4b - diversity, classification, and variation Flashcards
1
Q
gametes
A
the sperm cells in males and egg cells in females, they join together at fertilisation to form a zygote which dives and develops into a new organism
2
Q
normal body cells chromosomes
A
have a diploid number of chromosomes, meaning each cell contains two of each chromosome, one from mum and one from dad.
3
Q
gametes chromosomes
A
haploid number of chromosomes - only one copy of each chromosome
4
Q
what happens at fertilisation
A
a haploid sperm fuses with a haploid egg, making a cell with a normal diploid number of chromosomes. half from the father aka the sperm half from mother aka the egg
5
Q
why is fertilisation random
A
any sperm can fertilise any egg during sexual reproduction
6
Q
what does random fertilisation produce
A
zygotes with different combinations of chromosomes to both parents
7
Q
what does the mixing of genetic information in sexual reproduction increase
A
genetic diversity within a species
8
Q
how are gametes formed
A
meiosis
9
Q
what is meiosis
A
a type of cell division
10
Q
where does meiosis take place
A
reproductive organs
11
Q
what kind of cells divide by meiosis
A
diploid cells
12
Q
what kind of cells are formed by meiosis
A
haploid cells
13
Q
meiosis step 1
A
before meiosis starts, the DNA unravels and replicates so that there are two copies of each chromosome, called chromatids.
14
Q
meiosis step 2
A
the DNA condenses to form double armed chromosomes each made from two sister chromatids. the sister chromatids are joined in the middle by a centromere
15
Q
meiosis step 3 (meiosis 1)
A
first division
- the chromosomes arrange themselves into homologous pairs
- these homologous pairs are then seperated halving the chromosome number
16
Q
meiosis step 4 (meiosis 2 )
A
second division
- the pairs of sister chromatids that make up each chromosome are separated, the centromere is divided)
- four haploid cells that are genetically different from each other are produced
17
Q
what can chromatids do during meiosis 1
A
cross over
18
Q
how do chromosomes cross over during meiosis 1
A
the chromatids twist around each other and bits of chromatids swap over. the chromatids still contain the same genes but now have a different combination of alleles
19
Q
what are the two main events during meiosis that lead to genetic variation
A
- crossing over of chromatids
- independent segregation of chromosomes
20
Q
what does the crossing over of chromatids cause
A
each of the four daughter cells to contain chromatids with different alleles
21
Q
independent segregation of chromosomes
A
each homologous pair of chromosomes in your cell is made up on one from your mum and one from you dad. when the pairs are separated in meiosis 1 its completely random which chromosome ends up in which daughter cell. so the four daughter cells produced have completely different combinations of the maternal and paternal chromosomes
22
Q
what causes chromosome mutations
A
errors in cell division
23
Q
what happens when meiosis goes wrong
A
the cells produced contain variations in the numbers of whole chromosomes or parts of chromosomes
24
Q
what can chromosome mutations lead to
A
inherited conditions because the errors are present in the gametes (the hereditary cells)
25
what is downs syndrome caused by
a person having an extra copy of chromosome 21 (or an extra copy of a part of chromosome 21). non-disjunction means that chromosome 21 fails to separate properly during meiosis , so one cell gets an extra copy of 21 and another gets none. when the gamete with the extra copy fuses to another gamete at fertilisation, the resulting zygote will have 3 copies of chromosome 21.
26
what does a gene mutation involve
a change in the DNA base sequence of chromosomes
27
what are the two types of errors that can occur with gene mutations
substitution and deletion
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substitution
one base is substituted with another
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deletion
one base is deleted
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what does the order of bases in a gene determine
the order of amino acids in a particular protein
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what happens if a mutation occurs in a gene
the sequence of amino acids it codes for could be altered
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what does the degenerate nature of the genetic code mean
that some amino acids are coded for by more than one DNA triplet, meaning that not all substitution mutations will result in a change to the amino acid sequence of the protein
33
substitution mutations dont always..
lead to changes in the amino acid sequence
34
what will deletion mutations always do
change the number of bases present which will cause a shift in all the base triplets after it meaning there will be changes to the amino acid sequence
35
when do mutations occur
spontaneously
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mutagenic agents
factors that increase the rate of mutations
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examples of mutagenic agents
- UV radiation
- ionising radiation
- some chemicals
- some viruses
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what does lots of different alleles mean
high genetic diversity
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alleles
different versions of a single gene
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genetic diversity
the number of different alleles of genes in a species or population
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how is genetic diversity increased within a population
- mutations in the DNA forming new alleles
- different alleles being introduced into a population when individuals from another population migrate into them and reproduce. (gene flow)
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gene flow
different alleles being introduced into a population when individuals from another population migrate into them and reproduce
43
what does genetic diversity allow
natural selection to occur
44
genetic bottleneck
an event that causes a big reduction within a population, reducing the number of different alleles in the gene pool therefore reducing genetic diversity. the survivors reproduce and a larger population is created from few individuals
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founder effect
describes what happens when just a few organisms from a population start a new colony and there are only a small number of different alleles in the initial gene pool
46
how might the frequency of each allele differ from a new colony to the original population
might be very different, an allele that was rare in the original colony may be more common in the new colony, which may lead to a higher incidence of genetic disease
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how can the founder effect occur
as a result of migration leading to geographical separation or if a new colony is separated from the original population for another reason such as religion
48
what can randomly occuring mutations mutations sometimes result in
a new allele being formed
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what are the dangers of new alleles being formed
they can be harmful which usually means that the mutated allele quickly dies out.
50
what are the positives of new alleles being formed
some mutations can be beneficial to an organism helping the organism to survive in certain environments
51
natural selection
when the allele codes for a characteristic that increases the chances of an organism surviving and reproducing, increasing its frequency within a population
52
process of natural selection
1. not all individuals are as likely to reproduce as each other. there is differential reproductive success in a population - individuals that have an allele that increase their chance of survival are more likely to survive reproduce and pass on their genes than individuals with different alleles
2. this means that a greater proportion of the next generation inherits the beneficial allele.
3. they in turn are more likely to survive, reproduce and pass on their genes
4. so the frequency of the beneficial allele increases from generation to generation
5. over generations this leads to evolution as the advantageous alleles become more common in the population
53
what are two key factors of evolution
adaptation and selection
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evolution
the gradual change in species over time
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what has evolution led to
huge diversity of living organisms on earth
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what does natural selection lead to
populations becoming better adapted
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adaptations
help organisms to survive in their environment
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three types of adaptations
- behavioural
- physiological
- anatomical
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behavioural adaptation
ways an organism acts that increase its chance of survival and reproduction
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physiological adaptation
processes inside an organisms body that increases its chance of survival
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anatomical adaptations
structural features of an organisms body that increase its chance of survival
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what do different types of natural selection lead to
different frequency patterns
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directional selection
where individuals with alleles for characteristics of an extreme type are more likely to survive and repoduce
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causes of directional selection
environmental change. etc.
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how does directional selection work ( e.g. antibiotic resistance)
1. some individuals in a population have alleles that give them resistance to an antibiotic
2. the population is exposed to the antibiotic, killing bacteria without the resistant allele.
3. the resistant bacteria survive and reproduce without competition, passing on the allele that gives antibiotic resistance to their offspring
4. after some time, most organisms in the population will carry the antibiotic resistance allele
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stabilising selection
where individuals with alleles for characteristics towards the middle of the range are more likely to survive and reproducee
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when does stabilising selection occur
when the environment isnt changing ad it reduces the range of possible characteristics
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how does stabilising selection work (e.g. human birth weights)
1. humans have a range of birth rates
2. very small babies are less likely to survive - partly because they find it hard to maintain their body temperature.
3. giving birth to large babies can be difficult, so large babies are less likely to survive too
4. conditions are most favourable for medium-sized babies - so the weight of human babies tends to shift towards the middle of the range
69
how can you test the effects of antibiotics using agar plates
1. bacteria is likely to have been grown in liquid broth.
2. use a sterile pipette to transfer the bacteria from broth to an agar plate
3. spread the bacteria over the plate using sterile plastic spreader
4. use sterile forceps to place paper discs soaked with different antibiotics spaced apart on the plate
5. add a negative control disk soaked in sterile water
6. lightly tape a lid on, invert and incubate the plate at about 25 degrees for 48 hours
7. anywhere bacteria cant grow is called an inhibition zone
8. size of inhibition tells us how well the antibiotic works
70
liquid broth
a mixture of distilled water, bacterial culture and nutrients
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agar plate
a petri dish containing agar jelly
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why are aseptic techniques used
to prevent contamination of cultures by unwanted microorganismsw
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why are aseptic techniques important
because contamination can effect the growth of the microorganism you are working with, and disease causing microbes could make you ill
74
aseptic techniques
- regularly disinfect surfaces to minimise contamination
- use sterile equipment and discard safely after use
- work near a bunsen flame as hot air rises , so any microbes in the air should by drawn away from your culture
- minimise the time spent with the lid off the agar plate, to reduce chance of airborn microorganisms contaminating the culture
- briefly flame the neck of the glass container of broth just after its opened and just before its closed. prevent unwanted organisms from falling in.
75
phylogeny
the study of the evolutionary history of groups of organisms
- tells us who is related to whom and how closely related they are
76
what have all organisms evolved from
shared common ancestors
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phylogenetic trees
shows the relationship between members of families, first branch point represents a common ancestors of all family members which is now extinct. each of the following points represents another common ancestor of which a different group emerged. closely related species diverged away from eachother most recently.
78
taxonomy
the science of classification
- involves naming organisms and organising them into groups making it easier to identify and study them.
79
what are the eight levels of groups used to classify organisms called as a whole
taxa
80
what is each group called
a taxon
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how are groups arranged in classification
in a hierarchy with the largest groups at the top and smallest groups at the bottom
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how many groups can an organism belong to
one at each level in the hierarchy there is no overlap
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what is the first level
domain
84
what are the three domains
eukarya, bacteria, and archaea
85
what happens as you move down the hierarchy
there are more groups at each level but fewer organisms in each group
86
what are the eight levels of classification in order
domain
kingdom
phylum
class
order
family
genus
species
87
species
a group of similar organisms able to reproduce to give fertile offspring
88
what is the naming system for classification called
thee binomial system
89
what is the two parts of the binomial system name for classification
first part is the genus name (capital letter)
second part is the species name (lowercase letter)
in latin
90
what does the binomial system help avoid
confusion of using common names
91
courtship behaviour
behaviour carried out by organisms to attract a mate of the right species
- series of displays
- releasing chemicals
92
courtship behaviour is...
species specific
- only members of the same species will do and respond to that courtship behaviour
- allows members of the same species to recognise eachother, preventing interbreeding and making reproduction more successful
- also allows courtship behaviour to be used to classify organisms
93
examples of courtship behaviour
1. fireflies give off pulses of light
2. crickets make sounds that are similar to morse code
3. male peacocks show off their colourful tails
4. male butterflies use chemicals to attract females
94
what can new or improved technologies result it
new discoveries being made and the relationships between organisms being clarified. leading to the classification system being updated
95
genome sequencing
advances have meant that the entire base sequence of an organisms DNA can be determined. The DNA base sequence of one organisms can then be compared to the DNA base sequence of another organism to see how closely related they are. closely related species will have a higher percentage of similarity in their DNA base order
96
comparing amino acid sequence
proteins are made of amino acids. the sequence of amino acids in a protein is coded for by the base sequence in DNA. related organisms have similar DNA sequences and so similar amino acid sequences in their proteins.
97
immunological comparisons
similar proteins will also bind the same antibodies
98
how were early estimates of genetic diversity made
by looking at the frequency of measurable or observable characteristics in a population.
99
what do different alleles of the same genes have
slightly different DNA base sequences, therefore comparing the DNA base sequences of an organism allows scientists to find out how many alleles of that gene there are in that population
100
what will different alleles produce
slightly different mRNA base sequences, and may produce proteins with slightly different amino acid sequences, so these can also be compared
101
what can these new technologies allow us to do
get more accurate estimates of genetic diversity within a population or species. and the genetic diversity of different species to be compared more easily
102
variation
the differences that exist between individuals. between species and within species
103
what causes variation
genetic factors, different species have different genes which causes variation between species
environmental factors individuals of the same species have the same genes, but different alleles which causes variation within a species
104
what do you look at when investigating variation
a sample of the population
105
what is sample data used for
to draw conclusions about a whole population
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what should a sample be
- random to make sure sample isnt biased
- results should be analysed statistically
107
when can mean be used
to look for variated between samples
108
mean
an average of the values collected in a sample
109
standard deviation
how much the values in a single sample vary, its a measure of the spread of values about the mean
110
what does a large standard deviation mean
the values in the sample vary a lot
111
what does a small standard deviation mean
that most of the sample data is around the mean so varies little
112
how can standard deviations be plotted
on a graph or chart of mean values
113
biodiversity
the variety of living organisms in an area
114
habitat
the place where an organism lives
115
community
all of the populations of different species in a habitat
116
what are areas of high biodiversity
areas with lots of different species
117
local biodiversity
considers the variety of different species living in a small habitat thats local to you
118
global diversity
the variety of species on earth. varies in different parts of the world
119
species richness
a measure of the number of different species in a community.
can be worked out by taking random samples of a community and counting the number of different species
120
what effects biodiversity
population sizes of species
121
index of diversity
calculated using an equation that taken both the number of species in a community and the abundance of each species into account
122
formula for index of diversity
d = N(N-1) / (sigma) n(n-1)
where N = total number of organisms of all species
n= total number of organisms of one species
(sigma) = sum of
123
what does a high index of diversity mean
the area is more diverse
124
how do farmers reduce biodiversity
by maximising the amount of food they can produce from a given area of land
125
woodland clearance
increases the area of farmland. but directly reduces number of trees and sometimes the number of different tree species. destroys habitats causing species to lose shelter and food source. causing species to die or forced to migrate to another area, reducing biodiversity
126
hedgerow removal
increases the area of farmland by turning lots of small fields into fewer larger fields. reduces biodiversity for same reasons as woodland clearances
127
pesticides
chemicals that kill organisms that feed on crops. reduces diversity by directly killing the pests and an species that feed on the pests will lose a food source so their numbers may decrease aswell
128
herbicides
kill unwanted plants. reduces plant diversity and could reduce the number of organisms that feed on the weeds
129
monoculture
when farmers have fields containing one kind of plant. a single type of plant reduces biodiversity directly and will support fewer organisms
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conservation schemes to protect biodiversity
- giving legal protection to endangered species
- creating protected areas, restrict further development including agricultural development
- the environmental stewardship scheme which encourages farmers to conserve biodiversity.
