Full biology unit 4 powerpoint

Biology 4

•Populations

•ATP

•Photosynthesis

•Respiration

•Energy and Ecosystems

•Nutrient cycles

•Ecological succession

•Inheritance and selection

Populations• Ecology- study of inter-relationships between organisms and

environment• Ecosystem- interacting biotic and abiotic factors in a specific area• Populations- group of inter-breeding organisms of 1 species• Community- all populations living and interacting in a specific area• Habitat- place where community of organism lives• Niche- how an organism fits into the environment (no two species

occupy same niche)• Abiotic- temperature, light, PH, water and humidity• Biotic- living organisms (competition and predation)• Intraspecific competition- same species for; food, water, breeding

site• Interspecific- Different species; food, light, water

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Investigating populations

• Quadrats- factors, size, number and position should be considered

• Random Sampling- avoid bias -1. long tape measures at right angles -2. Co-ordinates from random number generator -3. place quadrat on intersection

• Systematic sampling- distribution of species- straight line or belt (two lines)

• Measuring abundance- -Frequency: e.g. 15/30= 50%- useful for species such as grass-Percentage Cover: estimate area within quadrat that particular plant species covers, useful for abundance of hard to count species

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Mark-Release-Recapture:

Estimatedpopulation size =

Total no. of individuals in 1st samplex

Total no. of individuals in 2nd sample

No. of marked individuals recaptured

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Human populations

• Immigration and emigration (leaving)

• Pop. Growth= (births+immigration) - (death+emmigration)

• %pop. Growth rate= pop. Change during period pop. At start of period

x100

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Birth and Death rates• Birth:

-Economic conditions-cultural/ religious-social pressures & conditions-Birth control-political factors

• Birth rate= no. of births per year total pop. In same year

• Death:-age profile-life expectancy at birth- food supply -safe drinking water and sanitation-medical care-natural disasters-warDeath Rate= no. of deaths per year

x1000

Tot. pop. In same yearx1000

Change in population= demographic translation

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ATP & Energy

• ATP is an energy source for:metabolism, maintenance, movement, active transport, repair and division, production of substances, maintenance of body temperature

• ATP+ H20 ADP + Pi + E• Hydrolysis reaction

• Synthesis of ATP:reversible reaction (Pi to ADP – condensation reaction)

ATP immediate energy source-released in small bursts of energy from mitochondria-manageable-fast reaction

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Photosynthesis

• 6CO + 6H 0 C H O + 6O

• Light energy Electrical Chemical energy

• Chloroplasts:Grana (Thylakoids) – light dependant stage- pigment chlorophyllStroma- fluid-filled matrix – light independent stage- starch grains

• Factors effecting photosynthesis rate:light intensityCO2 Temperature

2 2 6 12 2

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Light- dependant reaction• Involves capture of light for:

-to add Pi to ADP for ATP-to split H+ ions (protons) and OH- ions by light known as photolysis

• Making of ATP:-Chlorophyll molecules absorb light energy, boosts energy of electrons

raising energy level (excited state)- then leave chlorophyll-electrons taken up by electron carrier -Having lost electrons the chlorophyll has been oxidised- electron carrier gains electrons (reduced)-In thylakoids they pass through oxidation-reduction reactions-energy along is lost for ATP production

• Photolysis of water:-2H O 4H+ + 4e- + O

protons electrons• H+ ions (protons) taken up by electron carrier NADP. NADP

becomes reduced• Reduced NADP aand electrons from chlorophyll enters light

independent reaction• Oxygen waste product/ used for respiration

2 2

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Light- independent reaction• ATP and reduced NADP from light dependant reaction used to reduce CO2• Calvin cycle in stroma• Stages:

1. CO2 diffuses into leaf through stomata2. In stroma CO2 combines with 5-carbon compund (RUBp) using an enzyme3.Combination of CO2 & RuBP produces 2x molecules of glycerate 3 phosphate (GP)4. ATP & reduced NADP from light-dependant reaction used to reduce activated glycerate 3-phosphate to triose phosphate (TP)5. NADP re-formed and goes back to light dependant reaction to be reduced by accepting Hydrogen6. Some triose phosphate molecules are converted to useful organic substances, such as glucose7. Most triose phosphate used to regenerate ribulose biphosphate using ATP from light dependant

Site of light independent reaction:fluid of stroma- contains all enzymes for Calvin cycle

stroma fluids surrounds grana, so products of light dependant reaction in grana caneasily diffuse

Contains both DNA and ribosome's, so quickly and easily manufacture proteins forCalvin cycle

Respiration• Aerobic respiration- needs O2, produces CO2, water and

ATP• Anaerobic respiration (fermentation)- takes place without

O2, produces lactate in animals and or ethanol/CO2 in plants but only a little ATP in both cases

• Aerobic can be divided in to four stages:1.Glycolysis- splitting 6-carbon glucose to two 3-carbon pyruvate2.link reaction- conversion of 3-carbon pyruvate molecule into CO2 and a 2-carbon molcule= acetylcoenzyme A3.Krebs cycle-acetylcoenzyme A into cycle of oxidation-reduction reactions that yield ATP and a large no. of electrons4.electron transport chain-use of electrons produced by krebs to synthesise ATP (water is by-product)

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Glycolysis

• Initial stage of aerobic and anaerobic respiration. Occurs in cytoplasm of all living cells

• Four stages:1.activation of glucose by phosphorylation- glucose more reactive by adding 2 phosphate molecules so it can split. Phosphate comes from hydrolysis of ATP to ADP- provides energy to activate glucose

2.splitting phosphorylated glucose- split into 3-carbon molecules known as triose phosphate.

3.Oxidation of triose phosphate- Hydrogen removed from each 2 triose phosphate & transferred to hydrogen-carrier molecule known as NAD to form reduced NAD

4.production of ATP- ezyme controlled reactions convert each triose phosphate to another 3-carbon molecule- pyruvate. In process two molecules of ATP regenerated from ADP.

Energy yield from Glycolysis:-two ATP molecules (two were used for phosphorylation)-two molecules of reduced NAD (has potential to produce more ATP-two molecules of pyruvate

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Link Reaction

• Pyruvate produced during glycolysis can only release energy using oxygen in krebs cycle.-1st oxidised in link reaction-Krebs & Link take place in eukaryotic cells inside mitochondria

• Link reaction: Pyruvate actively transported to matrix of mitochondria.-Pyruvate oxidised by removing hydrogen- hydrogen is accepted by NAD to form reduced NAD (later used to produce ATP)-2-carbon molecule, called acetyl group, combines with a molecule called coenzyme A (COA) to produce acetylcoenzyme A- a CO2 molecule is formed from each pyruvate

Pyruvate + NAD + COA acetyleCOA +reduced NAD + CO2

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Krebs Cycle

1. 2-Carbon acetylcoenzyme A combines with 4-carbon molecule to produce 6-carbon molecule

2. 6- Carbon loses CO2 and hydrogens to give a 4-carbon molecule & single ATP

3. The 4-carbon molecule can now combine with new molecule acetylcoenzyme A to begin cycle again

Link & Krebs produce:-reduced coenzymes NAD & FAD potential to produce ATP-one molecule of ATP-3 molecules of CO2

Because 2 pyruvate molecules are produced for each original glucose, yield is double of quantities above

Significance of Krebs:-break down macromolecules into smaller ones-production of ATP provides metabolic energy-regenerates 4-carbon molecules which would otherwise -accumulate-source of intermediate compounds used by cells in manufacture of fatty acids, amino acids and chlorophyll

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Coenzymes

• Coenzymes are molecules that some enzymes acquire for energy

• Carry Hydrogen atoms from one molecule to anotherExamples:NAD- important throughout respiration FAD- important in Krebs cycleNADP- important in photosynthesis

• In respiration NAD is most important carrier. Works with dehydrogenase enzymes that catalyse removal of hydrogen ions from substrates and transfer them to other molecules

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Electron transport Chain

• Cristae (inner folds) in mitochondria is the sight of electron transport chain

• Hydrogen carried by coenzymes NAD and FAD to electron transport chain from Krebs are 1st attached to cristae

• Releases protons from H-atoms- protons actively transported across inner membrane

• Electrons meanwhile pass along chain in oxidation-reduction reactions- elec. Lose energy down chain- some used to combine ADP and Pi. Remaining energy released as heat

• Protons accumulate in space between 2 mitochondrial membranes before diffusing back into matrix through protein channels

• End of chain electrons & protons and O2 combine to form H2O. O2 is the final acceptor of electrons in chain

Importance of O2:H-atoms (protons) and electrons would otherwise back- up-

respiration would come to a haltCyanide (non-competitive inhibitor)

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Anaerobic Respiration• In eukaryotic cells:

plants convert ethanol to CO2animals pyruvate to lactase

• Pyruvate + reduced NAD ethanol + CO2 + NAD (plants)• When O2 is low:

lactate production occurs mostly in musclereduced NAD must be removed for glycolysis- each pyruvate takes up 2 H-atoms from reduced NADpyruvate + reduced NAD lactate + NAD (animals)

• Lactate can cause cramp and muscle fatigue- must be oxidised back to pyruvate

Energy Yields from anaerobic and aerobic respiration:Substrate level phosphorylation in glycolysis and Krebs produces ATP

Oxidative phosphorylation- electron transport chain- ATPIn aerobic respiration Krebs or electron chain can’t take place.

Less ATP for anearobic- only from glycolysis

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Energy and ecosystems

• Consumers (Primary, secondary and tertiary)

• Decomposers- fungi and bacteria

• Detritivores- certain animals such as earthworms

• Each stage in the food chain is a Trophic level

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Energy transfer between trophic levels

• Energy losses in food chains:90% of suns energy reflected back in space by clouds and dustnot all wavelengths can be absorbedlight may not fall on chlorophylllow CO2 may limit photosynthesis

• Gross production= total quantity of energy that plants in community convert to organic matter

• Net production= gross production – respiratory losses

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Low percentage energy transferred at each stage:-some of organism is not eaten-some parts are eaten but can’t be digested & therefore lost in faeces-some energy is lost in excretory materials, such as urine-Heat respiration/ body to environment

Must food chains have 4/5 trophic levels, insufficient energy for more

Total mass of organisms (biomass) is less at higher trophic levels

Total amount of energy stored is less at each level

Calculating efficiency of energy transfers:Energy transfer= energy available after transfer

energy available before transfer

x100

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Ecological pyramids

• Pyramids of number- no account is taken for sizeno. of individuals is so great that its impossible to represent them accurately

• Pyramids of biomass-water in organism may make it unreliableno seasonal difference apparent in both pyramids

• Pyramids of energy-energy through food chaindifficult and complex to obtain the results

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Agricultural ecosystems

• Gross productivity- rate plants assimilate chemical energy

• Net productivity= gross productivity- respiratory losses• Net productivity is affected by:

-efficiency of crop carrying out photosynthesis-are of ground covered by leaves/crops

• Comparisons of natural & agricultural ecosystems:

• Energy input – only source is sun- additional energy- food and or fossil fuels

• Productivity- Natural eco. Prod. Is low, fertilisers and pesticides added

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• Pesticides effectiveness:specificbiodegradecost-effectivenot accumulate

• Biological control:not as quickcontrol organism may itself become pest

• Intensive rearing and energy conversion: Movement restricted (less energy used by muscle

contraction)Environment kept warmFeeding controlledPredators excludedSelective breedingHormones to increase growth rates

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Nutrient Cycles

• Basic sequence for nutrient cycles:

-nutrient taken up by plants (producers) as simple, inorganic molecules-producer incorporates nutrient into complex organic molecules-when producer eaten, nutrients pass into consumers-passes along food chain-when producers/consumers die, complex molecules broken down by saprobiotic microorganisms that release nutrient in simple form

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Carbon Cycle

Carbon containing compounds in

producers(plants)

Carbon-containingcompounds in

Decomposers (sapro-biotic microorganisms)

Carbon-containingcompounds in

consumers(animals)

CO2 in atmosphere

& dissolved inoceans

FossilFuels

Respiration

Photosynthesis

Decay

Death

Decay Prevented

Combustion

Feeding

Living component

Non- Living componentBasic sequence Additional pathways

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Greenhouse effect & Global warming

• Greenhouse effect- solar radiation reflected back into space, some reflected back- gas traps heat near earths surface

• Global Warming:-melting of ice caps-rise in sea level-faliure of crops-disease may spread

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Nitrogen Cycle• Four main stages: Ammonification, nitrification, nitrogen fixation

and denitrification each involving saprobiotic organisms A>N>N>D

Ammoniumions

Nitrogen inatmosphere

Nitrate ions

Nitrite Ions

Ammonium-containing molecules

e.g. proteins, in producers

Ammonium- containingmolecules e.g. proteins

in decomposerssaprobiotic microorganisms

Ammonium- containing molecules e.g. proteins

in consumers

Ammonification

DeathDeath & excretion

Feeding and

digestion

Nitrogen fixation by free- living bacteria

Nitrification Nitrification Denitrification

Absor

ptio

n

Nitrogen fixation

By mutualistic bacteria

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Ammonification:Production of ammonia from organic ammonium containing compounds

Sprobiotic microorganisms (fungi/bacteria) release ammonia which forms ammonium ions in soil. Returns to non living component.

Nitrification:Conversion of ammonium ions to nitrate ions, using oxidation

reactions (release energy)- carried out by free-living soil microorganisms called: nitrifying bacteria. 2 stages:1.Oxidation of ammonium ions to nitrite ions (NO2-)2.Oxidation of nitrite ions to nitrate ions (NO3-)Needs O2 so ploughing (aerated) and good drainage (no water)

Nitrogen fixation:Nitrogen gas is converted to nitrogen-containing compounds, carried out by:

free-living nitrogen-fixing bacteria: reduce gaseous nitrogen to ammonia, used to manufacture amino acids mutualistic nitrogen fixing bacteria: Nodules of roots/plants- obtain carbohydrates plant and plant acquires amino acids from bacteria

Denitrification:Soil becomes waterlogged, so short of O2= few nitrogen fixing bacteria and

increase denitrifying bacteria (convert soil nitrates to gaseous nitrogen)

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• Levels of mineral ions in agriculture falls• To replenish this fertilisers are used:

Natural (organic) fertilisers- dead, decaying animals/plantsArtificial inorganic fertilisers- mined from rocks & deposits- contains three compounds: nitrogen, phosphorus and potassium

• Effects of nitrogen fertilisers:Reduced species diversity e.g. nettles and grasses out compete other

speciesLeaching- may lead to pollution of watercoursesEutrophication- caused by leaching of fertiliserLeaching –Nitrates with rain draining into streams/rivers then drain into

freshwater lakes- harmful effect to humans if source of drinking water- cause eutrophication

Eutorphication –In lakes/rivers a limiting factor for plants/algae is nitrate- as nitrate

increases the algae & plants grow Upper layers of water become densely populated with algae (algal bloom) Absorbs light and prevents light at bottom. Plants at bottom die. Saprobiotic algae feed on dead plants but they need oxygen. O2 concentration is reduced in lake so fish has no O2 and die- further decompose (dead organism) more nitrate water is putrid

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Ecological succession

• First stage is colonisation of inhospitable environment by organisms called pioneer species.

• The abiotic environment is continuously changing• Climax community- final stage of ecological succesion• During succession:

-non-living environment becomes less hostile- e.g. soil-great number/variety of habitats produce:-increased biodiversity-more complex food webs-increased biomass

• Primary colonisers secondary colonisers Tertiary colonisers shrubland Climatic climax

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Conservation of habitats

• Main reasons for conservation:Ethical- other species have inhabited earth longerEconomic- may be useful in long termCultural/ aesthetic- habitats/organisms enrich and inspire lives (writer, artists and composers)

• Succession- changes over time

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Inheritance and Selection• Genotype- genetic composition of organism• Phenotype- visible characteristics of an organism resulting from

genotype & environment• Gene-section of DNA that determines characteristics of DNA• Allele-different forms of a gene• Homologous chromosomes-pair of chromosomes that have same

loci therefore determine same features• Homozygous-alleles are identical for particular gene• Heterozygous-alleles of gene different• Dominant-allele that is always expressed in phenotype of organism• Recessive-allele only present in diploid phenotype if another

identical allele is present• Diploid- when nucleus contains 2 sets of chromosomes • Haploid-only contain 2 set of chromosomes e.g. Sex cell/ gametes• Co-dominant-both alleles code for one gene in heterozygous

individual• Multiple alleles-gene that has more than two possible alleles

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Monohybrid Inheritence• Law of Segregation:

In diploid organisms, characteristics are determined by alleles that occur in pairs. Only one of each pair of alleles can be present in a single gamete”

• Sex Inheritance and Sex linkage:As males have one X and one Y chromosome they produce 2 different types of gamete-X chromosome is longer so there is no equivalent homologous portion with Y. Haemophilia is inherited from the mother to male- Pedigree charts are a good representation of inheritance

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Co-dominance and multiple alleles

• Co-dominance example: Red and white snapdragon = pink snapdragon

• Multiple Alleles example: Blood groups- Io is recessive in B.G

• Hardy Weinberg:Frequencies of alleles- proportion of dominant and recessive

Five conditions:-No mutation-Population isolated-No selection-large population-Random mating

p + q = 1.0

p2 + 2pq + q2 = 1.0

Heterozygote= 2pq

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Selection

• All organisms produce more organisms than food, light and space can support

• Therefore Intraspecific competition • Organisms with the better fitting alleles survive and then

reproduceTypes of Selection: • Directional selection: individuals that vary in one direction

to the mean of populationsome individuals that fall to left/right of mean will possess a phenotype more suited to new conditions-extreme of the populations

• Stabilising selection: favour average individuals- preserves characteristics of a species-If environmental conditions stay stable individuals with closest phenotype to mean are favoured

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Speciation

• Speciation: evolution of new species from existing species • Geographical Isolation:When a physical barrier prevents 2 populations from breeding

with one another

-In the split Land A has organisms with more suitable phenotypes and Land B has organisms with more suitable phenotypes-In time difference becomes so great in gene pools that they become 2 separate species-Once united they cannot breed

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