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B - Biology > Topic 6 - Inheritance, Variation and Evolution > Flashcards

Topic 6 - Inheritance, Variation and Evolution 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 contain?

A

coded information, all the instructions to put an organism together and make it work.
so whats inside your DNA determines what inherited characteristics you have

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4
Q

where is DNA found?

A

in the nucleus of animal and plant cells, in really long structures called chromosomes, which normally com in pairs

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5
Q

what is DNA made of?

A

it’s a polymer made up of 2 strands coiled together in the shape of a double helix

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6
Q

what is a gene?

A

a small section of DNA found on a chromosome

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7
Q

what does each gene do?

A

it codes for (tells the cells to make) a particular sequence of amino acids which are put together to make a specific protein. they just tell cells the order to put the amino acids together in

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8
Q

how many amino acids are used to make proteins?

A

only 20 amino acids are used but hey make up thousands of different proteins

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9
Q

what does DNA determine?

A

what protein the cell produces, which determines what type of cell it is

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10
Q

what does genome mean?

A

the entire set of genetic material in an organism. scientists have worked out the complete human genome

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11
Q

why is understanding the human genome an important science tool for science and medicine?

A

it allows scientists to identify genes in the genome that are linked to different types of disease
scientists can look at genomes to trace the migration of certain populations of people around the world

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12
Q

why is knowing which genes link to disease important?

A

knowing which genes are linked to inherited diseases could help us understand them better and develop effective treatments for them

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13
Q

what can we tell about migration of humans from the human genome?

A

All humans are descended from a common ancestor from Africa, but humans can be found all over the planet. the human genome is most identical in individuals, as different populations migrated from Africa they developed tiny differences in their genomes. by investigating this scientists can work out when new populations split off in a different direction and what route they took

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14
Q

what are DNA strands?

A

polymers made up of lots of repeating repeating units called nucleotides

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15
Q

what do nucleotides consist of?

A

a sugar, a phosphate group and one ‘base’

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16
Q

what forms the ‘backbone’ of the DNA strands?

A

the sugar and phosphate groups in the nucleotides form a ‘backbone’. the sugar and phosphate groups alternate, one of 4 different bases (A,T,C or G) joins to each sugar

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17
Q

what is each base linked to?

A

each base links to a base on the opposite strand in the helix. A always pairs with T and C with G. this is called complementary base pairings

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18
Q

what determines the order of amino acids in a protein?

A

the order of bases in a gene. each amino acid is coded for by a sequence of 3 bases in the gene. the amino acids are joined together to make various proteins, depending on the order of the genes bases

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19
Q

what controls whether or not a gene is expressed?

A

there are parts of DNA that don’t code for proteins. some of these non-coding parts switch genes on and off, to control whether a gene is used to make a protein or not

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20
Q

where are proteins made?

A

the cell cytoplasm on tiny structures called ribosomes

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21
Q

how do ribosomes make proteins?

A

they use the code in the DNA. DNA is too big to move out of the nucleus so mRNA is used to get the code from the DNA to the ribosome

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22
Q

what is mRNA?

A

a molecule which is made by copying the code from DNA. it acts as a messenger between the DNA and the ribosome

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23
Q

how do ribosomes get the right amino acids?

A

the correct amino acids are brought to the ribosomes in the correct order by a carrier molecule

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24
Q

what happens when a chain of amino acids has been assembled?

A

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

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25
Q

what are some examples of types of proteins?

A

enzymes
hormones
structural proteins

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26
Q

what do enzymes do?

A

they act as biological catalysts to speed up chemical reactions in the body

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27
Q

what do hormones do?

A

they are used to carry messages around the body. e.g. insulin is a hormone released into the blood by the pancreas to regulate the blood sugar level

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28
Q

what do structural proteins do?

A

they are physically strong e.g. collagen is a structural protein that strengthens connective tissues (like ligaments and cartilage)

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29
Q

what is a mutation?

A

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

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30
Q

when do mutations occur?

A

they occur continuously. they can occur spontaneously, e.g. when a chromosome isn’t quite replicated properly.

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31
Q

what increases the chance of mutation?

A

exposure to certain substances or some types of radiation

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32
Q

what do mutations do?

A

they change the sequence of the DNA bases in a gene, which produces a genetic variant. as the sequence of DNA bases codes for the sequence of amino acids that make up a protein, mutations to a gene sometimes lead to changes in the protein that it codes for.

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33
Q

what effects do mutations have on proteins?

A

most have very little or no effect on the protein. some will change it to such a small extent that its function or appearance is unaffected. some mutations can seriously affect a protein, the mutation can code for an altered protein with a change in its shape. this could affect its ability to perform its function

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34
Q

how can a mutation affect a proteins ability to perform its function?

A

if the shape of an enzymes active site is changed, its substrate may no longer be able to bind to it
structural proteins like collagen could lose their strength if their
shape is changed, making them pretty useless at providing structure and support

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35
Q

what happens if there’s a mutation in the non-coding DNA?

A

it can alter how genes are expressed

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36
Q

what are examples of different types of mutation?

A

insertions
deletions
substitutions

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37
Q

what are insertion mutations?

A

this is where a new base is inserted into the DNA base sequence where it shouldn’t be. it changes the way the groups of 3 bases are ‘read’, which can change the amino acids they code for

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38
Q

how can insertions change more than one amino acid?

A

they can change more than 1 amino acid because they have a knock-on effect on the bases further on in the sequence

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39
Q

what are deletion mutations?

A

this is when a random base is deleted from the DNA base sequence. this changes the way the base sequence is ‘read’ and has a knock on effect further down the sequence.

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40
Q

what are substitution mutations?

A

this is when a random base in the DNA base sequence is changed to a different base

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41
Q

what happens during sexual reproduction?

A

genetic information from 2 organisms is combined to produce offspring which are genetically different to either parent. the mother and father produce gametes by meiosis e.g. egg and sperm cells

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42
Q

how many chromosomes do gametes have?

A

in humans, each gamete contains 23 chromosomes. half the number of chromosomes in a normal cell (1 of each instead of 2)

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43
Q

what do gametes do to form a normal cell?

A

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

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44
Q

what does sexual reproduction involve?

A

the fusion of male and female gametes. because there are 2 parents, the offspring contain a mixture of their parent’s genes.

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45
Q

why does offspring of sexual reproduction have variation?

A

it inherits a mixture of genetic information from both parents through a mixture of chromosomes from both its mum and dad

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46
Q

other than animals, what else can sexually reproduce?

A

flowering plants can reproduce this way because they also have egg cells, but their version of sperm is known as pollen.

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47
Q

what is asexual reproduction?

A

in asexual reproduction there’s only 1 parent. there’s no fusion of gametes, or mixing of chromosomes or genetic variation between parent and offspring. the offspring are genetically identical to the parent - they are clones

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48
Q

how does asexual reproduction happen?

A

it happens by mitosis - an ordinary cell makes a new cell by dividing in 2, the new cell has exactly the same genetic information

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49
Q

what can reproduce asexually?

A

bacteria, some plants and some animals

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50
Q

why do gametes only ave 1 copy of each chromosome?

A

so that when gamete fusion takes place, you get the right amount of chromosomes

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51
Q

how do gametes only get half the original number of chromosomes?

A

they divide by meiosis, this involves 2 cell divisions. in humans it only takes place in the reproductive organs

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52
Q

what does the cell do before it starts to divide in meiosis?

A

it duplicates its genetic information, forming 2-armed chromosomes- each arm is a copy of the other. then the chromosomes arrange themselves into pairs

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53
Q

what happens in the 1st division of meiosis?

A

the chromosome pairs line up in the centre of the cell then they are pulled apart so each new cell only has 1 copy of each chromosome. some of the fathers chromosomes and some of the mothers go into each cell

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54
Q

what happens in the 2nd division of meiosis?

A

the chromosomes line up again in the centre of the cell and the arms of the chromosome are pulled apart

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55
Q

what do you get after meiosis?

A

4 gametes, with only a single set of chromosomes in each. each of the gametes is genetically different from the others because the chromosomes all get shuffled up during meiosis and each gamete only gets half of them

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56
Q

what do gametes do after being formed in meiosis?

A

they fuse together during fertilisation to create a new cell

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57
Q

what happens to the new cell after fertilisation?

A

it divides by mitosis to make a copy of itself, mitosis repeats many times to produce lots of new cells in an embryo

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58
Q

what happens to all the cells in an embryo as it develops?

A

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

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59
Q

what advantage does sexual reproduction have over asexual reproduction?

A

offspring has a mixture of 2 sets of chromosomes, it inherits genes from both parents, which produces variation.

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60
Q

how is variation advantageous?

A

variation increases the chance of a species surviving a change in the environment. they have a survival advantage

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61
Q

what is natural selection?

A

individuals with characteristics better adapted to the environment have a better chance of survival, they are more likely to breed successfully and pass genes on

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62
Q

what advantages does asexual reproduction have over sexual?

A

only 1 parent needed
uses less energy because organisms don’t need to find mates
faster than sexual reproduction
many identical offspring can be produced in favourable conditions

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63
Q

what organisms can reproduce both sexually and asexually?

A

malaria
many species of fungus
lots of species of plant

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64
Q

how does malaria produce sexually and asexually?

A

its a parasite spread by mosquitoes, the parasite is transferred to human when the mosquito bites them. the reproduce sexually in the mosquito and asexually when its in the human

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65
Q

how do spores reproduce sexually and asexually?

A

asexually-produced spores form fungi that are genetically identical. sexually produced spores introduce variation and are often produced in an unfavourable change in the environment, increasing the chance the population will survive the change

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66
Q

how do fungi reproduce?

A

they release spores which become new fungi when they land in a suitable place. spores can produce sexually and asexually.

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67
Q

how does asexual reproduction take place in strawberries?

A

strawberry plants produce ‘runners’ which are stems that grow horizontally on the surface of the soil away from the plant, at various points along the runner a new identical strawberry plant forms

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68
Q

how can plants produce asexually?

A

for example runners from strawberries and plants that grow from bulbs

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69
Q

how do plants that grow from bulbs reproduce asexually?

A

new bulbs can form from the main bulb and divide off. each new bulb can grow into a new identical plant

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70
Q

how many pairs of chromosomes do human have?

A

23, 22 are matched pairs that control characteristics the 23rd are labelled XX or XY that decide gender

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71
Q

what 23rd chromosome do men have and which do women have?

A

males have an X and a Y chromosome, Y causes male characteristics
females have 2 X chromosomes, the combination allows female characteristics to develop

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72
Q

what do X and Y chromosomes do when making sperm?

A

they are drawn apart in the 1st division in meiosis, there’s a 50% chance each sperm will get an X and 50% for the Y. A similar thing happens for eggs but they all get 1 X chromosome

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73
Q

what must you do when using a punnett square?

A

you must write the percentages of each outcome and what it is

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74
Q

what controls what characteristics people develop?

A

what genes you inherit, different genes control different characteristics. some characteristics are controlled by a single gene but most are controlled by several genes interacting

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75
Q

examples of characteristics controlled by a single gene:

A

mouse fur colour and red-green colour blindness

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76
Q

what are alleles?

A

the different versions of a gene - there’s 1 on each chromosome in a pair. that are represented by letters in genetic diagrams. you have 2 versions (alleles) of every gene in your body

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77
Q

what does homozygous mean?

A

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

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78
Q

what does heterozygous mean?

A

when an organisms alleles for a gene are different. this means only 1 can determine what characteristic is present. this would be the dominant allele

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79
Q

what causes an organism to display a recessive characteristic?

A

both its alleles would have to be recessive whereas for dominant characteristics the gene only needs 1 dominant allele

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80
Q

what is a genotype?

A

the combination of alleles you have.

81
Q

what is a phenotype?

A

the characteristics you have

82
Q

how do genetic diagrams or punnett squares work?

A

make a 4 by 4 grid and put the 2 genotypes on the top of the grid and on the left, each allele will line up with a row or column of the square. you then combine the 2 alleles (write the dominant capital letter 1st) and you will create the outcomes

83
Q

how does the other kind of genetic diagram work?

A

you write out the genotypes of both parent then just the alleles, then combine them so that all the alleles are crossed with 1 another.

84
Q

how do family trees work?

A

people will be represented by different shapes and male and female will be different shapes, an empty shape represents an unaffected person, half is a carrier and coloured means they have the disease or characteristic

85
Q

what is cystic fibrosis?

A

a genetic disorder of the cell membranes, it results in the body producing a lot of thick sticky mucus in the air passages and in the pancreas

86
Q

is cystic fibrosis dominant or recessive?

A

the recessive allele causes cystic fibrosis, and if someone has 1 dominant allele then they will be a carrier (1/25 are carriers)

87
Q

what is polydactyly?

A

a genetic disorder where someone is born with extra fingers or toes

88
Q

is polydactyly dominant or recessive?

A

its caused by the dominant allele so anyone with a defective allele will have it and has the possibility of producing offspring with it

89
Q

what happens during IVF?

A

embryos are fertilised in a lab and then implanted in the woman’s womb

90
Q

what does IVF stand for?

A

in vitro fertilisation

91
Q

how can genetic disorders be detected using IVF?

A

its possible to remove a cell from each embryo and analyse its genes. DNA from an embryo in the womb can also be taken and tested

92
Q

arguments against embryonic screening:

A

it implies people with genetic problems are undesirable
its expensive
there may be a point where everyone wants to do it to pick the most desirable one

93
Q

what types of concerns are there about embryonic screening?

A

ethical, social and economic, it is controversial because of the choices it can lead to

94
Q

why might screening be bad both in IVF and in the womb?

A

embryos with bad alleles would be destroyed and screening could lead to the decision to terminate the pregnancy

95
Q

arguments for embryonic screening:

A

it will help to stop people suffering
treating disorders costs the government a lot of money
there are laws to stop it going too far so parents can’t select the gender of their baby

96
Q

who was Gregor Mendel?

A

an Australian monk in the mid 19th century who trained in maths and natural history at the university of Vienna

97
Q

what did Mendel do on his garden plot at the monastery?

A

he noted how characteristics in plants were passed on from 1 generation to the next. he published his research in 1866 and became the foundation of modern genetics

98
Q

what did Mendel show about the heights of plea plants?

A

that the characteristics were determined by separately inherited “hereditary units” passed on from each parent. he found that the unit for tall plants was dominant over the unit for dwarf plants

99
Q

what 3 conclusions did Mendel reach about heredity in plants?

A

characteristics in plants are determined by “hereditary units”
these units are passed on to offspring unchanged from both parents, 1 unit from each parent
these units can be dominant or recessive - if an individual has the dominant and recessive unit for a characteristic the dominant 1 will be expressed

100
Q

how have the observations of many different scientists contributed to the understanding of genes?

A

late 1800’s - scientists were able to observe how chromosomes behave during cell division
early 20th century - scientists found similarities in how chromosomes and Mendel’s “units” acted. these are now known as genes
1953 - the structure of DNA was determined. so scientists could find out exactly how genes work

101
Q

what is variation?

A

differences in organisms in the same species

102
Q

what are the 2 types of variation?

A

genetic variation and environmental variation

103
Q

what are genes?

A

the codes inside your cells that control how you’re made

104
Q

how are genes passed on?

A

they are passed on in sex cells (gametes) from which the offspring develop. some are from the mother and some from the father.

105
Q

what is genetic variation?

A

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

106
Q

what are some characteristics determined only by genes?

A

eye colour, blood group and inherited disorders

107
Q

what is environmental variation?

A

when the environment, including the conditions that organisms live and grow in, cause differences between members of the same species

108
Q

what some examples of environmental variation?

A

suntans, yellow leaves, and a plant grown in light will be different to the same plant grown in darkness

109
Q

examples of characteristics determined by a mixture of genetic and environmental factors:

A

body weight, height, skin colour, condition of teeth, academic or athletic prowess

110
Q

how can mutations introduce variation?

A

rarely mutations result in new phenotypes being seen in a species, but it could make an individual better suited for a change in the environment, then this characteristic can become common through natural selection

111
Q

what is the theory of evolution?

A

all of today’s species have evolved from simple life forms that 1st started to develop over 3 billion years ago

112
Q

who came up with the theory of evolution?

A

Charles Darwin

113
Q

what is Darwin’s theory?

A

he knew organisms in a species show wide variation in their characteristics, they also have to compete for limited resources
survival of the fittest means organisms survive, reproduce and pass on genes.
less adapted organisms don’t
over time, beneficial characteristics become more common in the population and the species evolves

114
Q

what is survival of the fittest?

A

organisms with the most suitable characteristics for the environment would be more successful competitors and would be more likely to survive

115
Q

what is phenotypic variation?

A

when organisms in a species show wide variation in their characteristics

116
Q

how did Darwin come up with his theory?

A

he made a huge round-the -world trip, along with experiments, discussions and new knowledge of fossils and geology

117
Q

why was Darwin’s theory not perfect?

A

the relevant scientific knowledge wasn’t available at the time, he couldn’t give a good explanation for why new characteristics appeared or exactly how individual organisms passed on beneficial adaptations to their offspring

118
Q

what do we now know about evolution that Darwin didn’t?

A

phenotype is controlled by genes. new phenotypic variations arise because of genetic variants produced by mutations. beneficial variations are passed on to future generations in the genes that parents contribute to their offspring

119
Q

what is speciation?

A

when the phenotype of organisms change so much because of natural selection that a completely new species is formed.

120
Q

when does speciation happen?

A

when populations of the same species change enough to become reproductively isolated - they can’t interbreed to produce fertile offspring

121
Q

why do species become extinct?

A

the environment changes too quickly
a new predator kills them all
a new disease kills them all
they can’t compete with another species for food
a catastrophic event happens that kills them all

122
Q

why was Darwin’s idea very controversial?

A

went against common religious beliefs about God creating the world

he couldn’t explain why new characteristics appeared or how they were passed on. this was because he hadn’t heard of genes or mutations

there wasn’t enough evidence to convince scientists because not many other studies had been done into how organisms change

123
Q

who else, other than Darwin, had theories about evolution?

A

Jean-Baptise Lamarck (1744 - 1829)

124
Q

what was Lamarck’s theory of evolution?

A

changes that an organism acquires during its lifetime, will be passed on to its offspring. if a characteristic was used a lot it would become more developed and the offspring would inherit the characteristic

125
Q

how are different hypotheses made and proven?

A

hypotheses are made to explain similar observations.
they ma be different because the scientist has different beliefs, influences or just think differently
evidence must be found to support or disprove a hypothesis to find out if its right

126
Q

why was Lamarck’s hypothesis rejected?

A

experiments didn’t support his hypothesis. if you dye an animals fur the offspring won’t necessarily have the same dyed fur colour

127
Q

why was Darwin’s hypothesis accepted?

A

the discovery of genetics supported his theory because it provided an explanation of how organisms with beneficial characteristics can pass them on. evidence was also found through fossil records and bacteria evolving to become resistant to antibiotics

128
Q

what is selective breeding?

A

when humans artificially select individuals with a desirable characteristic so that genes for articular characteristics remain in the population

129
Q

why are organisms selectively bred?

A

to develop features that are useful or attractive. e.g.
animals that produce meat or milk
disease resistant crops
calm dogs
decorative plants with big / unusual flowers

130
Q

what is the basic process involved in selective breeding?

A

select organisms with desired characteristics from existing stock
breed them together
select best offspring and breed them
continue over several generations so the characteristic gets stronger

131
Q

how is selective breeding used in agriculture?

A

to improve yield. e.g. by breeding cows with best meat producing characteristics, after several generations the will have cows with high meat yield

132
Q

what’s the problem with selective breeding?

A

it reduces the gene pool. this is because the best animals are bred that are closely related and leads to inbreeding

133
Q

what is the problem with inbreeding?

A

it can cause health problems because there’s more chance of the organisms inheriting harmful genetic defects when the gene pool is limited. they are all susceptible to the same diseases and so are in danger if a new disease appears

134
Q

What is the basic idea of genetic engineering?

A

To transfer a gene responsible for a desirable characteristic from 1 organisms genome into another organism, so it’s got the desired characteristic

135
Q

how is genetic engineering done?

A

Useful gene is isolated from 1 organisms genome using enzymes and inserted into a vector.
when the vector is introduced to the target organism, the useful gene is inserted into its cell(s)

136
Q

in genetic engineering what is usually used as the vector?

A

a virus or a bacterial plasmid (circular DNA in bacterial cells) depending on the type of organism that the genes being transferred to

137
Q

what can genetic engineering be used on?

A

bacteria
crops
sheep
treating inherited disease

138
Q

how can genetic engineering be used on bacteria?

A

they can genetically modified to produce human insulin that can be used to treat diabetes

139
Q

how can genetic engineering be used on crops?

A

GM crops have had their genes modified. e.g. to improve the size and quality of their fruit, or make them resistant to disease, insects and herbicides

140
Q

how can genetic engineering be used on sheep?

A

so that they can produce substances. like drugs, in their milk that can be used to treat human disease

141
Q

how can genetic engineering be used on treating inherited diseases caused by faulty genes?

A

through gene therapy - by inserting working genes into people with the disease

142
Q

how can an organism be genetically modified to develop with the characteristic coded for by the gene?

A

transfer the gene when the organism receiving the gene is at an early stage of development(e.g. egg or embryo)

143
Q

why do some people disagree with genetic engineering?

A

there are worries that changing an organism’s genes might accidentally create unplanned problems, which could get passed on to future generations

144
Q

what are the disadvantages of GM crops?

A

could affect the number of wild flowers that live in and around the crops - reducing farmland biodiversity
people are worried about negative effects on humans e.g. allergies
transplanted genes could get out into the natural environment. e.g. weeds getting herbicide resistant genes

145
Q

what are the advantages of GM crops?

A

characteristics can increase yield
they can contain nutrients that people in developing countries are missing. e.g. ‘golden rice’ contains beta-carotene which prevents blindness
they are already being grown, without problems

146
Q

what 2 ways can plants be cloned?

A

tissue culture

cuttings

147
Q

what is cloning using tissue culture?

A

where a few plant cells are put in a growth medium with hormones, and they grow into clones of the parent plant.

148
Q

what are the advantages of tissue culture?

A

they can be made very quickly, in very little space, and be grown all year

149
Q

what is tissue culture used for?

A

its used by scientists to preserve rare plants that are hard to reproduce naturally and by plant nurseries to produce lots of stock quickly

150
Q

how can cuttings be used to clone a plant?

A

gardeners can take cuttings from good parent plants, and then plant them to produce genetically identical copies

151
Q

what are the advantages of taking cuttings to clone plants?

A

they can be produced quickly and cheaply. its an older, simpler method than tissue culture

152
Q

how can farmers produce cloned offspring?

A

using embryo transplants

153
Q

how are embryo transplants done?

A

sperm and egg cells are taken from best animals. sperm used to artificially fertilise an egg. the embryo that develops is split many times (to form clones) before any cell’s specialised. they grow into identical calfs

154
Q

what is adult cell cloning?

A

taking an unfertilised egg cell and removing its nucleus. the
nucleus is then removed from an adult body cell and inserted into the empty egg cell. the egg cell is electrically stimulated to make it divide.
when the embryo is a ball of cells its implanted into the womb of a female then it grows into a genetically identical clone of the adult body cell

155
Q

what are the advantages of cloning?

A

you get lots of “ideal” offspring
led to greater understanding of the development of embryos, ageing and age-related disorders
could preserve endangered species

156
Q

what are the disadvantages of cloning?

A

reduced gene pool, which is dangerous if a new disease appears and no allele in the gene pool is resistant to it
cloned animals might not be as healthy as normal ones
if humans are cloned in the future unsuccessful attempts may be made before a success

157
Q

what is a reduced gene pool?

A

this means there are fewer different alleles in a population

158
Q

what are fossils?

A

the remains of organisms from many thousands of years ago, which are found in rocks

159
Q

what can fossils do for humans?

A

provide evidence that organisms lived ages ago.

tell us how much or little organisms have evolved over time

160
Q

what 3 ways can fossils form in rocks?

A

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

161
Q

how does gradual replacement happen?

A

things that don’t decay easily (teeth, shells, bones etc.) last ages when buried,
they’re replaced by minerals as they decay forming a rock-like substance in that shape
surrounding sediments turn into rock but the fossil stays distinct

162
Q

how do casts and impressions form?

A

if fossils are buried in a soft material like clay it will harden and the organism decays, leaving a cast.
animal burrows, footprints or plant’s roots can be preserved as casts

163
Q

how are organisms preserved?

A

in amber and tar pits there’s no oxygen or moisture so decay microbes can’t survive
in glaciers its too cold
in peat bogs its too acidic

164
Q

what are the different hypotheses of how life first began?

A

1st life forms came into existence in a primordial swamp or under the sea
simple organic molecules came on comets and evolved into complex molecules then simple life forms

165
Q

why is there little evidence to support hypotheses about how life began?

A

early life forms were often soft-bodied and so decayed completely - so fossil record is incomplete
fossils were destroyed by geological activity e.g. moving tectonic plates could’ve crushed fossils

166
Q

what is a species?

A

a group of similar organisms that can reproduce to give fertile offspring

167
Q

what is speciation?

A

the development of a new species

168
Q

when does speciation happen?

A

when populations of the same species become so different that they can no longer successfully interbreed to produce fertile offspring

169
Q

what is isolation?

A

where populations of a species are separated

170
Q

what can cause isolation?

A

a physical barrier e.g. floods and earthquakes can cause barriers that geographically isolate some individuals from the main population

171
Q

what happens when different groups from the same species are isolated?

A

conditions will be slightly different
each population shows genetic variation because they have a wide range of alleles
individuals with advantageous characteristics will survive and reproduce.
alleles that control the beneficial characteristic are more likely to be passed down
this leads to speciation

172
Q

who was 1 of the 1st scientists to work on speciation?

A

Alfred Russel Wallace

173
Q

what did Alfred Wallace do?

A

independently came up with the idea of natural selection and published work with Darwin in 1858.
he collected evidence to support his theory as he travelled the world.
he realised warning colours are used to deter predators which is a beneficial characteristic obtained through natural selection

174
Q

how do strains of bacteria become resistant to antibiotics?

A

they develop a random mutation in their DNA which can lead to a change in characteristics like being antibiotic resistant. as the gene becomes more common in a population antibiotic resistant strains develop

175
Q

why are antibiotic resistant bacteria populations growing fast?

A

bacterium reproduce rapidly so they evolve quickly

they live longer so can reproduce more which increase the population of the antibiotic resistant strain

176
Q

why are antibiotic resistant bacteria dangerous?

A

people aren’t immune to the new strain and there is no effective treatment. so infection spreads easily

177
Q

what are superbugs?

A

bacteria that are resistant to most known antibiotics e.g. MRSA which often affects people in hospitals and can be fatal if it gets into the bloodstream

178
Q

how is bacteria becoming antibiotic-resistant?

A

overuse and inappropriate use of antibiotics
doctors prescribing drugs for non-serious conditions or infections
through animals being given drugs to prevent them getting ill

179
Q

why do doctors only need to prescribe drugs when necessary?

A

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

180
Q

what is done to prevent bacteria becoming resistant?

A

don’t over prescribe drugs
finish courses of antibiotics
restricting use of antibiotics on farm animals

181
Q

why must you take all the antibiotics you are prescribed?

A

taking the full course makes sure all the bacteria are destroyed, so none are left to mutate and develop into resistant strains

182
Q

how can people get antibiotic resistant bacteria from animals?

A

in farming antibiotics are used to prevent animals becoming ill and to make them grow faster. this can lead to the development of antibiotic resistant bacteria, which can spread to humans through meat preparation and consumption

183
Q

why is it difficult to make new drugs for antibiotic resistant bacteria?

A

the rate of development is slow so its hard to keep up with demand as more superbug strains develop and spread. it is also expensive

184
Q

who thought of the Linnaean system and when?

A

Carl Linnaeus in the 1700’s

185
Q

what is the Linnaean system?

A

a system to classify organisms into groups according to their characteristics and the structures that make them up

186
Q

what are the 7 groups that the Linnaean system subdivides into? in order

A 
kingdom
phylum
class
order
family
genus
species
187
Q

who thought of the three-domain system and when?

A

Carl Woese in 1990

188
Q

what was discovered about many closely related species thanks to new technologies in 1990?

A

using evidence from new chemical analysis techniques e.g. RNA sequence analysis. some species thought to be closely related according to traditional classification systems, weren’t actually

189
Q

in the 3-domain system, what are the 3 domains that organisms are split up into?

A

Archaea
Bacteria
Eukaryota

190
Q

what organisms are in the archaea domain?

A

organisms once thought to be primitive bacteria, they’re actually a different type of prokaryotic cell, 1st found in extreme places like hot springs and salt lakes

191
Q

what does the bacteria domain contain?

A

true bacteria like E.coli and Staphylococcus. they often look similar to archaea but there are lots of biochemical differences

192
Q

what does the Eukaryota domain contain?

A

a broad range of organisms including fungi, plants, animals and protists

193
Q

what is the binomial system?

A

where every organism is given a 2 part Latin name using the genus and the species

194
Q

what do the 2 parts of an organisms binomial name mean?

A

genus - information on the organisms ancestry

the 2nd part is just the species. in humans homo is the genus and sapiens is the species

195
Q

why is the binomial system helpful?

A

its used worldwide so scientists in different countries can avoid confusion by using the same name for a speies

196
Q

what do evolutionary trees show?

A

they show common ancestors and relationships between species. the more recent the common ancestor, the more closely related the 2 species and the more characteristics they share

197
Q

how are evolutionary trees made?

A

scientists analyse lots of data to work out evolutionary relationships.

198
Q

how are evolutionary relationships of living organisms worked out?

A

current classification is used e.g. DNA analysis and structural similarities

199
Q

how are evolutionary relationships of extinct organisms worked out?

A

information from the fossil record is used

B - Biology (8 decks)

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