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A Level Biology > Topic 4 > Flashcards

Topic 4 Flashcards

1
Q

Give 3 differences between plant and animal cells

A

Plants contain chloroplasts

Plant cells have a vacuole

Plants have a rigid cells wall

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2
Q

What are amyloplasts

A

They are in the cytoplasm and it’s where starch is found in storage vacuoles

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3
Q

What is parenchyma

A

Plant tissue that help in supporting plants as well as filling in spaces between speculated tissue,they may have specialised functions

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4
Q

What is cellulose

A

A polysaccharide that give cell walls there strength

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5
Q

What is cellouse made out of and how is it formed

A

It’s made out of beta glucose as a result of condensation reactions and it contains 1,4 glycosidic bonds

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6
Q

What’s the difference between beta and alpha glucose

A

The OH group are on opposite sides on the first carbon

Ie beta high and alpha low

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7
Q

What do cellulose form bundles of

A

They form microfibriles which is when cellouse chains develop hydrogen bonds between them

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8
Q

State the structure of microfibres and what holds them together

A

They are wound in helical arrangement around a cell wall and a polysaccharide glue sticks it together parallel chains

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9
Q

What are the two branches polysaccharide that hold microfibrils together called

A

Pectins and hemicellolses

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10
Q

What are plasmodesmata

A

They are fluid channels that cross cell walls which enable the transport of substances and communication between cells (enable cytosplasm of cells to link

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11
Q

What is the pit in a cell wall

A

The thin part within a cell wall enables transport of substances between cells

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12
Q

What are the 3 specialised cells for transport in a cell

A

Xylem vessels
Sclenrencyma fibres
Phloem sieve tube cells

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13
Q

What are xylem vessels

A

They form tubes that aid in transporting water and minerals and they stiffen cell walls

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14
Q

What are sclerencyma fibres

A

They provide support for the plant as they stiffen cell walls

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15
Q

What are phloem sieve tubes

A

They form lung tubes that aid in transportation of sugars and amino acids and organic solute

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16
Q

What about the cell walls of xylem vessels enables them to carry water

A

They are water proof which allows them to carry water

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17
Q

How do cell walls of xylem vessels become water proof

A

The plant produces lignin which impregnate the cell wall making it water proof

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18
Q

What is autolysis

A

The action of enzymes which means they break down cell organelles,cytoplasm and cSM and its leads to dead empty cells forming xylem vessels

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19
Q

What is transpiration

A

The evaporation of water from the surface of leaves

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20
Q

How is water lost form leaves replaced

A

By xylem vessels carrying water from the roots

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21
Q

How do xylem vessels carry water up through the plant

A

They contain minute channels that act like capillaries and by capillary action they draw to water by surface tension between it and water and it’s a continuous process

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22
Q

What is the transpiration stream

A

The process of s steam of water passing through a plant

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23
Q

What is the middle lamella

A

It sticks adjacent plant cells together which gives them stability

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24
Q

What is the function of vacuole and tonoplast

A

The vacuole contains cell sap which keeps the cells turgid

Tonoplast controls what enters and leaves the vacuole

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25
Q

When being carried up a plant why doesn’t water break down

A

They have cohesive forces between them due to hydrogen bonding

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26
Q

What is cohesion tension theory

A

The concept of water movement that it’s pulled under tension and molecules are linked cohesively

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27
Q

What are nitirate,magnesium and calcium ions used for in a plant

A

Nitrate ions are used to make amino acids which enable the plant to grow

Magnesium ions are needed to make chlorophyll which allows the plant to photosynthesis

Calcium ions are needed in the plant cell wall to allow it to grow

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28
Q

Give 4 properties of water

A

Solvent
Thermal
Density and freezing cohesive

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29
Q

How is water a solvent and why is this useful In a plant

A

It can dissolve substances as a result of hydrogen bonding

Means substances can be easily transported around the xylem

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30
Q

What thermal properties do plants have

A

The strength of hydrogen mean its difficult to raise temperate of water

It enables plants to avoid rapid changes in internal temperatures

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31
Q

Why is frozen water less dense than liquid

A

Frozen water expands and a lot of hydrogen bonds form between these molecules these bonds hold water molecules further apart than in liquid water making water less dense

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32
Q

What are sieve plates

A

They are at the end of sieve tubes and they have holes in them

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33
Q

What are phloem sieve tubes

A

They are mostly made of lumen and they remain alive

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34
Q

What is translocation

A

The transport of organic molecules within in the phloem which requires photosynthesis

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35
Q

What are companion cells and what’s there role

A

They are along side the sieve tubes and they perform the metabolic functions that maintain the sieve tube and they contain mitochondria ribosomes and RER

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36
Q

What are phloem parenchyma cells

A

They aid in transporting sugars amino acids and other organic substances
Into the sieve tubes

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37
Q

How are parenchyma transfer cells adapted for their functions

A

They have lots of plasmodesmsts that link their cytoplasm with adjacent cells

They have increased surface area

They have lots of mitochondria that provides energy to load solutes into sieve tube

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38
Q

What is the method of transport in phloem sieve tubes

A

Mass transport

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39
Q

Describe stages of transport in phloem sieve tubes

A

Phloem parenchyma transfer cells load solutes into the phloem,this means by osmosis water to be drawn out into sieve tube from xylem cells

The hydrostatic pressure increase inside the lumen of sieve tube at the loading end

At sinks the solutes are unloaded and in the sieve tube the solute concentration is lowered

The hydrostatic pressure is lowered due to water being moved back into xylem by osmosis

Mass flow occurs as a result of the pressure difference at the loading and unloading sites that

40
Q

What are sinks in a plant

A

Parts of the plant where sugar is used not produced

41
Q

What features of plant fibres enable it to be used for things such as clothing

A

Strong
Flexible
Long thin

42
Q

Describe ways in which plant fibres can be extracted

A

It can be done mechanically which involves pulling them out called retting

43
Q

What chemical defences do plants produce which prevents attacks

A

They produce chemicals that may be toxic or distasteful

Have a bitter taste when eaten which may kill the predator

44
Q

State the way bacteria grow

A

By binary fission which is an asexual process in which the circular DNA will replicate and new cell content is synthesised before a cell wall forms and divides the cell into equal parts

45
Q

State the ideal conditions affecting the rate of growth in bacteria

A

Optimum temperature and ph

No bulid up of toxic products.

Sufficient oxygen

46
Q

On a graph state each stage in bacteria growth and what occurs in each stage

A

Lag phase-when cells are adjusting to their conditions

Exponential growth-in their current conditions the cells are starting to divide exponentially at the fastest rate possible

Stationary phase-growth is limited e due to change in conditions

Death phase-the amount of cell firing is greater than amount of cells being formed

47
Q

State the 5 stages of drug testing

A

Pre clinical

Clinical

Licensing trials

48
Q

What happens in pre clinical trials

A

Thousands of chemicals are used in animal and human tissue cells

They are used to asses safety and to see if the compound is effective against the target disease

(Of

49
Q

What happens in each of the clinical trials

A

Clinical trial phase 1- the drug is given to a number of volunteers and they are given different doses the volunteers are are healthy it’s done to see if the compound is absorbed,distributed,metabolised by the body properly

Clinical trials phase 2-a group of between 100-300 people with the disease are treated with the drug to see its effectiveness

Clinical trial phase 3 a large group of volunteers 1000-3000 are selected and divided into 2 groups one group is given the actually drug while the other is given a placebo it’s double blind

The compound being investigated is effective if it shows higher improvement in results than the placebo

50
Q

What is a placebo

A

An inactive form of the drug/dummy

51
Q

What is meant by drug trials being double blind

A

That neither patient nor doctor is aware of who has the actually drug or placebo

52
Q

What is speciation

A

The formation of new species from a group of previously interbreeding organisms that had been geographically isolated

53
Q

Describe the stages in speciation

A

A geographical feature like a river/mountain separated a group of individuals from the rest of the population meaning they can’t breed

As a result of different selection pressure and random mutation( which cause change in allele frequency the population become less like on another

If the differences are big enough natural selection occurs in which the two populations will not be able to interbreed

As a result of not being able to interbreed with one another they are considered two different species( they can’t produce fertile offspring)

This leads to speciation

54
Q

What is biodiversity

A

The variety of species that belong to different groups of organisms and that’s there’s is genetic diversity in their species

55
Q

What is the binomial system

A

The system of coming up with Latin names from groups of organisms

56
Q

What is the genus

A

The first part of the name given to species

57
Q

What is meant by gene pool

A

It consists of all the alleles present within a population

58
Q

What is genetic diversity

A

Measuring of natural variation within the genetic code of a species or population

59
Q

What is the hardy Weinberg equation used

A

Measuring allele frequency

60
Q

Give the hardy Weinberg equation and state what each letter represents

A

P2+2PQ+Q2

P2- frequency of homozygous dominant individuals

2PQ- frequency of heterozygous individuals

Q2-frequency of homozygous recessive individuals

61
Q

What is taxonomy

A

The placing of organisms into groups based on the features they share

62
Q

What are the 3 domains

A

Archea
Eurkaryote
Bacteria

63
Q

What is molecular phylogeny

A

Looks at DNA molecules and proteins to see how closely organisms are

similar molecules means they are closely related share same bases

64
Q

How is scientific work like woeses varified

A

Conferences- in which scientists go and discus there theories to other
scientists

Peer review in which their work is examined and checked by other scientists for validity

Scientific journals in which they publish their work and any experiments they conducted

65
Q

What are sources of genetic variation

A

Crossing over

Muatations

Independent assortment

66
Q

What are the 3 ways of measuring biodiversity and state the difference

A

Using the biodiversity index
Species richness
Species eveness

Species richness is counting the number of species present in a given area

Species eveness- is a comparison of the size of populations of different species in a particular area

67
Q

How is genetic diversity measured

A

Number of heterozygous/

Number of individual in a population

68
Q

What are the aims of captive breeding programmes

A

Animals to be reintroduced into the wild

Exchange animals and gamates between zoos

For genetic diversity to be maintained in a captive population

Allowing unrealated mates to mate using stud books

Increasing the number of individuals of a species of numbers are low

69
Q

What is genetic drift

A

This is the change in allele frequency some alleles aren’t passed onto offspring

70
Q

How does inbreeding depression occur and why is it an issue

A

It results from inbreeding among closely related individuals meaning homozygous genotype rise they are passed into offspring who are less able to survive as a result

71
Q

State the ways genetic diversity is maintained in zoos

A

Use of stud books

IVF/new gamates

Exchange animals,gamates between zoos

Allow untealated mates to mate

72
Q

What does the millennium seed bank do

A

It aims to maintain and conserve seed samples from threaten plant species

73
Q

State the ways seeds are stored

A

They are kept dry in cool conditions to stop them freezing

They are germinated on an agar plate to see if they survive in storage conditions

74
Q

What happens if germination is below a certain point

A

The seeds will be grown to collect new seed samples that are placed back in storage

75
Q

How did withering test the for the correct dosage for dropsy

A

He used trial and error in which he would gradually increase dosage until side effects showers then would reduce it to get more effective dose

76
Q

What is a species

A

A group of organisms that Can interbreed to produce fertile offspring

77
Q

What is a habitat

A

A place in which an organisms lived it has a certain set of conditions that enable an organism to thrive in that area

78
Q

What is a population

A

A group of interbreeding individuals of the same species found in a area

79
Q

What is a community

A

Various populations of organisms within a habitat

80
Q

What is a niche

A

The way an organism exploits its environment

81
Q

What are adaptations and give the 3 types of adapatations

A

They are features that enable an organism to survive

Behavioural

Anatomical

Physiological

82
Q

What is meant by behavioural adaptations

A

Any action by an organisms that enables to survive and reproduce

Ie plants turn their leaves towards to the sun to maximise

83
Q

What are physiological adaptations

A

Process inside an organisms body the increase its chance of survival

84
Q

What are anatomical adaptations

A

Structural features in an organism and that increase its chance of survival

85
Q

What is meant by co adaptation

A

When two organisms become dependent on each other as a result of becoming closely adapated

86
Q

What is natural selection

A

The survival of the fittest and the organisms that are well adapted to their environments are more likely to survive and reproduce

87
Q

What is evolution

A

A change in allele frequency over time in a population

88
Q

State the stages of natural selection

A

As a result of a mutation alleles are created in their are some genetic variation

Change in selection pressures acting on the population occur due to change in environment (create struggle for survival)

An allele that had no previous advantages becomes favourable

Organisms that have that allele as a result are likely to survive and reproduce and pass it on organisms with out the allele die out

The offspring they produce are more likely to reproduce as these alleles become more common in the population

89
Q

Why are secs stored in dry and cold conditions

A

This is done to prevent enzyme activity

To prevent germination of seeds as well as them decay

90
Q

State how in terms of function xylem and sclerenchyma are similar and different

A

They both provide support for the plant with lignin

They are both waterproof as a result

Differences:
Xylem transports water and inorganic molecules through the plant under tension

While scelrencyma doesn’t

91
Q

State how terms of function phloem and xylem are similar and how they differ

A

They both transport substances around the plant

Differences
Phloem transports in both directions
Xylem transports in one direction

92
Q

State how in terms of structure xylem,phloem and scelrencyma differ

A

All contain cellouse

Xylem and phloem contain pits while scelrencyma don’t

Phloem and scelrencyma have end walls xylem don’t

Phloem doesn’t contain lignin while the others do

Phloem is alive the others are dead it has companion cells the others don’t

93
Q

Give two reasons why plant fibres are useful to humans

A

The arrangements of cellulose microfibrils in the cell wall

Secondary thickening of cell walls

94
Q

What does the hardy eirinberg equation predict

A

That allele frequency won’t change over time

95
Q

What is secondary cell wall thickening and why is it benefitcal

A

It’s when xylem and scelrencyma produce a secondary cell wall between the normal cell wall and cell membrane

It’s thicker and contains more lignin and it makes plant fibres stronger

A Level Biology (9 decks)

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