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biology AS > diversity, classification and variation > Flashcards

diversity, classification and variation Flashcards

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1
Q

what is a gamete?

A

reproductive cells. they joint together to form a zygote

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2
Q

what does diploid and haploid mean?

A

diploid means that the cells have two of each chromosome, in a haploid cell there is only one copy of each chromosome humans have 46 chromosomes - 23 chromosome pairs

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3
Q

explain the idea of random fertilisation

A

any sperm can fertilise any egg. it can produce zygotes with different combinations of chromosomes to both parents. this icing of genetic material increases the genetic diversity within a species

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4
Q

what is meiosis?

A

meiosis is a type of cell devision. it takes place in the reproductive organs

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5
Q

describe the process of meiosis I

A

Interphase - the DNA unravels and replicates so that there are two copies of each chromosome called chromatids
Prophase I - the DNA condenses to form a double armed chromosome made from sister chromatids which are joined in the middle via a centromere. each of these chromosomes joins up with its homologous partner to form a tetrad
Metaphase I - spindle fibres attach to each of the homologous CHROMOSOMES
Anaphase I - the fibres contract and pull the chromosomes to opposite ends of the cell this halves the number of chromosomes.

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6
Q

describe the process of meiosis II

A

Metaphase II - the chromatids line up in a similar way to that of mitosis. the spindle fibres attach to the centromeres
Anaphase II - the sister chromatids separate and move toward opposite ends of the cell
Telophase II - meiosis II results in four haploid daughter cells

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7
Q

give three reasons why sexual reproduction gives varied offspring

A

crossing over - prophase I
independent assortment - Metaphase I
random fertilisation

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8
Q

wat is synapsis?

A

where homologous chromosomes come together to form a tetrad - these chromosomes carry the same genes at the same loci

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9
Q

what is chromosome closing over?

A

during Prophase I homologous chromosomes come together and pair up. the chromosomes twist around each other and its of chromatids swap over, the chromosomes still have the same genes but they now have different combinations of alleles

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10
Q

what is the process of independent segregation?

A

each homologous pair of chromosomes in a cell is made up of maternal and paternal chromosomes. when they are separated it is completely random which ends up un the daughter cell. so the four daughter cells produced have completely different combinations of maternal and paternal chromosomes.

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11
Q

what is the mutation non-disjunction?

A

the failure of the chromosomes to separate properly. this can lad to down syndrome.

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12
Q

what is down syndrome?

A

it is caused by a person having an extra copy o the chromosome 21 so one cell gets an extra copy of 21 and another gets none

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13
Q

what is substitution?

A

when one base is substituted with another

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14
Q

what is deletion?

A

when one base is deleted

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15
Q

what do mutations mean?

A

the order of bases in the DNA codes for specific amino acids. a mutation within these bases could alter the sequence of amino acids. however due to the degenerate nature of the genetic code more than one DNA triplet codes for one amino acid meaning that not all substitutions will result in a change however deletions will (it will cause a shift in all of the bases after it)

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16
Q

what will mutagenic agents do?

A

they increase the rate of mutation

e.g. ultraviolet light, ionising radiation and smoking the tar in cigarettes.

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17
Q

what can increase the genetic diversity within a population?

A

Mutations in the DNA
gene flow - different alleles being introduced into a population from another population which has migrated into them and reproduced

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18
Q

what is a genetic bottleneck and what does it do?

A

an event that causes a big reduction in a population. this reduces the number f different alleles in the gene pool and so reduces genetic diversity.

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19
Q

what is the founder effect?

A

the founder effect describes what happens when just a few organisms dorm a population start a new colony ans there are only a small number of different alleles in the initial gene pool. the frequency of each allele in the new colony might be very different to the frequency of those allies in the original population. the risk of genetic disease is therefore increased.

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20
Q

why does natural selection increase advantageous alleles in a population?

A

some mutations can form mutations that are beneficial to an organism helping the organism to survive in certain environments. when this happens its frequency within a population therefore increases - this is known as natural selection.

21
Q

how does natural selection work?

A

there is differential reproductive success in a population - individuals that have an allele that increases their chance of survival are more likely to survive, reproduce and pass on their genes, this means that a great number often next generation will have this beneficial allele they in turn are more likely to survive, reproduce and pst on their genes

22
Q

Natural selection leads to populations becoming better adapted. give the different ways in which this is possible

A

behavioural adaptation - ways in which an organism acts that increase its chance of survival
physiological adaptations - processes inside an organisms body that increase its chances of survival
anatomical adaptation - structural features of an organism’s body that increase its chance of survival

23
Q

what is directional selection?

A

where individual alleles for characteristics of an extreme type are more likely to survive and reproduce. this could be in response to an environmental change, bacteria evolving antibiotic resistance is and example of this

24
Q

how does directional selection work?

A

some individuals in a population have alleles that give them resistance. the population is exposed to the antibiotic and so all non resistant bacteria die. the resistant ones survive and reproduce without competition passing on the allele, after some time most organism are resistant

25
Q

what is is stabilising selection?

A

where individuals with alleles for characteristics towards the middle of he range are more likely to survive and reproduce. it occurs when an environment is not changing and reduces the range of possible characteristics

26
Q

what is phylogeny?

A

the study of the evolutionary history of groups of organisms, it tells us who’s related to whom and how closely related they are

27
Q

what does a phylogenetic tree show?

A

it shows the relationship between embers of a family showing a common ancestor and then the devision of each of the species after that showing which developed before which.

28
Q

what is a species?

A

a group of similar organisms able to reproduce to give fertile offspring.

29
Q

what are the groups in classification?

A 
domain 
kingdom
phylum 
class
order
family 
genus 
species
30
Q

explain the binomial naming system that is used in classification.

A

all organisms are given one international exerted scientific name in latin that has two parts.
the first part of the name is the genus and has a capital letter, the second part is the species and starts with a lower case letter

31
Q

how can courtship behaviour be used to help classify a species?

A

it is carried out by organisms to attract a mate of the right species. it is specific - only members of the same species will do and respond to that courtship behaviour.
it allows members of the same species to recognise each other,prevent inbreeding and make reproduction more successful.

32
Q

give some examples of courtship behaviour

A

fireflies give off pulses of light - the pattern is specific to each species.
Crickets make sounds that are similar to morse code
Male peacocks show off their colourful tails.
Male butterflies use chemicals to attract females - only those of the correct species respond.

33
Q

how can Advances in techniques clarify evolutionary relationships?

A

Genome sequencing
comparing amino acid sequence
immunological comparisons

34
Q

what is genome sequencing?

A

it means that the entire base sequence of an organisms DNA can be determined. it can then be compares to that of another to see how closely related they are.

35
Q

how does comparing amino acid sequences help to clarify evolutionary relationships?

A

proteins are made up of amino acids. the sequence of amino acids in a protein is coded for by the base sequence in on DNA. as the organisms have similar DNA sequences they have similar amino acid sequences in their proteins

36
Q

how does immunological comparisons help to clarify evolutionary relationships?

A

similar proteins will also bind the same antibodies.

37
Q

how have gene technologies changed the way genetic diversity assessed?

A

early estimates of genetic diversity were assessed by looking at the frequency of measurable or observable characteristics in a population since different alleles determine different characteristics a wide variety of each characteristic in a population indicates a high number of alleles and so a high genetic diversity

38
Q

what is genetic diversity?

A

the number of alleles in a species or population.

39
Q

what can variation be caused by?

A

genes, the environment or both. variation is the difference that exists between individuals there is variation between species and within species.
it can can be caused by genetic factors. individuals of the same species have the same genes but different alleles.
variation within a species can be caused by a change in environment - how most genetic variation is caused by a mixture of the two.

40
Q

what does the standard deviation tell you about variation within a sample?

A

it tells you how much the blues in a single sample vary. it is a measure of the spread of values about the mean. a large deviation means that the values in a sample vary a lot and vice versa.

41
Q

how can you use standard deviation to draw error bars?

A

the standard deviation can be plotted on a graph or chart of mean values using error bars. they extent one standard deviation above and one below the mean. the larger the bar the larger standard deviation.

42
Q

what is biodiversity?

A

the variety of living organisms in an area

43
Q

what is species diversity?

A

the number of different species and the number of individuals within that species within any one community.

44
Q

what is ecosystem diversity?

A

the range of different habitats.

45
Q

what re the different levels that biodiversity can be considered at?

A

local biodiversity - the variety of different species living in a small habitat.
global biodiversity - the variety of species on earth

46
Q

how can biodiversity be measured?

A

by using the index of diversity. t is calculated by using an equation that takes both the number of species in a community and the abundance of each species into account. look in book for the equation

47
Q

what is species richness?

A

a measure of the different species within a community

48
Q

how can agricultural process reduce biodiversity?

A

woodland clearance o done to increase the area of farmland, it directly reduces the number of trees destroying habitats
hedgerow removal - done to increase the area of farmland by turning lots of small fields into fewer larger fields
pesticides - kill organisms that feed on crops
herbicides
monoculture - where farmers have fields containing one type of plant

49
Q

what are some examples of conservation schemes?

A

giving legal protection for endangered species.
creating protected areas
environmental stewardship scheme.

biology AS (11 decks)

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