Biology Unit 2 Q And A

Front 1

What is variation?

Back 1

Differences between organisms.

Front 2

Intraspecific vs interspecific variation?

Back 2

Intraspecific = differences between organisms of the same species.
Interspecific = difference between organisms of different species.

Front 3

Discontinuous vs continuous variation?

Back 3

Discontinuous = characteristics fall into certain groups with no overlap (e.g. blood group) – determined by genetics only.
Continuous = characteristics show a range (e.g. height) – determined by genetic and environmental factors

Front 4

What is standard deviation?

Back 4

Spread of data around the mean.

Front 5

Why is SD better than range?

Back 5

Range is largest minus the smallest, range is affected by outliers.

Front 6

If the SD of 2 different means overlap, what does it imply?

Back 6

The difference between the 2 means is not significant but is due to chance.

Front 7

If the SD of 2 different means do not overlap, what does it imply?

Back 7

The difference between the 2 means is significant, it is not due to chance.

Front 8

What do twin studies test?

Back 8

The influence of genetics and environment on characteristics.

Front 9

What do identical twins share?

Back 9

Same alleles and same environment.

Front 10

What if non-identical twins are similar?

Back 10

Due to similar environment.

Front 11

What if non-identical twins are different?

Back 11

Due to different alleles.

Front 12

Building block of DNA?

Back 12

Nucleotide (phosphate, deoxyribose sugar, nitrogenous base)

Front 13

DNA structure?

Back 13

2 polynucleotides joined by hydrogen bonds between the complementary bases (AT, CG) – coils to form a helix.

Front 14

Benefits of DNA as a double helix?

Back 14

More stable, beneficial in semi-conservative replication, more compact.

Front 15

What is a gene?

Back 15

A section of DNA that codes for a protein, made out of intron (non-coding dna) and exon (coding dna).

Front 16

How does a gene/exon code for a protein?

Back 16

1) Made out of a sequence of bases.
2) Each 3 bases code for 1 amino acid (triplet code)
3) Therefore sequence of bases determines sequence of triplet codes which determine the sequence of AAs
4) = primary structure (folds to secondary, then to tertiary/quaternary)

Front 17

Properties of triplet code?

Back 17

1) Degenerate = each AA has more than one triplet code,
2) Non-overlapping = each base is read only once,
3) Stop codes = occur at end of sequence – do not code for an AA

Front 18

How does a mutation lead to a non-functional enzyme?

Back 18

1) Change in base sequence
2) Change in sequence of triplet codes
3) Change in sequence of AAs
4) Change in primary structure
5) Change in tertiary structure
6) Change in active site shape
7) Substrate no longer complementary
8) Can no longer form enzyme-substrate complex

Front 19

What is a chromosome?

Back 19

Formed during interphase - made of 2 identical chromatids joined by a centromere (carries 2 copies of the same dna molecule)

Front 20

What is a homologous pair of chromosomes?

Back 20

A pair of chromosomes, 1 from mother, 1 from father, carries same genes but different alleles – there are 23 pairs in humans.

Front 21

What does cell cycle (mitosis) produce?

Back 21

2 genetically identical cells, diploid (full set of dna).

Front 22

Benefit of Mitosis?

Back 22

Growth and repair of tissues.

Front 23

Stages of Cell Cycle?

Back 23

Interphase/Mitosis/Cytokinesis.

Front 24

Interphase?

Back 24

G1: protein synthesis
S: dna replication
G2: organelle synthesis

Front 25

Mitosis?

Back 25

Prophase: dna coils to form chromosomes, nucleus breaks down, spindle fibres form.
Metaphase: chromosomes line up in middle of cell and attach to spindle fibre via centromere.
Anaphase: spindle fibres pull, centromere splits, sister chromatids move to opposite sides.
Telophase: chromatids uncoil, nucleus reforms (left with 2 identical nuclei).

Front 26

What happens to DNA mass in mitosis?

Back 26

Halves.

Front 27

What happens to Chromosome number in mitosis?

Back 27

Doubles.

Front 28

What does Meiosis produce?

Back 28

Produces gametes, 4 genetically different cells, haploid (half the dna).

Front 29

How does Meiosis produce variation?

Back 29

Crossing Over and Independent Assortment.

Front 30

What is crossing over?

Back 30

Occurs in Prophase I of Meiosis I, homologous pairs of chromosomes wrap around each other and swap equivalent sections of chromatids – produces new combination of alleles.

Front 31

What is independent assortment?

Back 31

In Anaphase I of Meiosis I – the homologous pairs of chromosomes separate, in Anaphase II of Meiosis II – the chromatids separate. Independent assortment produces a mix of alleles.

Front 32

Difference between Metaphase I and Metaphase II?

Back 32

Metaphase I = homologous pairs line up in centre of cell (23 pairs).
Metaphase II = single chromosomes line up in middle of cell (23 chromosomes at this stage).

Front 33

What happens to DNA mass in meiosis?

Back 33

Quarters.

Front 34

What happens to Chromosome number in meiosis?

Back 34

Halves.

Front 35

Describe Semi-Conservative Replication?

Back 35

Produces 2 identical copies of the DNA – each has half the old strand and half the new strand. Process:

1) DNA Helicase breaks hydrogen bonds between the complementary bases.
2) Double strand separates, leaves 2 template stands.
3) Free complementary nucleotides bind (A-T, C-G).
4) DNA Polymerase joins the sugar-phosphate backbone of the new strand.

Front 36

Evidence for Semi-Conservative Replication?

Back 36

DNA made of 15N (heavy nitrogen) is replicated in an environment of 14N (light nitrogen) – produces DNA molecules with half 15, half 14 – medium density.

Front 37

What is cancer?

Back 37

Uncontrolled cell division (uncontrolled mitosis) leading to formation of a tumour.

Front 38

Define a tissue, organ and organ system?

Back 38

Tissue = a group of specialised cells,
Organ = made of different tissues,
Organ system = different organs working together.

Front 39

What is genetic diversity?

Back 39

The variety of alleles within a population of a species.

Front 40

Benefit of high genetic diversity?

Back 40

Species able to adapt with changes in the environment.

Front 41

What is selective breeding?

Back 41

Interbreeding males and females with desired characteristics to produce offspring with the desired characteristics (inherit alleles).
It lowers genetic diversity as all other alleles are excluded.

Front 42

What is founder effect?

Back 42

1) Small group from the main population becomes isolated, small number of individuals = low variety of alleles = low genetic diversity.
2) If this group interbreeds and repopulates – all the individuals will have alleles from this limited range.
3) If a mutated allele is present, individuals would be more likely to inherit the allele.

Front 43

What is genetic bottleneck?

Back 43

Large reduction in population size due to a natural disaster (or hunting).
Low number of individuals = low variety of alleles = low genetic diversity.

Front 44

Role of haemoglobin in oxygen transport?

Back 44

1) Haemoglobin loads oxygen in the lungs – due to high partial pressure of oxygen and low partial pressure of carbon dioxide, haemoglobin has a high affinity and becomes saturated (full).
2) The haemoglobin is transported in the blood in the red blood cell.
3) At the respiring tissues, oxygen is unloaded – due to low partial pressure of oxygen and high partial pressure of carbon dioxide, haemoglobin has low affinity and becomes unsaturated.

Front 45

What is affinity?

Back 45

How well haemoglobin carries oxygen, its level of attraction.

Front 46

Affects of high levels of carbon dioxide on affinity?

Back 46

1) High partial pressure of carbon dioxide lowers affinity – occurs at the site of respiring tissues.
2) The carbon dioxide lowers the pH of the blood, makes the haemoglobin change shape, so oxygen is released.
3) This shifts the ODC to the right, called the bohr shift.
4) Benefit = more oxygen delivered to respiring cells.

Front 47

Benefit of fetal haemoglobin having high affinity?

Back 47

1) Fetal haemoglobin's ODC will be to the left, it has high affinity.
2) In the placenta, there is low partial pressure of oxygen – so the oxygen will dissociate from the mother's haemoglobin, however the fetal haemoglobin will readily associate with the oxygen at the low partial pressures, so it has enough oxygen for its demands.

Front 48

Affinity of organisms in a low oxygen environment?

Back 48

Has a high affinity, curve to the left, therefore it can readily associate oxygen at the low partial pressures.

Front 49

Affinity of active organisms?

Back 49

Has a low affinity, curve to the right, therefore more oxygen can be unloaded to meet it cells demand for respiration.

Front 50

Affinity of small organisms?

Back 50

Have a large surface area to volume ratio, lose a lot of heat, needs to respire to generate heat, therefore has a low affinity, curve to the right, so unloads enough oxygen for the cells demand of respiration.

Front 51

Properties of Starch and Glycogen as energy stores?

Back 51

1) Insoluble = do not affect water potential of the cell, do not diffuse out of the cell.
2) Coiled/Branched = compact, more can fit into a cell.
3) Branched/Chained = glucose removed from the end.

Front 52

Structure of Cellulose?

Back 52

1) Beta glucose arranged in a straight chain (each alternative beta glucose is rotated 180 degrees) = cellulose straight chain.
2) Many cellulose chains are cross linked by hydrogen bonds to form microfibrils.
3) Many microfibrils are cross linked to form marcrofibirils (fibres).
4) Forms structure of cell wall.
5) Strong material (prevents plant cell from bursting or shrinking).

Front 53

Why do large organisms need specialised exchange and transport systems?

Back 53

1) Have a small surface area to volume ratio.
2) Multicellular (high demand and large diffusion distance).
3) Impermeable surface (prevent pathogens entering and reduce water loss).

Front 54

Structure of exchange system in insects?

Back 54

Has openings on body called Spiracles – connects to the trachea which connects to tracheoles which connects directly to the cells.

Front 55

Adaptation of the gills in fish?

Back 55

1) Many gill filaments and gill lamellae = large surface area.
2) Gill lamellae have a thin wall (short diffusion distance) and are permeable.
3) Ventilation brings in pure water (high oxygen, low carbon dioxide) and circulation brings in deoxygenated blood (low oxygen, high carbon dioxide), 4) The water and blood pass over in opposite directions (countercurrent flow), maintains concentration gradient.

Front 56

Adaptation of palisade cells for photosynthesis?

Back 56

1) Located near top of leaf, closer to light.
2) Large size, large surface area for light.
3) Thin cell wall, short diffusion distance for carbon dioxide.
4) Contains many chloroplasts, site of photosynthesis.
5) Large vacuole, pushes chloroplast to the edge of the cell closer to light.

Front 57

Structure of chloroplast?

Back 57

1) Double membrane.
2) Contains discs called thylakoids.
3) Thylakoids contain chlorophyll.
4) Stack of thylakoids called granum.
5) Thylakoids surrounded by a fluid called stroma.

Front 58

Stomata?

Back 58

Opening in the lower epidermis of the leaf formed when a pair of guard cells are turgid.

Front 59

Why is the transport system in mammals called a double circulatory system?

Back 59

The heart pumps twice, the blood goes thru the heart twice – generates enough pressure to supply all body cells.

Front 60

Why is the transport system in mammals called a closed circulatory system?

Back 60

Blood is transported in blood vessels – helps to maintain pressure and redirect blood flow.

Front 61

Role of Hepatic Artery, Hepatic Vein, Hepatic Portal Vein?

Back 61

1) Hepatic artery = takes oxygenated blood to the liver. 2) Hepatic vein = takes deoxygenated blood from the liver back to the heart.
3) Hepatic portal vein = takes deoxygenated blood from the digestive system to the liver to be filtered.

Front 62

Structure of arteries?

Back 62

1) Narrow lumen = maintains pressure.
2) Lining made of squamous epithelial cells = smooth lining.
3) Thick wall = withstand pressure.
4) Elastic tissue in wall = ventricle contract – elastic tissue stretches to withstand pressure, ventricle relax – elastic tissue recoils to maintain pressure and smooth out flow.
5) Smooth muscle in wall = smooth muscle contracts – lumen narrows and arteriole constricts, smooth muscle relaxes – lumen widens and arteriole dilates.
6) Collagen in wall – prevents artery from tearing.

Front 63

Structure of veins?

Back 63

1) Wide lumen = ease of blood flow.
2) Lining made of squamous epithelial cells = smooth lining.
3) Thin wall = vein can be squashed by skeletal muscle pushing blood back to the heart.
4) Valve in lumen = prevents backflow of blood.

Front 64

Adaptation of Capillaries?

Back 64

1) Many small capillaries = large surface area.
2) Thin wall, one cell thick, squamous epithelial cells = short diffusion distance.
3) Pores between cells = allows fluid to move in and out.
4) Narrow lumen = increase diffusion time and decrease diffusion distance.

Front 65

How is tissue fluid formed and returned to circulatory system?

Back 65

1) At the arterial end of the capillary there is a build up hydrostatic pressure.
2) This pushes fluid out of the capillary through the pores
3) The fluid surrounds the cells, this is called tissue fluid.
4) At the venous end of the capillary the fluid moves back in by osmosis.
5) The capillary has low water potential due to the presence of proteins (too large to move out of capillaries).
6) Any excess tissue fluid is picked up by the lymph system and deposited in the vena cava.

Front 66

Why does high blood pressure cause accumulation of tissue fluid?

Back 66

Increases hydrostatic pressure, so more tissue fluid is formed – not as much can be returned to the circulatory system.

Front 67

Why does diet low in protein cause accumulation of tissue fluid?

Back 67

The water potential in the capillary is not as low as normal, so not as much fluid can move back into the capillary by osmosis.

Front 68

Why is there a large decrease in pressure in the arterioles?

Back 68

Increase in total cross-sectional area.

Front 69

Describe the structure of the xylem?

Back 69

1) Long continuous hollow tube
2) Wall contains pits/pores
3) Wall made out of lignin
4) Lignin: strong, waterproof, adhesive

Front 70

How is water absorbed at the roots?

Back 70

1) Mineral ions are actively transported from the soil into the roots.
2) From the soil into root hair cells into cortex cells into endodermis cells into the xylem.
3) This lowers water potential so water follows by osmosis.
4) Water can move by symplast or apoplast.
5) Symplast is when the water moves directly through the cells, passing through the cell membrane.
6) Apoplast is when the water moves between the cells or in the cell wall.
7) Apoplast continues until the endodermis cells – these cells have a casparian strip around them (a waterproof, impermeable barrier), so water enters the cell by symplast and then the xylem.

Front 71

What is root pressure?

Back 71

When the water is absorbed by the root and enters the xylem – this applies hydrostatic pressure to the column of water in the xylem, pushing the water up slightly.

Front 72

How does water move up the xylem?

Back 72

1) Loss of water at the leaves (transpiration).
2) Water moves from the top of the xylem into the leaf by osmosis (transpirational pull).
3) This applies TENSION to the column of water in the xylem.
4) The column of water moves up as one as the water particles stick together - COHESION.
5) It is supported by adhesion and root pressure
(adhesion = water particles stick to lignin in wall of xylem).

Front 73

Why does the diameter of a tree decrease during the day?

Back 73

1) More light and higher temperature.
2) Increase rate of transpiration.
3) Increase transpirational pull.
4) Water pulled up xylem by cohesion-tension
because the water particles stick to the wall of the xylem (adhesion).
5) The walls of the xylem are pulled inwards.

Front 74

What is transpiration?

Back 74

Loss of water vapour from the leaf via the stomata.

Front 75

Factors that increase rate of transpiration?

Back 75

1) Light = more light, more stomata open, increase surface area for transpiration.
2) Temperature = more temperature, more evaporation (increase concentration of water vapour), higher kinetic energy, less water vapour in the surrounding air.
3) Wind = more wind, maintains concentration gradient.
4) Humidity = less humidity, less water vapour in the surrounding air.

Front 76

How to set up a potometer?

Back 76

1) Choose healthy leaf and shoot.
2) Cut shoot underwater and connect to potometer underwater (maintains continuous column and prevents air entering/blocking xylem).
3) Ensure potometer is air tight and water tight.

Front 77

How to measure rate of transpiration?

Back 77

1) Measure distance bubble moves in a certain time, measure cross-sectional area of tube for answer in volume.

Front 78

What does a potometer actually measure?

Back 78

1) Measures rate of water uptake (due to: transpiration, photosynthesis, making cells turgid).

Front 79

What is a xerophyte?

Back 79

A plant adapted to reduce water loss (reduce transpiration).

Front 80

Adaptations of Xerophyte?

Back 80

1) Spiky, needle like leaves = reduced surface area.
2) Thick waxy cuticle = waterproof, impermeable barrier.
3) Densely packed spongy mesophyll = less air spaces, less water vapour build up.
4) Sunken stomata/hairy leaves/rolled up leaves = traps moist layer of air, reduces concentration gradient.

Front 81

What is classification?

Back 81

Placing organisms into groups.

Front 82

What is hierarchical classification?

Back 82

Large groups divided into smaller groups with no overlap.

Front 83

What is a species?

Back 83

A group of individuals with similar characteristics that can interbreed to produce fertile offspring.

Front 84

What is phylogenetic classification?

Back 84

Based on evolutionary relationships – how closely related different species are and how recent a common ancestor they have.

Front 85

3 ways of comparing different species?

Back 85

1) DNA Hybridisation: comparing dna base sequence.
2) AA Sequence: compare for the same protein (e.g. haemoglobin).
3) Protein Shape: compare shape of the same protein (e.g. albumin) using immunological technique.

Front 86

Benefits of courtship behaviour?

Back 86

1) Identify same species.
2) Identify opposite gender.
3) Identify when individual is ready for mating.
4) Form a pair bond.

Front 87

5 ways an antibiotic can destroy a bacteria?

Back 87

1) Prevent cell wall from forming, water enters bacteria by osmosis – it swells and bursts (osmotic lysis).
2) Increase membrane permeability.
3) Inhibit dna replication.
4) Inhibit protein synthesis.
5) Inhibit respiration.

Front 88

How a population of bacteria may become resistant to an antibiotic?

Back 88

1) Variation in the population.
2) Some of the bacteria are resistant to the antibiotic – have an antibiotic resistant gene (carried on plasmid, appeared by random mutation).
3) If antibiotic is used – the ones with the resistant gene will survive and the others will dies out (selection).
4) The resistant ones that survive will pass on their resistant gene by vertical gene transmission (asexual reproduction) and horizontal gene transmission (conjugation).
5) If this occurs for many generations, then most of the bacteria will be resistant to the antibiotic (adaptation).

Front 89

What is species diversity?

Back 89

Number of different species and the number of individuals for each species.

Front 90

Benefit of high species diversity?

Back 90

Stable ecosystem – each species is less likely to become extinct and if a species does it will not affect the food chain as there are other species available.

Front 91

How does deforestation lower species diversity?

Back 91

1) Reduces variety of plants.
2) Less habitat.
3) Less variety of food sources.
4) Lowers animal species diversity.