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AQA A Level Biology > Topic 4 - Genetic Infomation, variaton and relationships between organisms > Flashcards

Topic 4 - Genetic Infomation, variaton and relationships between organisms Flashcards

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1
Q

Define Gene

A

a short section of DNA that codes for a polypeptide or functional RNA

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2
Q

Define allele

A

a version of a gene

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3
Q

Define locus

A

a position on a chromosome

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4
Q

Define homologous

A

the structural features and pattern of genes are the same

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5
Q

For maternal and paternal chromosomes where are same genes found

A

in the same positions on the chromosomes

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6
Q

The genetic code is:

A
  • Non overlapping
  • A triplet code
  • Universal
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7
Q

What is meant by a triplet code?

A

every 3 base pairs (nucleotides) codes for 1 amino acid

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8
Q

What is meant by universal?

A

the code is the same in all species, ATA codes for the same thing in every species

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9
Q

What is meant by non overlapping?

A

Each base is discrete (123456 is 123, 456 and NOT 123, 234, 345, 456) so that the bases don’t get mixed up when they are being read, meaning the wrong amino acid is formed

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10
Q

How many possible triplet codes are there?

A

64

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11
Q

How many possible amino acids are there?

A

20

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12
Q

The genetic code is degenerate, what does this mean?

A

Some amino acids are coded by more than one triplet, e.g. tyrosine is TAT or TAC

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13
Q

What do some triplet codes act as?

A

Some triplet codes act as punctuation marks
Some indicate start and stop points for start/end of an amino acid chain:
- A start codon is ATG

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14
Q

What is transcription?

A

formation of pre mRNA in the nucleus

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15
Q

What is translation?

A

formation of polypeptides in the ribosomes

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16
Q

How does transcription work?

A

.Parental DNA has its hydrogen bonds broken by DNA helicase, leaving a template strand
.Free RNA nucleotides are attracted to it and form weak hydrogen bonds with the DNA nucleotides that are complementary to their bases
.RNA polymerase comes along and resynthesizes the sugar phosphate backbone along the RNA nucleotides and breaks the hydrogen bonds, making a strand of pre mRNA
.The pre mRNA is then spliced, which removes introns and joins together exons, turning into mRNA (no longer pre)

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17
Q

What are introns?

A

non-coding DNA

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18
Q

What are exons?

A

coding DNA

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19
Q

What is translation?

A

The process by which mRNA is used to make a specific protein

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20
Q

Describe how translation happens

A

Translation is the process by which mRNA is used to make a specific protein, after mRNA has been produced through transcription and splicing it then moves through the cytoplasm to a ribosome and enters between the two sub units and attaches to it. Here a start codon (AUG) tells the ribosome to start reading the RNA on it. Each triplet of bases is called a codon, and after the initial start codon tells the ribosome to read it the ribosome then moves along the mRNA and reads the codons, attaches (with temporary hydrogen bonds) tRNA with a complementary anticodon to the mRNA’s codon. Each tRNA has a specific amino acid attached, as one tRNA binds to the mRNA so does another one next to it, then their amino acids form polypeptide bonds to join them together and the first tRNA leaves and another one joins as the ribosome moves along the mRNA and forms a polypeptide bond in a condensation reaction with the amino acid there. This continues till a stop codon is reached which has no complementary anticodon so the chain stops and the polypeptide chain formed leaves the ribosome and coils up into an amino acid which join using energy from ATP.

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21
Q

What does tRNA do?

A

.Transport specific amino acids

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22
Q

How many different tRNA’s are there?

A

20

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23
Q

Do all tRNA’s have the same structure?

A

Yes

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24
Q

What is a tRNA made up of?

A

codon, anti codon, hydrogen bonds, ester bonds, amino acids

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25
Q

Describe the structure of tRNA

A

.Each consists of a single polynucleotide strand of RNA
.Folded to form a clover arrangement
.Held in place by hydrogen bonds between complementary base pairs
.One end acts as an attachment site for the amino acid
.The other end is called the anti-codon

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26
Q

What is a mutation?

A

Any change in one or more nucleotide base or a change in the sequence of the bases in DNA

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27
Q

Characteristic of mutations

A

.Random
.Spontaneous
.Natural
.Positive or negative

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28
Q

Three types of mutations

A

.Insertion
.Deletion
.Substitution

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29
Q

Define insertion

A

A nucleotide is added to the DNA sequence

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30
Q

Define deletion

A

A nucleotide is lost from the DNA sequence

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31
Q

Define subsitution

A

One nucleotide is replaced by another nucleotide with a different base

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32
Q

What is a frame shift?

A

every amino acid after the insertion or deletion will move one place

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33
Q

What will substitution affect?

A

Only one triplet code

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34
Q

What will deletion and insertion affect?

A

the whole amino acid sequence, by causing a frame shift

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35
Q

What is a mutagen?

A

A physical or chemical agent that changes the genetic material of an organism

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36
Q

What do mutagenic agents do?

A

increase the frequency of a mutation occurring above the natural

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37
Q

Name 4 things that act as mutagenic agents

A

Caffeine, x-rays, mustard gas and UV radiation

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38
Q

What are chromosomal mutations?

A

Changes in the structure or number of whole chromosomes

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39
Q

What are the two types of chromosomal mutations?

A

.Polyploidy

.Nondisjunction

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40
Q

What is polyploidy?

A

.Changes in whole sets of chromosomes

.Cells have multiple sets of chromosomes

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41
Q

What form of polyploidy is very common in plants?

A

.3n = triploid

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42
Q

What is non-disjunction?

A

.Homologous pairs fail to separate

.Changes in number of individual chromosomes per cell

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43
Q

What is down’s syndrome caused by?

A

extra chromosome 21

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44
Q

Define meiosis

A

the process by which a diploid nucleus (2n) divides to produce four haploid daughter nuclei (n)

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45
Q

Name the phases in meiosis

A

Interphase, prophase I, Metaphase I, Anaphase I, Telophase I, cytokinesis, Prophase II, Metaphase II, Anaphase II, telophase II and cytokinesis

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46
Q

What is a homogolous pair?

A

one chromatid of mum and one chromatid of dad

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47
Q

What are sister chromatids?

A

identical chromatids together

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48
Q

What two forms of genetic variation are there?

A

Crossing over and independent segregation

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49
Q

What is crossing over?

A

Crossing over is the exchange of alleles

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50
Q

What is independent segregation?

A

Independent segregation is the random arrangement of chromosomes

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51
Q

State what happens in each phase of meiosis.

A

Interphase – The cell is synthesising DNA and checking it (2 chromatid per chromosome)
Prophase I – The chromosomes thicken and get bigger, shorten and condense, the nuclear membrane breaks down
Metaphase I – The chromosomes line up along the equator and attach the spindle fibres from the poles to their centromeres
Anaphase I – The pair of chromosomes are split as each is pulled to opposite poles in the cell by the spindle fibres contracting – the homologous chromosomes are separated from each other but the chromosome stays tgther
Telophase I & Cytokinesis – The cells form two nucleus, one for each set of new chromosomes, and pull apart while forming a membrane to produce two daughter cells
Prophase II – The chromosomes thicken and get bigger, shorten and condense, the nuclear membrane breaks down
Metaphase II – The chromosomes line up along the equator and attach the spindle fibres from the poles to their centromeres
Anaphase II – The sister chromatids are split as each chromatid is pulled to opposite poles in the cell by the spindle fibres
Telophase II & cytokinesis – The cells form two nucleus, one for each set of new chromatids, and pull apart while forming a membrane to produce two more daughter cells each (4 cells now altogether)

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52
Q

What is a genotype?

A

The genetic makeup of an organism, the genes and alleles that they have

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53
Q

What is a phenotype?

A

Observable characteristics, genotype + environment = phenotype

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54
Q

What are the causes of genetic variation?

A

.Mutations, sexual reproduction, meiosis

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55
Q

How does crossing over work?

A

Homologous pairs line up, chromatids of each pair become twisted, section of chromatid breaks off and re-joins chromatid of the other homologous chromosome, sections have different alleles, new combination of linked alleles

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56
Q

With crossing over, what happends to the amount of possible versions of allele combinations?

A

No crossing over = 2 versions

With crossing over = 4 possible versions

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57
Q

Who discovered independent segregation? When?

A

.Gregor Mendel (19th Century)

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58
Q

What is independent segregation?

A

the random segregation of chromosomes during anaphase

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59
Q

What did Gregor Mendel say about independent segregation?

A

.Genes are inherited independently of one another

.BUT genes close together have a high likelihood of being inherited together

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60
Q

Independent segregation key points

A

.Homologous pairs line up along the equator randomly
.Combination of chromosomes pulled to each pole is random
.Daughter cells produced are genetically different

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61
Q

The formula for the number of combinations of genes after independent segregation

A

2^n

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62
Q

The formula for the number of combinations of genes after fertilisation after independent segregation

A

(2^n)^2

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63
Q

Why does the formula (2^n)^2 not work for crossing over?

A

Crossing over is completely random

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64
Q

What is the ‘n’ in the formula (2^n)^2?

A

number of chromosomes

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65
Q

What is the first ‘2’ in the formula (2^n)^2?

A

possible number of routes the chromosomes could go to (pulled to two poles)

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66
Q

Define genetic diversity

A

The total number of different alleles in a population

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67
Q

What must happen for a genetic mutation to occur?

A

.There must be a change in the DNA
.A random mutation
.Resulting in:
.Polyploidy, non-disjunction, substitution, insertion, deletion

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68
Q

High genetic diversity within a species =

A

large number of different alleles

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69
Q

Low genetic diversity within a species =

A

small number of different alleles

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70
Q

Advantages of High Genetic DIversity

A

.Higher survival rate, we might have some people with genes to survive in certain climates and some who don’t, if we had LGD and all had the other climates genes we would all die
.Higher resistance to disease, as it won’t spread as easily
.Low chance of inbreeding
.Less competition for same habitat
.Larger food web, not solely reliant on one food

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71
Q

Disadvantages of High Genetic DIversity

A

.Fewer organisms with characteristics for human’s

.Fewer organisms adapted to an environment at a specific time or place

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72
Q

What is natural selection?

A

The differential survival and reproduction of individuals due to differences in their phenotype

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73
Q

Define phenotype

A

Observable physical characteristics that an organism has

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74
Q

Define genotype

A

Genetic makeup of an organism

75
Q

Define allele frequency

A

The number of times an allele occurs within in the gene pool

76
Q

Define genepool

A

The total number of alleles in a particular population at a specific time

77
Q

Why does allele frequency change?

A

Not all alleles are equally likely to be passed to the next generation
Those better adapted to their environment tend to survive and breed, at the expense of those less well adapted

78
Q

Key points of a normal distribution curve

A

.No bias
.Data surrounds a central point
.Curve is symmetrical
.Curve is bell shaped

79
Q

Mode

A

The most frequent value

80
Q

Mean

A

the average, every value added together divided by the amount of values

81
Q

Median

A

the value in the middle when the in ascending order

82
Q

Describe the shape of a normal distribution curve

A

The curve is shaped like a bell, near 0 on the y axis at the extremes of the x axis and increasing like a curve to a maximum in the middle

83
Q

In a normal distribution curve, what is the mean the same as?

A

The mode and the median

84
Q

Why does the mean of a distribution curve change?

A

Most characteristics area a result of multiple genes (poly genes)
Each gene is affected by the environment
Changes in environment = changes in the mean

85
Q

How does directional selection occur?

A
  1. Mutation occurs
  2. Change in the environment occurs
  3. Selection favours individuals that vary in one direction from the mean
  4. One extreme is favoured for
  5. Allele frequency changes
86
Q

Define selection

A

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

87
Q

Essentially, what is directional selection?

A

.Phenotypes of one extreme in the population is selected for
.The other phenotype is selected against
.Change in allele frequency

88
Q

In stabilising selection, what happens?

A 
.Selection acts against both extremes in a range of phenotypes
.Mean is favoured
.Phenotypic variation is reduced
.Both extremes are selected against
.Environment has remained stable
89
Q

Why is birth rate an example of stabilising selection?

A

.The extremes are favoured against since too low or too high birth weights can result in death of the child
.Too low, going to die
.Too high, going to take lots of resources and energy from the mother when alive or could kill the mother in birth so a low survival rate for the baby

90
Q

What is aseptic technique?

A

‘Method designed to prevents contamination form microorganisms’

91
Q

When is aseptic technique important?

A

.Handling surgical equipment
.Surgery
.During labour
.Inserting catheters or IV drips

92
Q

Phenotype selected, directional selection

A

The one best suited to the changing environment, one of the extremes

93
Q

Phenotype selected, Stabilising selection

A

The mean/medium/mode

94
Q

Effect on the characteristics of a population, directional selection

A

Changes the overall characteristics to make it advantageous in the given environment

95
Q

Effect on the characteristics of a population, stabilising selection

A

Increases the frequency of the mean/medium/mode allele at the expense of the extreme alleles to make the population as a whole better suited to their stable environment

96
Q

Shape of the distribution curve, directional selection

A

Shifts the normal curve to one extreme or the other

97
Q

Shape of the stabilising curve, directional selection

A

Narrows the normal curve and increases its height (frequency) for the mean/medium/mode

98
Q

Example, directional selection

A

Moths in the industrial revolution or antibiotic resistance

99
Q

Example, stabilising selection

A

Weight of babies after birth

100
Q

What is a species?

A

A species is a group of individuals that area capable of breeding to produce living and fertile offspring.

101
Q

What happens to a species genes in sexual reproduction?

A

Two individuals of a species can combine their genes during sexual reproduction but selection can act to favour different phenotypes presence within species depending on where they are found

102
Q

What is an anatomical adaptation? Example

A

Anatomical – structure, how the organism is shaped – appearance, e.g. shorter ears and thicker fur in arctic foxes

103
Q

What is an physiological adaptation? Example

A

inside, how the organism works internally – chemical reactions/processes internally, e.g. oxidising of fat rather than carbohydrates to produce extra water

104
Q

What is a behavioural adaptation? Example

A

behaviour, how you the organism acts – actions of the organisms, e.g. migration of swallows from UK to Africa

105
Q

Key information of binomial names

A

.Universal naming system
.Written in italics or underlined
.Given two names

106
Q

What is the first name in binomial names?

A

Generic name
.Denotes the genus
.Upper case

107
Q

What is the second name in binomial names?

A

Used to identify
.Denotes the species
.Lower case

108
Q

Binomial names, order of Latin things

A 
Kingdom
Phylum
Class
Order
Family
Genus
Species
109
Q

State the difference between pre-mRNA and mRNA

A

mRNA has introns removed

110
Q

Birth weight is a form of stabilizing selection, why?

A

Both extremes have a disadvantage, too heavy or too light and it’ll die

111
Q

Why is splicing required?

A

So it is small enough to leave the nuclear envelope and doesn’t disrupt the formation of a polypeptide

112
Q

Examples of courtship displays

A 
.Bright colours
.Patterns
.Feathers
.Birds tweeting/songs
.Building rock piles
.Fighting
.Ritualised movements (dancing)
.Displays of beauty or strength
113
Q

Stimuli to male response of a courtship display happening

A

Stimuli  the male communicates a courtship signal  this acts as a visual stimulus to the females and is detected by the eyes (a receptor)  sends a message to female nervous system (CNS)  effector contracts or releases a hormone  effector causes a specific innate/stereotyped behaviour of her own (response)  acts as a stimulus to the male  the male responds

114
Q

Why do males impress the females?

A

They are the ones that are needed to carry the children

115
Q

Why are courtship displays important?

A

they help an organism to reproduce

116
Q

How do courtship displays help an organism to reproduce?

A
  • Enabling an organism to recognise one of their own species – so they can produce fertile off spring and prevent cross breeding, ensures genes are passed on, use similarities in physical characteristics and behaviours
  • Identifying if a mate is capable of breeding – both partners need to be sexually mature, fertile and receptive to mating, females may only be ‘in season’ once a year
  • Forming pair bonds (lifelong pairings) – ensures successful breeding (more investment), successful raising of the offspring/pass on genes
  • Synchronising mating season – determines whether the female is in receptive (fertile) state, correct female response then mating will take place
117
Q

Define classification

A

the organisation of living organisms into groups

118
Q

Define taxonomy

A

the theory and practice of biological classification

119
Q

Key points of classification

A

Carl Linnaeus
Not random
Based on accepted principles

120
Q

Define analogous

A

have the same function but do not have the same evolutionary origin

121
Q

Define homologous

A

similar evolutionary origins/structures regardless of their function

122
Q

What is artificial classification? With example

A

Based on analogous classification
Not based on evolutionary relationship
For example, wings on a bat and a butterfly

123
Q

What is phylogenetic classification?

A

Classifies species based on shared features
Characteristics derived from ancestors
Based on evolutionary relationships
Partly based on homologous characteristics

124
Q

What is each group called in phylogenetic classification?

A

a taxon (taxa)

125
Q

Who developed domains and what are they?

A

Carl Woese developed domains – the highest taxonomic rank

126
Q

Name the 3 domains

A

Bacteria, archea and eukarya

127
Q

Key features of bacteria

A 
Unicellular
Non-membrane bound organelle
Non-membrane bound DNA
Has plasmids
Has 70S ribosomes
Small
DNA is free floating
DNA is not associated with histones
Cell wall (murein)
Some may cause disease
128
Q

Key features of archea

A 
Single celled prokaryotes
Similar shape and size to bacteria
DNA/genes and protein synthesis like eukaryotes
No murein in cell wall
No membrane bound organelle
129
Q

Key features of eukrya

A 
Multicellular
Membrane bound organelle
Membrane bound DNA
Doesn’t have plasmids
Has 70S and 80S ribosomes
Large
DNA is in the nucleus
DNA is associated with histones (proteins)
No cell wall
Split into four kingdoms (protoctista, fungi, plantas, animals)
130
Q

How to read phylogenetic trees

A

Oldest ancestral species at base, most recent divergence at the end of branches

131
Q

Define hierarchy

A

smaller groups within larger groups with no overlap

132
Q

Advantages of classifying by observable characteristics

A

.Easier
.Anybody could do it
.Does not require any advanced equipment

133
Q

Disadvantages of classifying by observable charcateristcs

A

.Patterns of inheritance aren’t always clear
.Differences aren’t often discrete
.Interpretation subjective
.Fossil data is hard to find
.Most genes are polygenetic
.May be a result of similar environments not similar evolutionary history

134
Q

How can DNA Base Sequences be used to see evolutionary relationships?

A

Compare the exact order of nucleotides on the DNA
Mutation occurs causing a difference between individuals
More differences in bases = fewer similarities
Individuals more distantly related

135
Q

How can mRNA Base Sequences be used to see evolutionary relationships?

A

mRNA is complementary to DNA
Differences in mRNA = differences in DNA
Compare the exact order of nucleotides on the DNA
Mutation occurs causing a difference between individuals
More differences in bases = fewer similarities
Individuals more distantly related

136
Q

How can amino acid sequences in proteins be used to see evolutionary relationships?

A

Differences in DNA = differences in mRNA
Differences in mRNA = differences in amino acids
Compare the exact order of nucleotides on the DNA
Mutation occurs causing a difference between individuals
More differences in bases = fewer similarities
Individuals more distantly related

137
Q

Adv of using DNA and mRNA when finding evolutionary relationships

A

.Determine the exact order of nucleotide bases
.Determine how diverse organisms are
.Determine the time since divergence through the number of mutations present

138
Q

Disadv of using DNA and mRNA when finding evolutionary relationships

A

.Can cost a lot
.Can take a long time to sequence the full genome
.Requires specialist equipment and personnel

139
Q

Adv of using amino acids when finding evolutionary relationships

A

.Determines the DNA and mRNA sequence

.Usually easier to identify amino acids present

140
Q

Disadv of using amino acids when finding evolutionary relationships

A

.Can cost a lot
.Can take a long time
.DNA may be non-coding so not detected as difference
.The genetic code is degenerate so the same amino acid may be a result of very different DNA sequences

141
Q

How can we identify genetic diversity?

A

.DNA Hybridisation

.Biochemical analysis

142
Q

What is hybrid?

A

combination of two different elements

143
Q

What is DNA hybridisation?

A

direct comparison between the DNA sequences of different organisms

144
Q

What is a hybrid strand?

A

one strand from one set of DNA and one strand from another

145
Q

How does DNA Hybridisation work?

A
  1. DNA from two species is heated
  2. Denatures DNA and breaks the hydrogen bonds
  3. Strand A given radioactive labels or fluorescent markers
  4. Strand A and B are mixed
  5. Strands are cooled
  6. Two strands recombine and hydrogen bonds can reform between
  7. Gaps are present when no complimentary base pairing has occurred
  8. The higher percentage f hydrogen bonds formed = greater similarity in genetic material
146
Q

How does biochemical analysis work?

A

Serum containing many human antigens is injected into another species, rabbits are commonly used. The rabbit responds by producing anti-human antibodies, anti-human antibodies from rabbit are extracted in a serum and mixed with other species. The antihuman antibodies will bind to human antigens in the serum of other species, the more human like antigens in the serum (similar in structure), the more antigen-antibody complexes formed (as they are complementary), the more precipitate seen in the serum. The more precipitate seen, then the more closely related to the human the other species are (if there is similarity in protein structure, there is similarity in DNA).

147
Q

In biochemical analysis, the human serum first must be added to a different species, why?

A

so that antibodies complementary to the human antigens can be formed, and then used to test for the complementary human antigens

148
Q

Why are species like rabbits used in biochemical analysis?

A

Species like rabbits are used since they are small, easy to keep, produce lots of young and cheap

149
Q

Define biodiversity

A

The range and variety of genes, species and habitats within a particular region.

150
Q

What are the 3 types of biodiversity?

A

Species diversity, genetic diversity and ecosystem diversity

151
Q

What is species diversity?

A

the number of different species and the number of individuals of each species within any one community

152
Q

What is genetic diversity?

A

the variety of genes possessed by the individuals that make up any one species

153
Q

What is ecosystem diversity?

A

the range of different habitats within a particular area

154
Q

What is species richness?

A

Species richness is the number of different species in a particular area at a given time (community)

155
Q

Equation for species diversity index? With meaning for each letter

A 
d = species diversity
N = total number of organisms of all species
n = total number of organisms of each species
Σ = the sum of
156
Q

Human factors affecting biodiversity

A

.Agriculture – demand for food has more than doubled
.Increased use of herbicides and pesticides
.Use land for homes and industry
.Increased waste and land fill
.Deforestation

157
Q

How does agriculture affect biodiversity?

A
  1. Monoculture (growing only one species)
  2. Lack of intercropping (not rotating what is grown each season)
  3. Competition for space
  4. Use of pesticides and herbicides
  5. Cattle in the field where species may grow
  6. Draining wetland and marshes
  7. Removing hedgerows (replacing hedge borders with fences)
158
Q

How do monocultures affect biodiversity?

A

reduction in species and genetic diversity directly and indirectly as fewer food sources and habitats

159
Q

how does lack of intercropping affect biodiversity?

A

Drains the soil of nutrients, results in monoculture

160
Q

How does competition for space affect biodiversity?

A

Natural species habitats cannot grow/are outcompeted by dominant

161
Q

How does use of pesticides and herbicides affect biodiversity?

A

Can be toxic to species, enters water cycle, eutrophication

162
Q

How does cattle in the field where species may grow affect biodiversity?

A

Over grazing, trampling, reduction in species diversity

163
Q

How does draining wetland and marches affect biodiversity?

A

Removes nutrients and moisture from soil so species cannot grow

164
Q

How does removing hedgerows affect biodiversity?

A

Removes habitats and food sources

165
Q

What is deforestation?

A

The permanent clearing of forests and the conversion of land to other uses, such as agriculture, grazing or settlement

166
Q

How many species are being lost each year due to deforestation?

A

50,000

167
Q

How does deforestation reduce biodiversity?

A

by clearing the forests you are not only killing the trees (a species) and so reducing the species diversity index directly but the trees may also act as a habitat or food source to other animals so by killing the trees you are killing the animals that rely on the tree as well – thereby indirectly reducing biodiversity as well.

168
Q

How can maintaining biodiversity bring economic benefit?

A
  1. By maintaining biodiversity, you can keep biodiverse areas (like the coral reef or forests) which attract tourists and people for days out, thereby benefiting the economy. Also extracts of plants can be used for medicine, so you keep the biodiversity and keep the money.
169
Q

How can you reduce human impacts of deforestation?

A

.Eco charges

.Increased taxes/fines

170
Q

Define intraspecific

A

variation within a species, eye colour or blood group

171
Q

Define interspecific

A

variation between a species, food source or pollinator

172
Q

State when you would use quadrats and transects with examples

A
  1. You use quadrats to compare how common an organism is in two or more sample areas (shady and sunny spots in a playing field). You use transects to find out how organisms are distributed across an area (if an organism becomes more or less common as you move from a hedge towards the middle of a field).
173
Q

How would you use quadrats?

A

Place a 1m^2 quadrat on the ground at a random point within the first sample area, count all the organisms within that quadrat, repeat as many times as possible, work out the mean number of organisms per quadrat within the first sample area. Repeat this all for the second sample area. Compare the two means.

174
Q

How would you use trasects?

A

Mark out a line in the area you want to study using a tape measure, collect data along this line (this can be done by counting the amount of organisms touching the line or by placing quadrats down as you go down the line at even intervals). Interpret the data.

175
Q

What is sampling bias and how is it avoided?

A
  • Biased choices made by the investigator
  • Deliberate or unwillingly
  • Sample is unrepresentative
  • Avoided using random sampling
176
Q

What is chance variation and how is it avoided?

A
  • Even if sampling bias is avoided, this can still occur
  • Not a representative sample
  • I.E. all individuals are the same
  • Avoided by increasing sample size
  • Repeat lots
177
Q

Define distribution

A

the way in which data is spread/shared out

178
Q

What is standard deviation a form of?

A

A statistical test

179
Q

What is standard deviation and what does it do?

A

.A measure of the width of the curve
.Indicates of the range
.The distance from the mean until the curve goes from convex to concave
.Determines how likely it is that results are due to chance

180
Q

With standard deviation, the closer to the mean values (less spread), the ____ reliable

A

more

181
Q

__% of data lies within 1 s.d

A

68

182
Q

__% of data lies within 2 s.d

A

95

183
Q

Standard deviation equation

A

root((Σ(x-(Σx/n))^2)/(n-1))

AQA A Level Biology (19 decks)

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