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jan synoptic Flashcards

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1
Q

What is the function of the Ribosomes

A

Site of Protein synthesis;

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2
Q

What is the function of the Nucleus

A

Contains genetic material / DNA;
Controls cell activity;

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3
Q

What is the function of the Mitochondria

A

Site of aerobic respiration;
ATP production;

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4
Q

What is the function of the Smooth Endoplasmic Reticulum

A

Site of lipid synthesis;

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5
Q

What is the function of the Rough Endoplasmic reticulum

A

Encrusted in Ribosomes;
Site of protein synthesis;
Transports and stores protein within the cell

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6
Q

What is the function of Golgi Apparatus

A

Modifies/packages/sorts proteins;
Produces vesicles;

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7
Q

What is the function of Lysosomes

A

Contains digestive enzymes;
Digests worn out organelles/autolysis;

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8
Q

What is the function of Cell surface membrane

A

Made of a Phospholipid Bi-layer;
Controls what enters the cell/ is selectively permeable;
Can be folded to increase SA;

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9
Q

What is the function of Chloroplasts

A

Contain thylakoids, stacked into Granum;
Site of photosynthesis;

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10
Q

What is the function of Capsule

A

What is the function of Capsule Protects cell from immune systems;
Aids bacteria sticking together;

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11
Q

What is the function of Plasmid

A

Circular DNA;
Contains antibiotic resistance genes;

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12
Q

What is the function of Cell Wall

A

Provides rigid shape / structure;
Stops osmotic lysis;

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13
Q

What is the function of Flagellum

A

Allows movement/propulsion;

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14
Q

Eukaryotic cells produce and release proteins. Outline the role of organelles in the production, transport and release of proteins from eukaryotic cells.

A
  1. DNA in nucleus is code (for protein);
  2. Ribosomes/rough endoplasmic reticulum produce (protein);
  3. Mitochondria produce ATP (for protein synthesis);
    4 Golgi apparatus package/modify; OR Carbohydrate added/glycoprotein produced by Golgi apparatus;
    5 Vesicles transport OR Rough endoplasmic reticulum transports;
  4. (Vesicles) fuse with cell(-surface) membrane;
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15
Q

Describe the differences between Eukaryotic and Prokaryotic cells

A

comparisons:
1. Nucleotide structure is identical;
2. Nucleotides joined by phosphodiester bond;
OR Deoxyribose joined to phosphate (in sugar, phosphate backbone);
3. DNA in mitochondria / chloroplasts same / similar (structure) to DNA in prokaryotes;
Contrasts:
4. Eukaryotic DNA is longer;
5. Eukaryotic DNA contain introns, prokaryotic DNA does not;
6. Eukaryotic DNA is linear, prokaryotic DNA is circular;
7. Eukaryotic DNA is associated with / bound to protein / histones, prokaryotic DNA is not;

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16
Q

State three differences between DNA in the nucleus of a plant cell and DNA in a prokaryotic cell.

A

Plant v prokaryote
1. (Associated with) histones/proteins v no histones/proteins;
2. Linear v circular;
3. No plasmids v plasmids;
4. Introns v no introns;
5. Long(er) v short(er);

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17
Q

The structure of a cholera bacterium is different from the structure of an epithelial cell from the small intestine. Describe how the structure of a cholera bacterium is different

A
  1. Cholera bacterium is prokaryote;
  2. Does not have a nucleus/nuclear envelope/ has DNA free in cytoplasm/has loop of DNA;

3 and 4 Any two from: [No membrane-bound organelles/no mitochondria / no golgi/no endoplasmic reticulum];
5 Small ribosomes only;
6 and 7 Any two from [Capsule/flagellum/plasmid / cell wall]

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18
Q

Give one advantage of using a TEM rather than a SEM.

A
  1. Higher resolution;
  2. higher (maximum) magnification / higher detail (of image);
    OR
  3. Allows internal details / structures within (cells) to be seen / cross section to be taken;
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19
Q

Give one advantage of using a SEM rather than a TEM.

A

Thin sections do not need to be prepared / shows surface of specimen / can have 3-D images;

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20
Q

Scientists use optical microscopes and transmission electron microscopes to investigate cell structure. Explain the advantages and limitations of using a TEM to investigate cell structure.

A

Advantages:
1 Small objects can be seen;
2 TEM has high resolution;
3 Electron wavelength is shorter;

Limitations:
4 Cannot look at living cells;
5 Must be in a vacuum;
6 Must cut section / thin specimen;
7 Preparation may create artefact;

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21
Q

Scientists isolated mitochondria from liver cells. They broke the cells open in an ice-cold, buffered isotonic solution. Explain why the solution was:
a) Isotonic
b) Ice cold
c) buffered

A

a) Prevents osmosis / no (net) movement of water So organelle/named organelle does not burst/shrivel;
b) Reduce/prevent enzyme activity so organelles are not digested / damaged;
c) Maintain a constant pH so proteins do not denature;

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22
Q

Describe and explain how cell fractionation and centrifugation can be used to isolate mitochondria from a suspension of animal cells. (6)

A
  1. Cell homogenisation to break open cells and release organelles;
  2. Filter to remove (large) debris/whole cells;
  3. Use isotonic solution to prevent osmotic damage to mitochondria / organelles;
  4. Keep cold to prevent/reduce damage to organelles by enzyme;
  5. Use buffer to maintain pH and prevent protein/enzyme denaturation;
  6. Use differential Centrifuge (at high speed/1000 g) to separate nuclei / cell fragments / heavy organelles;
  7. Re-spin (supernatant / after nuclei/pellet removed) at higher speed to get mitochondria in pellet/at bottom;
  8. Observe pellet with a microscope to identify mitochondria;
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23
Q

Describe the structure of a phospholipid molecule and explain how phospholipids are arranged in a plasma membrane (3 marks).

A
  1. Glycerol joined to two fatty acid tails Phosphate group joined to glycerol on opposite side. (joined by condensation reaction with ester bond).;
  2. Phospholipid has hydrophilic head (phosphate and glycerol) and hydrophobic tails (fatty acid chains)
  3. Arrange to form a phospholipid bilayer; (Hydrophilic head facing out. Hydrophobic fatty acid chains facing in)
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24
Q

Describe the non-specific defence mechanisms the body may launch against pathogens (5 marks)

A

The process is called phagocytosis – No Mark
1. Pathogen is engulfed by the phagocyte.
2. Engulfed pathogen enters the cytoplasm of
the phagocyte in a vesicle;
3. Lysosomes fuse with vesicle releasing
digestive enzymes;
4. Lysosome enzymes break down the pathogen.
5. Waste materials are ejected from the cell by exocytosis;

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25
Q

Describe how a phagocyte destroys a pathogen present in the blood.

A
  1. Engulfs;
  2. Forming vesicle/phagosome and fuses with lysosome;
  3. Enzymes digest/hydrolyse;
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26
Q

Give two types of cell, other than pathogens, that can stimulate an immune response.

A
  1. (Cells from) other organisms/transplants;
  2. Abnormal/cancer/tumour (cells);
  3. (Cells) infected by virus;
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27
Q

When a vaccine is given to a person, it leads to the production of antibodies against a disease-causing organism. Describe how

A
  1. Vaccine contains antigen from pathogen;
  2. Macrophage presents antigen on its surface;
  3. T (helper) cell with complementary receptor protein binds to antigen;
  4. T cell stimulates B cell;
  5. (With) complementary antibody on its surface;
  6. B cell divides to form clone secreting / producing same antibody;
  7. B cell secretes large amounts of antibody;
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28
Q

Explain how the humoral response leads to immunity

A
  1. B cells specific to the antigen reproduce by mitosis.
  2. B cells produce plasma and memory cells
  3. Second infection produces antibodies in larger quantities AND quicker.
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29
Q

Describe and explain the role of antibodies in stimulating phagocytosis.

A
  • Bind to antigen OR Are markers;
  • (Antibodies) cause clumping/agglutination OR Attract phagocytes;
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30
Q

Describe the difference between active and passive immunity.

A
  1. Active involves memory cells, passive does not;
  2. Active involves production of antibody by plasma cells/memory cells;
  3. Passive involves antibody introduced into body from outside/named source;
  4. Active long term, because antibody produced in response to antigen;
  5. Passive short term, because antibody (given) is broken down;
  6. Active (can) take time to develop/work, passive fast acting;
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31
Q

State why some antibodies are referred to as monoclonal

A

(Antibodies) produced from a single clone of B cells / plasma cells;
OR
(Antibodies) produced from the same B cell / plasma cell;

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32
Q

Tests using monoclonal antibodies are specific. Use your knowledge of protein structure to explain why.

A
  • Specific) primary structure / order of amino acids;
  • (Specific) tertiary / 3D structure / shape;
  • (So) Only binds to / fits / complementary to one antigen;
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33
Q

Describe the structure of the human immunodeficiency virus (HIV).

A
  1. RNA (as genetic material);
  2. Reverse transcriptase;
  3. (Protein) capsomeres/capsid;
  4. (Phospho)lipid (viral) envelope OR Envelope made of membrane;
  5. Attachment proteins;
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34
Q

Describe how a person infected with HIV will develop AIDS (if untreated) and die of secondary infections.

A
  • High viral load leads to increased destruction of helper T/CD4 cells;
  • Less activation of B cells/cytotoxic T cells/phagocytes;
  • Less production of plasma cells/antibodies OR (With cytotoxic T cells) less able to kill virus infected cells;
  • (More able to) destroy other microbes/pathogens OR (More able to) destroy mutated/cancer cells;
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35
Q

Describe the role of antibodies in producing a positive result in an ELISA test.

A
  1. (First) antibody binds/attaches /complementary (in shape) to antigen; 2. (Second) antibody with enzyme attached is added;
  2. (Second) antibody attaches to antigen;
  3. (Substrate/solution added) and colour changes;
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36
Q

How does oxygen move through the insect?

A
  1. Oxygen diffuses in through the spiracles;
  2. Spiracle closes;
  3. Oxygen moves through the trachea into the tracheoles;
  4. Oxygen delivered directly to the respiring tissues;
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37
Q

Explain three ways in which an insect’s tracheal system is adapted for efficient gas exchange.

A
  1. Tracheoles have thin walls so short diffusion distance to cells;
  2. Highly branched / large number of tracheoles so short diffusion distance to cells;
  3. Highly branched / large number of tracheoles so large surface area (for gas exchange);
    4.Tracheae provide tubes full of air so fast diffusion (into insect tissues);
  4. Fluid in the end of the tracheoles that moves out (into tissues) during exercise so faster diffusion through the air to the gas exchange surface;
    OR
    Fluid in the end of the tracheoles that moves out (into tissues) during exercise so larger surface area (for gas exchange);
  5. Body can be moved (by muscles) to move air so maintains diffusion / concentration gradient for oxygen / carbon dioxide;
38
Q

Describe and explain the advantage of the counter-current principle in gas exchange across a fish gill.

A
  1. Water and blood flow in opposite directions;
  2. Maintains diffusion/concentration gradient of oxygen OR Oxygen concentration always higher (in water);
  3. (Diffusion) along length of lamellae/filament/gill/capillary;
39
Q

A fish uses its gills to absorb oxygen from water. Explain how the gills of a fish are adapted for efficient gas exchange.

A

A fish uses its gills to absorb oxygen from water. Explain how the gills of a fish are adapted for efficient gas exchange. 1 Large surface area provided by many lamellae over many gill filaments;
2 Increases diffusion/makes diffusion efficient;
3 Thin epithelium/distance between water and blood;
4 Water and blood flow in opposite directions/countercurrent;
5 (Point 4) maintains concentration gradient (along gill)/equilibrium not reached;
6 As water always next to blood with lower concentration of oxygen;
7 Circulation replaces blood saturated with oxygen;
8 Ventilation replaces water (as oxygen removed);

40
Q

Describe the gross structure of the human gas exchange system and how we breathe in and out.

A

Describe the gross structure of the human gas exchange system and how we breathe in and out. 1. Named structures – trachea, bronchi, bronchioles, alveoli;
2. Above structures named in correct order OR Above structures labelled in correct positions on a diagram;
3. Breathing in – diaphragm contracts and external intercostal muscles contract;
4. (Causes) volume increase and pressure decrease in thoracic cavity (to below atmospheric, resulting in air moving in);
5. Breathing out - Diaphragm relaxes and internal intercostal muscles contract;
6. (Causes) volume decrease and pressure increase in thoracic cavity (to above atmospheric, resulting in air moving out);

41
Q

Describe how carbon dioxide in the air outside a leaf reaches mesophyll cells inside the leaf. (4)

A
  1. (Carbon dioxide enters) via stomata;
  2. (Stomata opened by) guard cells;
  3. Diffuses through air spaces;
  4. Down diffusion gradient;
42
Q

Explain why plants grown in soil with very little water grow only slowly

A
  1. Stomata close;
  2. Less carbon dioxide (uptake) for less photosynthesis/glucose production;
43
Q

Explain how an arteriole can reduce the blood flow into capillaries.

A
  1. Muscle contracts;
  2. Constricts/narrows arteriole/lumen
44
Q

Describe how the heart muscle and the heart valves maintain a one-way flow of blood from the left atrium to the aorta.

A
  1. Atrium has higher pressure than ventricle (due to filling / contraction);
  2. Atrioventricular valve opens;
  3. Ventricle has higher pressure than atrium (due to filling / contraction);
  4. Atrioventricular valve closes;
  5. Ventricle has higher pressure than aorta;
    Points 1, 3, 5, and 7 must be comparative: eg higher
  6. Semilunar valve opens;
    Marks 2, 4, 6, 8 given in the correct sequence can gain 4 marks
  7. Higher pressure in aorta than ventricle (as heart relaxes);
  8. Semilunar valve closes;
  9. (Muscle / atrial / ventricular) contraction causes increase in pressure
45
Q

Describe how the movement of the diaphragm leads to air movement into the lungs

A
  1. Diaphragm contracts and flattens.
  2. Volume of lungs increases.
  3. Pressure inside the lungs is lower than
    atmospheric pressure.
  4. Air moves into the lungs.
46
Q

Describe and explain how the lungs are adapted to allow rapid exchange of oxygen between air in the alveoli and blood in the capillaries around them.

A
  • Many alveoli/ alveoli walls folded provide a large surface area;
  • Many capillaries provide a large surface area (So) fast diffusion;
    Alveoli or capillary walls/ epithelium/ lining are thin/ one cell thick / short distance between alveoli and blood;
  • Flattened/ squamous epithelium (So) short diffusion distance/ pathway / (So) fast diffusion;
  • Ventilation / circulation; So Maintains a diffusion / concentration gradient (So) fast diffusion;
47
Q

Describe the gross structure of human gas exchange system and how we breathe in and out

A
  • Named structures – trachea, bronchi, bronchioles, alveoli
  • Above structures named in correct order
    o OR
    o Above structures labelled in correct positions on a diagram
  • Breathing in – Diaphragm contract and external intercostal muscles contract
  • Volume increases and pressure decreases in thoracic cavity.
  • Breathing out – Diaphragm relaxes and internal intercostal muscles contract
  • Volume decrease and pressure increase in thoracic cavity
48
Q

Describe the pathway taken by an oxygen molecule from an alveolus to the blood

A
  1. (Across) alveolar epithelium;
  2. Endothelium of capillary;
49
Q

Arteries and arterioles take blood away from the heart. Explain how the structures of the walls of arteries and arterioles are related to their functions. (6)

A

Elastic tissue
1 Elastic tissue stretches under pressure/when heart contracts;
2 Recoils/springs back;
3 Evens out pressure/flow;
Muscle
4 Muscle contracts;
5 Reduces diameter of lumen/vasoconstriction/constricts vessel;
6 Changes flow/pressure;
Epithelium
7 Epithelium smooth;
8 Reduces friction/blood clots/less resistance;

50
Q

The thickness of the aorta wall changes all the time during each cardiac cycle.
Explain why. (5)

A
  1. (Aorta wall) stretches;
  2. Because ventricle/heart contracts / systole / pressure increases;
  3. (Aorta wall) recoils;
  4. Because ventricle relaxes / heart relaxes /diastole / pressure falls;
  5. Maintain smooth flow / pressure;
51
Q

Describe how tissue fluid is formed and how it is returned to the circulatory system. (6)

A

Formation
1. High blood / hydrostatic pressure / pressure filtration;
2. Forces water / fluid out;
3. Large proteins remain in capillary;

Return
4. Low water potential in capillary / blood;
5. Due to (plasma) proteins;
6. Water enters capillary / blood;
7. (By) osmosis;
8. Correct reference to lymph;

52
Q

Heat from respiration helps mammals to maintain a constant body temperature.
Use this information to explain the relationship between the surface area to volume ratio of mammals and the oxygen dissociation curves of their haemoglobins. (5)

A
  1. Smaller mammal has greater surface area to
    volume ratio;
  2. Smaller mammal/larger SA:Vol ratio more
    heat lost (per unit body mass);
  3. Smaller mammal/larger SA:Vol ratio has
    greater rate of respiration/metabolism;
  4. Oxygen required for respiration;
    (Haemoglobin) releases more oxygen / oxygen released more readily / haemoglobin has lower affinity;
53
Q

Describe how haemoglobin normally loads oxygen in the lungs and unloads it in a tissue cell.

A
  • Oxygen combines (reversibly) to produce oxyhaemoglobin;
  • each haemoglobin molecule/ one haemoglobin may transport 4 molecules of oxygen;
  • high partial pressure of oxygen / oxygen tension / concentration in lungs;
  • haemoglobin (almost) 95% / 100% saturated;
  • unloads at low oxygen tension(in tissues);
  • presence of carbon dioxide displaces curve further to right / increases oxygen dissociation;
  • allows more O2 to be unloaded;
  • increase temp/ acidity allows more O2 to be unloaded;
  • low pO2 / increase CO2 / increase term / increase acid occur in vicinity of respiring tissue;
54
Q

Explain how oxygen in a red blood cell is made available for respiration in active tissues.

A
  • CO2 (increased) respiration;
  • (increased) dissociation oxygen from haemoglobin;
  • Low partial pressure in tissues/plasma;
  • Oxygen diffuses from r.b.c. to tissues;
55
Q

The oxygen dissociation curve of the foetus is to the left of that for its mother. Explain the advantage of this for the foetus.

A
  • Higher affinity / loads more oxygen;
  • At low/same/high partial pressure/pO2;
  • Oxygen moves from mother/to fetus;
56
Q

Explain how oxygen is loaded, transported and unloaded in the blood. (6)

A
  • Haemoglobin carries oxygen / has a high affinity for oxygen / oxyhaemoglobin;
  • In red blood cells;
  • Loading/uptake/association in lungs at high p.O2;
  • Unloads/ dissociates / releases to respiring cells/tissues at low p.O2;
  • Unloading linked to higher carbon dioxide (concentration);
57
Q

Binding of one molecule of oxygen to haemoglobin makes it easier for a second oxygen molecule to bind.
Explain why.

A
  1. Binding of first oxygen changes tertiary / quaternary (structure) of haemoglobin; [conformational shift caused]
  2. Creates / leads to / uncovers second / another binding site OR Uncovers another iron / Fe / haem group to bind to;
58
Q

Describe and explain the effect of increasing carbon dioxide concentration on the dissociation of oxyhaemoglobin.

A
  1. Increases/more oxygen dissociation/unloading OR Deceases haemoglobin’s affinity for O2;
  2. (By) decreasing (blood) pH/increasing acidity;
59
Q

Explain how water enters xylem from the endodermis in the root and is then transported to the leaves. (6)

A

(In the root)
1. Casparian strip blocks apoplast pathway / only allows symplast pathway;
2. Active transport by endodermis;
3. (Of) ions/salts into xylem;
4. Lower water potential in xylem / water enters xylem by osmosis /down a water potential gradient;

(Xylem to leaf)
5. Evaporation / transpiration (from leaves);
6. (Creates) cohesion / tension / H-bonding between water molecules / negative pressure;
7. Adhesion / water molecules bind to xylem;
8. (Creates continuous) column of water

60
Q

Root pressure moves water through the xylem. Describe what causes root pressure. (4)

A
  1. Active transport by endodermis;
  2. ions/salts into xylem;
  3. Lowers water potential (in xylem);
  4. (Water enters) by osmosis
61
Q

Name a factor that can affect transpiration

A

Light (intensity) / temperature / air movement / humidity;

62
Q

Give two precautions the students should have taken when setting up the potometer to obtain reliable measurements of water uptake by the plant shoot.

A
  1. Seal joints / ensure airtight / ensure watertight;
  2. Cut shoot under water;
  3. Cut shoot at a slant;
  4. Dry off leaves;
  5. Insert into apparatus under water;
  6. Ensure no air bubbles are present;
  7. Shut tap;
  8. Note where bubble is at start / move bubble to the start position;
63
Q

Describe the mass flow hypothesis for the mechanism of translocation in plants.

A
  1. In source/leaf sugars actively transported into phloem;
  2. By companion cells;
  3. Lowers water potential of sieve cell/tube and water enters by osmosis;
  4. Increase in pressure causes mass movement (towards sink/root);
  5. Sugars used/converted in root for respiration for storage;
64
Q

Define the term exon.

A

Base/nucleotide/triplet sequence coding for polypeptide/sequence of amino acids/primary structure;

65
Q

Describe Transcription in Eukaryotes

A
  1. Hydrogen bonds (between DNA bases) break;
  2. (Only) one DNA strand acts as a template;
  3. (Free) RNA nucleotides align by complementary base pairing;
  4. (In RNA) Uracil base pairs with adenine (on DNA) OR (In RNA) Uracil is used in place of thymine;
  5. RNA polymerase joins (adjacent RNA) nucleotides;
  6. (By) phosphodiester bonds (between adjacent nucleotides);
  7. Pre-mRNA is spliced (to form mRNA) OR Introns are removed (to form mRNA);
66
Q

Describe Translation

A
  1. (mRNA attaches) to ribosomes OR (mRNA attaches) to rough endoplasmic reticulum;
  2. (tRNA) anticodons (bind to) complementary (mRNA) codons;
  3. tRNA brings a specific amino acid;
  4. Amino acids join by peptide bonds;
  5. (Amino acids join together) with the use of ATP;
  6. tRNA released (after amino acid joined to polypeptide);
  7. The ribosome moves along the mRNA to form the polypeptide;
67
Q

Give two structural differences between a molecule of messenger RNA (mRNA) and a molecule of transfer RNA (tRNA).

A
  1. mRNA does not have hydrogen bonds / base pairing, tRNA does; OR mRNA is linear / straight chain, tRNA is cloverleaf;
  2. mRNA does not have an amino acid binding site, tRNA does;
  3. mRNA has more nucleotides;
  4. (Different) mRNAs have different lengths, all tRNAs are similar / same length;
  5. mRNA has codons, tRNA has an anticodon;
68
Q

What is an allele?

A

(Different) form/type/version of a gene / different base sequence of a gene;

69
Q

Explain how selection occurs in living organisms

A
  1. Variation due to mutation;
  2. Different environmental/abiotic/biotic conditions / selection pressures;
  3. Selection for different/advantageous, features/characteristics/mutation/ /allele;
  4. Differential reproductive success / (selected) organisms survive and reproduce;
  5. Leads to change in allele frequency;
  6. Occurs over a long period of time;
70
Q

Define degenerate code

A

more than one codon for one amino acid

71
Q

Explain what the term non-overlapping DNA means.

A

A base from one triplet cannot be used in an adjacent triple

72
Q

A mutation in a gene coding for an enzyme
could lead to the production of a non-functional enzyme. Explain how

A
  1. Change in base sequence (of DNA/gene);
  2. Change in amino acid sequence / primary structure (of enzyme);
  3. Change in hydrogen/ionic/ disulphide bonds;
  4. Change in the tertiary structure/active site (of enzyme);
  5. Substrate not complementary/cannot bind (to enzyme / active site) / no enzyme-substrate complexes form;
73
Q

Not all mutations in the nucleotide sequence of a gene cause a change in the structure of a polypeptide. Give two reasons why.

A
  1. Triplets code for same amino acid
  2. Occurs in introns /non-coding sequence;
74
Q

What is a species?

A
  1. Group of similar organisms / organisms with similar features / / organisms with same genes / chromosomes;
  2. Reproduce to produce fertile offspring;
75
Q

Explain what is meant by a heirarchy

A
  1. Groups within groups;
  2. No overlap (between groups);
76
Q

Explain what is meant by a phylogenetic group

A

(Grouped according to) evolutionary links/history/relationships / common ancestry;

77
Q

Explain what is meant by genetic
diversity.

A

Difference in DNA/base sequence/alleles/genes;

78
Q

The number of species present is one way to measure biodiversity. Explain why an
index of diversity may be a more useful measure of biodiversity.

A

Also measures number of individuals in a species / different proportions of species;
Some species may be present in low/high numbers;

79
Q

What is meant by species richness

A

The number of different species in a community

80
Q

Explain how natural selection produces changes within a species.

A
  1. Variation [caused by mutation] between members of population / species;
  2. Predation / disease / competition results in differential survival;
  3. Some have adaptations that favour survival;
  4. Differential reproductive success / survive to reproduce/ have more offspring/
  5. Pass on their advantageous alleles /
  6. Changes allelic frequencies
81
Q

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

A

Genetic variation:
Compare DNA base sequence;
Compare RNA base sequence;
Compare sequence of amino acids /primary structure (of named / same protein);

DNA hybridisation by separating DNA strands / break hydrogen bonds;
Mix DNA/strands (of different species);
Temperature/heat required to separate (hybrid) strands indicates relationship;

Immunological evidence – not a mark
Inject (seahorse) protein/serum into animal;
(Obtain) antibodies/serum;
Add protein/serum/plasma from other (seahorse) species;
Amount of precipitate indicates relationship;

82
Q

In classification, comparing the base sequence of a gene provides more information than comparing the amino acid sequence for which the gene codes. Explain why.

A
  • Reference to base triplet/triplet code / more bases than amino acids / longer base sequence than amino acid sequence;
  • Introns/non-coding DNA;
  • Same amino acid may be coded for / DNA code is degenerate;
83
Q

Scientists’ analysis of blood proteins has indicated a lack of genetic diversity in populations of some organisms.

Describe the processes that lead to a reduction in the genetic diversity of populations of organisms. (6)

A
  1. Mark for general principle of - reduced variety/number of different alleles/DNA / reduced gene pool (in new population);
  2. Founder effect;
  3. A few individuals from a population become isolated/form colonies:
  4. (Genetic) bottlenecks;
  5. (Significant) fall in size of population
  6. Selective breeding / artificial selection;
  7. Using organisms with particular alleles / traits / phenotypes / characteristics
84
Q

Scientists can use protein structure to investigate the evolutionary relationships
between different species.

Explain why.

A
  1. Amino acid sequences / primary structure;
  2. Closer the (amino acid) sequence the closer the relationship;
  3. (Protein structure) related to (DNA) base/triplet sequence;
85
Q

A forest was cleared to make more land available for agriculture.
After the forest was cleared the species diversity of insects in the area decreased.
Explain why. (4)

A
  1. Decrease in variety of plants / fewer plant species;
  2. Fewer habitats/niches;
  3. Decrease in variety of food / fewer food sources;
  4. Aspect of clearing forest (killing insects) eg machinery, pesticides
86
Q

What is meant by a genetic bottleneck

A
  1. Sudden decrease in population / many killed by an event eg earthquake;
  2. Idea of reduced/low genetic variation/diversity / reduction in (variety of) alleles / smaller gene pool;
87
Q

Suggest one ethical argument for maintaining biodiversity.

A

Prevent extinction /loss of populations/ reduction in populations /loss of habitats / save organisms for future generations (idea of);

88
Q

Suggest one economic argument for maintaining biodiversity.

A

A suitable example of how some species may be important financially e.g.
1. medical / pharmaceutical uses;
2. commercial products / example given;
3. tourism;
4. agriculture;
5. saving local forest communities;

89
Q

Farmers clear tropical forest and grow crops instead. Explain how this causes the
diversity of insects in the area to decrease.

A
  1. Lower diversity of plants/ few species of plants/less variety of plants/few plant layers;
  2. Few sources/types of food/feeding sites;
  3. Few habitats/ niches;
  4. Fewer (species of) herbivore so few (species of) carnivores;
  5. Aspect of agriculture (killing insects);
90
Q

Describe how courtship behaviour increases the probability of successful mating.

A
  1. Attracts/recognises same species;
  2. Attracts/recognises mate/opposite sex;
  3. Indication of sexual maturity/ fertility / synchronises mating;
  4. Stimulates release of gametes;
  5. Form pair bond;

biology (7 decks)

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