Biology (salters Nuffield)

Topic 5 - On the wild side.

  • Created by: HASNAAN
  • Created on: 03-06-09 16:24


1) the variety of different organisms.

2) The diversity within species. (genetic DIversity)

3) The diversity of ecosystems.

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Definition of a species.

A group of organisms with simillar morphology, physiology, behaviour.

Can interbreed to produce fertile offspring and are reproductively isolated from other species.

Same speciers or different species?

Group A has 98% of its genes in common with group B. (different)

Group C can interbreed wit group A to produce fertile offspring. ( either the same or very simillar.)

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Naming species.

Binomial system

1st part is called the genus.

Genus is hared by all closely related species. (i.e zebras and horses.)

2nd part defines a particular species in the genus.

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Five kingdoms

1) Kingdom Animalia

2) Kingdom plantae

3) kingdom Fungi.

4) Kingdom prtoctista

5) Kingdom prokaryotae.

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Kingdom animalia.

1) multi-cellular eukaryotes with differentiated cells organised into special organs

2) no cell walls or large vacuoles

3) cannot photosynthesise.

4) Heterotrophic - rely on other organiss for nutrition.

5) most can move from place to place and have a nervous co-ordination.

6) Includes phyla such as jelly fish round worms arthropods molluscs.

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Kingdom plantae.

Multi - cellular eukaryotes. with differentiated cells organised into special organs.

Cell wall contain cellulose.

cell contains chloroplast and large vacuoles.

autotrophic - make organic compounds via photosynthesis exept for a few parasytes.

Includes mosses liverworts, ferns, conifers and flowering plants.

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Kingdom fungi.

1) Multi - cellular eukaryotes. (although most do not have seperate cells.)

2) most are made up of a network of thread like strands called multi - nucleate hyphae.

3) Cells walls made of chitin. (A mucopolysaccharide simmilar to cellulose but amino acids attached.)

4) Cannot photosynthesise.

5) Heterotrophic. Most absorb nutrients from the deecaying matter after extra cellular digestion.

6) includes moulds, yeast, and mushrooms.

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kingdom protoctista.

Multi cellular and unicellular eukaryotes.

Basic body structure is simple.May either photosynthesise or feed on organic matter from other sources.

Include single celled protozoa, such as amoeba, paramecium, and algae.

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Kingdom prokaryotae

prokarotic cells are very small and Typically less than 10 micro-metres across.

cells have no distinct nucleus.

Nucleic acid in a single circular chromosome.

Cells do not have organelles such as mitochondria and chloroplasts.

May either photosynthesis or feed on organic matter from other sources.

Includes bacteria and blue green bacteria (cyanobacteria.)

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Change DNA sequencein the cells of an organism.

Create new alleles.

Genetic diversity increased by the introduction of these new alleles into the gene pool.

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Sources of genetic variation,

Mutations:- source of new genetic materioal

1) Gene point mutations. -

  • Alterations of dna base sequence.
  • Often arise during DNA replication

2) Chromosome mutations.-

  • Small section of chromosome re arranged during meiosis.
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Preperation for sexual reproduction.

1) Independent assortment.

  • Each homologous pair of chromosomes is sorted independent of the others.
  • Random process.

2) Crossing over

  • Pieces of genetic material are exchanged between homologous chromosomes.
  • Chromatids come together, break apart, and rejoin exchanging DNA.
  • Points of breakage called chiasma.
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Abiotic factors. (non living or physical factors.)

1) Solar energy input - is affected by lattitude, season, cloud cover, and changes in earths orbit

2) Climate - Rainfall, wind exposure, and extremes of temprature

3) Topography - lattitude, slope, aspect, and drainage

4) Oxygen availability- important in aquatic systems. Fast flowing streams are better oxygenated.

5) Edaphic factrors - Soil pH, mineral salt availability and soil texture

6) Pollution - Can be of air, water or land

7) Catastrophies - Disturb conditions considerably. earthquakes, floods, volcanic erruptions

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Biotic factors. (living factors.)

1) Competition - food,light,water and space can be interspecific or intraspecific.

2) Grazing, predation, parasitism - relationship between 2 organisms one benefits at others expense.

3) Mutualism - A relationship in whic both partners benefits.

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photosynthesis (overview.)

6CO2 + 6H2O ----> C6H12O6 + H2O

Products at higher energy level than reactants.

O2 is a waste product

Glucose can be oxidised during respiration to release energy.

Hydrogen separated from water and stored in carbohydrate.

When energy required in cell H2 reacts with O2 releasing large amount of energy.

Splitting of water into hydrogen and oxygen through photolysis.

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Photosynthesis. (Storage of carbohydrates,)

H2 reacted with CO2 to store as an "organuic fuel"

CO2 reduced to form glucose which is then stored.

Photosynthesis converts CO2 into carbohydrates using light energy and hydrogen from water.

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Photosynthesis (how it works.)

Two stages.

1) Light dependent reactions - use energy from light and hydrogen from photolysis of water to produce reduced NADP and ATP.

2) Light independent reactions. - Reduced NADP and ATP used to reduce carbon dioxide to carbohydrates.

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Photosynthesis (summary questions)

Q) which molecule provides the source of hydrogen for photosynthesis.

A) Water

Q) What is the source of energy for photosynthesis.

A) Light energy from sun

Q) which molecule provides the hydrogen for the light independent reaction.

A) Reduced NADP.

Q) Which molecule provides a source of energy for the ligh independent reaction.


Q) write equation for the splitting of water.

A) H2O ---> 2H+ + 2e- + 1/2 O2

Q) Write equation for the reduction of NADP

A) 2H+ + 2e- + NADP ---> reduced NADP.

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Photosynthesis (light dependent reactions)

Light absorbed by photosynthetic pigments in the thylakoid membranes of the chloroplast.

1) light energy raises energy levels of two electrons in each chlorophyll molecule.

2) Chlorophyll molecules are now in "excited state".

3) Electron leave chlorophuyll molecules.

4) Pass along series of electron carrier molecules.

5) electrons pass from one molecule to the next via oxidation and reduction reactions. (Energy lost in this process.)

6) Energy used in the synthesis of ATP.

7) Ezyme catalyse splitting of water to give oxygen, hydrogen gas and electrons.

8) Electron replaced to maintain flow of electrons.

9) Electrons which have passed through chain combine with the coenzyme NADP and hydrogen ions from water to form reduced NADP.

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Structure and function of chloroplast. (Thylakoid

Interconnectedflattened membrae biund sacs.

Protiens including photyosynthetic pigments, and electron carriers

involved in light dependent reactions.

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Fluid surrounding thylakoid membrane. Contains

enzymes needed to carry out light independent reactions.

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Thylakois space.

Fluid within thylakoid membrane.

Contain enzymes needed for photolysis.

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Stacks of thylakoids joined together.

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smooth outer membrane.

Freely permeable to molecules such as CO2 and H2O

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smooth inner membrane.

Contains many transporter molecules.

Membrane protiens reguolate the passing of substances in and out of the chloroplast.

Includes sugars and synthesised protiens .

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Summary of light dependent reactions.

1) energy from sunliught excite chlorophyll molecules.

2) High energy electrons leave the chlorophyll.

3) Electron pass along carrier protiens in electron transport chain.

4) Ionised chlorophyll causes photolysis of water. raising local Hydrogen in conc in thylakoid.

5) ATP formed as phosphate group added to ADP.

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Role of ATP.

Most importanty energy transfer molecule in the cell.

Takes energy from energy yielding reaction to energy requiring reactions.

Consists of Adenine, ribose and 3 phosphate groups.

£rd phosphate group loosely bonded and is easily removed.

When this phosphate group is lost ATP becomes ADP.l

Phosphate group becomes hydrated. Forms bonds with water molecules.

Alot of energy released.

Energy used to drive energy requiring reactions.

(ATPase catalyses tghe breakdown of ATP to ADP and Pi)

ATp created when PI group added to ADP.

Pi group must be torn away from water which requires energy

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Photosynthesis. (Light independent reactions.)

Take place in the stroma.

Use reduced NADP and ATP from light dependent reactions.

CO2 reduced to carbohydrate.

Reduced NADP acts as Hydrogen carrier.

Series of reactions which form a cyclic pathway. (calvin Cycle.)

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Calvin Cycle.

1) CO2 combines with RuBP reaction catalysed by RuBISCO

2) 6 Carbon compound formed is unstable. It immediately breaks down into 3 carbon compound. (glycerate -3- phosphate.) [GP]

3) GP then reduced to form another 3 carbon compound called ( Glyceraldehyde- - phosphate.) [GALP]

4) 2 out of 12 GALP's are involved in carbohysrate synthesis which can be converted into other organic compounds, for example amino acids or lipids.

5) 10 out of 12 GALPs' are involved in the recreation of of RuBP. The 10 GALP molecules re-arrange to form six 5 - carbon compounds then phosphorylation using ATP and RuBP.

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Thylakoids and the light dependent reaction.

Electron carriers located in the thylakoid membranes in the chloroplast.

Positioning of these membranes creates electron transport chain.

Electrons pass effecient across chain.

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Stroma in light independent reaction.

The compartmentalisation of the light independent reaction within in chloroplast stroma

mean that the subtrate and enzymes can be at concentrations which allows the reactions to be successfully catalysed as quickly as possible.

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