Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Biology A-level > 4B Diversity, Classification and Variation > Flashcards

4B Diversity, Classification and Variation Flashcards

You may prefer our related Brainscape-certified flashcards:
AP® Biology flashcards Biology 101 flashcards
1
Q

How is DNA passed on from one generation to the next?

A

By gametes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What are gametes?

A

The sperm cells in males and egg cells in females

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is a zygote?

A

When a sperm cell fertilises an egg cell, the zygote divides and develops into a new organism

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

How many chromosomes do normal body cells have?

A

They have the diploid number (2n)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What does the ‘diploid number’ mean?

A

It means each cell contains two of each chromosome, one from the mum and one from the dad

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

How many chromosomes do gametes have?

A

The haploid number (n)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What does the ‘haploid number’ mean?

A

There’s only one copy of each chromosome

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

How is the diploid number of chromosomes achieved?

A

At fertilisation, a haploid sperm fuses with a haploid egg, making a cell with the normal diploid number of chromosomes

Half the chromosomes are from the father (the sperm) and half are from the mother (egg)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

How is fertilisation random?

A

During sexual reproduction, any sperm can fertilise any egg

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

How does random fertilisation affect the zygotes?

A

It produces zygotes with different combinations of chromosomes to both parents

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

How does random fertilisation affect diversity?

A

The mixing of genetic material in sexual reproduction increases genetic diversity within a species

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

How are gametes formed?

A

Via meiosis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What is meiosis and where does it take place?

A

It is a type of cell division and it takes place in the reproductive organs

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Why is meiosis necessary for gametes?

A

Cells that divide by meiosis are diploid to star with, but the cells formed from meiosis are haploid (halved)

Without meiosis you’d have double the no. chromosomes when the gametes are fused which would not be good

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What happens in the first 2 stages of meiosis?

A

1) Before meiosis starts, the DNA unravels & replicates so there are two copies of each chromosome, called chromatids.
2) The DNA condenses to form double-armed chromosomes, each made from two sister chromatids. Sister chromatids are joined in the middle by a centromere.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What happens in Meiosis I (stages 3 & 4 of meiosis)?

A

3) (First division) - the chromosomes arrange themselves in homologous pairs
4) These homologous pairs are then separated, halving the chromosome number

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What happens in Meiosis II (stages 5 & 6 of meiosis)?

A

5) (second division) - the pairs of sister chromatids that make up each chromosome are separated (the centromere is divided)
6) Four haploid cells (gametes) that are genetically different from each other are produced

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

How many cells are produced from meiosis?

A

4

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

When in Meiosis do the chromatids cross over?

A

In Meiosis I

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

How do the chromatids cross over in Meiosis I?

A

Homologous pairs of chromosomes come together & pair up

The chromatids twist around each other & bits of chromatids swap over

The chromatids still contain the same genes but now have a different combination of alleles

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What are the cells like that meiosis produces?

A

They are genetically different

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What are the two main events in meiosis that lead to genetic variation?

A

1 - Crossing over of chromatids

2 - Independent segregation of chromosomes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

How does the crossing over of chromatids in meiosis create genetic variation?

A

The crossing over of chromatids in meiosis I means that each of the four daughter cells formed from meiosis contains chromatids with different alleles

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

How does independent segregation of chromosomes in meiosis create genetic variation?

A

1) Each homologous pair of chromosomes in your cells is made up of one chromosome from your mum (maternal) and one from your dad (paternal)
2) When the homologous pairs are separated in meiosis I, it’s completely random which chromosome from each pair ends up in which daughter cell
3) So the four daughter cells produced by meiosis have completely different combinations of those maternal and paternal chromosomes
4) This is called independent segregation (seperation) of the chromosomes
5) This ‘shuffling’ of chromosomes leads to genetic variation in any potential offspring

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

What are the stages of crossing over in meiosis?

A

1 - The chromosomes of homologous pairs come together

2 - Chromatids cross over

3 - One chromosome from each homologous pair ends up in each cell

4 - Each cell has a different chromatid and therefore a different set of alleles, which increases genetic variation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

How are the number of chromosomes produced different in meiosis vs mitosis?

A

Mitosis –> Produces cells with the same no. chromosomes as the parent cell

Meiosis –> Produces cells with half the no. chromosomes as the parent cell

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

How is the genetic material produced different in meiosis vs mitosis?

A

Mitosis –> Daughter cells are genetically identical to each other and to the parent cell

Meiosis –> Daughter cells are genetically different from one another and the parent cell

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

How are the number of cells produced different in meiosis vs mitosis?

A

Mitosis –> Produces two daughter cells

Meiosis –> Produces four daughter cells

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

How many divisions do mitosis and meiosis involve?

A

Mitosis - one

Meiosis - two

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

Why can’t crossing over or independent segregation take place during mitosis?

A

There’s no pairing or separation of homologous chromosomes so they can’t cross over etc

This produces genetically identical daughter cells - unlike meiosis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

What are chromosome mutations caused by?

A

Errors in cell division (during meiosis)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

When an error in cell division occurs, how can this affect the chromosomes?

A

When meiosis goes wrong the cells produced can contain variations in the numbers of whole chromosomes or parts of chromosomes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

What do chromosome mutations lead to?

A

Inherited conditions - because the errors are present in the gametes (the hereditary cells)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

What is non-disjunction?

A

It’s a failure of the chromosomes to separate properly

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
35
Q

What causes Down’s Syndrome in humans?

A

The non-disjunction of chromosome 21 during meiosis

Someone having an extra copy of chromosome 21

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
36
Q

How does the non-disjunction of chromosome 21 cause someone to have Down’s Syndrome

A

It means that chromosome 21 fails to separate properly during meiosis - one cell will have 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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
37
Q

What are mutations?

A

Changes to the base sequence of DNA

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
38
Q

What are the two types of mutations that can occur?

A

Substitution and deletion

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
39
Q

What is a substitution mutation?

A

One base is substituted with another

e.g. AAGCT becomes ATGCT (A is swapped for T)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
40
Q

What is a deletion substitution?

A

One base is deleted

e.g. AAGCT becomes AGCT (A is deleted)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
41
Q

What does the order of DNA bases in a gene determine and how does a mutation affect this?

A

The particular protein that is going to be made

If a mutation occurs, the sequence may be changed and the protein formed could be altered

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
42
Q

Do all mutations affect the order of the amino acid chain?

A

No - some substitutions and have no effect on the order

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
43
Q

How does the degenerate nature of the genetic code affect mutations?

A

It means that some amino acids are coded for by more than one DNA triplet - therefore not all substitutions will change the amino acid sequence

e.g. TAT, TAC both code for tyrosine

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
44
Q

Will substitutions always lead to a change in the amino acid sequence?

A

No - due to the degenerative nature of the genetic code, some amino acid sequences code for the same proteins so there can be no change

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
45
Q

Will deletions always lead to a change in the amino acid sequence?

A

Yes - the deletion of a base will change the number of bases present, which will cause a shift in all the base triplets after it

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
46
Q

What are mutagenic agents?

A

They increase the rate of mutation

Mutations occur randomly, however some things can cause an increase in the rate of mutations

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
47
Q

What are some examples of mutagenic agents?

A
  • Ultraviolet radiation
  • Ionising radiation
  • Some chemicals
  • Some viruses
48
Q

What do lots of different alleles mean for a species?

A

There is high genetic diversity

49
Q

What is genetic diversity?

A

The number of different alleles of genes in a species or population

50
Q

What can increase genetic diversity in a population?

A
  • Mutations in the DNA

- Different alleles being introduced into a pop.

51
Q

How do mutations in DNA cause genetic diversity?

A

They form new alleles

52
Q

What is gene flow?

A

Different alleles being introduced into a pop. when individuals from another pop. migrate into them & reproduce

53
Q

Genetic diversity allows what to occur?

A

Natural selection

54
Q

What can reduce genetic diversity?

A

A genetic bottleneck

55
Q

What is a genetic bottleneck?

A

An event that causes a big reduction in a population

e.g. when a large no. organisms within a population die before reproducing

56
Q

How does a genetic bottleneck reduce genetic diversity?

A

It reduces the no. different alleles in the gene pool - so reduces genetic diversity

Survivors reproduce & a larger pop. is created from a few individuals

57
Q

Give an example of a genetic bottleneck

A

Northern Elephant Seals

They were hunted by humans in the late 1800s - their original pop. was reduced to around 50 seals who then produced a pop. of around 170 000
New pop. has little genetic diversity compared to Southern elephant seals who didn’t suffer this reduction in numbers

58
Q

What is the founder effect?

A

A type of genetic bottleneck

59
Q

Define the founder effect

A

It describes what happens when just a few organisms from a pop. start a new colony & there are only a small no. different alleles in the initial gene pool

60
Q

What does Phylogeny tell us about?

A

Evolutionary history of organisms

61
Q

Where have all organisms evolved from?

A

From shared common ancestors

62
Q

What are the domains?

A 
Kingdom 
Phylum 
Class 
Order
Family
Genus
Species
63
Q

What is taxonomy?

A

Science of classification, organising organisms into groups

64
Q

What are the 3 domains?

A

Eukarya, Bacteria and Archaea

65
Q

What is the order for naming an animal?

A

Genus - Species

66
Q

What is courtship behaviour?

A

Behaviour carried out by animals to attract mate of right species

67
Q

What can courtship behaviour help to identify?

A

Used to classify organisms through there specific behaviour

68
Q

Give 3 examples of animals courtship behaviour

A
  • Fireflies give off pulses of light
  • Crickets make sounds similar to morse code
  • Male peacocks show off colourful tails
69
Q

What has technological advances been useful for?

A

Clarifying evolutionary relationships

70
Q

What 3 things has technology been useful in?

A
  • Genome sequencing
  • Comparing amino acid sequence
  • Immunological comparison
71
Q

What has advancements in genome sequencing allowed us to do?

A
  • Determine entire base sequence of organisms DNA

- Help compare how closely related species are

72
Q

How does genome sequencing tell you species are closely related?

A

Shows closely related species will have higher % of similarity in DNA base order

73
Q

How does comparing amino acids tell you species are closely related?

A

Related organisms have similar amino acid structure

74
Q

How does immunological comparisons tell you species are closely related?

A

Similar proteins bind to same antibodies, if add antibodies to isolated sample any similar antibodies will be recognised

75
Q

When can the founder effect occur?

A

It can occur as a result of migration leading to geographical seperation or if a new colony is seperated from the original population for another reason, such as religion

76
Q

Give an example of the founder effect

A

The Amish - they descended from a small number of Swiss who migrated there

They have remained isolated due to their religious beliefs - showing little genetic diversity

The population has an unusually high incidence of certail genetic disorders

77
Q

How is natural selection beneficial to populations?

A

It increases advanageous alleles in a population

Also leads to populations becoming better adapted

78
Q

What are the 3 types of adaptions that organisms can gain through natural selection?

A
  • Behavioural adaptions
  • Physiological adaptions
  • Anatomical adaptions
79
Q

What are behavioural adaptions?

A

Ways an organism acts that increase its chance of survival & reproduction

e.g. possums sometimes ‘play dead’ if they’re being threatened by a predator to escape attack

80
Q

What are physiological adaptions?

A

Processes inside an organism’s body that increase its chance of survival

e.g. brown bears hibernate over winter - they lower their rate of metabolism. This conserves energy, so they don’t need to look for food in the months when its scarce

81
Q

What are anatomical adaptions?

A

Structural features of an organism’s body that increase its chance of survival

e.g. whales have a thick layer of blubber (fat) which helps them to keep warm in the cold sea

82
Q

What are the two key factors in evolution?

A

Adaption and selection

83
Q

What is evolution?

A

The gradual change in species over time

Evolution has led to huge diversity of living organisms on earth

84
Q

How were early estimates of genetic diversity found?

A

Observing characteristics

85
Q

How can befenficial mutations allow for natural selection?

A

The beneficial mutations allow the organism to survive better than other members of the species, therefore allowing for natural selection

e.g. giraffes having longer necks

86
Q

How can advantageous alleles increase in a population through natural selection?

A

1) Not all individuals are as likely to reproduce as each other. Differential reproductive sucess in a pop. - individuals that have allele that increases their chance of survival & are more likely to survive, reproduce and pass on their genes
2) This means that a greater proportion of the next generation inherits the beneficial allele
3) They are more likely to survive, reproduce & pass on their genes
4) So the freq. of the beneficial allele increasesfrom generation to generation
5) Over generations leads to evolution as the advantageous alleles become more common in the pop.

87
Q

Why can some mutations be better than others?

A

Harmful mutations normally lead to the the allele quickly dying out

Beneficial mutations may help the organism to survive in their environment - this allows for natural selection

88
Q

How can befenficial mutations allow for natural selection?

A

The beneficial mutations allow the organism to survive better than other members of the species, therefore allowing for natural selection

e.g. girrafes having longer necks

89
Q

What can cause genetic variation between/within species?

A

Different species have different genes - causes variation between species

Individuals of same species have same genes but different alleles - causes variation within a species

90
Q

What can variation be caused by?

A

Genes, the environment or both

91
Q

How can genetic & environmental factors cause variation within a species?

A

Genes determine how tall an organism can grow, but nutrient availability affects how tall the organism actually grows

92
Q

yo

A

man

93
Q

How can variation within a species be caused by the environment?

A

Climate, food, & lifestlye

94
Q

How can genetic & environmental factors cause variation within a species?

A

Genes determine how tall an organism can grow, but nutrient availability affects how tall the organism actually grows

95
Q

What is biodiversity?

A

Variety of living organisms in an area

96
Q

What is a habitat?

A

Place where organism lives

97
Q

What is a community?

A

All the populations of different species in a habitat

98
Q

What are the 2 types of biodiversity?

A
  • Local biodiversity

- Global biodiversity

99
Q

What is local biodiversity?

A

Variety of different species living in a small habitat thats local

100
Q

What is global biodiversity?

A

Variety of species on earth

101
Q

How can biodiversity be measured?

A

Using index of diversity

species richness, population size

102
Q

What is species richness?

A

Number of species in a community

103
Q

What does a high index of diversity show?

A

A more diverse area

104
Q

What agricultural methods reduce biodiversity?

A
  • Woodland clearance
  • Hedgerow removal
  • Pesticides
  • Herbicides
  • Monoculture
105
Q

How do conservations protect biodiversity?

A
  • Legal protection to endangered species
  • Protected areas like the SSSI
  • Environmental Stewardship scheme
106
Q

What is monoculture?

A

Farmers have fields containing one type of plant

107
Q

What is variation?

A

Differences that exists between individuals

108
Q

How is there variation between different species?

A

Different species have different genes

109
Q

How is there variation within a species?

A

Same genes but different alleles

110
Q

What is most variation within a species caused by?

A

Combination of genetic and environmental factors

111
Q

How can you study a whole population?

A

Use a sample of the population

112
Q

What does the sample need to be?

A

Random so its more accurately representative

113
Q

How can you test if there is variation between samples?

A

Mean

114
Q

How can you test variation within a sample?

A

Standard deviation

115
Q

What does a large standard deviation mean?

A

Means values in sample vary a lot (values are not close to mean)

116
Q

What can standard deviation be used to draw?

A

Error bars (longer the bar the larger the SD)

Biology A-level (20 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions