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

4B - Diversity, Classification and Variation Flashcards

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1
Q

What happens before meiosis starts?

A
  • DNA unravels and replicates so there are two copies of each chromosomes (chromatids)
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2
Q

What happens after DNA unravels?

A
  • DNA condenses to form double-armed chromosomes, each made from two sister chromatids
  • sister chromatids are joined in the middle by a centromere
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3
Q

What happens during Meiosis I?

A
  • chromosomes arrange themselves into homologous pairs

- homologous pairs are separated, halving the chromosome number

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4
Q

What happens during Meiosis II?

A
  • pairs of sister chromatids that make up each chromosome are separated
  • four haploid cells that are genetically different from each other are produced
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5
Q

In Meiosis I, the chromatids cross over, what does this mean?

A
  • homologous pairs of chromosomes come together and pair up
  • chromatids twist around each other and bits of chromatids swap over
  • chromatids still contain same genes but have different combination of alleles
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6
Q

What two events during meiosis lead to genetic variation?

A
  • crossing over

- independent segregation of chromosomes

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7
Q

How does independent segregation of chromosomes lead to genetic variation?

A
  • when the pairs are separated, its completely random which chromosome from each pair ends up in which daughter cell
  • shuffling of chromosomes leads to daughter cells having different combinations
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8
Q

What are the outcomes of mitosis?

A
  • cells have same number of chromosomes as parent cell
  • daughter cells are genetically identical to each other and parent cell
  • produce 2 daughter cells
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9
Q

What are the outcomes of meiosis?

A
  • cells have half the number of chromosomes as parent cell
  • daughter cells are genetically different to each other and parent cell
  • produce 4 daughter cells
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10
Q

What is meant by non-disjunction?

A
  • failure of chromosomes to separate properly

- one type of chromosome mutation

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11
Q

What condition is caused by a person having an extra copy of chromosome 21?

A
  • Down’s syndrome
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12
Q

What type of errors can occur in gene mutations?

A
  • substitution - one base is substituted with another

- deletion - one base is deleted

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13
Q

What would happen if a mutation occurs in a gene?

A
  • sequence of amino acids it codes for could be altered
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14
Q

Why won’t substitution always change the amino acid sequence?

A
  • the degenerate nature of the genetic code means some amino acids code for more than one DNA triplet
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15
Q

Mutagenic agents increase the rate of mutations, give an example of a mutagenic agent?

A
  • ultraviolet radiation
  • ionising radiation
  • viruses
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16
Q

What is meant by genetic diversity?

A
  • number of different alleles of genes in a species or population
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17
Q

What increases genetic diversity within a population?

A
  • mutations in DNA, form different alleles

- different alleles being introduced when organisms migrate and reproduce (gene flow)

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18
Q

What is meant by a genetic bottleneck?

A
  • an event that causes a big reduction in a population
  • reduces number of alleles in gene pool and reduces genetic diversity
  • survivors reproduce
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19
Q

Describe the process of natural selection.

A
  • those with the allele that increases their chance of survival are more likely to survive, reproduce and pass on their genes
  • a greater proportion inherits the beneficial gene
  • next generation can then survive, reproduce and pass on their genes
  • leads to evolution as the advantageous alleles become more common
20
Q

What types of adaptations help organisms to survive in their environment?

A
  • behavioural e.g. possums ‘play dead’ to escape predators
  • physiological e.g bears lower their rate of metabolism to conserve energy in winter
  • anatomical e.g whales have a thick layer of blubber which helps them keep warm in the cold sea
21
Q

Antibiotic resistance shows directional selection. What is directional selection?

A
  • individuals with alleles for characteristics of an extreme type are more likely to survive and reproduce.
  • could be in response to an environmental change.
22
Q

How does directional selection work?

A
  • some individuals have alleles that give them antibiotic resistance
  • population is exposed to antibiotic, killing bacteria w/o resisting allele
  • resistant bacteria survive and reproduce w/o competition, passing on allele to offspring
  • most organisms in population will carry resistant allele.
23
Q

Human birth weight shows stabilising selection. What is stabilising selection?

A
  • individuals with alleles for characteristics towards the middle of the range are more likely to survive and reproduce.
24
Q

How does stabilising selection work?

A
  • very small babies are less likely to survive; hard to maintain body temperature
  • giving birth to large babies can be difficult; less likely to survive
  • conditions are most favourable for medium sized babies
25
Q

What aseptic techniques are used to prevent contamination of microbial cultures?

A
  • regularly disinfect work surfaces
  • work near Bunsen flame
  • sterilise wire inoculation loop before and after each use passing through hot Bunsen flame for 5 secs
  • briefly flame neck of glass container of broth just after its opened and just before its closed
  • sterilise all glassware before and after use, also wash hands thoroughly before and after handling cultures
26
Q

What is meant by phylogeny?

A
  • study of evolutionary history of groups of organisms
27
Q

What is meant by taxonomy?

A
  • science of classification

- involves naming organisms and organising them into groups

28
Q

What are the 8 groups in an evolutionary relationship heirarchy?

A
  • Domain
  • Kingdom
  • Phylum
  • Class
  • Order
  • Family
  • Genus
  • Species
29
Q

What is the binomial system?

A
  • all organisms are given one internationally accepted scientific name in Latin that has two parts
30
Q

What is each part of the Latin names of organisms?

A
  • first part is genus, has capital letter
  • second part is species, lower case letters
  • e.g humans are Homo sapiens
31
Q

What is courtship behaviour and how does it work?

A
  • carried out by organisms to attract a mate of right species
  • can be fairly simple or quite complex
  • species specific
32
Q

Why is it important that courtship behaviour is species specific?

A
  • allows members of same species to recognise each other, preventing interbreeding and making reproduction more successful
33
Q

How have gene technologies changed the way genetic diversity is assessed?

A
  • allows us to measure genetic diversity directly
  • give more accurate estimates of genetic diversity within a population
  • allow genetic diversity of different species to be compared more easily
34
Q

What is meant by biodiversity?

A
  • variety of living organisms in an area
35
Q

What is a habitat?

A
  • place when an organism lives
36
Q

What is a community?

A
  • all the populations of different species in a habitat
37
Q

What is local biodiversity?

A
  • variety of different species living in small habitat that’s local to you
38
Q

What is global biodiversity?

A
  • variety of species on Earth
39
Q

What is species richness?

A
  • measure of number of different species in a community
40
Q

What is meant by index of diversity?

A
  • relationship between no. of species in a community and no. of of individuals in each species
41
Q

How do you calculate index of diversity?

A
  • d = N(N-1) / sum of n(n-1)
  • N is total no.of organisms of all species
  • n is total no.of organisms of one species
42
Q

What are common agricultural practices which reduce biodiversity?

A
  • woodland clearance
  • hedgerow removal
  • pesticides
  • herbicides
  • monoculture
43
Q

How does woodland clearance and hedgerow removal reduce biodiversity?

A
  • reduces number of trees and sometimes number of different tree species
  • destroys habitats, means that species will die or migrate to another area
44
Q

How do pesticides reduce biodiversity?

A
  • directly killing pests

- species who eat pests will lose food source

45
Q

How do herbicides reduce biodiversity?

A
  • reduces plant biodiversity and could reduce no. of organisms that feeds on weeds
46
Q

How does monoculture reduce biodiversity?

A
  • single type of plant reduces biodiversity directly

- will support fewer organisms as a habitat or food source

47
Q

What are examples of conservation schemes that protect biodiversity?

A
  • giving legal protection to endangered species
  • creating protected areas, restricts agricultural development
  • Environmental Stewardship Scheme encourages farmers to conserve biodiversity

A-Level Biology (19 decks)

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