A Biology Unit 2 Model Answers

Question 1

How have large organisms evolved to be efficient at diffusion?

Answer 1

A flattened shape
So that no cell is ever far from the surface
Specialised exchange surfaces with large areas
To increase the surface area to volume ratio
E.g. Lung or gills

Question 2

Vein structure and functions

Answer 2

Muscle layer is thin as their constriction and dilation cannot control blood flow

Elastic layer is thin as pressure is low

Wall thickness is small as pressure is low

Valves present to prevent back flow

Question 3

What are the features of specialised exchange surfaces?

Answer 3

Large surface area to volume ratio
Thin so shorter diffusion pathway
Partially permeable
Movement of environmental medium to maintain a concentration gradient
Movement of internal medium to maintain a concentration gradient

Question 4

How do respiratory gases move in and out of the tracheal system?

Answer 4

Down a concentration gradient (air moving in has high oxygen content, at the tissues the oxygen content is low as cells are using up oxygen in respiration)

Ventilation by the movement of muscles in the abdomen creates mass air movement

Question 5

Why fish gils are efficient at diffusion of oxygen

Answer 5

Numerous gill filaments with numerous lamallae
To increase surface area
Thin / squamous epithelium cells of gill and capillaries
So short diffusion pathway
Gills are well supplied with numerous small capillaries
This also increases the surface area
Steep concentration gradient maintained by countercurrent flow
Oxygen diffuses into blood along the whole length of the gill
Constant circulation of blood always takes blood high in oxygen away
Constant ventilation always increases oxygen content at gas exchange surfaces

Question 6

What else happens when spiracles close?

Answer 6

Conserve water

Question 7

Due to insects not having a blood system what happens to the oxygen?

Answer 7

The oxygen diffuses straight into the tissues from the tracheae

Question 8

What causes the spiracles to open?

Answer 8

The build up of carbon dioxide

Question 9

Gas exchange in plants

Answer 9

During respiration oxygen diffuses
Into the plant when the stomata are open
Carbon dioxide diffuses out of the plant
During photosynthesis carbon dioxide diffuses
Into the plant and oxygen diffuse out
In the mesophyll layer the plant has numerous interconnecting air spaces to aid gaseous diffusion
Gases do not have to be dissolved in water for diffusion through the stomata
Stomata can close to conserve water
When this happens no gas exchange can occur through the stomata

Question 10

What is the relationship between an organisms size and its surface are to volume ratio?

Answer 10

The bigger the organism, the smaller the ratio therefore the slower the rate of diffusion across the exchange surface

Question 11

How insects are adapted to conserve water?

Answer 11

Small surface area to volume ratio
Waterproof coverings on body surfaces
Ability to close spiracles

Question 12

How insects are adapted to increase gas exchange

Answer 12

Numerous spiracles to increase surface area

Sort diffusion pathway as air in tracheoles connects direct to tissues (no blood)

Many numerous tracheoles to increase surface area

Concentration gradient maintained by ventilation and the removal of oxygen by respiring tissues

Question 13

Gas exchange in fish

Answer 13

Water enters through the mouth
And is forced across the gill filaments
The water flows on an opposite direction to the blood in the gill lamallae- this is countercurrent flow
This produces a concentration gradient
To promote the diffusion if oxygen from the water into the blood along the whole length of the gill
Water passes out through the operculum

Question 14

How plants are adapted to increase gas exchange

Answer 14

Numerous stomata increase surface area
Diffusion takes place in gas phase
No living cell is far from external air ( long, thin, flat shape of leaves)
Air spaces in spongy mesophyll
Sort diffusion pathway
Concentration gradient maintained by photosynthesis and respiration

Question 15

Structure of haemoglobin

Answer 15

Primary structure consists of 4 polypeptide chains built up of amino acids
Secondary structure consists of these chains coiled into alpha helices connected with hydrogen bonds
Tertiary structure provides a specific globular shape with further bonding
Quaternary structure - 4 chains are linked together to form a spherical molecule
Each polypeptide is associated with a haem group containing iron (II) ions

Question 16

Oxygen dissociation curves

Answer 16

Further to the left, greater affinity for oxygen ( takes it up readily but releases it less readily)

Further to the right; lower affinity for oxygen (takes up less readily but releases it more easily)

Question 17

Low oxygen environments include…

Answer 17

High altitude
Underwater
Burrows
In the uterus 
This also applies to myoglobin which has a high affinity for oxygen that haemoglobin does

Question 18

Effects of carbon dioxide concentration

Answer 18

Greater concentration of carbon dioxide, the more readily haemoglobin releases its oxygen (Bohr effect)

Oxygen dissociation curve shifts to the right

Question 19

Explain why haemoglobin unloads oxygen

Answer 19

Carbon dioxide level increase

pH becomes lower so is more acidic

Haemoglobin changes shape ( ionic bonds are changed

More oxygen is dissociated

Question 20

Loading, transport and unloading of oxygen

Answer 20

Carbon dioxide is constantly removed at the gas exchange surfaces
pH is higher due to low level of carbon dioxide
Haemoglobin loads oxygen more readily
Haemoglobin has a high affinity in this state so does not release oxygen during transport
Carbon dioxide is acidic in solution so pH is lower
Shape of haemoglobin changes into one with a lower affinity for oxygen
Haemoglobin releases its oxygen into respiring tissue

Question 21

Roles of haemoglobin

Answer 21

Readily associated with oxygen at surface where gas exchange takes place as it has a high affinity here

Readily dissociate from oxygen at respiring tissues as it has a lower affinity here

Question 22

Explain the advantage of the curve being to the left in an organism in a low oxygen environment

Answer 22

High percentage saturation of haemoglobin with oxygen

At low ppO2⃣

Question 23

Explain the advantage of the curve being to the right in an organism with a high level of activity/ high metabolic rate/ high exercise

Answer 23

Haemoglobin has a lower affinity for oxygen

So releases oxygen more readily to respiring tissue

Question 24

Explain how root pressure and cohesion-tension are responsible for the movement of water in xylem vessels

Answer 24

Salts are actively transported into the xylem
This causes the xylem to have a more negative water potential
Water enters the xylem by osmosis
Evaporation of water from the stomata causes transpiration pull
This lowers the water potential of the mesophyll
Water molecules cohere due to hydrogen bonding
And adhere to xylem walls
This pulls water up the xylem

Question 25

Why do cells have to have oxygen to respire

Answer 25

To produce ATP to provide energy for processes such as active transport, muscle contraction etc The most active cells will respire the most and therefore need the most oxygen

Question 26

Arteriole structure and function

Answer 26

Structure - thick muscle layer which contracts and relaxes Function - reduces / controls blood pressure and flow into the capillaries

Question 27

Artery structure and function

Answer 27

Structure - thick elastic layer, which stretches and recoils and narrows lumen Function- maintains a which blood pressure which is created by heart contraction Structure - thick walls Functions - prevents damage caused by high pressure

Question 28

Gas exchange in insects

Answer 28

Air enters through the spiracles And passes along the tracheae There is a diffusion gradient in the trachea Causing oxygen to diffuse into cells Ventilation ( movement of muscles ) replaces air in the tracheae maintaining a concentration gradient Spiracles are able to close

Question 29

Capillaries structure and function

Answer 29

Ficks law Rate of diffusion ( oxygen, carbon dioxide and glucose ) is increases Numerous and branched So surface area is large Thin endothelium So diffusion pathway is short Constant circulation of blood maintains a steep concentration gradient Red blood cell is approximately same size as capillary lumen so passage of blood is slow Allows more time for diffusion to occur

Question 30

Formation, reabsorption and drainage of tissue fluid

Answer 30

High hydrostatic pressure at the arteriole end of the capillary Forces water out through the thin capillary walls into tissue Plasma proteins are too large too pass through the capillary wall So they become more concentrated in the blood This makes the water potential inside the capillary more negative Compared to the less negative tissues Water moves back into the capillary by osmosis Along a water potential gradient The hydrostatic force outside the capillary also helps to push water back in

Question 31

Why a person experiencing high blood pressure may get swelling?

Answer 31

Hydrostatic pressure of the blood is high so more water is forced out of arteriole end of capillary Some tissue fluid accumulates as not all of it can be reabsorbed

Question 32

Why a starving person may get swelling

Answer 32

Fewer plasma proteins in the blood So concentration gradient is not as steep and inside of capillary is less negative Therefore less water can be reabsorb into the capillary by osmosis

Question 33

The body makes more tissue fluid over a day that it can reabsorb. What happens to the excess

Answer 33

The excess is drained by the lymph vessels Accumulation of fluid may lead to tissue swelling ( oedema )

Question 34

Gravity pulls tissue fluid down so it tends to accumulate in ankles and feet then...

Answer 34

Feet have very few lymph vessels Blockages of lymph vessels can result form some bacterial infections and this would also lead to excess tissue fluid and swelling There are some metabolic diseases which could lead to low levels of plasma proteins Contraction of body muscles surrounding the lymph vessels squeeze the lymph back to the chest where it can be drained and eventually excreted

Question 35

Features of binomial system

Answer 35

Universal system Generic names indicates the genus the organism belongs to Specific names denotes the particular species

Question 36

Explain how active transport of mineral ions into xylem vessels results in water entering and being moved up the tissue

Answer 36

The water potential in the xylem is made more negative By the active transport of ions into the xylem This establishes a water potential gradient So water moves from an area with less negative water potential to an area with a mo negative water potential By osmosis This increases pressure in the xylem

Question 37

Using Fick's law to explain how the structural adaptation of xerophytes reduce the rate of water diffusion

Answer 37

Ficks law states that the rate of diffusion is proportional to the surface area times the concentration gradient divided by the length of the diffusion pathway Xerophytes have a reduced number of stomata This decreases the surface area These plants also have a waxy cuticle This increases the length of the diffusion pathway These features mean that the water potential gradient is reduced So less water is lost it the atmosphere

Question 38

Use cohesion-tension theory to explain why the presence of an air bubble in a xylem vessel blacks the movement of water

Answer 38

``` The presence of the air bubble breaks the continuous column of water And prevents cohesion of water molecules Water in the xylem is under tension Due to transpiration from leaves The air bubble inhibits this tension ```

Question 39

Factors affecting transpiration

Answer 39

Light - stomata open in the light for photosynthesis therefore an increase in light intensity increases transpiration rate Temperature - increase in temperature increases kinetic energy and decreases the water potential of the air therefore increases transpiration rate Humidity - increase of water molecules in air decreases the water potential gradient therefore an increase in humidity decreases transpiration rate Air movement - an increase in air movement increases the rate of diffusion if water molecules out of the stomata and therefore increases transpiration rate

Question 40

Explain how after enters a plant root from the soil and travels through to the endodermis

Answer 40

Water enter root hair cells By osmosis As the active uptake of ions into the roots create a water potential gradient I.e. the root has a moe negative water potential Water moves through the root cortex Via the cell walls - the apoplastic pathway or via the cell cytoplasm - the symplastic pathway

Question 41

What can a potometer for?

Answer 41

To calculate rate of transpiration by measuring the uptake of water on a mm or cm scale over a set amount of time

Question 42

Why cut the shoot and connect to the potometer under the water

Answer 42

To prevent air entering, to maintain a continuous water column

Question 43

What measurements would have taken in order to calculate rate of water uptake in cm^3 min^-1

Answer 43

Time Distance moved in cm Radius/ diameter of capillary tube

Question 44

Explain how evaporation of water from the leaves causes the water to move upwards

Answer 44

The water potential in the mesophyll becomes more negative Water moves out of the xylem by osmosis And is evaporated from the open stomata This creates a transpiration pull Caused by cohesion of the water molecules to each other And adhesion to the xylem wall

Question 45

Founder effect

Answer 45

Occurs when a few individuals from a population colonise a new region Alleles carried by the individuals may not be representative of the original population Therefore they show less genetic diversity The few individuals then give rise to a genetically different population

Question 46

Limiting water loss in xerophytes

Answer 46

Thick waxy cuticle to increase diffusion pathway Rolled up leaves to decrease surface area for diffusion Hairy leaves to trap a layer of moisture and decrease water potential gradient Sunken stomata to trap moist air and reduce water potential gradient Reduced surface area to volume ratio

Question 47

Describe the structure if cellulose

Answer 47

Made of molecules of beta glucose Joined together by condensation reactions between hydroxyl groups Glycosidic bonds form Polymer chains are unbranched and join together by numerous hydrogen bond cross bridges Molecules are grouped together into microfibrils The numerous hydrogen bonds give cellulose high tensile strength

Question 48

Functions of cellulose cell wall

Answer 48

To provide mechanical strength to prevent cell bursting under the pressure created by osmotic entry of water To give strength to the plant for support To allow water to pass along it and contribute to the movement of water through the plant

Question 49

Comparison of starch, cellulose and glycogen

Answer 49

Starch and glycogen consists of chains of alpha glucose Cellulose consists of chains of beta glucose All molecules have glucose joined by glycosidic bonds in a condensation reaction Starch is made up of C1-4 linkages and C1-6 linkages Glycogen has more 1-6 linkages that starch and therefore is more branched Cellulose forms microfibrils joined by hydrogen bonds

Question 50

Hierarchy of classification (taxonomy)

Answer 50

``` Kingdom | Phylum | Class | Order | Family | Genus | Species ```

Question 51

Roles of starch

Answer 51

Insoluble therefore does not affect osmotic movement of water in and out of cells Insoluble so does not easily diffuse out of cells - good for storage Compact so lots can be stored in a small place When hydrolysed it forms alpha glucose which is easily transported

Question 52

What do members of a species have in common

Answer 52

They are similar to one another but different from members of other species They are capable of breeding to produce living, fertile offspring

Question 53

The structure of cellulose is related to its role in plant cell walls. Explain how

Answer 53

Long, straight (unbranched) chains of glucose Joined by hydrogen bonds To form microfibrils Which provide rigidity / strength / support

Question 54

Explain what is meant by hierarchy

Answer 54

Groups within larger groups | No overlap

Question 55

What is phylogenetic tree

Answer 55

A diagram showing evolutionary relationships between organisms

Question 56

Causes of variation

Answer 56

Random mutations in DNA due to a chance event producing a useful protein Meiosis (crossing over and independent assortment) Fusion of gametes during sexual reproduction

Question 57

Removal of chance from sampling procedures

Answer 57

Use a large sample size, as it is more representative Statistically analyse the data collected You would also need to remove bias by conducting a random sample Also need to repeat to achieve concordancy which make your results more reliable this then relates to standard deviation

Question 58

Standard deviation

Answer 58

The standard deviation, the greater the variation about the mean Results at more widespread and so are less reliable

Question 59

What are the reasons for the occurrence of resistance

Answer 59

Antibiotics are used to treat minor ailments with short lived symptoms Antibiotics are sometimes used to treat secondary infections associated with viral disease Patients do not always complete the full course Patients stockpile used antibiotics from previous infections and may self proscribe Doctors accept patients demands Antibiotics are used to treat minor ailment in domestic animals Antibiotics are used to increase productivity in farm animals or can be used to prevent disease In intensive conditions

Question 60

Why might the rate of water uptake NOT be equivalent to the rate of transpiration

Answer 60

Water used in photosynthesis Water produced by respiration May be used in tissue to support the stem

Question 61

Genetic bottlenecks

Answer 61

A chance event e.g. Natural disaster, may cause a population to drop in number dramatically The survivors posses a smaller variety of alleles than the original population So the genetic diversity is less As the individual breeds the genetic diversity of the new population is restricted

Question 62

Selective breeding

Answer 62

Individuals with desired characteristics are selected and used to parents the next generation with the same characteristics Offspring that do not exhibit the desired characteristics are killed or prevented from breeding Alleles for unwanted characteristics are breed out of the population This leads to reduced genetic diversity

Question 63

How are proteins compared using immunology

Answer 63

Serum protein from species A is injected into species B Species B produces antibodies specific to the antigen sites on the protein from species A Serum is extracted from species B (contains antibodies specific to the antigens from species A) Serum from species B is mixed with serum from the blood of a third species C Antibodies respond to their corresponding antigens on the protein in the serum of species C A precipitate forms - the greater the number of similar antigens, the more precipitate is formed and the more closely the species are related

Question 64

Describe how comparisons of biological molecules in 2 species could be used to find out if they are closely related

Answer 64

Compare DNA sequence of bases DNA hybridisation Break hydrogen bonds Mix DNA strands of the two species Temperature required to separate indicates relationship (higher temperature means that they are more closely related) Compare protein Primary structure / sequence of amino acids Inject serum from species A into an animal Obtain antibodies from this animal Add antibodies to species B Amount of precipitate indicates a relationship ( more precipitate means they are more closely related)

Question 65

How do mutations result in different characteristics?

Answer 65

Mutations change the base sequence of DNA This may change the sequence of triplets (codons) That code for amino acids As a result the amino acid sequence may change Enoch could affect the structure and function of the protein If this protein is an enzyme then the change may affect the metabolism of the organism and therefore other characteristic

Question 66

Why might comparing the base sequence of a gene provide more information than comparing the amino acid sequence for which the gene codes

Answer 66

Because of the triplet code there are more bases than amino acids There may be introns - areas of non coding DNA same amino acids may be coded for by more than be triplet I.e. code is degenerate

Question 67

What is DNA hybridisation

Answer 67

DNA from each species is extracted, purified and cut into short sections DNA from one species is radioactivity labeled and to mixed with the unlabelled DNA from the other species Mixture is heated to separate the strands then cooled to allow them to recombine Some of the newly formed double strands are made up of one strand from each species (these are hybrids and can be identified because 50% of their DNA is radioactively labeled) Hybrid strands are separated and the temperature is increased in stages The degree to which the two strands are linked is measured If the two species are closely related the will be many complementary bases and therefore many hydrogen bonds (the greater the number of hydrogen bonds, the stronger the hybrid will be) The stronger the hybrid, the higher the temperature needed to separate them The higher the temperature at which the hybrid splits, the more closely the two species are related

Question 68

Why is courtship behaviour necessary

Answer 68

To recognise members of their own species ( to produce fertile offspring) To identify a mate that is capable of breeding and recognition of opposite gender To form a pair bond leading to successful raising of offspring To synchronise mating so it takes place with maximum probability of the sperm and egg meeting ( indicate of fertility) Stimulate release of gametes

Question 69

What is the difference between horizontal and vertical gene transmission

Answer 69

Vertical is where genes are passes from parents to offspring within the same species Horizontal is where genes are passed from one species to another

Question 70

How do antibiotics work

Answer 70

Some antibiotics prevent the formation of the bacterial cell wall By inhibiting the synthesis of peptide cross linkages Water enters the bacterium by osmosis So the bacterium swells and cell lysis occurs

Question 71

What are the implications of antibiotics resistance

Answer 71

TB ( people who have TB may have to take a long course of antibiotics but there is a danger that they will stop taking them when they start to feel better - this means the most resistant strains may not be killed and so may be passed on. Hence a cocktail of 4 drugs is usually used) MRSA ( a strain of the Staphylococcus bacterium that is resistant to one or more antibiotics - is a danger to vulnerable people, transmission higher in crowded conditions e.g. Hospitals, resistant strains develop more easily in hospitals where lots of antibiotics are used)

Question 72

How do bacteria become resistant to penicillin

Answer 72

A chance mutation results in the production of penicillinase This enzyme is able to prevent the breakdown of cell walls by penicillin by destroying the penicillin Therefore the enzyme was able to prevent osmotic lysis

Question 73

What is species diversity?

Answer 73

Comprised of The number of different species in a given area The proportion of the community that is made up of an individual species

Question 74

What is biodiversity?

Answer 74

Comprised of Species diversity - different number of species and number of individual of each species with a community Genetic diversity - variety of genes possessed b the individuals that make up one species Ecosystem diversity - range of different habitats within a particular area

Question 75

How genes transfer genes by conjugation

Answer 75

One bacterium produces a thin protection that forms a conjugation tube when it meets another cell Donor cell replicated its plasmid Circular DNA is broken into a linear strand Linear strand passes down the conjugation tube to the other cell Recipient cell acquires genes from the donor and therefore new characteristics

Question 76

Impact of deforestation

Answer 76

This is the permanent clearing of forests and the conversion of land to other uses e.g. Grazing This reduced species diversity

Question 77

Impacts of agriculture

Answer 77

Farmers select species for qualities that make them more productive Number of species and genetic variety are reduced Pesticides are used to exclude any species that compete with the desired species for light, water, food and mineral ions Species diversity index is low

Question 78

what is the difference between a nucleotide and nucleic acid? (2)

Answer 78

A nucleotide is a monomer | Nucleic acid is a polymer

Question 79

Replication of DNA (4)

Answer 79

Double helix unzips Catalysed by helicase Hydrogen bonds break Free DNA nucleotides in the nucleus complementary base pair with exposed bases on both strands DNA polymerase joins nucleotides together on new strands (catalyse formation of ester bonds) Results in the formation of identical strands

Question 80

Key features of DNA

Answer 80

Stable so can be passed on from generation to generation Hydrogen bonds between strands are easily broken for DNA replication Large so can carry a lot of genetic information Base pairs are contained within the helix and are protected from corruption by the strong sugar phosphate backbone Complementary base pairs allow the synthesis of an identical daughter molecule

Question 81

Important features of the genetic code (4)

Answer 81

It is non overlapping (specific start and stop codons) It is degenerate (some amino acids are coded for by more than one codon) It is read in only one direction It is universal - the same codes apply to all organism

Question 82

Definition of a gene (1)

Answer 82

A section of double stranded DNA coding for a single polypeptide

Question 83

What does semiconservative replication means? (3)

Answer 83

Two new molecules are formed which are exact copies of the original One of the chains in each new molecule was present in the original molecule The other chain is newly synthesised from free nucleotide

Question 84

Definition of an allele

Answer 84

One alternative form of a gene

Question 85

Explain why it may be more useful to calculate index of diversity than to record only the number of species present

Answer 85

Measure the number of individuals of each species and the number of species Some species may be present but only in small numbers

Question 86

Definition of a triplet code

Answer 86

Three bases in a particular sequence code for one amino acid

Question 87

What are non coding sections of DNA called?

Answer 87

Introns

Question 88

Relationship between DNA and protein

Answer 88

DNA has a specific sequence of bases Arranged into specific codons (triplet) Each codon codes for one amino acid The ribosome reads the code and arranges the amino acids in the correct order (determined by the DNA sequence) Peptide bonds form between amino acids making a polypeptide chain This is then folded to make a protein with specific tertiary structure

Question 89

If you are given the number of amino acid and asked to calculate the minimum number of DNA bases needed to calculate the minimum number of DNA bases what do you do?

Answer 89

X the number of amino acids by 3

Question 90

Definition of a locus

Answer 90

The position of a particular allele on a chromosome

Question 91

How a mutation may result in a non functional protein (5)

Answer 91

DNA bases sequence changes Codons change So amino acid sequence changes Secondary structure changes - bonds form in different places Tertiary structure changes, as folding pattern has changed

Question 92

Chromosome movement during meiosis

Answer 92

In first division, homologous chromosomes pair up Equivalent portions of chromatids may cross over Homologous pairs separate during meiosis 1, with one chromosome from each pair going into the two daughter cells This happens randomly and is called independent segregation Chromatids move apart during anaphase and of the second meiotic division After the second division, four haploid daughter cells are formed with half the amount of DNA/ chromosomes as the original parent cell

Question 93

How does DNA control the phenotype of an organism?(3)

Answer 93

DNA control the production of enzymes Enzymes control metabolic pathways Metabolic pathways influence the phenotype of an organism

Question 94

Stages of cell division

Answer 94

Interphase - cells grows more cytoplasm; DNA replication; organelle replication; build up of ATP (G1, S, G2) Prophase - chromosomes condense (shorter and fatter); nuclear envelope disappears; spindle (protein fibre) forms in the cell Metaphase - spindle fibres attach to chromosomes at centromeres; chromosomes line up on equator of spindle Anaphase - spindle fibres contract (shorten) and pull sister chromatids towards opposite ends of the spindle Telophase - new nuclear envelope forms; chromosomes uncoil Cytokinesis - cytoplasm divides and new cell membrane forms

Question 95

Explain how a chain in base sequence may result in the production of a non functional enzyme (4)

Answer 95

Changes sequence of amino acids Changes shape of active site (affects tertiary structure) Substrate may no longer be complementary Enzyme substrate complexes cannot form

Question 96

Preparing a mitotic squash

Answer 96

Cut end tip off growing root Add aceto orcein stain Squash

Question 97

Percentage increase

Answer 97

New value - original value. X 100 ------------------------------- Original value

Question 98

If you are given the number of bases/base sequence and are asked to calculate the number of amino acids coded for, what do you do?

Answer 98

Divide the number of bases by 3

Question 99

Similarities and differences between mitosis and meiosis

Answer 99

Meiosis produces gametes; mitosis produces other body cells Meiosis produces cells with haploid number of chromosomes; mitosis produces cells with diploid number of chromosomes Meiosis produces cells that are genetically different; mitosis produces cells that are genetically identical Both go through prophase, metaphase, anaphase and telophase Meiosis 2 is the same as mitosis - both involve the separation of sister chromatids Meiosis involves the separation of homologous pairs; mitosis does not have homologous pairs of chromosomes

Question 100

Mutations

Answer 100

The change in alleles may change the base sequences in the DNA So the codons change So the amino acid sequence changes So the primary and tertiary protein structure may also change This is how we get genetic variation

Question 101

Purpose of mitosis

Answer 101

Produces identical body cells for growth and repair of tissues

Question 102

Definition of cancer

Answer 102

Rapid and uncontrollable cell division by mitosis

Question 103

Drugs used to treat cancer

Answer 103

Drug to prevent DNA replication Drug to prevent the spindle fibres from attaching They are both used to inhibit cell division therefore cell division slows down

Question 104

What is the difference between a tissue and an organ?

Answer 104

A tissue is a group of similar cells organised to carry out a specific function An organ is a combination of tissues that a coordinated to preform a variety of functions

Question 105

What is cell differentiation?

Answer 105

The process of a cell becoming specialised in structure to carry out a specific role

Question 106

How does meiosis produce genetic variation? (4)

Answer 106

Recombination of sister chromatids after crossing over during prophase of meiosis 1 Produces new combinations of alleles Independent segregation of homologous chromosomes during anaphase of meiosis 1 Produces gametes with randomly assorted chromosome combinations

Question 107

Overlap in standard deviation then...

Answer 107

We can't make a conclusion about the data

Question 108

Why do you follow the steps to preparing mitotic squash

Answer 108

Root tip end has fast growing cells, dividing by mitosis Stain to make chromosomes visible Squash to get a thin tissue layer letting enough light through for the optical microscope

Question 109

Points to consider for evaluation question

Answer 109

``` Sample size Repeats Scientists vested interest Peer reviewed Human experiments if for humans Control experiment ```

Question 110

Standard deviation

Answer 110

The bigger the value +/- mean, the greater the standard deviation so the more variation there is in the data The smaller the value +/- mean, the lower the standard deviation so the less variation there is in the data