CHAPTER 4 - DNA AND RNA Flashcards
- DNA - genes - chromosomes - RNA - protein synthesis - transcription - translation - genetic code - diversity and selection - diversity and classification
1
Q
is DNA stored the same or differently in prokaryotic and eukaryotic cells
A
differently
2
Q
how is DNA stored
A
- STRUCTURE of DNA is the same in all organisms
- they way DNA is STORED is different in eukaryotes and prokaryotes
3
Q
how is DNA stored in eukaryotic cells
A
- cells contain linear DNA molecules that are CHROMOSOMES
- each chromosome is made of 1 long molecule of DNA and its associated proteins
- chromosomes are found in the NUCLEUS
- DNA molecule is really long, so it needs to be wound up so it can fit into the nucleus
- DNA is wound around HISTONES
- histone proteins also help to support the DNA
- DNA is coiled up very tightly to make up a compact chromosome
4
Q
what is DNA like in the mitochondria and chloroplasts in eukaryotic cells
A
- have their own DNA
- similar to prokaryotic DNA because its CIRCULAR AND SHORTER than the DNA molecules in the nucleus
- NOT assosciated with histone proteins
5
Q
what is DNA like in prokaryotic cells
A
- also carry DNA as chromosomes
- DNA molecules are shorter and circular
- DNA is NOT wound around histones
- instead it condenses to fit into the cell by SUPERCOILING
6
Q
does a small or large amount of the DNA in a cell carry genetic info
A
a small amount
7
Q
what is the most important part of DNA
A
genes
8
Q
what are genes
A
a sequence of DNA bases that codes for a polypeptide or functional RNA
9
Q
what does the sequence of amino acids code for in a polypeptide
A
the primary structure of a protein
10
Q
what is the reason for polypeptides differing from eachother
A
- a different number and order of amino acids
11
Q
what does the order of bases in a gene determine
A
the order of amino acids in a polypeptide
12
Q
what is a triplet/codon
A
- codes amino acids
- is a sequence of 3 bases in a gene
13
Q
describe how polypeptides are made in a very basic way
A
- DNA is first copied into mRNA (messenger RNA)
- first stage of protein synthesis
14
Q
if genes dont code for a polypeptide, what do they code for
A
functional RNA
15
Q
what is functional RNA
A
- RNA molecules other than mRNA
- they perform special tasks during protein synthesis
- ex, tRNA and rRNA (ribosomal RNA)
16
Q
what is the term for a full set of genes in a cell
A
genome
17
Q
what is the term for a full set of proteins that a cell is able to produce
A
proteome
18
Q
what is non coding DNA
A
- genes that do code for polypeptides contain sections which dont code for amino acids : this is non coding DNA
19
Q
what is the term for non coding DNA
A
- introns
- (think of intervals, like adverts, in a movie - not part of the movie)
20
Q
describe introns
A
- non coding DNA
- can be several introns in a. gene
- purpose is NOT known
21
Q
what happens to introns in eukaryotes
A
- removed during protein synthesis
- as they are removed, they dont affect the amino acid order
22
Q
what happens to introns in prokaryotes
A
- prokaryotic DNA does NOT contain introns
23
Q
what is the term for the parts of a gene which do code for amino acids
A
exons
24
Q
what are non coding multiple repeats
A
- in eukaryotic DNA
- regions of multiple repeats outside of genes
- DNA sequences that repeat over and over
- these areas dont code for amino acids
- ex, CCTTCCTTCCTTCCTT
25
what are alleles
- a gene can exist in more than one form : alleles
- order of bases in each allele is slightly differently, therefore they code for slightly different versions of the same polypeptide
26
what are homologous chromosomes
- in a eukaryotic cell nucleus, DNA is stored as chromosomes
- humans have 23 pairs of chromosomes = 46 in total
- pairs of matching chromosomes = homologous pairs
- in a homologous pair, both chromosomes are the same size and have the same genes, however they can have different alleles
- alleles coding for the same characteristics will be found at the same fixed position (LOCUS) on each chromosomes in a homologous pair
27
how many types of RNA play a key role in protein synthesis
2
28
what are the 2 types of RNA that play a key role in protein synthesis
- mRNA
- tRNA
29
what is protein synthesis
- the production of proteins/polypeptides from the info contained in the cells DNA
- also called polypeptide synthesis
- involves both transcription and translation
30
what is transcription
where the DNA code is copied into mRNA
31
what is translation
where the mRNA joins with a ribosome and the code it carries is used to synthesise a protein
32
what is RNA
- a single polynucleotide strand
- bases : A, U, C and G
- A and U pair during protein synthesis
- C and G pair
- 2 types of RNA : mRNA and tRNA
33
what is mRNA
- messenger RNA
- made during transcription
- carries the genetic code from the DNA -> ribosomes : used to make PROTEIN during TRANSLATION
- mRNA is a single polynucleotide strand
- 3 adjacent bases in mRNA are called CODONS (sometimes called triplets or base triplets)
34
what is tRNA
- transfer RNA
- involved in translation
- carries the amino acids used to make proteins -> ribosomes
- tRNA is a single polynucleotide strand folded into a CLOVER shape
- hydrogen bonds between specific base pair holds the molecule in this shape
- every tRNA molecule has a specific sequence of 3 BASES at one end : ANTICODON
- opposite end has an AMINO ACID BINDING SITE
35
how are proteins synthesised
using the instructions in DNA
36
what 2 steps takes place in protein synthesis
- transcription
- translation
37
simply describe what happens in transcription
- an mRNA copy is made from DNA
38
where does transcription take place in eukaryotic cells
nucleus
39
where does transcription take place in prokaryotic cells
because they have no nucleus, it takes place in the CYTOPLASM
40
describe how transcription takes place
- RNA polymerase attaches to the DNA double helix at the start of the gene
- in eukaryotes, the hydrogen bonds between the 2 DNA strands in the gene are broken by the DNA HELICASE attached to the RNA polymerase
- 2 strands are separated and the DNA molecule uncoils -> this exposes some of the bases
- one of these strands is used as a template strand
- the RNA polymerase lines up free RNA nucleotides alongside the exposed bases on the template strand
- specific complementary base pairing causes the mRNA to be a complementary copy of the DNA template strand (but thymine is replaced with uracil)
- once RNA nucleotides have paired up with their specific bases on the DNA strand, they are joined up by RNA polymerase -> forms mRNA strand
- RNA polymerase moves along the DNA strand, assembling the mRNA strand
- the hydrogen bonds between the uncoiled strands of DNA reform once the RNA polymerase has passed by it
- strand coils back into a double helix
- when RNA polymerase reaches a stop signal, a particular DNA sequence, it STOPS making mRNA and then detaches from DNA
- in eukaryotes, mRNA moves out of the nucleus through the nuclear pore and attaches to a ribosome in the cytoplasm, then translation takes place
41
how are the DNA strands separated in prokaryotes
by RNA polymerase
42
are free RNA nucleotides attached to anything
no
they are freely floating in the nucleus
43
does transcription produce the same or different products in eukaryotes and prokaryotes
different products
44
what is mRNA like in eukaryotes prior to splicing
- both introns and exons are copied into mRNA during transcription
- mRNA strands contain introns and exons = pre mRNA
45
what is splicing and what happens in it
- splicing is where introns are REMOVED and the exons are joined together
- this forms mRNA strands
- takes place in the nucleus
- the mRNA leaves the nucleus after this, for translation
46
does prokaryotic mRNA go through splicing
- mRNA is produced DIRECTLY from DNA, therefore splicing does not take place
- no need for splicing as there are no introns in prokaryotic DNA
47
what is translation in simple terms
- second stage of protein synthesis
- takes place in RIBOSOMES in both eukaryotes and prokaryotes
- during translation, amino acids are joined together to make a polypeptide chain
48
describe the process of translation
- the mRNA attaches itself to a ribosome and tRNA molecules carry amino acids to it
- ATP provides the energy needed for the bond to form between the amino acid and tRNA molecule
- a tRNA molecule, which carries an amino acid, with an anticodon thats complementary to the first codon on the mRNA - it attaches itself to the mRNA by complementary base pairing
- a second tRNA molecule attaches itself to the next codon on the mRNA in the same way
- the 2 amino acids attached to the tRNA molecules are joined by a PEPTIDE BOND
- first tRNA molecule moves away, leaving its amino acid behind
- a third tRNA molecule binds to the next codon on the mRNA
- its amino acid binds to the first 2 and the second tRNA molecule moves away
- this process continues and produces a chain of linked amino acids until there is a stop signal on the mRNA molecule
- PP chain moves away from the ribosome and translation is complete
49
what is another name of protein synthesis
polypeptide synthesis
50
give an example of the codon on the mRNA which is complementary to the anticodon on tRNA
anticodon on tRNA = UAC
codon on mRNA = AUG
51
what is the genetic codes purpose
encodes info in genes which determine what we look like, how we develop
52
what is the genetic code
- sequence of base triplets (codons) in mRNA which code for specific amino acids
- each base triplet is read in sequence, separate from the triplet before and after it
53
what does non overlapping mean in context of the genetic code
base triplets dont share their bases
54
what does degenerate mean in context of the genetic code
- there are more possible combinations of triplets than there are amino acids
- some amino acids are coded for by more than one base triplet
- not all triplets code for amino acids
55
there are only 20 amino acids, but how many possible triplets from these
64
56
what are stop signals
- triplets which are used to tell the cell when to stop production of a protein
- found at the end of mRNA
57
give an example of a stop signal and its purpose
UAG
58
what is a start signal
- at the start of mRNA
- tell the cell when to start protein production
- code for a specific amino acid called methionine
59
what does universal mean in the context of the genetic code
- the same specific base triplets code for the same amino acids in all living thing
- ex, UAU codes for TYROSINE in all organisms
60
what is a gene mutation
- change in the base sequence of DNA
- can arise spontaneously in DNA replication (in interphase specifically)
- ex, base deletion or substitution
61
what is a mutagenic agent
a factor that increases the rate of genetic mutation
62
give an ex of a mutagenic agent
- UV light
- alpha particles
63
how can a mutation lead to the production of a non - functional protein or enzyme
- changes sequence of base triplets in DNA/in a gene = changes codons on mRNA
- therefore changes sequence of amino acids in the PP
- therefore changes position of hydrogen/ionic/dispute bonds between amino acids
- therefore changes the TERTIARY structure of the protein
- in enzymes, this causes the active site changes shape so the substrate cant bind and therefore an E-S complex cant form
64
what are the possible effects of a substitution mutation
- base/nucleotide is replaced by a different base/nucleotide
- changes one triplet = changes one mRNA codon
- one amino acids in PP changes -> can cause the tertiary structure to change if the position of H/I/D bonds change
OR
- amino acid does NOT change due to the degenerate nature of the genetic code (triplet could code for the same amino acid) OR if the mutation is in an intron (gets spliced and introns are non-coding DNA anyways)
65
explain the possible effects of a deletion mutation
- one nucleotide/base is removed from the DNA sequence
- changes the sequence of DNA triplets from the point of mutation -> FRAMESHIFT
- changes the sequence of mRNA codons after the point of mutation
- changes the sequence of the amino acids in the PRIMARY structure of the PP
- changes the position of H/I/D bonds in TERTIARY structure
- changes the TERTIARY structure/shape of protein
66
what are homologous chromosomes
- same length
- same genes at same loci
- may have different alleles
67
what is a diploid cell
- have 2 complete sets of chromosomes
- represented as 2n
- DIPLOID = DOUBLE = 2
68
what is a haploid cell
- has a SINGLE set of unpaired chromosomes
- represented as n
69
what happens in interphase for meiosis
- DNA replicates
- 2 copies of each chromosome (sister chromatids) joined by a centromere
70
what happens in meiosis 1
- first nuclear division
- separates homologous chromosomes
steps
- chromosomes arrange into homologous pairs
- crossing over between homologous chromosomes
- independent segregation of homologous chromosomes
71
what happens in meiosis 2
- second nuclear division
- separation of chromatids due to centromere being split
72
what is produced from meiosis
- 4 genetically VARIED daughter cells
- daughter cells are normally HAPLOID (if the parent cell is diploid)
73
why is the number of chromosomes halved during meiosis
as homologous are separated during meiosis 1
74
how does crossing over create genetic variation
- homologous pairs of chromosomes associate/form a bivalent
- chiasmata form (point of contact between non sister chromatids)
- alleles/lengths of non sister chromatids are exchanged between chromosomes
- results in the creation of new combinations of maternal and paternal alleles on chromosomes
75
how does independent segregation creates genetic variation
- homologous pairs randomly align at equator -> random which chromosome from each pair goes into each daughter cell
- creates different combinations of maternal and paternal chromosomes/alleles in daughter cells
76
excluding mutations and meiosis, how else is genetic variation within a species increased
- random fertilisation/fusion of gametes
- creating new allele combinations/new maternal and paternal chromosome combinations
77
explain the different outcomes of mitosis and meiosis
mitosis
- produces 2 daughter cells
- only 1 division
- maintains chromosomes number, ex diploid parent cell and diploid daughter cells
- genetically identical daughter cells
meiosis
- produces 4 daughter cells
- 2 divisions
- halves the chromosome number, ex diploid parent cell and haploid daughter cell
- genetically varied daughter cells due to crossing over and independent segregation
78
explain the importance of meiosis
- 2 divisions create haploid gametes
- diploid number is restored at fertilisation
-> chromosome number maintained between generations
- independent segregation and crossing over creates genetic variation
79
how can you tell where meiosis and mitosis occur in a life cycle
- mitosis occurs between stages where chromosomes number is maintained (diploid parent cell -> diploid daughter cell)
- meiosis occurs between stages where the chromosome number halves (diploid parent cell -> haploid daughter cell)
80
describe how mutations in the number of chromosomes arise
- spontaneously by chromosome non disjunction during meiosis
- homologous chromosomes or sister chromatids fail to separate during meiosis
- gametes have an extra copy (n+1) of a particular chromosome and others have none (n-1)
81
what is genetic diversity
- there can be different versions of a single gene : alleles
- alleles code for different versions of characteristics, like blonde or brown hair
- genetic diversity : the number of different alleles of genes in a species or population
- a large number of alleles in a population = large variety of different characteristics AND a high genetic diversity
82
why is genetic diversity important
- because if a population has a low genetic diversity, it may not be able to adapt to a change in the environment
- leading to the whole population possibly being wiped out by a single event, like a disease
83
how is genetic diversity increased within a population
- mutations in the DNA forming new alleles : some of these can be advantageous, whilst others can lead to problems
- different alleles being introduced into a population when individuals from another population migrate into it and reproduce : GENE FLOW
84
what does genetic diversity allow to occur and how is this advantageous
- natural selection
- some characteristics are more advantageous than others
85
what is a genetic bottleneck
- an event which causes a big reduction in a population
- ex, when a large number of organisms within a population die before reproducing
- leads to a reduction in the number of different alleles in the gene pool = reduced genetic diversity
- survivors reproduce and a larger population is created from a few individuals
86
what is the founder effect
- what happens when just a few organisms from a population start a new colony and there are only a small number of different alleles in the INITIAL gene pool
- the frequency of each allele in the NEW colony may be very different to the frequency of those alleles in the ORIGINAL
- ^ could lead to a higher incidence of genetic disease
- can occur as a result of migration leading to geographical separation
- or if a NEW colony is separated from the ORGINAL population for another reason, like religion
- ex, amish people who have an unusually high incidence of certain genetic disorders
87
why is natural selection advantageous
increases the proportion of advantageous alleles within a population
88
what is the positives and negatives of natural selection
- randomly occurring mutations sometimes result in a NEW allele being formed
negatives
- can be harmful, meaning the mutated allele quickly dies out
positives
- some mutations can produce alleles which are BENEFICIAL to an organism = helps organism to survive in certain environments
89
describe the process of natural selection
- natural selection = when the allele codes for a characteristic that increases the chances of an organism surviving, its frequency within the population INCREASES
- there is a differential reproductive success in a population = not all individuals are as likely to reproduce as each other
- individuals that have an allele that increases their chance of survival are MORE LIKELY to survive, reproduce and pass on their genes (including the beneficial allele) COMPARED TO individuals with less advantageous alleles
- GREATER population of the next generation inherits the BENEFICIAL allele
- FREQUENCY of the BENEFICIAL allele in the population INCREASES from generation to generation
- over generations this leads to evolution as the ADVANTAGEOUS alleles become MORE COMMON in the population
90
what is evolution
the gradual change in species over time
91
what is the advantage of evolution
it has led to the huge diversity of living organisms on earth
92
what are the 2 other key factors in evolution
- adaptation
- selection
93
what are adaptions
features that help organisms to survive in their environment
94
what are the 3 types of adaptations
- behavioural
- physiological
- anatomical
95
what are behavioural adaptations and give an example
- ways an organism acts that INCREASES its chance of survival
- possums sometimes 'play dead' if they are being threatened by a predator
- to escape attack
- INCREASES their chance of survival
96
what are physiological adaptations and give an example
- processes inside an organisms body that INCREASES its chance of survival
- brown bears hibernate, they lower their rate of metabolism over winter
- this conserves energy, so they dont need to look for food in the months when its scarce
- INCREASES their chance of survival
97
what are anatomical adaptations and give an example
- anatomical = structural
- these are structural features of an organisms body that INCREASES its chance of survival
- whales have a thick layer of blubber/fat
- helps keep them warm in the cold sea
- INCREASES their chance of survival in places where there food is found
98
what does natural selection do to allele frequency
it alters allele frequency in a population
99
what are the 2 types of selection
- directional
- stabilising
100
what is directional selection and give an example of this
- where individuals with alleles for characteristics of an EXTREME type are MORE likely to survive and reproduce
- could be in response to an environmental change
- ex, bacteria evolving antibiotic resistance
- some individuals in a bacterial population have alleles that give them antibiotic resistance
- population = exposed to the antibiotic, killing the bacteria without the resistance allele
- resistant bacteria survive and reproduce without competition = pass on the allele which gives them antibiotic resistance to their OFFSPRING
- after some time, most organisms in the population will carry the antibiotic resistance allele
101
what is stabilising selection and give an example of this
- where individuals with alleles for characteristics towards the middle of the range are MORE likely to survive and reproduce
- occurs when the environment isn't changing and it REDUCES the range of possible characteristics
-ex, human birth weight
- humans have a range of birth weights
- very small babies are LESS likely to survive and they have a high SA:VR = find it hard to maintain their body temp
- puts pressure on their respiratory and cardiac system which can be FATAL
- very large babies are LESS likely to survive as well
- giving birth to large babies can be hard as their large size would make it harder to fit through the mothers pelvis = can lead to COMPLICATIONS for mother and child
- conditions are most favourable for medium - sized babies
- so weight of human babies tends to shift towards the middle of the range
102
what is the term used for the groups scientists use to study organisms more easily
classification
103
what is phylogeny
- study of the evolutionary history of groups of organisms
- phylogeny tells us who's related to whom and how closely related they are
104
what is phylogenic tree
- shows the relationship between members of the family
- first branch point represents a common ancestor of all the family members
- each of the following branch points represent another common ancestor from which a different group diverged
- closely related species diverged away from each other most recently
105
what is taxonomy
- science of classification
- involves naming organisms and organisms them into groups
- this makes it easier to identify and study them
- scientists account phylogeny when classifying organisms and group organisms according to their evoloutionary relationships
106
what is the term for the groups used to classify organisms
- taxa
- there are 8 levels
- each group : taxon
107
how are the groups arranged
- in a hierarchy
- largest groups at the top
- smallest groups at the bottom
108
why is there no overlap between organisms in the taxa
- organisms can only belong to one group at each level in the hierarchy
- no overlap
109
what are the levels taxa
- domain
- kingdom
- phylum
- class
- order
- family
- genus
- species
110
what is the classification of humans
- domain = EUKARYA
- kingdom = ANIMALIA
- phylum = CHORTADA
- class = MAMMALIA
- order = PRIMATES
- family = HOMINIDAE
- genus = HOMO
- species = SAPIENS
111
explain the classification system of human
- as you go down the hierarchy, there are MORE groups but FEWER organisms in each group
- as you go down the hierarchy, organisms also become MORE CLOSELY RELATED
- hierarchy ends with SPECIES, the group that only contains ONE type of organism = HUMANS
112
what is 'species'
a group of similar organisms which are able to REPRODUCE to give FERTILE offspring
113
why do scientists constantly update classification systems
due to discoveries about NEW species and NEW evidence about known organisms, like DNA SEQUENCE DATA
114
what is the binomial system
- the naming system used for classification
115
describe the binomial system
- all organisms are given 1 INTERNATIONALLY accepted scientific name in latin which has 2 PARTS
- first part of name
- GENUS name
- has a CAPITAL letter
second part of name
- SPECIES name
- begins with a lower case letter
names are ALWAYS written in ITALICS or UNDERLINED (if handwritten)
116
why is useful to give organisms a scientific name
- enables them to communicate about organisms in a standard way (same name for each organism internationally)
- helps to avoid the confusion of using COMMON names
117
what can be used to classify organisms
their behaviour
118
what specific type of behaviour can be used to classify organisms
courtship behaviour
119
what is courtship behaviour
- it is carried out by organisms to attract a mate of the right species
- can be fairly simple or quite complex
120
give examples of simple courtship behaviours
- releasing a chemical
- ex -> male bumble bees produce chemicals called pheromones to attract female bumble bees to their territory
- using sound
- ex -> male red deer make a roaring noise to attract a mate
- visual displays
- ex -> the great tit will attract a mate by puffing out its chest to show off its black stripe
121
give examples of complex courtship behaviours
- dancing
- ex -> blue footed boobies perform a complex dance which involves lifting up their feet to show off their blue colour
- building
- ex -> bowerbirds construct bowers (shelters) made of leaves, twigs, flowers, shells, stones and whatever else the male can find
122
is courtship behaviour limited to the sex of the animal
- no
- can be performed by either the male or the female
- may sometimes involve both sexes
123
how can courtship behaviour be used as a way to classify species
- courtship behaviour is species specific
- only members of the same species will do and respond to that courtship behaviour
- allows members of the same species to recognise each other
- prevents interbreeding
- makes reproduction more successful (because mating with the wrong species will NOT produce fertile offspring)
- more closely related species = more similar their courtship behaviour is
124
give examples of how courtship behaviour can be used to classify species
- fireflies
- give off pulses of light
- pattern of flashes is SPECIFIC to each species
- crickets
- make sounds that are similar to morse code
- code is different for different species
- male peacocks
- show off their colourful tails
- tail pattern is ONLY found in peacocks
- male butterflies
- use chemicals to attract females
- only those of the correct species RESPOND
125
advances in DNA and molecular technology have led to classification using ...
... = DNA or proteins
126
what are the 3 types of technologies which are useful for clarifying evolutionary relationships
- genome sequencing
- comparing amino acid sequence
- immunological comparisons
127
describe genome sequencing in clarifying evolutionary relationships
- advances in genome sequencing allow the entire base sequencing of an organisms DNA can be determined
- the DNA base sequence of one organism can then be compared to the DNA base sequence of ANOTHER organism -> allows to see how closely related they are
- closely related species will have a higher % of similarity in their DNA base sequence
128
give an example of how genome sequencing is used in clarifying evolutionary relationships
- has clarified the relationship between the skunks and members of the mustelidae family (weasels and badgers)
- skunks were classified as part of the mustelidae family, until their DNA sequence was revealed to be significantly DIFFERENT to other members of that family -> led to them being reclassified into the MEPHITIDAE family
129
how is the technique of comparing amino acid sequences used to clarify evolutionary relationships
- proteins are made of amino acids
- sequence of amino acids in a protein are coded for by the BASE SEQUENCE in DNA
- related organisms have SIMILAIR DNA sequences = SIMILAIR amino acids in their PROTEINS
130
give an example of how comparing amino acid sequences is used in clarifying evolutionary relationships
- cytochrome C is a protein found in many species
- more similar the amino acid sequence of cytochrome C in 2 DIFFERENT species = the MORE closely related the species are likely to be
131
how is the technique of immunological comparisons
used to clarify evolutionary relationships
- SIMILAR proteins will also bind to the SAME antibodies
132
give an example of how immunological comparisons can be used in clarifying evolutionary relationships
- if antibodies to a HUMAN version of a protein are ADDED to isolated samples from some OTHER species
- ANY protein that is like the HUMAN version will also be bound/recognised by THAT antibody
133
name the 2 ways gene technologies are used in classification
- classification of evolutionary relationships
- changed how genetic diversity is assessed
134
how are gene technologies used to assess genetic diversity
- early estimates of genetic diversity were made by looking at the FREQUENCY OF MEASURABLE OR OBSERVABLE CHARACTERISTICS IN A POPULATION
- ex, the number of different eye colours in a population AND the number of people with each particular eye colour
- ex, the number of people with each certain eye colour
- different alleles = determine different characteristics
- wide variety of each characteristics in a pop = high number of diff alleles = high genetic diversity
135
give examples of how gene technologies used to assess genetic diversity
- different alleles of the same gene will have slightly diff DNA base sequences
- comparing the DNA base sequences of the SAME gene in DIFFERENT organisms in a population allow scientists to find out how many alleles of that gene there are in THAT population
- different alleles will also produce slightly different mRNA base sequences
- may produce proteins with slightly diff amino acid sequences = can also be compared
136
what are the advantages of gene technologies used to assess genetic diversity
- new technologies can be used to give MORE accurate estimates of genetic diversity within a population/species, compared to if the frequency was only looked at based on OBSERVABLE CHARACTERISTICS
- allow the genetic diversity of different species to be compared more EASILY
137
what is variation
- the differences that exists between individuals
- variation between species and within species
138
what are causes of variation
- genetic factors
- different species = different genes = this causes variation between species
- individuals of the SAME species have the SAME genes, but DIFFERENT ALLELES = causes variation within a species
- variation within a species
139
how do genetic factors cause variation
- different species have different genes = causes variation between genes
- individuals of the SAME species have the SAME genes but DIFFERENT alleles = causes variation within a species
- alleles = versions of genes
140
how do differences in environment cause variation
- variation WITHIN a species can be due to differences in env
ex
- climate
- food
- lifestyle
141
how does a combination of genetic and environmental factors cause variation
- most variation is caused by a COMBINATION of genetic AND env factors
- ex, genes determine how tall an organism CAN grow, but nutrient ability affects how tall the organism ACTUALLY grows
142
what is a population sample
- when studying variation, you look at a SAMPLE of the population, NOT the WHOLE population
- it is too time consuming OR impossible to catch all the individuals in the group
- samples are used as MODELS for the WHOLE population
143
what is a random sample
- SAMPLE data will be used to draw conclusions about the WHOLE population
- important that it ACCURATELY represents the WHOLE population
- important any patterns are TESTED, ensures they are NOT due to chance
- random sample = NO BIAS
144
what is interspecific variation
variation BETWEEN species
145
what is intraspecific variation
variation WITHIN a species
146
if a sample is biased, it doesn't X the population as a whole, what is X?
X = represent
147
give an example of how a random sample can be generated
ex
- investigation is looking at the plant species in a field
- could pick random sample sites by DIVIDING the field into a GRID
- use a RANDOM NUMBER GENERATOR to select coordinates
- sample chosen (coordinates) = NO BIAS = representative of WHOLE population (field)
148
what is needed to ensure variation in a sample IS NOT due to chance and why is this necessary
- results need to be analysed statistically
- allows more confidence that the results ARE true and reflect what is going on in the WHOLE population
149
what is the formula for the mean
TOTAL of all values in data / NUMBER of values in data
150
what does a normal distribution look like
SYMMETRICAL about the mean
151
what is standard deviation
- tells you how much the values in a single sample VARY
- measure of the SPREAD of values about the mean
152
what do values with a larger standard deviation indicate about the variation
greater variation
larger standard deviation = greater variation
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what is the WORD formula used to calculate standard deviation
standard deviation =
square root of (sum of mean of data set - each value in data set ) ^ 2 / the number of values - 1
154
define biodiversity
the variety of living organisms in an area
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what does a high biodiversity in an ecosystem indicate about that ecosystem
that is it healthier
higher biodiversity in an ecosystem = healthier the ecosystem
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define habitat
place where an organism lives
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define community
ALL the populations of DIFFERENT species in a habitat
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what are the 2 scales of measuring biodiversity
- local biodiversity
- global biodiversity
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what is local biodiversity
- the variety of different species living in a small habitat thats local to you
- ex, pond or meadow
- some habitats will be more biodiverse than others
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what is global biodiversity
- the variety of species on earth
- estimate of total species on earth = 8.7 million
- biodiversity varies in different parts of the world
- greater biodiversity at EQUATOR
- lower biodiversity at POLES
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what are the 2 ways biodiversity can be measured
- species richness
- index of diversity
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what is species richness and how is it used to measure biodiversity
- species richness is a measure of the number of diff species in a COMMUNITY
- simple measure of biodiversity
- worked out by taking RANDOM SAMPLES of a COMMUNITY and counting the number of DIFF species
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what does the species richness measure of biodiversity not account for
- population of those species
- species that are in a community in a very SMALL numbers should NOT be treated the SAME as those with BIGGER populations
164
because species richness doesn't account for biodiversity fully, what is another way of measuring biodiversity that accounts for this
index of diversity
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what is index of diversity
- another way of measuring biodiversity
- calculated using an equation which takes BOTH the number of species in a community (species richness) AND the abundance of each species (population sizes) into account
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what is the word formula for the index of diversity
index of div =
(the total number of organisms of all species) x (the total number of organisms of all species - 1) / (the sum of the total number of organisms of one species) x (the sum of the total number of organisms of one species - 1)
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what does a higher index of diversity indicate
higher the num = more diverse the area is
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what does it mean if the index of diversity is 1
all individuals are the same species
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what is one thing humans do that affects biodiversity
agriculture
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what is agriculture and what is its purpose
- its one way of producing the resources we need from the environment
- we need it to produce food and fibres for clothing
- sometimes need it to produce some medicines and fuels
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list the methods of agriculture that farmers use which have a negative impact on biodiversity
- woodland clearance
- hedgerow removal
- pesticide use
- herbicide use
- monoculture
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how does woodland clearance have a negative impact on biodiversity
- done to increase the area of farmland
- directly reduces the number of TREES and sometimes the number of DIFFERENT tree species
- destroys habitats, so some species could lose their SHELTER and FOOD SOURCE
- species will die or be forced to migrate to another suitable area -> further REDUCES biodiversity
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how does hedgerow have a negative impact on biodiversity
- done to increase the AREA of farmland by turning LOTS of SMALL field into FEWER LARGE fields
- REDUCES biodiversity for the SAME reasons as woodland clearance : reduces number of trees, reduces the number of tree species, destroys habitats which could lead to loss of shelter and food source AND species death or migration
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how does the use of pesticides have a negative impact on biodiversity
- chemicals that kill organisms/pests that feed on crops
- reduces diversity by directly killing the pests
- any species that feed on pests will LOSE A FOOD SOURCE -> numbers of that species could also DECREASE
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how does the use of herbicides have a negative impact on biodiversity
- chemicals that kill unwanted plants/weeds
- reduces plant diversity
- could reduce the number of organisms that feed on the weeds
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how does monoculture have a negative impact on biodiversity
- monoculture is where farmers have fields containing only ONE type of plant
- a SINGLE type of plant reduces biodiversity DIRECTLY
- ^ will support FEWER organisms, as a HABITAT or FOOD SOURCE for example -> further reduces biodiversity
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why is biodiversity important
- helps maintain the environment
- provides us with new sources of food and medicines
- benefits agriculture
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does there need to be a balance between agriculture and conservation
yes
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how do conservationists try achieve this
through conservation schemes
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give examples of conservation schemes
- giving legal protection to endangered species
- creating protected areas like SSSIs and AONBs = these restrict further development, including agricultural development
- the environmental stewardship scheme encourages farmers to CONSERVE biodiversity, ex -> replanting hedgerows and leaving margins around fields for wild flowers to grow
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what are SSSIs
sites of special scientific interest
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what are AONBs
areas of outstanding natural beauty
183
what stats test is used to analyse the effect of agriculture on biodiversity
spearmans rank correlation coefficient
184
what is the word formula for spearman's
spearmans =
1 - (6) x (difference in rank between data pairs)^2 / (total number of data pairs) x (total number of data pairs ^2 - 1)
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what should the result of the test be
between -1 and 1
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what does it mean if the result is -1
perfect NEGATIVE correlation between the 2 variables
187
what does it mean if the result is 1
perfect POSITIVE correlation between the 2 variables
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what does it mean if the result is closer to 0
the weaker the correlation is
