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gcse science > Science - Biology - Inheritance, Variation and Evolution - B6 > Flashcards

Science - Biology - Inheritance, Variation and Evolution - B6 Flashcards

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1
Q

what does DNA stand for ?

A

deoxyribonucleic acid

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2
Q

what is DNA ?

A

the chemical that all of the genetic material in a cell is made up from

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3
Q

what does DNA do ?

A

have all of the information to put an organism together and make it work

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4
Q

what does DNA determine ?

A

what inherited characteristics you have

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5
Q

where is DNA found ?

A

in the nucleus

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6
Q

what really long structures are DNA found in ?

A

chromosomes

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7
Q

what does DNA form in a chromosome ?

A

the arms of a chromosome

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8
Q

what number do chromosomes come in ?

A

pairs

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9
Q

DNA is a polymer - what does this mean ?

A

it is made up of a large molecule built from a chain of smaller molecules

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10
Q

what shape do the 2 strands of DNA form ?

A

double helix

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11
Q

what is a gene ?

A

a small section of DNA found on a chromosome

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12
Q

what does a gene do ?

A

tell cells what order to put the amino acids together

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13
Q

what do amino acids form ?

A

proteins

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14
Q

how many types amino acids are used in DNA ?

A

20

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15
Q

does DNA determine what proteins the cell produces, and therefore determines what cell is produced ?

A

yes

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16
Q

what is a genome ?

A

the entire set of genetic material in an organism

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17
Q

what does understanding the human genome tell scientists ?

A
  • it helps them identify genes in the genome which are linked to different types of disease
  • knowing which genes are linked to inherited diseases helps us understand them better and could help us develop treatment
  • genomes can trace the migration of certain populations around the world - scientists can work out when and where populations went
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18
Q

how did the human genome change ?

A

it is mostly identical in all humans
but as different populations migrated away from Africa they developed tiny differences in their genomes

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19
Q

what are nucleotides ?

A

strands of polymers made up of lots of repeating units which help form DNA

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20
Q

what does a nucleotide consist of ?

A
  • a sugar
  • a phosphate group
  • one of 4 different bases
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21
Q

how many types of nucleotides are there ?

A

4

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22
Q

what are the 4 different bases ?

A

A
T
C
G

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23
Q

what do the 4 different bases join to ?

A

a sugar

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24
Q

what forms the backbone to the DNA strands ?

A

the sugars and phosphate groups in the nucleotides

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25
Q

what does the order of bases determine ?

A

the order of amino acids in a protein

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26
Q

how many bases is each amino acid coded by ?

A

3

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27
Q

what do amino acids join together to make up ?

A

proteins

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28
Q

what does the base A always pair up with ?

A

T

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29
Q

what does the base C always pair up with ?

A

G

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30
Q

what do the non - coding parts of DNA do ?

A

switch genes on and off
control whether or not a gene is used

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31
Q

where are proteins made ?

A

in the ribosomes in the cytoplasm

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32
Q

what do ribosomes do to make up proteins ?

A
  • use the code in DNA
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33
Q

how does the cell get the code needed to make up proteins from DNA in the nucleus to the ribosomes ?

A

mRNA

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34
Q

why can’t DNA move out of the cell nucleus ?

A

it is too big

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35
Q

what is mRNA ?

A

a molecule which acts as a messenger between the DNA and the ribosome by carrying the code between the 2 and by acting as a template

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36
Q

what do carrier molecules do in mRNA ?

A

bring the correct amino acids to the ribosomes in the correct order

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37
Q

what do amino acids do when they have been assembled ?

A

folds into a unique shape which allows the protein to perform the task it is meant to do

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38
Q

what are proteins used for ?

A
  • enzymes
  • hormones
  • structural proteins
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39
Q

what is a mutation ?

A

a random change in an organisms DNA
they can sometimes be inherited

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40
Q

how do mutations occur ?

A
  • continuously
  • randomly
  • when a chromosome isn’t replicated properly
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41
Q

how can the chances of a mutation be increased ?

A
  • when exposed to some types of radiation
  • when exposed to certain substances
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42
Q

what do mutations do ?

A

change the sequence of the DNA bases in the gene which produces a genetic variant

as the sequence of DNA bases codes for the sequences of amino acids which make up proteins, mutations can lead to cell changes

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43
Q

what is a genetic variant ?

A

a different form of the gene

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44
Q

do mutations have an effect on the protein ?

A

most of the time no

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45
Q

what could happen if a mutation changes a proteins shape ?

A
  • if an enzyme’s active site is changed its substrate may not be able to bind to it
  • structural proteins like collagen could lose their strength if their shape has changed
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46
Q

what are the 3 ways DNA can change the DNA base sequence ?

A
  • insertions
  • deletions
  • substitutions
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47
Q

what are insertions ?

A

where a base is inserted into the DNA base sequence where it shouldn’t be

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48
Q

what can insertions cause ?

A

amino acids to change, as they have a knock-on effect so the bases further on in the sequence can be altered

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49
Q

what are deletions ?

A

where a random base is deleted from the DNA base sequence

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50
Q

what are substitutions ?

A

where a random base in the DNA sequence is changed to a different base

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51
Q

what is sexual reproduction ?

A

where genetic information from 2 organisms is combined to produced offspring which are genetically different to either parent

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52
Q

what are gametes ?

A

things produced by the mother and father in sex

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53
Q

what is the female gamete ?

A

egg

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54
Q

what is the male gamete ?

A

sperm

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55
Q

how many chromosome does each gamete contain in humans ?

A

23

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56
Q

what happens during fertilisation ?

A

the egg and sperm cell fuse together to form a cell with the full number of chromosomes

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57
Q

what is the fusion of gametes known as ?

A

fertilisation

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58
Q

why does the offspring inherit features from both parents ?

A

it recieves a mixture of chromosomes from its mum and dad which causes variation

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59
Q

what does sexual reproduction involve the fusion of ?

A

female and male gametes

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60
Q

what is the sperm version of a gamete in a flowering plant ?

A

pollen

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61
Q

how does asexual production happen ?

A

mitosis

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62
Q

what is asexual reproduction ?

A

there is only 1 parent, no fusion of gametes and no genetic variation between the parent and offspring

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63
Q

the offspring and the parent are identical in asexual reproduction - what are they ?

A

clones

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64
Q

how do you make gametes ?

A

meiosis

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65
Q

how many cell divisions does meiosis involve ?

A

2

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66
Q

where does meiosis happen in humans ?

A

reproductive organs

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67
Q

describe the steps of meiosis ?

A
  1. before cell divides it duplicates its genetic information, forming 2 armed chromosomes which are identical, after replication chromosomes arrange themselves into pairs
  2. in the first division pairs line up in the centre of the cell
  3. the pairs are then pulled apart so each cell has 1 copy of each chromosome - some of the fathers - some of the mothers
  4. in the 2nd division chromosomes line up again in the centre of the cell - arms of the chromosomes are pulled apart
  5. you get 4 sets of gametes with only 1 set of chromosomes in it
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68
Q

why are the gametes produced genetically different from the others ?

A

the chromosomes get shuffled up during meiosis and each gamete only gets 1 of them - at random

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69
Q

what happens to the cells when the embryo starts to develop ?

A

they differentiate into different types of specialised cell that make up a whole organism

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70
Q

what are the advantages of sexual reproduction ?

A
  • offspring will have a mixture of 2 sets of chromosomes - the organism inherits genes from both parents giving variation
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71
Q

what are the advantages of variation ?

A

it increases the chance of species surviving a change in environment as some of the varied organisms may be able to survive in the new environment whilst others are killed off

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72
Q

what is natural selection ?

A

individuals with characteristics which make them better adapted to the environment are more likely to breed successfully and pass the genes for the characteristics on

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73
Q

what is used to speed up natural selection ?

A

selective breeding

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74
Q

what is selective breeding ?

A

where individuals with a desirable characteristic are bred to produce more offspring that also have the desired characteristic

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75
Q

why can we use selective breeding to increase food production ?

A
  • breeding animals that have lots of meat
  • breeding cows which have a high milk yield
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76
Q

what are the advantages of asexual reproduction ?

A
  • needs 1 parent so it uses less energy because organisms don’t have to find a mate
  • identical offspring can be produced in favourable conditions
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77
Q

give an example of how asexual production can be used successfully ?

A
  • dandelion plants can grow quicker and spread faster if grown in a good environment and because all offspring have the same genes as the parent they’re all likely to survive in these conditions
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78
Q

give examples of when organisms can reproduces both asexually and sexually ?

A
  • malaria = reproduces sexually when in mosquito and asexually when it is in human host
  • fungus = spores
  • plants = runners, bulbs
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79
Q

how many pairs of chromosomes are in every human body cell ?

A

23

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80
Q

how are the 23rd pair of chromosomes labelled ?

A

xx
xy

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81
Q

what do the 23rd pair of chromosomes determine ?

A

your sex

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82
Q

what sex has xy characteristics ?

A

male

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83
Q

what sex has xx characteristics ?

A

females

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84
Q

what chromosome causes male characteristics ?

A

y

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85
Q

what is the % chance of a sperm cell getting a y chromosome ?

A

50 %

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86
Q

what is the % chance of the eggs getting an x chromosome ?

A

100 %

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87
Q

what depends on whether the individual is male or female ?

A

the sex chromosomes it recieves - its sex inheritance

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88
Q

what can genetic diagrams be used to show ?

A

sex inheritance

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89
Q

what are genetic diagrams ?

A

models that are used to show all the possible genetic outcomes when you cross together different genes or chromosomes

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90
Q

what is probability ?

A

the measure of how likely something is to happen

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91
Q

what are alleles ?

A

an alternative version of a gene

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92
Q

how many alleles to gametes have ?

A

1

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93
Q

how many alleles do all the other cells in an organism - apart from gametes have ?

A

2

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94
Q

why do all cells except for gametes get 2 alleles?

A

we inherit half our alleles from our mother and half from our father

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95
Q

what represents alleles in genetic diagrams ?

A

letters

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96
Q

what does homozygous mean ?

A

if an organism has 2 alleles that are the same for a particular gene

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97
Q

what does heterozygous mean ?

A

if an organism has 2 alleles that are different for a particular gene

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98
Q

what is a dominant allele ?

A

the allele for the characteristic that is shown

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99
Q

what is the recessive allele ?

A

the allele for the characteristic which isn’t shown

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100
Q

how can an organism display a recessive characteristic ?

A

both its alleles must be recessive

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101
Q

how can an organism display a dominant characteristic ?

A

whenever a dominant allele is present as it overrules the recessive one if the organism is heterozygous

102
Q

what is a genotype ?

A

the combination of alleles you have

103
Q

give an example of a genotype ?

A

you could have the genotype Bb for hair colour

104
Q

what is a phenotype ?

A

the characteristics you have

105
Q

how can you study characteristics that are determined by a single gene ?

A

using monohybrid crosses

106
Q

what are monohybrid crosses ?

A

where you cross 2 parents to look at just one charactersistic

107
Q

why do we need genetic diagrams ?

A

to predict and explain the outcomes of single gene crosses between individuals and lots of different combinations of alleles

108
Q

how are the outcomes of genetic diagrams shown ?

A

ratios to work out the probability of having offspring with a certain characteristic

109
Q

what are inherited disorders ?

A

disorders that are caused by a faulty allele which can be passed onto an individuals offspring

110
Q

give examples of 2 inherited disorders ?

A
  • cystic fibrosis
  • polydacyly
111
Q

what is cystic fibrosis ?

A

an inherited disorder of the cell membranes which results the body in producing a lot of sticky mucus in the air passages and in the pancreas

112
Q

what are the problems of cystic fibrosis ?

A

it makes breathing difficult

113
Q

what kind of allele causes cystic fibrosis ?

A

recessive allele

114
Q

why people who have the recessive allele for cystic fibrosis but don’t actually have cystic fibrosis known as carriers ?

A

because it is recessive people with 1 copy of the allele won’t have the disorder - they carry the faulty allele but do not have any symptoms

115
Q

how can a child get cystic fibrosis ?

A

both parents must either be carriers or have the disorder themselves

116
Q

what are the chances of a child having a disorder if both of the parents are carriers ?

A

1/4

117
Q

what is polydactyly ?

A

an inherited disorder where a baby is born with extra fingers or toes

118
Q

is polydactyly dangerous ?

A

no

119
Q

how polydactyly caused ?

A

a dominant allele so can be inherited if 1 parent carries the defective allele

120
Q

will the parent of the offspring that has polydactyly have the disorder ?

A

yes

121
Q

what are the chances of a child getting polydactyly if 1 parent has the polydactyly allele ?

A

50 %

122
Q

what is a family tree ?

A

a diagram that shows how a characteristic is inherited in a group of related people

123
Q

what is embryonic screening ?

A

a way of detecting inherited disorders

124
Q

what are the 2 ways of embryonic screening ?

A
  • pre-implantation genetic diagnosis
    -chorionic villus sampling
125
Q

what is pre implantation genetic diagnosis - step by step ?

A
  • during IVF embryos are fertilised in a laboratory then implanted into a mothers womb
  • before being implanted you can remove a cell from each embryo and analyse its genes - embryos with healthy alleles would be implanted into the mother, the faulty ones destroyed
126
Q

what is chronic villus sampling - step by step ?

A
  • carried out between 10-13 weeks of pregnancy
  • involves taking sample cells from part of the placenta and analysing their genes
  • the part of the placenta that’s taken and the embryo develops from the same cell with the same genes
  • if the embryo is found to have an inherited disorder the parents can decide whether to end the pregnancy
127
Q

what are the arguments for embryo screening ?

A
  • helps people stop suffering from inherited disorders
  • treating the disorders is costly
  • during IVF embryos are destroyed anyway PGD just ensures the chosen ones are healthy
  • if an inherited disorder is diagnosed through CVS parents have a choice whether to terminate or not
128
Q

what are the arguments against embryo screening ?

A
  • there may be a time everyone wants to screen their embryos so they can pick the most desirable one
  • it implies people with genetic problems are undesirable
  • after PGD rejected embryos are destroyed - unethical
  • risk that CVS could cause miscarriage
  • after CVS and a disorder is highlighted an abortion may happen
  • expensive
129
Q

who was Gregor Mendel ?

A

an Austrian monk who trained in mathematics and natural history

130
Q

what did Mendel do ?

A

at his garden plot he noticed how characteristics of plants were passed on from 1 generation to the next - his research became the foundation of modern genetics

131
Q

what experiments did Mendel carry out ?

A

he crossed 2 pea plants of different heights - a tall and dwarf pea plant - the offspring produced were all tall pea plants

132
Q

what did Mendels results show ?

A

the height characteristics in his pea plants were determined by separately inherited ‘hereditary units’ passed on from each parent

133
Q

what are the suggested alleles of the pea plants after Mendel’s experiment ?

A

tall plants were dominant over the herditary unit for dwarf plants

134
Q

what were Mendel’s conclusions from his experiment ?

A
  • characteristics in plants are determined by ‘hereditary units’
  • hereditary units are passed on to offspring unchanged from both parents - 1 unit from each parent
  • hereditary units can be dominant or recessive
135
Q

what is the timeline of studies about DNA after Mendel’s death ?

A

1866 - Mendel published his research
1884 - Mendel died
Late 19th C - Scientists became familiar with chromosomes and observed how they behaved during cell division
Early 20th C - scientists discovered a similarity between the way chromosomes and Mendels units acted showing these units were found in chromosomes - units are now known as genes
Mid 20th C - structure of DNA was determined so scientists discovered exactly how genes worked

136
Q

what is variation within a species ?

A

where organisms of the same species look slightly different

137
Q

what are the 2 types of variation ?

A
  • genetic variation
  • environmental variation
138
Q

what is an organisms characteristics determined by ?

A

the genes inherited from their parents

139
Q

what causes genetic variation ?

A

the combining of genes from 2 parents so no species are genetically identical

140
Q

give examples of characteristics determined by genes ?

A
  • violet flower colour
  • eye colour
  • blood group
  • inherited disorders
141
Q

what is environmental variation ?

A

the environment in which an organism lives and grows in causes differences between members of the same species

142
Q

what causes environmental variation ?

A

a difference caused by the conditions something lives in

143
Q

give an example of environmental variation ?

A

suntans
a plant grown in a sunny area would grow green and luscious

144
Q

give examples of characteristics which are caused by both genetic and environmental variation

A

height
intelligence
health

145
Q

give examples of when a gene mutation has no effect ?

A
  • it may produce a genetic variant that codes for the same sequence of amino acids so the same protein is produced
  • mutation may cause a change of 1 amino acid in a protein but doesn’t have an effect on the proteins function
146
Q

give an example of when a gene mutation slightly changes someones characteristics ?

A

a mutation in a gene may cause the eye colour to change slightly

147
Q

give an example of when a gene mutation causes a dramatic change on a species ?

A

cystic fibrosis

148
Q

how can a mutation make something better suited to survive its environment ?

A

the new phenotype might make an individual more suited to the environment which can cause an overall change in the species via natural selection

149
Q

what is the theory of evolution ?

A

all of today’s species have evolved from simple life forms that first started to develop over 3 billion years ago

150
Q

what did Charles Darwin do ?

A

make up a very important theory about evolution by making observations and experiments

151
Q

How does Darwins theory work ?

A

1- all of the individuals within a species show a wide range of variation for a particular characteristic

2- because of this range in variation some of these individuals will be better suited to the environment than others

3- these individuals are more suited to the environment so will be more likely to survive and breed more successfully

4- this useful characteristic is passed onto the offspring

152
Q

why was Darwin’s theory not fully accepted ?

A

the relevant scientific knowledge wasn’t available at the time so he couldn’t give a good explanation as to why his theory worked

153
Q

how do we now know Darwins theory works ?

A

we know the phenotype is controlled by genes
new genetic variants happen to phenotypes that are suited to the environment
beneficial genetic variants are passed on to the future generations in the DNA that parents contribute to their offspring

154
Q

why do individuals within a species show wide variation in their characteristics ?

A

there is a mix of genetic variants present in the population

155
Q

why do some genetic variants give rise to characteristics that are better suited to the environment ?

A

they have a better chance of survival so are more likely to breed successfully

156
Q

what is evolution ?

A

the changing of inherited characteristics of a population over time

157
Q

who’s theory for evolution is now the accepted hypothesis ?

A

Darwins

158
Q

where is there evidence for Darwins theory ?

A

looking at fossils of different ages allows you can see organisms changes developing over time
bacteria becoming resistant to antibiotics

159
Q

what is speciation ?

A

the phenotypes of organisms change so much because of natural selection, a new species is formed

160
Q

what is extinction ?

A

when no living individuals of a species remains

161
Q

give an example of a species which became extinct ?

A

dinosaurs
dodos

162
Q

why do species become extinct ?

A
  • environment changes too quickly
  • a new predator kills them
  • a new disease kills them
    -they can’t compete with another species for food
  • a catastrophic event happens which kills them all
163
Q

what book did Darwin publish ?

A

on the origin of species

164
Q

why was Darwins book and theories not accepted when he first published them ?

A
  • it went against religious beliefs because some people believe God creates earth
  • Darwin couldn’t explain why these new characteristics appeared as he didn’t know anything about genes or mutations
  • lack of evidence
165
Q

what was Lamarcks theory about evolution ?

A

he said changes in the organism happens during its lifetime will be passed onto its offspring - he thought if a characteristic was used a lot by an organism it would become more developed during its lifetime #dumb #loser

166
Q

why may scientists develop different hypothesis’s about evolution ?

A
  • religious beliefs
  • influenced by different people
  • they think differently
167
Q

why was Lamarcks theory rejected ?

A

his experiments didn’t support his hypothesis

168
Q

what is selective breeding ?

A

when humans artificially select the plants or animals that are going to breed so that the genes for particular characteristics remain in the population

169
Q

what are organisms selectively bred ?

A
  • animals produce more milk/meat
  • crops with disease resistance
  • dogs with good, gentle behaviours
  • decorative plants
170
Q

what is the step by step process of selective breeding ?

A

1- from the existing stock select the organisms with the desired characteristics
2- breed them with each other
3- select the best offspring, breed them together
4- continue this process over many generations and the desirable trait gets stronger until all the offspring has that characteristic

171
Q

give an example on how farmers use selective breeding to improve meat yields ?

A

they breed the cows and bulls with the best characteristics for producing meat

172
Q

what is inbreeding ?

A

when farmers breed the best animals and plants which are closely related

173
Q

what is the issues with selective breeding ?

A

it reduces the gene pool

174
Q

what is the issue with inbreeding ?

A

it reduces the gene pool

175
Q

what is a gene pool ?

A

the number of different alleles (forms of gene) in a population

176
Q

what can inbreeding cause ?

A
  • health problems because there’s more of a chance of the organisms inheriting harmful genetic defects
177
Q

how can inbreeding be a problem when a new disease shows up

A

there isn’t as much variation in the species so if all the stock are closely related and one of them is killed by a disease all of them probably will be too

178
Q

give a diagram of the problems associated with reducing the gene pool ?

A

selective breeding -
reduction of number of alleles-
less chance of any resistant alleles being present in the population

179
Q

what is genetic engineering ?

A

transferring a gene responsible for a desirable characteristic from 1 organism’s genome into another organism so it has the desired characteristic

180
Q

explain how genetic engineering works - step by step ?

A

1 - useful gene is cut from one organisms genome using enzymes and is inserted into a vector
2- the vector is usually a virus or bacterial plasmid
3- when the vector is introduced to target the organism, the useful gene is inserted into its cells

181
Q

show how the human insulin gene is inserted into bacteria to produce human insulin ?

A

1 - insulin gene is cut out of human DNA using enzymes
2- same enzymes are then used to cut the bacterial DNA and different enzymes are used to insert the human insulin gene
3- the bacteria are then allowed to multiply and the insulin they produce while they grow is purified and used by people with diabetes

182
Q

what is genetic engineering used for ?

A
  • bacteria is genetically modified to produce human insulin and treat diabetes
  • genetically modified crops have their genes modified to improve the size and quality of plants
  • sheep have been genetically modified to produce substances in their milk which can help treat diseases
  • treats inherited disorders
183
Q

what are the issues with genetic engineering ?

A
  • long term effects are unknown
  • unplanned problems may occur which can get passed down to future generations
184
Q

what are the benefits of genetically modified crops ?

A
  • they can increase yield - making more food
  • they can contain missing nutrients which people in developed countries lack
185
Q

what are the issues with genetically modified crops ?

A
  • affects number of wild flowers - reducing biodiversity
  • may not be safe/ effects are unknown
  • transplanted genes may get out into the natural environment, spread
186
Q

what is cloning ?

A

making an exact copy of an organism

187
Q

how do organisms naturally clone themselves ?

A

asexual reproduction

188
Q

what are the 2 ways of cloning ?

A

tissue culture
cuttings

189
Q

what is tissue culture ?

A

plant cells are put in a growth medium with hormones
they grow into new plants - clones from the parent

190
Q

what are the benefits of tissue culture ?

A
  • quick
  • uses little space
  • grown all year
191
Q

why is tissue culture used ?

A

to preserve rare plants which are hard to reproduce naturally

192
Q

what are cuttings ?

A

gardeners take cutting from good plants
they plant them to produce genetically identical copies

193
Q

what are the advantages of taking cuttings ?

A
  • reproduce quickly
  • cheap
194
Q

how do you clone animals ?

A

embryo transplants

195
Q

how do farmers clone cows using embryo transplants ?

A

1- sperm cells are taken from a prize bull and eggs are taken from a prize cow, the sperm are used to artificially fertilise an egg cell

2- embryos developed splits many times before any cells become specialised

3- cloned embryos are implanted into other cows

4- theys cows grow into calves identical to each other

196
Q

what is adult cell cloning used for ?

A

making animal clones

197
Q

what does adult cell cloning involve - step by step ?

A

1- an unfertilised egg cell is removed from its nucleus
2- the nucleus is removed from the adult body cell and inserted into the empty egg cell
3- egg cell is stimulated by an electric shock making it divide
4- when the embryo is a ball of cells it is implanted into the uterus of the mother
5- embryo grows into a clone of the original adult cell

198
Q

give an example of when adult cell cloning was used

A

dolly the sheep

199
Q

what are the benefits of cloning ?

A
  • gives you ideal offspring
  • leads to a greater understanding of the development of the embryo
  • helps preserves endangered species
200
Q

what are the issues with cloning ?

A
  • reduced gene pool
  • they may not be as healthy as normal organisms in the population
  • people worry humans may be cloned, which could lead to unsuccessful attempts and many humans with disabilities are born
201
Q

what are fossils ?

A

the remains of organisms from many years ago

202
Q

where are fossils found ?

A

in rocks

203
Q

what do fossils show ?

A

evidence that organisms lived many years ago - how much or little organisms have changed - development of species

204
Q

how do fossils form ?

A

gradual replacement by minerals
from casts and impressions
preservations in places where no decay happens

205
Q

how are fossils shown from gradual replacements from minerals ?

A

things like teeth and bones which don’t decay as easily are replaced by minerals forming a rock like substance shaped like the original hard part

206
Q

how are fossils formed from cast and impressions ?

A

when an organism is buried in a soft material like clay the material can harden around it and the organisms decays leaving a cast of itself

207
Q

what can be preserved as casts ?

A

an animals burrow
rootlet traces
footprints

208
Q

how are fossils made by preservation in places where no decay happens ?

A
  • microbes in decay need the right conditions to breakdown a material
  • if the conditions aren’t right decay can’t happen and organisms are preserved
209
Q

what are the conditions microbes need to decay ?

A

oxygen
moisture
the right temperature and pH

210
Q

why can’t the hypothesis’s of the origins of life on earth be supported or disproved ?

A

there’s lack of valid evidence

211
Q

why is there a lack of evidence of the origins of life on earth ?

A
  • scientists believed many early organisms were soft bodied and soft bodies decay quickly leaving few traces
  • fossils from many years ago may have been destroyed due to geological activity
212
Q

what does an incomplete fossil record mean ?

A

we do not have the fossils of every organisms or every type of organism that has ever existed

213
Q

what is isolation ?

A

where populations of species is separated

214
Q

why does isolation happen ?

A
  • physical barrier = floods/earthquakes
215
Q

how does variation happen to populations of species which have been isolated ?

A

1- each population shows genetic variation as they have a wide range of alleles
2- in each population individuals with characteristics that make them better adapted to their environment have a better chance of survival so breed more successfully
3- alleles that control the beneficial characteristics are more likely to be passed onto the next generation
4- eventually individuals from populations will have differentiated so much they cannot breed together so they are a separate species

216
Q

what did Russel Wallace do ?

A

worked on the ideas of speciation

217
Q

what did Wallace investigate ?

A

ideas about natural selection with Darwin, prompted Darwin to publish ‘on the origin of species’

218
Q

when travelling the world to investigate speciation, what did Wallace find ?

A

warning colours are used by some species to deter predators from eating them which was an example of a beneficial characteristic evolved by natural selection

219
Q

what is antibiotic resistant bacteria ?

A

a mutation which leads to bacteria being unaffected by antibiotics

220
Q

why is antibiotic bacteria really bad ?

A

bacteria spreads very quickly

221
Q

how can a resistant bacteria survive ?

A

it can survive even in a host who is being treated to get rid of the infection so it will live longer and reproduce

222
Q

why is antibiotic resistant bacteria bad for infected people ?

A

they aren’t immune to the new strain and there is no effective treatment so it can easily spread between people

223
Q

give examples of anti biotic resistant bacterium

A

MRSA
Multi drug resistant TB

224
Q

why is it important for you to take the anti-biotics doctors prescribe you ?

A

it decreases the chances of antibiotic resistant bacteria emerging - it makes sure the full bacteria is destroyed and there is none left to mutate

225
Q

why are antibiotics given to animas ?

A

so they grow faster
prevents them becoming ill

226
Q

why can giving antibiotics to animals be a concern ?

A

it can lead to antibiotic resistant bacteria in the animals which can spread to humans during meat preparation and consumption

227
Q

what has increasing concern about overuse of antibiotics lead to ?

A

some countries restricting their use

228
Q

why is the problems of antibiotic resistance getting worse ?

A

overuse and inappropriate use of antibiotics

229
Q

give examples of when antibiotics are over-used ?

A
  • doctors prescribing antibiotics for non-serious conditions
  • doctors prescribing antibiotics for infections caused by viruses
230
Q

what actually causes antibiotic resistance ?

A

the antibiotics cause a situation where naturally resistant bacteria have an advantage and so an increase in numbers

231
Q

what has the increase in antibiotic resistance caused ?

A

drug companies to work on developing new antibiotics that are effective against the strains

232
Q

what is the annoying things about creating new antibiotics to overcome strains ?

A
  • rate of development is slow
  • costly
  • can’t keep up with spread of demand for new drugs and antibiotic strains
233
Q

what does classification mean ?

A

sorting things into groups

234
Q

what is the Linnaean system ?

A

where living things are divided into kingdoms which are then subdivided into smaller and smaller groups

235
Q

when did Carl Linnaeus create the Linnaean system ?

A

1700s

236
Q

what is the order of classification ?

A
  • kingdom
  • phylum
  • class
  • order
  • family
  • genus
  • species
237
Q

what did Carl Woese propose as a classification species in 1990 ?

A

the 3 domain system

238
Q

how did Woese come up with the 3 domain system ?

A

he used evidence from the new chemical analysis techniques such as RNA

239
Q

what are the 3 domains ?

A
  • archaea
  • bacteria
  • eukaryota
240
Q

what is the archaea domain ?

A

organisms which were once thought to be primitive bacteria but are now a type of prokaryotic cell - found in hot springs and salt lakes = extreme conditions

241
Q

where are species in the Archaea domain found ?

A

extreme conditions - salt lakes, hot springs

242
Q

what is the bacteria domain ?

A

contains bacteria

243
Q

what is the eukaryota domain ?

A

included organisms such as fungi, plants, animals, protists

244
Q

what are the 3 domain groups divided into ?

A

kingdom
phylum
class
order
family
genus
species

245
Q

what is the binomal system ?

A

means scientists in different countries and speak different languages can all refer to the same species using the same name

246
Q

what language does the binomal system use ?

A

latin

247
Q

what are humans known as in the binomal system ?

A

homo sapiens

248
Q

what do evolutionary trees show ?

A

how scientists this different organisms are related to each other

249
Q

what do evolutionary trees do ?

A

show common ancestors and relationships between species - the more recent the ancestor, the more closely they are related and the more characteristics they share

250
Q

how do scientists work out evolutionary relationships in living things ?

A

using DNA analysis
structural similarities
classification data

251
Q

how do scientists work out evolutionary relationships in extinct things ?

A

information from fossil records

gcse science (27 decks)

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