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Molecules, Biodiversity, Food and Health

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Emily Summers AS Unit F212: Molecules, biodiversity, food and health Module 1 - Biological molecules Biological molecules Describe how hydrogen bonding occurs between water molecules, and relate this and other properties of water to the roles of water in living organisms. Describe, with the aid of diagrams, the structure of an amino acid. Structure of an Amino Acid Structure of Glycine 1 All amino acids have the same general structure, a carboxyl group, an amino group attached to a carbon atom (-NH 2 ) but the R group is variable, and that is the only difference between amino acids.
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Page 1: Molecules, Biodiversity, Food and Health

Emily Summers

AS Unit F212: Molecules, biodiversity, food and health

Module 1 - Biological molecules

Biological molecules

Describe how hydrogen bonding occurs between water molecules, and relate this and other properties of water to the roles of water in living organisms.

Describe, with the aid of diagrams, the structure of an amino acid.

Structure of an Amino Acid

Structure of Glycine

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All amino acids have the same general structure, a carboxyl group, an amino group attached to a carbon atom (-NH2) but the R group is variable, and that is the only difference between amino acids.

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Describe, with the aid of diagrams, the formation and breakage of peptide bonds in the synthesis and hydrolysis of dipeptides and polypeptides.

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Condensation reactions make peptide bonds between amino acids. A molecule of water is released.

It’s reversible, and by adding a water molecule you can break the peptide bonds. This is called hydrolysis.

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Explain, with the aid of diagrams, the term primary structure.

Explain, with the aid of diagrams, the term secondary structure with reference to hydrogen bonding.

Explain, with the aid of diagrams, the term tertiary structure, with reference to hydrophobic and hydrophilic interactions, disulphide bonds and ionic interactions

Ionic Interactions weak attractions between oppositely charged parts the molecule

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Disulfide Bonds Two molecules of an amino acid close together, the sulphur atoms in them bond together forming this bond. (E.g. Cysteine)

Hydrophobic Water repelling groups near together in a protein they clump.

Hydrophilic Water attracting groups are likely to be pushed outside, affecting the protein’s final structure.

Explain, with the aid of diagrams, the term quaternary structure, with reference to the structure of haemoglobin.

The quaternary structure tends to be determined by the tertiary, when it involves multiple polypeptides. E.g. Haemoglobin has a quaternary structure, it has 4 polypeptide chains.

Describe, with the aid of diagrams, the structure of a collagen molecule

Collagen is a strong protein that is fibrous. It is a supportive tissue in animals; it is made of three polypeptide chains that are very tightly coiled into a triple helix, interlinked by covalent bonds. Minerals are able to bind to this helix to increase rigidity.

Tendons are made up mostly of collagen Walls of arteries contain collagen to prevent

bursting from high pressure blood in them Cosmetic treatment for lips for a fuller appearance

Compare the structure and function of haemoglobin (as an example of a globular protein) and collagen (as an example of a fibrous protein).

Haemoglobin CollagenGlobular protein Fibrous ProteinLarge variety of amino acids in it’s primary structure

35% of primary structure is glycine

Has a prosthetic group- haem Doesn’t contain a prosthetic groupMostly wound into alpha helix structures Mostly left handed helix structures

Describe, with the aid of diagrams, the molecular structure of alpha-glucose as an example of a monosaccharide carbohydrate.

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Monosaccharide carbohydrate, a hexose sugar because it has six carbon atoms in every molecule. The structure determines its solubility so it can be easily transported. It’s a source of energy for animals and plants. Its chemical bonds have lots of energy in them.

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Emily Summers

State the structural difference between alpha- and beta-glucose.

Describe, with the aid of diagrams, the formation and breakage of glycosidic bonds in the synthesis and hydrolysis of a disaccharide (maltose) and a polysaccharide (amylose).

Compare and contrast the structure and functions of starch (amylose) and cellulose.

Starch CelluloseLarge molecules of many alpha glucose molecules joined with condensation reactions, insoluble in water and form granules

Large molecules of many beta glucose molecules joined with condensation reactions, they are insoluble in water and also strong

For energy storage in plants Structural found in plants where it forms cell walls

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Condensation- H2O removed!

Hydrolysis- H2O breaks glycosidic bond.

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Describe, with the aid of diagrams, the structure of glycogen.

Explain how the structures of glucose, starch (amylose), and glycogen and cellulose molecules relate to their functions in living organisms.

Carbohydrate Example Characteristics Function in Organisms

Monosaccharide monomers

Glucose (6 Carbon sugar)

Small, soluble, sweet, crystalline

Energy via respiration

Deoxyribose (5 Carbon sugar)

Part of DNA information molecule

Disaccharide dimers Maltose (2 glucoses) Small, soluble, sweet & crystalline

Sugar obtained when starch is broken down in hydrolysis, can be split to glucose for more respiration

Polysaccharide polymers

Starch & glycogen Large molecules, many alpha glucose molecules joined by condensation. Insoluble in H2O and form granules

Energy store in plants as cellulose and glycogen in animals and fungi

Cellulose Large molecules of many beta glucose molecules joined by condensation. Insoluble in H2O and are strong.

Structural in plants for cell walls.

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Excess glucose is stored as glycogen in animals.

The 1-4 and 1-6 glycosidic bonds cause branching!

Meaning that the glucose can be quickly released- good for animals!

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Compare, with the aid of diagrams, the structure of a triglyceride and a phospholipid.

Phospholipid

Triglyceride

Explain how the structures of triglyceride, phospholipid and cholesterol molecules relate to their functions in living organisms.

Triglyceride molecules are used as energy storage molecules. This is good because the hydrocarbon tails of the fatty acids have lots of chemical energy that is released when broken down, so lipids contain double the energy carbohydrates do.

They are insoluble because of their hydrophobic so they do not interfere with the water potential in cells that would cause water to enter cells by osmosis so they could swell/burst.

Phospholipid molecules have a hydrophilic head and a hydrophobic tail. The head faces outwards and the tail faces inwards in the phospholipid bilayer on cell surface membranes, making it difficult for water soluble substances like Na+ ions and glucose to pass through.

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Phospholipids are similar to triglycerides except that one of

the fatty acid molecules is replaced by a phosphate group.

Fatty acid tails are hydrophobic

Phosphate group is hydrophilic and faces outwards. Good in the

bilayer for cell membranes so water soluble substances find it

hard to get through.

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Cholesterol is a lipid found in cell membranes for mechanical stability, and is used to make steroids. It has a hydrocarbon ring structure attached to a hydrocarbon tail. The hydrocarbon ring has a polar hydroxyl group attached to it which makes it soluble.

Describe how to carry out chemical tests to identify the presence of the following molecules: protein (biuret test), reducing and non-reducing sugars (Benedict’s test), starch (iodine solution), and lipids (emulsion test).

Biuret’s Test

Add Benedict’s solution to the substance and heat to 80 degrees Celsius in a water bath. If the solution changes colour from blue to green-brick red then it is a reducing sugar. (Monosaccharide and disaccharide)

Non reducing sugars do not react with Benedict’s solution so there would be no colour change E.g. Sucrose, formed by a condensation reaction between glucose and fructose. The formation of this bond is different to reducing sugars, so it must be boiled with hydrochloric acid, to hydrolyse/split the sucrose molecules to give glucose and fructose monosaccharides. Then add an alkali to a cool solution to neutralise it, e.g. NaCO3 solution. Then do the reducing sugar test and you should get a positive result.

Starch

Add iodine in a potassium iodide solution to the sample, and if there is starch the sample solution will change from yellow/brown to a dark blue/black. Negative results present no colour change.

Lipids

Mix the sample with ethanol, dissolving lipids present. Pour the solution into water in a separate test tube. If there is a lipid there will be a cloudy white milky emulsion near the top of the water.

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Protein

Add biuret reagent to a sample. The reagent contains sodium hydroxide and copper sulphate, reacting with the peptide bonds in protein turning the solution to a purple colour if there is protein, and staying blue if there is no protein.

Describe how the concentration of glucose in a solution may be determined using colorimetry.

A colourimeter measures the absorbance of light of a solution; the more concentrated the colour the higher the absorbance is.

Make up several glucose solutions of known, different solutions Do a Benedict’s test on each solution, same amount in each case make sure

there is excess reagent Remove precipitate (Centrifuge/ leave for a day) Use colourimeter to measure absorbance of Benedict’s solution remaining in

each tube Record your results in a calibration curve (absorbance against glucose

concentration) Test the unknown solution by using the colourimeter and reading it’s absorbance

value across on the calibration graph, it will tell you the concentration.

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Nucleic Acids

State that deoxyribonucleic acid (DNA) is a polynucleotide, usually double-stranded, made up of nucleotides containing the bases adenine (A), thymine (T), cytosine (C) and guanine (G).

A phosphate group Adenine and Thymine bond together with 2 hydrogen bonds, Cytosine and guanine join with

3 hydrogen bonds Deoxyribose

Joined with covalent bonds (sharing of electrons)

State that ribonucleic acid (RNA) is a polynucleotide, usually single-stranded, made up of nucleotides containing the bases adenine (A), uracil (U), cytosine (C) and guanine (G).

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A nucleotide

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Describe, with the aid of diagrams, how hydrogen bonding between complementary base pairs (A-T, G-C) on two anti-parallel DNA polynucleotides leads to the formation of a DNA molecule, and how the twisting of DNA produces its double-helix shape.

Outline, with the aid of diagrams, how DNA replicates semi-conservatively, with reference to the role of DNA polymerase.

The enzyme called DNA helicase breaks the hydrogen bonds between the two polynucleotide DNA strands unzipping the helix to form two single strands, exposing the bases.

Each original strand is a template for a new strand, free floating DNA nucleotides join to exposed bases on each original template strand by complementary base paring (purine pyrimidine, A- -T, G- - -C)

The nucleotides on the new strand are joined by DNA polymerase, and new hydrogen bonds are formed between the bases on the old and new strand.

Each DNA molecule contains one strand from the original DNA molecule and one new strand.

State that a gene is a sequence of DNA nucleotides that codes for a polypeptide.

Gene A gene is a length of DNA that carries the code for the synthesis of one or more specific polypeptides.

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Outline the roles of DNA and RNA in living organisms (the concept of protein synthesis must be considered in outline only).

The sequence of bases on DNA are code instructions for proteins, they code for the amino acid sequence present in the protein. This is a gene.

There are three forms of RNA:

Messenger RNA Is a strand complementary to a strand of a DNA molecule, a template strand that is a copy of the coding strand of the double helix

Ribosomal RNA In ribosomes

Transfer RNA Carries amino acids to the ribosomes and they are bonded together to form polypeptides.

Enzymes

State that enzymes are globular proteins, with a specific tertiary structure, which catalyse metabolic reactions in living organisms.

Enzymes are:

Globular proteins and soluble in water

Able to break molecules down or build them up!

Biological catalysts

Specific- because they catalyse a reaction with only one type of substrate

Their globular structure has a pocket called an active site

Activity affected by temperature and pH (Rate of reaction)

Enzymes are large molecules with hundreds of amino acids. A lot of these amino acids work to keep the specific tertiary structure of the enzyme. The function of the enzyme depends on the shape, and for the enzyme to work correctly the tertiary structure must be maintained specifically.

All of the structures (primary, secondary, tertiary) of the enzyme is involved in the specific active site shape. (Where the catalytic activity of the enzyme happens)

Enzymes are faster than catalysts and because they are specific to one reaction they do not produce unwanted by products.

An individual cell could contain over one thousand enzymes to catalyse every process, like digestion, respiration, photosynthesis.

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State that enzyme action may be intracellular or extracellular.

Extracellular Enzymes catalase reactions outside of the cell

Intracellular Enzymes catalase reactions inside of the cell

Mould produces extracellular enzymes to digest bread.

Phagocytes take in and digest bacteria using lysosomal enzymes.

Describe, with the aid of diagrams, the mechanism of action of enzyme molecules, with reference to specificity, active site, lock-and-key hypothesis, induced-fit hypothesis, enzyme-substrate complex, enzyme-product complex and lowering of activation energy.

Enzymes reduce the amount of activation energy needed, so reactions happen quickly at lower temperatures, because of the way the active site is shaped to fit the substrate.

Enzyme’s active site is complementary to the shape of the substrate, they are specific.

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Describe and explain the effects of pH, temperature, enzyme concentration and substrate concentration on enzyme activity.

pH

pH is the measure of the H+ ion concentration. These ions are positive so they are attracted to negatively charged ions, or parts of molecules and repelled by positive parts. Hydrogen bonds and ionic bonds hold the tertiary structure of an enzyme in place so the active site is maintained in it’s correct shape. The bonds are there because of electrostatic attraction between opposite charges on the amino acids making up the enzyme.

Hydrogen ions interfere with these bonds and can alter the tertiary structure of an enzyme by altering their concentration.

Enzymes have their own optimum pH, the H+ ion concentration gives the enzyme the best overall shape. Enzymes work in a narrow pH range usually, and their pH range often changes with their location. E.g. Pepsin is in the stomach and has an optimum pH of 2. Handy! Whereas Trypsin has an optimum pH of 7 which is good for the conditions of the small intestine it works in, where it digests protein.

Temperature

When you apply heat to molecules, they move faster in a liquid or gas and they also vibrate.

The vibrations strain the bonds holding the molecules.

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In large molecules like enzymes the vibration of molecules can break weaker bonds like hydrogen or ionic bonds.

The weaker bonds are there in abundance in an enzyme molecule and hold the tertiary structure in place, so they maintain the active site’s correct, specific shape.

Increasing temperature = Increasing bonds broken

And the tertiary structure is held less in the shape of the active site needed for it to work.

So rate of reaction will decrease if the substrate can’t fit in the active site.

If enough of the bonds are broken, the entire tertiary structure unravels and the enzyme stops working.

If the tertiary structure of an enzyme is changed enough it will not function and it is not restorable denaturation.

Denaturation Changes only the tertiary structure of an enzyme so it can’t function and its function can’t be restored, which changes the active site of the enzyme.

Concentration

Increasing the enzyme concentration increases rate of reaction to a point, until it will not increase anymore because substrate concentration is the limiting factor. Reactions cannot be quick if there isn’t enough substrate left, and vice versa.

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Describe how the effects of pH, temperature, enzyme concentration and substrate concentration on enzyme activity can be investigated experimentally.

Variable Method of Keeping Constant

Reasons

Temperature Carrying out the enzyme controlled reaction in a water bath with thermostat

Room temperature changes and fluctuations in the temperature alters the enzyme controlled reaction so results will not reflect the true action of the independent variable that is being found

Enzyme Concentration Use an accurate measured volume of enzyme-solution

Rate of reaction depends on concentration of enzyme molecules present; using accurate volumes of enzyme solution gives a true constant conc. Of enzyme molecules

Living tissue Mass of tissue has to be accurate

Assume that the pieces of tissue have the same number of enzyme molecules

Whole pieces of tissue same surface area and mass

The number of enzymes that have contact with substrate affects rate of reaction, e.g. surface area

Substrate Concentration Accurately measured substrate volume/mass

Rate of reaction depends on substrate molecule concentration

pH value Use pH buffers by keeping H+ concentration constant

Rate of reaction depends on pH because it alters the shape of the active site of the enzyme

Explain the effects of competitive and non-competitive inhibitors on the rate of enzyme-controlled reactions, with reference to both reversible and non-reversible inhibitors.

Competitive inhibitors have a similar shape to the substrate so they occupy the active site and form an enzyme inhibitor complex but no product is made. So the enzyme cannot catalyse a reaction and rate of reaction slows down. Depends on inhibitor and substrate concentration, e.g. if you increase substrate rate of reaction may increase.

Non Competitive inhibitors don’t occupy the active site, but attach somewhere else on the enzyme to distort the tertiary structure of the enzyme. So the active site changes

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and the substrate can’t fit anymore, so no reaction can be catalysed and reaction rate decreases. Increasing substrate concentration has no effect.

Reversible inhibitors are when the inhibitor isn’t there permanently and afterwards the enzyme is unaffected.

Non Reversible inhibitors are usually non competitive and the enzyme is denatured.

Explain the importance of cofactors and coenzymes in enzyme-controlled reactions

Coenzymes take part in the reaction and are changed, but are recycled back to take place in the next reaction.

Cofactors are there to ensure an enzyme controlled reaction takes place at an appropriate rate, and some enzymes can only catalyse a reaction if a cofactor is there.

State that metabolic poisons may be enzyme inhibitors, and describe the action of one named inhibitor.

Lots of poisonous substances have their effects due to inhibiting or over-activating enzymes. For instance, Potassium Cyanide inhibits respiration of cells, because it is a non competitive inhibitor for a vital respiratory enzyme, cytochrome oxidase, in the mitochondria. When cytochrome oxidase is inhibited the use of oxygen is reduced and ATP cannot be produced. So the organism is only able to respire anaerobically, which builds up lactic acid in the blood increasing its acidity.

State that some medicinal drugs work by inhibiting the activity of enzymes.

Viral infections are treated using chemicals that act as protease inhibitors, which stop viruses from replicating by inhibiting the activity of protease- which are vital to viruses to build their new virus coats. Usually these inhibitors are competitive.

Cystic Fibrosis sufferers have the problem that the passage of digestive enzymes that are usually secreted from the pancreas into the gut is blocked, leading to digestive problems. Enzymes in a tablet can overcome the problem; they are in an acid resistant coat so they’re not destructed by acid/protein digesting enzymes located in the stomach.

Health and disease

Discuss what are meant by the terms health and disease

Health is a complete state of physical, mental and social well being as well as the absence of disease or infirmity.

Disease is a departure from full health caused by a malfunction of the mind or body

Define and discuss the meanings of the terms parasite and pathogen.

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Parasite Is an organism that lives in or on another living thing causing harm to the host. External head lice Internal Tapeworm

Pathogen A general term for any organism that causes disease

Bacteria, fungi, viruses, protoctista

Describe the causes and means of transmission of malaria, AIDS/HIV and TB.

Malaria is caused by a eukaryotic organism, from the genus Plasmodium and most commonly the species Plasmodium falciparum.

Malaria is spread by means of a vector. The female Anopheles mosquito carries the plasmodium from an uninfected to an infected person, they feed on blood with adapted mouthparts to penetrate a blood vessel and withdraw blood, malarial parasites live in the erythrocytes of humans and feed on Hb.

HIV/AIDS

The virus enters the body and is un-active, but once the virus is active and attacks/destroys T helper cells in the immune system your ability to resist infection is greatly decreased. You are open to opportunistic infections which will eventually kill the person with HIV/AIDS.

Exchange of bodily fluids, e.g. blood to blood, sharing needles, unprotected sex Unscreened blood transfusions Mother to baby- across the placenta or during breast feeding

TB

TB is caused by a bacterium, M Bovis and Mycobacterium tuberculosis.

It is usually in the lungs and although it is common it usually remains unactive or the immune system controls it, it is transmitted by a droplet infection.

Overcrowding Poor ventilation Poor health, especially with HIV/AIDS Poor diet Homelessness Contact with those who migrate from countries where TB is common

Discuss the global impact of malaria, AIDS/HIV and TB.

REMEMBER THE WORLD HEALTH ORGANISATION! They say good health is a human right and see that in LEDC countries there may be:

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Poverty Lack of shelter and pure water Poor nutrition and hygiene Insufficient health services and insufficient education of disease

Malaria kills three million a year, but is limited to where the Anopheles can survive which is tropical regions like Sub Saharan Africa. Global warming is a worry.

HIV/AIDS Pandemic. 45 million living with HIV/AIDS in 2005 and over half lived in sub Saharan Africa.

TB Worldwide disease, new strains of Mycobacterium are resistant to drugs available to treat it. Common in sub Saharan Africa but rising in Eastern Europe.

Define the terms immune response, antigen and antibody.

Immune response is the specific response to a pathogen involving the action of lymphocytes and the production of antibodies.

Antigens are molecules that stimulate an immune response.

Antibodies are protein molecules that identify and neutralise antigens.

Describe the primary defences against pathogens and parasites (including skin and mucous membranes) and outline their importance.

They try to prevent pathogens from entering the body, general mechanisms.The skin

Main primary defence Outer layer= epidermis Keratinocytes are made by mitosis at the base of the epidermis, during migration

they dry out and the cytoplasm is replaced by keratin- called keratinisation. When these cells reach the surface they aren’t alive anymore and the dead cells come off, but this layer of dead cells are a good barrier to pathogens.

Mucous Membranes In airways, lungs and digestive system Goblet cells secrete mucus and mucus lines airway passages to trap pathogens.

Cilliated epithelium beats rhythmically to waft mucus to the back of the mouth where it is swallowed down to the digestive system, the acidic stomach kills most pathogens by denaturing their enzymes

Eyes are protected by tear fluid antibodies and enzymes

Ear canals are lined with wax to trap pathgogens

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Describe, with the aid of diagrams and photographs, the structure and mode of action of phagocytes.

Describe, with the aid of diagrams, the structure of antibodies

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Outline the mode of action of antibodies, with reference to the neutralisation and agglutination of pathogens.

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Antibodies cover the pathogen binding sites and prevent the pathogen from binding to a host cell and entering the cell

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A large antibody can bind lots of pathogens together so the group of pathogens are too large to enter a host cell.

Compare and contrast the primary and secondary immune responses

Compare and contrast active, passive, natural and artificial immunity.

Active Immunity Artificial ImmunityExposure to antigen No exposure to antigenProtection development takes a longer period

Protection is instant

Protection lasts a long while Protection lasts a short periodMemory cells made No memory cells made

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Active Immunity Passive ImmunityNatural Catch the disease Antibodies from mother to

baby across placentaArtificial Vaccination Injected with antibodies

Module 3 Biodiversity & Evolution

Biodiversity

Define the terms species, habitat and biodiversity

A species is a group of similar individual organisms with similar appearance, biochemistry, physiology and genetics whose members are able to interbreed freely to produce fertile offspring

A habitat is a place where the organism lives

Biodiversity is the variety of life, the range of living organisms to be found

Use Simpson’s Index (D) to calculate the biodiversity of a habitat, using the formula D = (n/N)2.

D = (n/N)2.

There are three species of flower in a field, red, white and blue.There are eleven organisms all together, so N = 11

There are three of the red species, five of the white and three of the blue

D = 1 – ((3/11)2 + (5/11)2 + (3/11)2 = 1 – 0.36 = 0.64 Quite high!

Outline the significance of both high and low values of Simpson’s Index (D).

The closer to one the index is, the more diverse the habitat is. A high value indicates high biodiversity in a habit which is beneficial, a low one indicates low biodiversity in a habitat which isn’t so good, and may suggest that conservation methods might have to be put in place.

Classification

Define the terms classification, phylogeny and taxonomy.

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Classification is arranging organisms into groups based on similarities and differences in appearance.

Phylogeny is the study of the evolutionary history of groups of organisms

Taxonomy is the study of classification

Explain the relationship between classification and phylogeny.

Describe the classification of species into the taxonomic hierarchy of domain, kingdom, phylum, class, order, family, genus and species.

Outline the characteristic features of the following five kingdoms: Prokaryotae (Monera), Protoctista, Fungi, Plantae, Animalia.

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Kingdom Example Features

Prokaryote Bacteria Single cell, no nucleus, smaller than 5 micrometres

Protoctista Algae Eukaryotic, single celled or simple multicellular

Fungi Mould, yeast, mushroom Chitin cell wall, eukaryotic, saprotrophic

Plantae Moss, fern, roses Eukaryotic, multicellular, cellulose cell wal, autotrophic

Animalia Mammals, reptiles, birds, fish, insects

Heterotrophic, eukaryotic, no cell wall, multicellular

Outline the binomial system of nomenclature and the use of scientific (Latin) names for species.

One international name in latin with two parts is given to every organism. The first part is the genus and is a capital letter, and the second is the species and is lower case- typed in italics or underlined when written. E.g. Homo sapien

Helps to avoid confusion within scientists as they’re standard scientific names.

Use a dichotomous key to identify a group of at least six plants, animals or microorganisms.

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Discuss the fact that classification systems were based originally on observable features but that more recent approaches draw on a wider range of evidence to clarify relationships between organisms, including molecular evidence.

Early classification systems simply used observable features to put organisms into groups, but this is problematic because the fact that some organisms look similar doesn’t mean they’re closely related, e.g. sharks and whales look similar and live in the sea, but sharks are fish and whales are mammals! Classification systems today are based on more evidence, like:

Molecular evidence protein and DNA similarities, e.g. how it’s stored, closeness of bases.

Anatomical Similarities in structure and function of body parts Behavioural evidence Similarities in behavior and social organization of

organisms

Compare and contrast the five kingdom and three domain classification systems.

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Evolution

Define the term variation.

Variation Presence of variety of differences between individuals

Discuss the fact that variation occurs within as well as between species.

Describe the differences between continuous and discontinuous variation, using examples of a range of characteristics found in plants, animals and microorganisms.

Continuous variation Variation in which there is a full range of intermediate phenotypes between two extremes

Discontinuous variation Variation in which there are discrete groups of phenotypes with few or no individuals in between

Continuous DiscontinuousHeight Dangling/attached ear lobesHandspan GenderWeight Blood groupsShoe Size Bacteria with absence/presence of flagella

Continuous DiscontinuousAffected by environment & genes Unaffected by environment, just genesQuantitative overlaps Qualitative no overlapsControlled by a large number of genes (polygenic)

Controlled by few/one gene (monogenic)

No distinct categories Distinct categories

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Like heart rate, muscle efficiency, IQ, growth rate, rate of photosynthesis

This type of variation is rare in animals but abundant in plants, like seed colour, petal colour, etc.

Explain both genetic and environmental causes of variation.

Genetic Environmental Genes from our parents Combination of alleles Not the same in any other living

thing apart from identical twins Never a complete match Human cells have 25,000

different genes and a lot of them have more than one allele, so it isn’t likely that any two individuals will have the exact same allele combinations.

Linked with genetic Like height is somewhat

determined by your genes but the environment plays a part on the height you will reach. (diet)

Environmental changes affect what genes in animals and plants are activated, bringing about changes we see

Obesity diet socio-economic issues. Westernized society has more overweight people than ledc’s

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Outline the behavioural, physiological and anatomical (structural) adaptations of organisms to their environment

Explain the consequences of the four observations made by Darwin in proposing his theory of natural selection.

Individual in a species have differences from each other – so variation is present.

Offspring bare resemblance to their parents – those characteristics are inherited.

There are more offspring produced than survived to maturity - they suffer from predation, disease and competition.

Populations have constant sizes

“Darwin concluded that individuals that were better adapted to their environment compete better than the others, survive longer and reproduce more, so passing on more of their successful characteristics to the next generation. Darwin used the memorable phrases survival of the fittest, struggle for existence and natural selection.” Biology Mad

Define the term speciation.

Formation of a new species from the evolution of one species

geographical isolation which is an example of allopatric speciation

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Behavioural

Behaviour of an organism that enables it to survive it's living conditions. Like when you touch an earthworm it quickly contracts and goes back into it's burrow. This is a behavioural adaptation that avoids it being eaten.

Physiological/Biochemical

A physiological/biochemical adaptation that ensures correct functioning of cell processes. Like yeast can respire sigars an/aerobically to get energy depending on the amount of O2 in the environment. Producing correct enzymes to respire the sugars in the environment falls under this category.

Anatomical

Any structure that enhances survival of the organism is an adaptation. Like bacteria that have flagella to allow them to move indepedently. Structural adaptation.

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reproductive isolation which is an example of sympatric speciation

Discuss the evidence supporting the theory of evolution, with reference to fossil, DNA and molecular evidence.

Outline how variation, adaptation and selection are major components of evolution.

Discuss why the evolution of pesticide resistance in insects and drug resistance in microorganisms has implications for humans.

Conserving biodiversity

Outline the reasons for the conservation of animal and plant species, with reference to economic, ecological, ethical and aesthetic reasons.

Discuss the consequences of global climate change on the biodiversity of plants and animals, with reference to changing patterns of agriculture and spread of disease.

Explain the benefits for agriculture of maintaining the biodiversity of animal and plant species.

Describe the conservation of endangered plant and animal species, both in situ and ex situ, with reference to the advantages and disadvantages of these two approaches.

Discuss the role of botanic gardens in the ex situ conservation of rare plant species or plant species extinct in the wild, with reference to seed banks.

Discuss the importance of international cooperation in species conservation with reference to the Convention in International Trade in Endangered Species (CITES) and the Rio Convention on Biodiversity.

Discuss the significance of environmental impact assessments (including biodiversity estimates) for local authority planning decisions

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