BiologyUnit 4

AQA

Ecology DefinitionsHabitat – The place where an organism lives

Population – A group of organisms belonging to the same species

Community – All the populations of different organisms living and interacting in the same space at the same time

Ecosystem – A community of living organisms and the abiotic factors which affect them

Abiotic – The physical and chemical features of the environment

Biotic – The biological features of the environment (living)

Niche – A species role within it’s habitat

Adaptation – A feature that members of a species have to increase their chance of survival

Investigating Populations

Quadrats:- Set out 2 tape measure at right angles, forming the axes for

the chosen area- Generate 2 random numbers (using calculator) to use as co-

ordinates- Place quadrat where co-ords meet- Find mean number of species per quadrat - Multiply by size of area being sampled

Transects:- It’s a line through an area to be studied to identify changes

through an area

- Line Transects – a tape measure is placed along the transect and the species that touch the tape measure are recorded

- Belt Transects – quadrats are placed next to each other along the transect to work out species frequency & percentage cover along a transect

Measuring Abundance

Quadrats:- Have a known dimension- Used to:

- Estimate population density- Estimate % cover of an organism- Estimate the frequency of an organism

Factors:- Size of quadrat – More small quadrats = more representative

results- Number of quadrats – more quadrats = more reliable results- Position of quadrat – must be placed randomly to avoid bias

At least 20 samples taken. Eventually a sample size is big enough that the number of species doesn’t increase much more the sample is said to be representative.

Mark-Release Recapture

A known number of animals are caught and marked. They’re then released back.Later another sample are caught and the number of marked individuals is recorded

Assumptions:- No reproduction- No migration- Enough time for both marked & unmarked animals to mix- Marking doesn’t affect behaviour

Variation in Population Size

Abiotic Factors:- Affected by factors such as temperature, light, space, water

etc…- When conditions are ideal an organism will thrive and vice

versa

Biotic Factors:- Interspecific Competition:

- Competition between different species- Intraspecific Competition:

- Competition between the same species- Predation – Predator & Prey populations are linked

- Prey increases, more food, so predator increases.- Predator eats prey, prey decreases as they’re eaten- Predator decreases due to lack of food- Predator peaks after prey

Human PopulationsPopulation Growth = (BR + Immigration) – (DR + Emigration)

% Population Growth Rate = x 100

Demographic Transition Model:- Shows the change in BR, DR & population size over along period of time

Population ChangePopulation Start

Survival CurvesShow the percentage of all individuals that were born in a population that are still alive at a given age.

Life Expectancy – is the age someone is expected to live to- it’s the age at which 50% of the population are still alive

e.g. the life expectancy of this example is 81 as that is the age when 50% of the population are still alive

Age-Sex Population Pyramids

West Africa:- High BR- Short Life Expectancy- High DR- Developing Country

West Europe:- Lower BR- Long Life Expectancy- Lower DR- Developed Country

Ecosystem DefinitionsProducer – They’re photosynthetic organisms that manufacture organic substances using light energy, water and CO2Consumer – They’re organisms that obtain their energy by feeding on other organismsDecomposers – When consumers & producers die, the energy can be used by organisms that break down the complex materials into single components againFood Chains – Describes a feeding relationship in which the producer are eaten by the primary consumers. They’re then eaten by secondary consumerTrophic Level – The level between each stage in the food chain

Food Web – More than one food chain linked together

Grass Sheep Human(Producer) (1° Consumer) (2° Consumer)

Trophic Level

Energy Transfer Between Trophic Levels

Little solar energy converted to chemical energy in PS:- Some is reflected due to wrong wavelength/frequency/colour- Doesn’t hit chlorophyll molecule- Lost as heat during evaporation

Energy is lost along a food chain:- Not all the organism is eaten- Not all organism digested – lost in faeces- Urine- Heat in respiration- Movement- Birds & Mammals – energy used to maintain a constant body

temperature (homeostasis)

Not enough energy to support further trophic levels, so rarely more than 4 trophic levels present in a food chain

Gross Primary Productivity (GPP) – Amount of light energy that plants convert to chemical energy

Net Primary Productivity (NPP) – Total amount of energy stored in a plant that is available to the next trophic level

NPP = GPP - Respiration

Measured in kJ m-2 Year -1

Energy Energy after TransferTransfer (%) Energy before Transfer

Net Primary Productivity

= 100X

Production of ATP• ATP- Adenine TriPhosphate • Made from ADP + Pi• Energy stored in the phosphate bond• ATPase catalyses the breakdown of ATP into ADP + Pi• ATP synthase catalyses the production of ATP• The ADP + Pi is recycled and the process starts again

Properties:• Small compound – easily transported around

the cell• Easily broken down (Hydrolysed)• Cell has instant energy supply

Photosynthesis

Inner & Outer membrane

GranumContains Chlorophyll

Thylakoid StromaStarch Grain

Loop of DNA

2 Photo Systems capture light in a chloroplast PSI (best at 700nm) & PSII (best at 680nm)

Lamellae (Membrane joining Thylakoids)

6CO2 + 6H2O + Energy = C6H12O6 + 6O2

Number of Chloroplasts

Substomatal Cavity

Lower EpidermisSpongy Mesophyll

Airy Cells, lots of space

Palisade LayerUpper Epidermis

Waxy Cuticle

Absorption Spectrum

Plants absorb red & blue wavelengths only reflecting green. It’s why they’re green

LDS (Non-Cyclic Photophosphorylation)

Photolysis Of Water:

2H2O = 4H+ + 4e- + O2

Requires a photon to split water

Occurs in the Thylakoids of chloroplasts

Thylakoids adapted for their function:• Large SA, large area for attachment of chlorophyll, electron carriers and enzymes• Proteins in grana hold chlorophyll to allow max light intake• Granal membranes contain enzymes that help make ATP• Chloroplast contain DNA & Ribosomes to manufacture proteins for LDS quickly

Electron CarrierElectron Acceptor

Cyclic Photophosphorylation

Happens when lack of NADP

No light wasted

Only uses Photo System 1

Only ATP produced

LIS (Calvin Cycle)

In Stroma

RuBp – Ribulose BisphosphateTP – Triose Phosphate (GALP)GP – Glycerate 3-PhosphateRUBISCO – Enzyme used in CO2 Fixation

ATP and rNADP from LDS

6 Cycles = 1 Glucose Molecule

RespirationC6H12O6 + 6O2 = 6CO2 + 6H2O + Energy

1. Glycolysis:• Makes Pyruvate from Glucose• In cytoplasm• Anaerobic Process• Net Yield of 2ATP

Dehydrogenation – Removal of H2- Using dehydrogenase enzyme

Substrate Level Phosphorylation- ADP + Pi ATP

2. Link Reaction:• Pyruvate oxidised by removing H• Acetyl CoEnzyme A produced• Per Pyruvate a CO2 molecule produced

Pyruvate + NAD + CoA = Acetyl CoA + rNAD + CO2

Decarboxylation – Removal of CO2 - Using Decarboxylase enzyme

3. Krebs Cycle:• Acetyl CoA + oxaloacetate (4C) = Citrate• Citrate converted to 5C compound ( 2H+ & CO2 removed)• 5C to 4C Produces:

• 2 x rNAD• ATP• rFAD• CO2

NAD – Nicotinamide Adenine DinucleotideFAD – Flavine Adenine Dinucleotide

Electron Transfer Chain

When rFAD & rNAD are oxidised they release 2H & 2e-

Electrons used in transfer chain

Energy/ATP produced in ETC is used to power chemiosmosis

Hydrogen used in chemiosmosis

Oxygen is the last electron acceptor.O2 + 2e- + 2H H2O

ChemiosmosisIn Photosynthesis & RespirationEnergy (ATP) from ETC used to power Chemiosmosis

Active Transport

If ATP synthase not present energy lost in the form of Heat instead of forming ATP

Electro – Chemical Gradient

Respiration

Anaerobic Respiration

Instead of pyruvate being converted into Acetyl CoA it’s converted into ethanol (in plants and yeast) and lactic acid (in animals and some bacteria)