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Biology > Inheritance, Variation and Evolution > Flashcards

Inheritance, Variation and Evolution Flashcards

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1
Q

what is meiosis

A

the formation of four non identical cells from one cell

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2
Q

what is mitosis

A

the formation of two identical cells from one cell

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3
Q

what is sexual reproduction

A

the joining of male and female gametes, each containing genetic information from the mother or father

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4
Q

what are the gametes in animals

A

sperm and egg cells

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5
Q

what are the gametes in flowering plants

A

pollen and egg cells

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6
Q

how are gametes formed

A

meiosis

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7
Q

how do we know gametes are formed by meiosis

A

they are non identical

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8
Q

how many chromosomes does a normal cell have

A

46 chromosomes

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9
Q

how many chromosomes do gametes ahve

A

23 chromosomes

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10
Q

when do the gametes chromosomes fuse

A

fertilisation

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11
Q

what happens when gametes fuse

A

genetic information from each parent is mixed producing variation in the offspring

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12
Q

what is asexual reproduction

A

one parent with no gametes joining

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13
Q

how does asexual reproduction happen

A

mitosis

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14
Q

what does asexual reproduction lead to

A

clones that are genetically identical to eachother and the parent

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15
Q

examples of organisms produced by asexual reproduction

A

bacteria
some plants
some animals

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16
Q

process of meiosis

A

cell makes copies of its chromosomes so it has double the genetic information
the cell divides into two cells each with half the amount of chromosomes
the cell divides again predicting four cells each with a quarter of the amount of chromosomes
these cells are called gametes and are genetically different from eachother

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17
Q

why are gametes genetically different from eachother

A

the chromosomes are shuffled during the process resulting in random chromosomes ending up in each of the four cells

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18
Q

what happens during fertilisation of gametes

A

fuse and produce a cell with 46 chromosomes
this cell divides by mitosis to produce many copies
more and more cells are produced and an embryo forms
the cells are differentiated and take on different roles after this stage

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19
Q

advantages of sexual reproduction

A

produces variation in offspring
allows us to use selective breeding

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20
Q

advantages of asexual reproduction

A

only one parent is needed
uses less energy and is faster as organisms do not need to find a mate
in favorable conditions lots of identical offspring can be produced

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21
Q

why is producing variation in offspring an advantage

A

if the environment changes an organism of the species will have a characteristic that gives them a survival advantage

decreases the chance of the whole species becoming extinct

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22
Q

why is selective breeding an advantage of sexual reproduction

A

organisms with desirable characteristics can be bred
speeds up natural selection

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23
Q

which organisms use asexual and sexual reproduction to reproduce

A

malarial parasites
some fungi
some plants

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24
Q

how do malarial parasites use s and a reproduction

A

reproduce sexually in the mosquito
reproduce asexuallly in the human host in the liver and blood cells

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25
Q

how do some fungi reproduce both ways

A

spores produced asexually are genetically identical
spores are produced sexually when the conditions change in order to increase variation and avoid extinction

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26
Q

how do some plants reproduce both ways

A

many reproduce sexually using pollen which reaches egg cells int he female parts of another flower (pollination)]
strawberry plants reproduce asexually as they produce runners which new identical plants grow off
daffodils reproduce asexually and grow from bulbs that grow off the main one

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27
Q

why is asexual reproduction advantageous in plants

A

they can reproduce even if the flowers have been destroyed by frost or other animals

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28
Q

what is the genetic material in the nucleus composed of

A

a chemical called DNA

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29
Q

what is DNA

A

a polymer made of two strands which wrap around eachother in a double helix structure

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30
Q

where is the DNA in the nucleus contained in

A

chromosomes

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31
Q

what are between the 2 strands of DNA

A

four nitrogenous bases lined up in single rows that come together to form a series of complementary pairs

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32
Q

what is a gene

A

a small section of DNA on a chromosome

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33
Q

what does a gene compose of

A

a triplet of bases that codes for a specific protein

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34
Q

what does each gene code for

A

a particular sequence of amino acids that can chain together to make a protein

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35
Q

what is a genome

A

all the genes coding for all of the proteins within an organism

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36
Q

what has the human genome being studied helped with

A

improved understanding of genes linked to disease
treatment of inherited disorders
tracing human migration patterns from the past

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37
Q

what does DNA stand for

A

deoxyribonucleic acid

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38
Q

what are chromosomes

A

structures made up of long molecules of DNA found in the nucleus of a celll

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39
Q

what is DNA made up of

A

small parts called nucleotides

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40
Q

what is each nucleotide made up of

A

one sugar molecule
one phosphate molecule
one of the four types of organic bases

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41
Q

what are the four types of organic bases

A

A
C
G
T

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42
Q

what is each dna molecule made up fo

A

two dna strands twisted together

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43
Q

how are the bases connected in dna strands

A

each base is connected to another base in the other strand

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44
Q

what bases connect

A

A and T
G and C

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45
Q

what is bases connecting called

A

complementary base pairing

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46
Q

what do the order of different bases form

A

a code

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47
Q

what does each group of three bases code for

A

an amino acid

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48
Q

what determines the type of protein

A

the types and order of amino acids in the chain

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49
Q

how many types of amino acids are there

A

20

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50
Q

what do the non coding parts of dna do

A

do not code for proteins
some switch genes on or off

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51
Q

what is protein synthesis

A

the process of producing a protein from DNA

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52
Q

what does it mean if a gene is coded to make a protein

A

it has been expressed

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53
Q

process of protein synthesis

A

dna cannot move out of the nucleus as it is too big
the two strands pull apart from eachother and mRNA molecules match to their complementary base on the strand
the mRNA nucleotides are joined together creating an mRNA strand which is a template of the original dna
the mrna then moves out of the nucleus to the cytoplasm and onto ribosomes
at the ribosomes the bases on the mrna are read in threes to code for an amino acid
the corresponding amino acids are brought to the ribosomes by carrier molecules
these amino acids connect to form a protein
when the chain is complete the protein folds to form a unique 3D structure

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54
Q

what does the proteins specific shape help

A

helps it to carry out its role

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55
Q

what can proteins be

A

enzymes
hormones
structural protein

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56
Q

what are structural; protein

A

strong proteins in order to form structures such as collagen

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57
Q

what do mutations do

A

change the sequences of bases in DNA

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58
Q

which three ways can mutations occur

A

a base is inserted into the code
a base is deleted from the code
a base is substituted

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59
Q

how does a base being inserted into the code cause a mutation

A

as they are read in threes, it changes the way it is read
it may change all the amino acids coded for after this insertion

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60
Q

how does a base being deleted from the code cause a mutation

A

they change the way it is read
it may change all the amino acids coded for after this deletion

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61
Q

how does a base being substituted cause a mutation

A

changes one amino acid in the sequence
or it may not change the amino acid because the new sequence can sometimes still code for the same amino acid

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62
Q

what does a change in the sequence of amino acids affect

A

the way it folds and therefore the structure

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63
Q

how do most mutations affect the protein

A

do not alter it or only do so slightly

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64
Q

what can some mutations do to the protein

A

have a serious effect and change the shape

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65
Q

what is the effect of a mutation changign the shape of a protein

A

the substrate will not fit into the active side so it cannot act as a protein
a structural protein may lose its shape

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66
Q

where can mutations also occur

A

in the non coding parts of dna that control whether the genes are expressed

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67
Q

why does variation between two organisms arise

A

the coding DNA that determines the proteins and their activity
the non coding dna that determines which genes are expressed

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68
Q

what is an allele

A

the different forms of a gene

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69
Q

what is a dominant allele

A

only one out of the two alleles is needed for it to be expressed and for the corresponding phenotype to be observed

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70
Q

what is a recessive allele

A

two copies are needed for it to be expressed and for the corresponding phenotype to be observed

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71
Q

what does homozygous mean

A

when both inherited allele are the same

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72
Q

what does heterozygous mean

A

one of the inherited alleles is dominant and the other is recessive

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73
Q

what is a genotype

A

the combination of alleles an individual has e.g Bb

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74
Q

what is a phenotype

A

the physical characteristics that are observed in the individual

75
Q

what do family trees show

A

the inheritance of different phenotypes over generations in the same family

76
Q

what are genetic disorders caused by

A

inheriting certain alleles

77
Q

what is polydactyly

A

having extra fingers or toes

78
Q

what is polydactyly caused by

A

a dominant allele

79
Q

what is cystic fibrosis

A

a disorder of the cell membranes resulting in thick mucus in the airways and pancreas

80
Q

what is cystic fibrosis caused by

A

a recessive allele
both parents need to either be carriers or one must have CF themselves and the other is a carrier

81
Q

what does embryonic screening do

A

allow scientists to observe whether the child will have a genetic condition or not

82
Q

what happens if the embryo is developed in the lab

A

cells can be taken from it and analysed

83
Q

what are advantages of embryonic screening

A

reduces number of people suffering
treating disorders is very expensive
many regulations are in place to stop it getting out of hand

84
Q

disadvantages of embryonic screening

A

could encourage people to pick characteristics for babies
expensive to carry out screening
promote prejudice as it suggests those with genetic disorders are unwanted
decisions about terminating a pregnancy have to be made
procedure can lead to a miscarriage

85
Q

what do 22 of the pairs of chromosomes do

A

control characteristics and the chromosomes in each pair look very similar

86
Q

what does the 23rd pair of chromosomes do

A

carries sex determining genes and the two chromosomes can look different to eachother

87
Q

what are the two possible chromosomes in the 23rd pair

A

X and Y chromosomes

88
Q

what happens when cells undergo meiosis to form a gamete

A

one sex chromosome goes into each gamete

89
Q

how many x chromosomes do females have

A

two

90
Q

which chromosomes do females pass on in their eggs

A

only x chromosomes

91
Q

which chromosomes do males have

A

one x and one y chromosome

92
Q

which chromosomes do males pass on

A

x or y chromosomes in sperm

93
Q

what is the percentage of having a male pr female

A

50%

94
Q

what does the phenotype of an organism depend on

A

genotype
environment

95
Q

how does genotype change phenotype

A

genes are passed on from the parent in sex cells
the combining of genes from the mother and father creates genetic variation
only identical twins have the same genotype
there is lots of genetic variation in a population

96
Q

how does environment affect phenotype

A

the conditions the organism grows and develops in also affects its appearance

97
Q

examples of environmental changes to phenotype

A

scars in animals
smaller or yellow leaves in plants

98
Q

which phenotypes are a result of genetics and the environment

A

weight

99
Q

how is weight affected by genetics and environment

A

depends on the food you eat
but also how quickly your body breaks it down and how much fat it stores depends on genes

100
Q

what is genetic variation introduced by

A

introduced by mutations in the sequence of DNA

101
Q

how does genetic variation affect phenotype

A

most have no effect on phenotype
some influence phenotype but unlikely to bring a new phenotype
if brings a new phenotype and it is advantages natural selection will make it the most common phenotype quickly

102
Q

what is evolution

A

a change in the inherited characteristics of a population over time through a process of natural selection which may result in the formation of a new species

103
Q

what is the theory of evolution

A

all species have evolved from simple life forms that first developed more than three billion years ago

104
Q

why does evolution occur

A

natural selection

105
Q

process of natural selection

A

mutations occur which provide variation between organisms
if a mutation provides a survival advantage the organism is more likely to survive to breeding age
the mutation will then be passed onto offspring
over many generations the frequency of the mutation will increase within the population

106
Q

what can natural selection cause

A

speciation

107
Q

what is speciation

A

one population of a species becomes so different that they can no longer interbreed to produce fertile offspring so they have become a new species

108
Q

what is selective breeding

A

when humans choose which organisms to breed in order to produce offspring with certain desirable characteristics

109
Q

examples of desirable characteristics from selective breeding

A

animals with more meat
plants with disease resistance
big flowers

110
Q

when did selective breeding start

A

since animals were domesticated and plants were grown for food

111
Q

process of selective breeding

A

parents with desired characteristics are chosen
they are bred together
from the offspring those with desired characteristics are bred together
the process is repeated many times until all the offspring have the desired characteristic

112
Q

what can selective breeding lead to

A

inbreeding

113
Q

what does breeding those with similar desirable characteristics man

A

it is likely you are breeding closely related individuals

114
Q

what does inbreeding lead to

A

reduction of the gene pool as no of different alleles reduces

so if the environment changes or there is a new disease the species could become extinct as they ahve the same genetic makeup - less ahve survival advantages

greater chance of genetic defects in the offspring as recessive characteristics more present

115
Q

what is genetic engineering

A

modifying the genome of an organism by introducing a gene from another organism to give a desired characteristic

116
Q

how have plant cells been engineered

A

for disease resistance or to have larger fruits

117
Q

how have bacterial cells been engineered

A

to produce substances useful to humans such as human insulin to treat diabetes

118
Q

process of genetic engineering

A

1.genes from chromosomes are cut out using restriction enzymes leaving sticky ends (short sections of exposed, unpaired bases)
2. a virus or bacterial plasmid is cut using the same restriction enzyme to create sticky ends, this also contains an antibiotic marker gene
3. the loop and gene sticky ends are then joined together by DNA ligase enzymes
4. the combined loop is placed in a vector such as a bacterial cell ad allowed to multiple as it contains the modified gene
as the bacteria grows we can see which ones are resistant to antibiotics
the colonies are the bacteria that are also producing the modified gene as they were inserted together

119
Q

where is the vector put in genetic engineering in plants

A

vector is put into meristematic cells which can then produce identical copies of the modified plant

120
Q

what are genetically modified crops produced for

A

to be resistant to insects and herbicides
results in increased yields as less crops will die

121
Q

what is genetic modification in medicine used for

A

cure inherited disorders using gene therapy to transfer normal genes into patients so the correct proteins are produced

122
Q

benefits of genetic engineering

A

useful in medicine to mass produce certain hormones in microorganisms
used to crease yields in agriculture
crops with extra vitamins can be produced in areas where they are difficult to obtain
greater yields can solve world hunger which is increasing

123
Q

how does genetic engineering improve yields in agriculture

A

improves growth rates
introduces modifications that allow the crops to grow in different conditions
introduces modifications that allow plants to make their own pesticide or herbicide

124
Q

risks of genetic engineering

A

GM crops might have an effect on wild flowers therefore insects
we don’t understand the effects of GM crops on human health
GE in agriculture could lead to GE in humans - designer babies
selection pressure leading to increased resistance in other species

125
Q

how can genetically modified crops have an effect on wildflowers and insects

A

they are infertile and these genes could spread to wild plants leading to infertility in other species
growing with herbicides and pesticides can kill insects and other plants, reducing biodiversity

126
Q

what is cloning

A

creating genetically identical copies of an organism

127
Q

methods of plant cloning

A

tissue culture
cuttings

128
Q

methods of animal cloning

A

embryo transplants
adult cell cloning

129
Q

what is tissue culture important for

A

preserving rare plant species or commercially in plant nurseries

130
Q

process of tissue culture

A

plant cells are taken
they are placed in a growth medium with nutrients and hormones
they grow into new plants and are clones as they are genetically identical to the parent

131
Q

process of cuttings

A

cuttings such as a section of the stem are taken from a plant with a desirable feature
they are planted and produce clones as they are genetically identical to the parent

132
Q

embryo transplants process

A

sperm cells and egg cells from parents with desirable features are obtained
in the lab they are fertilised to form an embryo
the embryo divides many times and is then inserted into a host mother
the offspring which is eventually born is genetically identical as they have genetic information from the same mother and father

133
Q

adult cell cloning process

A

nucleus removed from an unfertilised egg cell
the nucleus is removed from an adult body cell and placed in the denucleated egg cell
electric shock stimulated the egg cell to divide to form an embryo
the embryo is implanted into the womb of a female
the offspring is born as a clone of the adult body cell

134
Q

benefits of cloning

A

produces lots of offspring with a specific desirable feature
study of clones could help research into embryo development
can help extremely endangered species or even bring back species that have become extinct

135
Q

risks of cloning

A

the gene pool is reduced so it is less likely that the population will survive if a disease arises with low diversity in the population
clones have a low survival rate and have some genetic problems
may lead to human cloning

136
Q

who was charles darwin

A

a scientist and naturalist

137
Q

what did charles darwin do

A

put forward the theory of evolution

138
Q

what was charles darwin’s theory of evolution supported through

A

the experimentation and his knowledge of geology and fossils that he discovered on a round the world expedition

139
Q

what did charles darwin publish

A

‘on the origin of species’ in 1859

140
Q

what is the theory of evolution

A

variation exists within species as a result of mutations in dna
survival of the fittest
beneficial characteristics are passed onto the next generation
over many generations the frequency of alleles for the advantageous characteristic increase in the population

141
Q

what is survival of the fittest

A

organisms with characteristics most suited to the environment are more likely to survive to reproductive age and breed successfully

142
Q

why was there controversy around the idea of evolution

A

contradicted idea that god was created of all species on earth
not enough evidence at the time as few studies had been done on how organisms change over time
mechanism of inheritance and variation not known at the time

143
Q

what did jean baptiste lamarck think about evolution

A

changes that occurred during the lifetime of an organism were passed onto offspring
if an indiviso continually repeated an action the characteristic that allowed it to do this would develop further eg a giraffe stretching neck
tu his characteristic would be passed onto its offspring

144
Q

when was lamarcks theory proven wrong

A

when it was understood that changes caused by the environment were not passed on in the sex cells

145
Q

why was darwin’s theory suppprted

A

suppported by genetics as it provided a mechanism for beneficial characteristics caused by mutations to be passed on
fossil evidence showed how developments in organisms arose slowly

146
Q

what is speciation

A

the process of a new species developing through the selection of different alleles which increases the genetic variation until the new population cannot breed with those in the old population to produce fertile offspring

147
Q

who developed the theory of speciation

A

alfred russel wallace

148
Q

how did alfred russel wallace develop theory of speciation

A

on his travels he had the idea that individuals who did not have characteristics to help them survive a change in the environment would die out
he published joint studies with darwin
he collected evidence eg warning colouration in animals

149
Q

what is the process of speciation

A

variation exists within a population as a result of genetic mutations
alleles which provide a survival advantage are selected for through natural selection
populations of a species can become isolated for example through physical barriers such as a rock fall preventing them from breeding together
different alleles may be advantageous to the new environments leading them being selected for
over time the selection of different alleles will increase the genetic variation between the two populations
when they are no longer able to breed together to produce fertile offspring, a new species has formed

150
Q

what did gregor mendel do

A

trained in mathematics and natural history in vienna
observed characteristics passed on to the next generation in plants
carried out breeding experiments on pea plants
used different types of peas and observed offspring to see which characteristics they inherited

151
Q

which conclusion did mendel come to

A

offspring have some characteristics that their parents have because they inherit hereditary units from each
one unit is received from each parent
units can be dominant or recessive and cannot be mixed together

152
Q

why was mendel not recognised until after his death

A

genes and chromosomes were not yet discovered so people could not understand

153
Q

when were chromosomes being part of cell division observed

A

late 19th century

154
Q

when was it understood that chromosomes and units had similar behaviours

A

late 20th century

155
Q

when was the structure of the dna determined

A

1953

156
Q

where is evidence for evolution seen

A

fossils
antibiotic resistance

157
Q

what are fossi;s

A

remains of organisms from millions of years ago which are found in rocks

158
Q

what are fossils formed from

A

parts of organisms that have not decayed because oxygen or moisture were not present - microbes that cause decay cannot survive
parts of organisms such as teeth shell and bones are replaces by minerals as they decay forming a rock structure of the original plant
preserved traces such as footprints burrows and rootlet traces remain due to the ground hardening around them and forming a cast

159
Q

what are fossils used to show

A

how the anatomy of organisms has changed over time
compare how closely related two organisms are

160
Q

what can fossils not be used for

A

tell us how life started on earth

161
Q

why can’t fossils be used to tell us how life started on earth

A

most early life forms are soft bodied and therefore decay completely so there are few fossils of them
any traces left have been destroyed by geological activity

162
Q

what is extinction

A

when an entire species has died out

163
Q

which factors contribute to extinction

A

changes in environment that species cannot adapt to
new predators evolved or migrated to area
new disease arises and no resistant alleles
have to compete with a species with advantageous mutations for the same food source
catastrophic event can wipe out a species
destruction of a habitat

164
Q

when are bacteria labelled resistant

A

when they are not killed by antibiotics which previously were used as cures against them

165
Q

how is antibiotic resistance caused

A

mutation during reproduction can result in a gene for antibiotic resistance

166
Q

what does exposure to antibiotics create

A

a selection pressure as those with antibiotic resistant genes survive and those without die
so those with antibiotic resistance can reproduce and pass on the advantageous gene to their offspring
the population of antibiotic resistant bacteria increases

167
Q

why do bacterial diseases spread rapidly

A

people are not immune to new resistant bacteria and there is no treatment for it

168
Q

what is MRSA

A

superbug that is resistant to many types of antibiotics

169
Q

where is mrsa common

A

hospitals as it spread when doctors and nurses move to different patients

170
Q

how to slow development of resistance in bacteria

A

antibiotics shouldn’t be given for viral or non serious infections
specific antibiotics should be given for specific bacteria
patients should complete their course of antibiotics so no bacteria survives and mutates
antibiotics should be used less in agriculture - antibiotic resistant bacteria transferred from livestock to humans in meat

171
Q

how to slow transmission of antibiotic resistant bacteria

A

maintain high standards of hygiene in hospitals
medical staff and visitors should wash hands regularly
medical staff should wear disposable clothing or clothing that is regularly sterilised

172
Q

why is it difficult to keep up with the development of resistant strains

A

the development of antibiotics is expensive and slow

173
Q

what is classification

A

putting organisms into groups depending on their structure and characteristic so

174
Q

who put forward the linnaean system

A

carl linnaeus in 1700s

175
Q

what does the linnaean system do

A

divides living things into
kindgoms
phylum
class
order
family
genus
species

176
Q

what does the binomial system do

A

gives each organism a name which is used worldwide
first part is their genus and second part is species

177
Q

why was the three domain system developed

A

developments in science such as improvement of the microscope and increased knowledge of biochemistry found some species were more distantly related than first thought

178
Q

who created the three domain system

A

carl woese

179
Q

what are the three groups called domains above kingdoms

A

archaea
bacteria
eukaryote

180
Q

what is archaea

A

primitive bacteria which live in extreme environments such as hot springs

181
Q

what are bacteria

A

true bacteria

182
Q

what are eukaryota

A

organisms who have a nucleus enclosed in membranes
includes the kingdoms protists , fungi, plants and animals

183
Q

what are evolutionary trees used for

A

to show how closely related organisms are

184
Q

how are evolutionary trees completed

A

they use classification data and fossils for extinct species

Biology (22 decks)

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