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Biology Edexcel A Alevel > Topic 4 > Flashcards

Topic 4 Flashcards

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1
Q

What has happened to the variety of life over time?

A

It has grown extensive but is now being threatened by human activity

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2
Q

What are the 3 definitions of biodiversity

A

Variety of life
Variety of a species that belongs to each different group of organisms
The diversity within a species

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3
Q

what is the equation for the heterozygosity index

A

H= No. of heterozygotes / no. of individuals in a population

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4
Q

what is the equation for calculating the index of diversity

A

D= N(N-1)/En(n-1)

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5
Q

what does N stand for in the index of diversity

A

number of organisms of all species

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6
Q

what does n stand for in the index of diversity

A

total no of organisms of each species

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7
Q

what does E stand for in the index of diversity

A

sum of

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8
Q

what does niche mean

A

the way an organism exploits its environment

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9
Q

what is a behavioural adaptation?

A

the actions by an organism that hekp them to survive or reproduce

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10
Q

what is a physiological adaptation?

A

the internal workings of organisms that help them to survive and reproduce

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11
Q

What is an anatomical adaptation

A

the structures we can see when we can see when we observe or dissect an organism

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12
Q

what is evolution

A

the change in allele frequency in a population over time

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13
Q

why might natural selection cause evolution

A

genetic variation occurs through mutations becomes favourable more likely to survive and reproduce

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14
Q

what is the hardy weinberg equation

A

p^2 + 2pq + q^2=1

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15
Q

What does p^2 represent

A

homozygous dominant

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16
Q

What does 2pq represent?

A

heterozygous

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17
Q

What does q^2 represent?

A

homozygous recessive

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18
Q

what can reproductive isolation lead to?

A

accumulation of different genetic information in populations potentially leading to the formation of a new species

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19
Q

How are species categorised

A

binomial system

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20
Q

What is classification?

A

a means of organising variety of life based on relationships between organisms using differences and similarities in phenotype and genotype

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21
Q

what are the hierarchal groups

A

Kingdom Phylum Class Order Family Genus Species

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22
Q

What are the 3 domains?

A

Bacteria, Archaea, Eukarya

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23
Q

what are the two main differences between plant and animal cells

A

cell walls and chloroplast

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24
Q

where is starch stored

A

amyloplasts

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25
Q

what surround the vacuole

A

vacuolar membrane - tonoplast

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26
Q

what makes the cytoplasm in one cell continuous with the next

A

plasmodesmata

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27
Q

what is a pit

A

where the cell wall is thin as only the first layer of cellulose is deposited

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28
Q

what is the middle lamella

A

a layer that cements the primary cell walls together of adjoining cell walls

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29
Q

what is the difference between starch and cellulose

A

B-glucose and A-glucose

30
Q

what is the difference between A and B glucose

A

1,6 bonds make up starch and 1,4 glyosidic bonds make up cellulose

31
Q

what reaction forms between the -OH groups of starch and cellulose

A

condensation

32
Q

what bond forms between the -OH groups of starch and cellulose

A

glyosidic

33
Q

due to the ….. bonds in cellulose, it is unbranched/branched

A

1,4 bonds and unbranched

34
Q

what bonds form between cellulose chains

A

hydrogen bonds

35
Q

what do bundles of cellulose chains form

A

microfibrils

36
Q

what polysaccharides make cellulose a very strong structure

A

hemicelluloses and pectins

37
Q

what polysaccharide is very important in the makeup of the middle lamella

A

pectin

38
Q

what makes xylem so strong

A

lignin

39
Q

what makes the xylem cells dead

A

autolysis- tonoplast breaks down and enzymes break down cell contents

40
Q

what does xylem carry

A

water

41
Q

what does water diffuse out through

A

down a diffusion gradient

42
Q

how does water move through the xylem

A

a transpiration stream bound by cohesion tension theory

43
Q

how does cohesion tension theory work

A

H-bonds between water molecules strong cohesive forces water evaporates and pulled up

44
Q

what order do the 3 parts of the stem go in (outside first)

A

sclerenchyma, phloem and xylem

45
Q

what is the function of the sclerenchyma

A

support

46
Q

what is the function of the xylem

A

support and transportation of water and minerals

47
Q

what is the function of phloem

A

translocation of organic solutes

48
Q

what are the 3 properties of plant fibres that make them ideal for humans

A

Long thin Strong Flexible

49
Q

why do plants need nitrate ions

A

nitrate ions are needed to make amino acids- cell cytoplasm is largely made of protiens

50
Q

what do plants need calcium ions

A

calcium helps make the structure of the cell walls and permeability of the membrane

51
Q

why do plants need magnesium ions

A

to make chlorophyll (yellow without)

52
Q

what is it called when organic molecules move within the phloem

A

translocation

53
Q

what is the purpose of the companion cell

A

perform metabolic functions that maintain the sieve tube

54
Q

what is the difference between the sieve tube and companion cell

A

companion cell still has nucleus, mitochondria, ribosomes and rough ER unlike the sieve tube

55
Q

what are sinks

A

places where photosynthetic products are unloaded eg roots

56
Q

what are sources

A

places where photosynthetic products are gathered eg leaf

57
Q

how do roots help plants survive in the winter

A

starch stored in roots. When growth starts again in spring, starch is converted back to sugar

58
Q

which direction does xylem travel

A

upwards

59
Q

which direction does phloem travel

A

downwards

60
Q

what is a double blind trial

A

when both patient and doctors don’t know who has real drug

61
Q

what happens in phase of 1 testing?

A

different doses healthy volunteers

62
Q

what happens in phase 2 of testing?

A

volunteers with disease small group

63
Q

what happens in phase 3 of testing?

A

large group one group placebo and other drug

64
Q

what 5 factors effect bacterial growth rate

A

nutrients pH Temperature Sufficient oxygen no build up of toxic waste products

65
Q

what are 3 reasons why fossil fuels are not sustainable

A

increases CO2 levels oil reserves will runout eventually plastics generate non-biodegradable waste

66
Q

give 2 ways that genetic diversity can be lost

A

genetic drift and inbreeding depression

67
Q

what is genetic drift

A

the change in allele frequency over time

68
Q

What is inbreeding depression?

A

the accumulation of the homozygous recessive genotypes which have negative effects due to a small breeding pool

69
Q

how might studbooks effect the natural breeding pattern

A

poor breeders must be encouraged and good breeders must be limited

70
Q

how do seed banks make sure that germination is still viable? and what happens if its not?

A

they are tested every 10years and if viability is dropping they will be germinated and seeds recollected.

Biology Edexcel A Alevel (15 decks)

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