

A
  • consists of a range of values between two extremes
  • most individuals are close to a mean value
  • low numbers of individuals at the extremes
  • usually polygenic and affected by the environment
99
Q

examples of continuous variation and how it would be plot

A
  • height in humans
  • length of stalks of a toadstool

usually a tally chart and plot result in a histogram - curve is bell-shaped

100
Q

discontinuous variation features

A
  • 2 or more distinct categories with no intermediate values
  • monogenic
  • the environment has little or no effect on discontinuous variation
101
Q

examples of discontinuous variation and how it would be plot

A
  • earlobes - attahced or unattahced
  • blood groups - A, B, AB, O

plot results on a bar chart

102
Q

directional selection

A

acts against one of the extremes in a range of phenotypes. One phenotype becomes rare, and an alternative phenotype becomes common

103
Q

stabilising selection features

A
  • acts against both extremes - choose median
  • leads to a reduction in variation
104
Q

disruptive selection

A

selection that removes individuals from the centre of the phenotypic distribution and causes the distribution to become bimodal (two peaks)

105
Q

features of disruptive selection

A
  • over time the extremes will become more common and the intermediate states will become less common or lost
  • can lead to different species
106
Q

what is speciation

A

development of a new species from an existing one. caused by reproductive isolation - can no longer breed to produce fertile offspring

107
Q

when can speciation occur

A

geographical barrier (physical) barrier - allopatric speciation, or without a barrier - sympatric speciation

Biology Paper 2 (3 decks)

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