jan synoptic Flashcards
What is the function of the Ribosomes
Site of Protein synthesis;
What is the function of the Nucleus
Contains genetic material / DNA;
Controls cell activity;
What is the function of the Mitochondria
Site of aerobic respiration;
ATP production;
What is the function of the Smooth Endoplasmic Reticulum
Site of lipid synthesis;
What is the function of the Rough Endoplasmic reticulum
Encrusted in Ribosomes;
Site of protein synthesis;
Transports and stores protein within the cell
What is the function of Golgi Apparatus
Modifies/packages/sorts proteins;
Produces vesicles;
What is the function of Lysosomes
Contains digestive enzymes;
Digests worn out organelles/autolysis;
What is the function of Cell surface membrane
Made of a Phospholipid Bi-layer;
Controls what enters the cell/ is selectively permeable;
Can be folded to increase SA;
What is the function of Chloroplasts
Contain thylakoids, stacked into Granum;
Site of photosynthesis;
What is the function of Capsule
What is the function of Capsule Protects cell from immune systems;
Aids bacteria sticking together;
What is the function of Plasmid
Circular DNA;
Contains antibiotic resistance genes;
What is the function of Cell Wall
Provides rigid shape / structure;
Stops osmotic lysis;
What is the function of Flagellum
Allows movement/propulsion;
Eukaryotic cells produce and release proteins. Outline the role of organelles in the production, transport and release of proteins from eukaryotic cells.
- DNA in nucleus is code (for protein);
- Ribosomes/rough endoplasmic reticulum produce (protein);
- 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; - (Vesicles) fuse with cell(-surface) membrane;
Describe the differences between Eukaryotic and Prokaryotic cells
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;
State three differences between DNA in the nucleus of a plant cell and DNA in a prokaryotic cell.
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);
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
- Cholera bacterium is prokaryote;
- 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]
Give one advantage of using a TEM rather than a SEM.
- Higher resolution;
- higher (maximum) magnification / higher detail (of image);
OR - Allows internal details / structures within (cells) to be seen / cross section to be taken;
Give one advantage of using a SEM rather than a TEM.
Thin sections do not need to be prepared / shows surface of specimen / can have 3-D images;
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.
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;
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) 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;
Describe and explain how cell fractionation and centrifugation can be used to isolate mitochondria from a suspension of animal cells. (6)
- Cell homogenisation to break open cells and release organelles;
- Filter to remove (large) debris/whole cells;
- Use isotonic solution to prevent osmotic damage to mitochondria / organelles;
- Keep cold to prevent/reduce damage to organelles by enzyme;
- Use buffer to maintain pH and prevent protein/enzyme denaturation;
- Use differential Centrifuge (at high speed/1000 g) to separate nuclei / cell fragments / heavy organelles;
- Re-spin (supernatant / after nuclei/pellet removed) at higher speed to get mitochondria in pellet/at bottom;
- Observe pellet with a microscope to identify mitochondria;
Describe the structure of a phospholipid molecule and explain how phospholipids are arranged in a plasma membrane (3 marks).
- Glycerol joined to two fatty acid tails Phosphate group joined to glycerol on opposite side. (joined by condensation reaction with ester bond).;
- Phospholipid has hydrophilic head (phosphate and glycerol) and hydrophobic tails (fatty acid chains)
- Arrange to form a phospholipid bilayer; (Hydrophilic head facing out. Hydrophobic fatty acid chains facing in)
Describe the non-specific defence mechanisms the body may launch against pathogens (5 marks)
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;
Describe how a phagocyte destroys a pathogen present in the blood.
- Engulfs;
- Forming vesicle/phagosome and fuses with lysosome;
- Enzymes digest/hydrolyse;
Give two types of cell, other than pathogens, that can stimulate an immune response.
- (Cells from) other organisms/transplants;
- Abnormal/cancer/tumour (cells);
- (Cells) infected by virus;
When a vaccine is given to a person, it leads to the production of antibodies against a disease-causing organism. Describe how
- Vaccine contains antigen from pathogen;
- Macrophage presents antigen on its surface;
- T (helper) cell with complementary receptor protein binds to antigen;
- T cell stimulates B cell;
- (With) complementary antibody on its surface;
- B cell divides to form clone secreting / producing same antibody;
- B cell secretes large amounts of antibody;
Explain how the humoral response leads to immunity
- B cells specific to the antigen reproduce by mitosis.
- B cells produce plasma and memory cells
- Second infection produces antibodies in larger quantities AND quicker.
Describe and explain the role of antibodies in stimulating phagocytosis.
- Bind to antigen OR Are markers;
- (Antibodies) cause clumping/agglutination OR Attract phagocytes;
Describe the difference between active and passive immunity.
- Active involves memory cells, passive does not;
- Active involves production of antibody by plasma cells/memory cells;
- Passive involves antibody introduced into body from outside/named source;
- Active long term, because antibody produced in response to antigen;
- Passive short term, because antibody (given) is broken down;
- Active (can) take time to develop/work, passive fast acting;
State why some antibodies are referred to as monoclonal
(Antibodies) produced from a single clone of B cells / plasma cells;
OR
(Antibodies) produced from the same B cell / plasma cell;
Tests using monoclonal antibodies are specific. Use your knowledge of protein structure to explain why.
- Specific) primary structure / order of amino acids;
- (Specific) tertiary / 3D structure / shape;
- (So) Only binds to / fits / complementary to one antigen;
Describe the structure of the human immunodeficiency virus (HIV).
- RNA (as genetic material);
- Reverse transcriptase;
- (Protein) capsomeres/capsid;
- (Phospho)lipid (viral) envelope OR Envelope made of membrane;
- Attachment proteins;
Describe how a person infected with HIV will develop AIDS (if untreated) and die of secondary infections.
- 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;
Describe the role of antibodies in producing a positive result in an ELISA test.
- (First) antibody binds/attaches /complementary (in shape) to antigen; 2. (Second) antibody with enzyme attached is added;
- (Second) antibody attaches to antigen;
- (Substrate/solution added) and colour changes;
How does oxygen move through the insect?
- Oxygen diffuses in through the spiracles;
- Spiracle closes;
- Oxygen moves through the trachea into the tracheoles;
- Oxygen delivered directly to the respiring tissues;
Explain three ways in which an insect’s tracheal system is adapted for efficient gas exchange.
- Tracheoles have thin walls so short diffusion distance to cells;
- Highly branched / large number of tracheoles so short diffusion distance to cells;
- 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); - 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); - Body can be moved (by muscles) to move air so maintains diffusion / concentration gradient for oxygen / carbon dioxide;
Describe and explain the advantage of the counter-current principle in gas exchange across a fish gill.
- Water and blood flow in opposite directions;
- Maintains diffusion/concentration gradient of oxygen OR Oxygen concentration always higher (in water);
- (Diffusion) along length of lamellae/filament/gill/capillary;
A fish uses its gills to absorb oxygen from water. Explain how the gills of a fish are adapted for efficient gas exchange.
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);
Describe the gross structure of the human gas exchange system and how we breathe in and out.
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);
Describe how carbon dioxide in the air outside a leaf reaches mesophyll cells inside the leaf. (4)
- (Carbon dioxide enters) via stomata;
- (Stomata opened by) guard cells;
- Diffuses through air spaces;
- Down diffusion gradient;
Explain why plants grown in soil with very little water grow only slowly
- Stomata close;
- Less carbon dioxide (uptake) for less photosynthesis/glucose production;
Explain how an arteriole can reduce the blood flow into capillaries.
- Muscle contracts;
- Constricts/narrows arteriole/lumen
Describe how the heart muscle and the heart valves maintain a one-way flow of blood from the left atrium to the aorta.
- Atrium has higher pressure than ventricle (due to filling / contraction);
- Atrioventricular valve opens;
- Ventricle has higher pressure than atrium (due to filling / contraction);
- Atrioventricular valve closes;
- Ventricle has higher pressure than aorta;
Points 1, 3, 5, and 7 must be comparative: eg higher - Semilunar valve opens;
Marks 2, 4, 6, 8 given in the correct sequence can gain 4 marks - Higher pressure in aorta than ventricle (as heart relaxes);
- Semilunar valve closes;
- (Muscle / atrial / ventricular) contraction causes increase in pressure
Describe how the movement of the diaphragm leads to air movement into the lungs
- Diaphragm contracts and flattens.
- Volume of lungs increases.
- Pressure inside the lungs is lower than
atmospheric pressure. - Air moves into the lungs.
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.
- 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;
Describe the gross structure of human gas exchange system and how we breathe in and out
- 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
Describe the pathway taken by an oxygen molecule from an alveolus to the blood
- (Across) alveolar epithelium;
- Endothelium of capillary;
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)
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;
The thickness of the aorta wall changes all the time during each cardiac cycle.
Explain why. (5)
- (Aorta wall) stretches;
- Because ventricle/heart contracts / systole / pressure increases;
- (Aorta wall) recoils;
- Because ventricle relaxes / heart relaxes /diastole / pressure falls;
- Maintain smooth flow / pressure;
Describe how tissue fluid is formed and how it is returned to the circulatory system. (6)
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;
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)
- Smaller mammal has greater surface area to
volume ratio; - Smaller mammal/larger SA:Vol ratio more
heat lost (per unit body mass); - Smaller mammal/larger SA:Vol ratio has
greater rate of respiration/metabolism; - Oxygen required for respiration;
(Haemoglobin) releases more oxygen / oxygen released more readily / haemoglobin has lower affinity;
Describe how haemoglobin normally loads oxygen in the lungs and unloads it in a tissue cell.
- 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;
Explain how oxygen in a red blood cell is made available for respiration in active tissues.
- CO2 (increased) respiration;
- (increased) dissociation oxygen from haemoglobin;
- Low partial pressure in tissues/plasma;
- Oxygen diffuses from r.b.c. to tissues;
The oxygen dissociation curve of the foetus is to the left of that for its mother. Explain the advantage of this for the foetus.
- Higher affinity / loads more oxygen;
- At low/same/high partial pressure/pO2;
- Oxygen moves from mother/to fetus;
Explain how oxygen is loaded, transported and unloaded in the blood. (6)
- 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);
Binding of one molecule of oxygen to haemoglobin makes it easier for a second oxygen molecule to bind.
Explain why.
- Binding of first oxygen changes tertiary / quaternary (structure) of haemoglobin; [conformational shift caused]
- Creates / leads to / uncovers second / another binding site OR Uncovers another iron / Fe / haem group to bind to;
Describe and explain the effect of increasing carbon dioxide concentration on the dissociation of oxyhaemoglobin.
- Increases/more oxygen dissociation/unloading OR Deceases haemoglobin’s affinity for O2;
- (By) decreasing (blood) pH/increasing acidity;
Explain how water enters xylem from the endodermis in the root and is then transported to the leaves. (6)
(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
Root pressure moves water through the xylem. Describe what causes root pressure. (4)
- Active transport by endodermis;
- ions/salts into xylem;
- Lowers water potential (in xylem);
- (Water enters) by osmosis
Name a factor that can affect transpiration
Light (intensity) / temperature / air movement / humidity;
Give two precautions the students should have taken when setting up the potometer to obtain reliable measurements of water uptake by the plant shoot.
- Seal joints / ensure airtight / ensure watertight;
- Cut shoot under water;
- Cut shoot at a slant;
- Dry off leaves;
- Insert into apparatus under water;
- Ensure no air bubbles are present;
- Shut tap;
- Note where bubble is at start / move bubble to the start position;
Describe the mass flow hypothesis for the mechanism of translocation in plants.
- In source/leaf sugars actively transported into phloem;
- By companion cells;
- Lowers water potential of sieve cell/tube and water enters by osmosis;
- Increase in pressure causes mass movement (towards sink/root);
- Sugars used/converted in root for respiration for storage;
Define the term exon.
Base/nucleotide/triplet sequence coding for polypeptide/sequence of amino acids/primary structure;
Describe Transcription in Eukaryotes
- Hydrogen bonds (between DNA bases) break;
- (Only) one DNA strand acts as a template;
- (Free) RNA nucleotides align by complementary base pairing;
- (In RNA) Uracil base pairs with adenine (on DNA) OR (In RNA) Uracil is used in place of thymine;
- RNA polymerase joins (adjacent RNA) nucleotides;
- (By) phosphodiester bonds (between adjacent nucleotides);
- Pre-mRNA is spliced (to form mRNA) OR Introns are removed (to form mRNA);
Describe Translation
- (mRNA attaches) to ribosomes OR (mRNA attaches) to rough endoplasmic reticulum;
- (tRNA) anticodons (bind to) complementary (mRNA) codons;
- tRNA brings a specific amino acid;
- Amino acids join by peptide bonds;
- (Amino acids join together) with the use of ATP;
- tRNA released (after amino acid joined to polypeptide);
- The ribosome moves along the mRNA to form the polypeptide;
Give two structural differences between a molecule of messenger RNA (mRNA) and a molecule of transfer RNA (tRNA).
- mRNA does not have hydrogen bonds / base pairing, tRNA does; OR mRNA is linear / straight chain, tRNA is cloverleaf;
- mRNA does not have an amino acid binding site, tRNA does;
- mRNA has more nucleotides;
- (Different) mRNAs have different lengths, all tRNAs are similar / same length;
- mRNA has codons, tRNA has an anticodon;
What is an allele?
(Different) form/type/version of a gene / different base sequence of a gene;
Explain how selection occurs in living organisms
- Variation due to mutation;
- Different environmental/abiotic/biotic conditions / selection pressures;
- Selection for different/advantageous, features/characteristics/mutation/ /allele;
- Differential reproductive success / (selected) organisms survive and reproduce;
- Leads to change in allele frequency;
- Occurs over a long period of time;
Define degenerate code
more than one codon for one amino acid
Explain what the term non-overlapping DNA means.
A base from one triplet cannot be used in an adjacent triple
A mutation in a gene coding for an enzyme
could lead to the production of a non-functional enzyme. Explain how
- Change in base sequence (of DNA/gene);
- Change in amino acid sequence / primary structure (of enzyme);
- Change in hydrogen/ionic/ disulphide bonds;
- Change in the tertiary structure/active site (of enzyme);
- Substrate not complementary/cannot bind (to enzyme / active site) / no enzyme-substrate complexes form;
Not all mutations in the nucleotide sequence of a gene cause a change in the structure of a polypeptide. Give two reasons why.
- Triplets code for same amino acid
- Occurs in introns /non-coding sequence;
What is a species?
- Group of similar organisms / organisms with similar features / / organisms with same genes / chromosomes;
- Reproduce to produce fertile offspring;
Explain what is meant by a heirarchy
- Groups within groups;
- No overlap (between groups);
Explain what is meant by a phylogenetic group
(Grouped according to) evolutionary links/history/relationships / common ancestry;
Explain what is meant by genetic
diversity.
Difference in DNA/base sequence/alleles/genes;
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.
Also measures number of individuals in a species / different proportions of species;
Some species may be present in low/high numbers;
What is meant by species richness
The number of different species in a community
Explain how natural selection produces changes within a species.
- Variation [caused by mutation] between members of population / species;
- Predation / disease / competition results in differential survival;
- Some have adaptations that favour survival;
- Differential reproductive success / survive to reproduce/ have more offspring/
- Pass on their advantageous alleles /
- Changes allelic frequencies
Describe how comparisons of biological molecules in two species could be used to find out if they are closely related.
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;
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.
- 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;
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)
- Mark for general principle of - reduced variety/number of different alleles/DNA / reduced gene pool (in new population);
- Founder effect;
- A few individuals from a population become isolated/form colonies:
- (Genetic) bottlenecks;
- (Significant) fall in size of population
- Selective breeding / artificial selection;
- Using organisms with particular alleles / traits / phenotypes / characteristics
Scientists can use protein structure to investigate the evolutionary relationships
between different species.
Explain why.
- Amino acid sequences / primary structure;
- Closer the (amino acid) sequence the closer the relationship;
- (Protein structure) related to (DNA) base/triplet sequence;
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)
- Decrease in variety of plants / fewer plant species;
- Fewer habitats/niches;
- Decrease in variety of food / fewer food sources;
- Aspect of clearing forest (killing insects) eg machinery, pesticides
What is meant by a genetic bottleneck
- Sudden decrease in population / many killed by an event eg earthquake;
- Idea of reduced/low genetic variation/diversity / reduction in (variety of) alleles / smaller gene pool;
Suggest one ethical argument for maintaining biodiversity.
Prevent extinction /loss of populations/ reduction in populations /loss of habitats / save organisms for future generations (idea of);
Suggest one economic argument for maintaining biodiversity.
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;
Farmers clear tropical forest and grow crops instead. Explain how this causes the
diversity of insects in the area to decrease.
- Lower diversity of plants/ few species of plants/less variety of plants/few plant layers;
- Few sources/types of food/feeding sites;
- Few habitats/ niches;
- Fewer (species of) herbivore so few (species of) carnivores;
- Aspect of agriculture (killing insects);
Describe how courtship behaviour increases the probability of successful mating.
- Attracts/recognises same species;
- Attracts/recognises mate/opposite sex;
- Indication of sexual maturity/ fertility / synchronises mating;
- Stimulates release of gametes;
- Form pair bond;
