AQA A-level Biology Unit 4 Intensive farming and Eutrophication
Brief important points on Unit 3 topics: intensive farming, food chains, energy transfer eutrophication, speciation, nitrogen cycle, carbon cycle, succession, conservation, researching population methods photosynthesis, respiration, brief genetic definitions. Enjoy :)
- Created by: cat baker
- Created on: 21-01-10 13:05
Intensive Farming
Purposes; Increase efficiency of energy conversion,
Increase energy input - more added to ecosystem
Ensure growth is not a limiting factor
1) Killing pest species; Biological control/ Chemical Pesticides /Integrated system
2) Fertilisers
3) Rearing livestock intensively
Killing Pest Species
Pests are organisms that inhibit crop productivity, so there is less energy for growth, so less biomass, and less profit.
Chemical pesticide; Insecticide ensures less biomass is lost
Herbicide reduces competition
Fungicide ensures less energy is wasted on fighting infections
Disadvantages;
Directly damage non-pest species (butterfly)
Indirectly affect non-pest by accumalating in tissue of pest and pass in to consumer
Economically Expensive
Biological control
Introduce natural predators into ecosystem to eat pests
use parasites to linve in/lay eggs on pest and reduce ability to function
Introduce pathogens to cause disease and kill pests
Disadvantages;
Natural predators become pests
parasites/ pathogens Affects Non-pests
Productivity short term so less cost effective
integrated System
Combining Chemical and Biological
Reduces cost, because more expensive method is reduced
Reduces enviromental impact, because less pesticide used
Killing Pest Species needs to be:
Specific Bio-degradable Cost effective Not Accumalate Easy & Safe to use
Intensive Farming - Fertilisers
Artificial/ inorganic - pure chemicals containing ammonium nitrate in the form of powders/pellets
Natural/organic matter - Sewage, manure.
Provide Crops with minerals and nitrates for growth
No longer limiting factor
replaces lost minerals -more energy to grow - Increased efficiency of energy conversion
Disadvantages; Changes balance of nutrients in soil and cause other species to die
Causes leaching, ( chemicals washed into rivers) Eutrophication kills fish/plants,
Intensive Farming - Rearing Livestock Intensively
Controlling conditions that the livestock live in
Warmth, movement restricted, feed higher in energy
Less energy wasted to maintain body temperature, or for movement
More energy used for growth - Efficiency of energy conversion increased - more biomass - productivity increased - less time wasted - more profit
Disadvantages; Ethics - Pain, Distress, Effects natural behaviour
Quality
Advantages for consumer - People in poverty can afford to eat.
Eutrophication
leaching - Water soluble compounds (fertilisers) in soil washed by rain or irrigation systems into rivers.
Nitrates/phosphates in water - Increased ion available for plants - Algae grows on surface and reduces light intensity - Increase of inter/intra-specific competition - Death - Saprobiotic nutrition (bacteria feeding on dead)- bacteria respire more (take in oxygen) - Increased BioChemical Demand (BOD) - 02 supply reduced - Death - more food for decomposers
Energy transfer and productivity
Ecosystem - All organisms living in an area inc. Abiotic conditions
Gross productivity - Remaining energy available
Respiratory losses - lost energy through movement/heat
Net Productivity - Amount of energy available to next trophic level
Energy Transfer Efficiency - Net Productivity / Energy received (Gross productivity)
Food chains
Pyramid of number
Pyramid of Biomass (Dry mass) ( kgm-2) Nearly always pyramid shaped
Pyramid of Energy (kjm-2yr-1) net productivity of each trophic level, Always pyramid.
Tertiary consumer
Secondary Consumer
Primary Consumer
Producer
Ecosystem terms
Habitat - the place where an organism lives
Population - All the organisms of 1 species in a habitat
Community - Populations of different species in a habitat
Ecosystem - All Abiotic conditions and organisms living in a particular area
Abiotic conditions - Non living
Biotic - Living
Niche - the role of a species within it's habitat
Adaptation - A feature that increases a member of a species chance of survival and reproduction
Speciation
Species- similar organisms with similarthat can breed and produce fertile offspring
Speciation - The evolution of 2 or more species from existing species
Isolation; Behavioural- no longer recognise courtship displays
Geographical- separated by a physical barrier (e.g river/ road)
Speciation: Single population- split due to isolation - different selection pressures - allele frequency differs - reproductively isolated (cannot interbreed) - become 2 separate species
Speciation, Selection
Differential reproductive success - individuals with beneficial alleles have selective advantage - thrive and reproduce - allele frequency increases.
Stabilising Selection - When environmental conditions are constant organisms within a species with phenotypes (medium length fur) towards middle of range have selective advantage - reduces phenotype range
Directional Selection - Extreme enviromental conditions, so organisms within a species with extreme phenotype (long fur) have selective advantage - causes genetic change
Succession
1) Pioneer (lichen/mosses) Harsh Abiotic Conditions (no soil) -Lichens colonise & fix nitrogen - Lichens decompose - humus forms
2) Dryas (grass/small plants) Simple soil developed through more nutrients - inter-specific competition so Pioneers die off
3) Alder (shrubs) Nutrients increased by animal faeces and nitrogen fixing plants
4) Spruce (big trees) - Soil deep enough for root growth of big trees - climax community*
* Growth, but no more Succession
Species diversity increases - more niches - more humus - more food
Stability increases -if one species dies off there are still other resources to feed on
Conservation Methods - seed banks/ fishing quotas
Conservation - Method of maintaining ecosystems and the organisms that occupy them
1)Seed Banks - Storing seeds with different characteristics
Pros: Needs little space
Cons: Expensive/ Time consuming, Need regular tests to prove viable
2)Fishing Quotas - International agreements that limit the amount a fisherman can catch
Pros: Reduces Number caught and killed
Cons: job losses
Conservation methods continued - Captive breeding
3) Capive Breeding Programmes
Pros:
Breeding in controlled enviroments increases number
Cons: When re-introduced into wild, can spread new diseases
Hard for animals to reproduce in unnatural habitat
4) Relocation - transfer organism to a location that is not under threat
Cons:
May be outcompeted in new location
Conservation - general pros/cons
Pros: Cons:
Without it resources may be lost (e.g drugs) Prevents Economic growth
Organisms have a right to exist time = money
Aesthetics - tourist attraction
Prevents disruption of food chains
Prevents climate change
(e.g less deforestation less C02 released)
Conservation methods of Succession
Pros:
A climax community may cause loss of habitats
Cons:
Less species diversity
Managed fires used, so Secondary Succession (not starting from rock) can occur, so larger species take longer to grow.
Animals Graze/ mowing keeps vegetation low
Investigating populations
Pitfall Traps
Steep containers in a hole underground
Lid partially open so curious insects can fall in, but have protection from predators
Pooters
Jars with rubber bungs, a long tube partially covered, and a short tube
**** through short tube to vacuum up insects - time consuming :(
Beating Tray
Tray/sheet held under vegetation to catch insects when you shake the plant
Large samples/good estimates :) Not random
Investigating Populations cont.
Quadrats [|||||||] are Random so eliminate Bias
placed on ground at different sections of ground
calculate species frequency or Number of individuals recorded
Percentage Cover - How much is covered by species (quick method)
Line Transects are Systematic to study a gradual change in precentage cover etc
Tape measure or Quadrats placed next to each other in a line
Evaluating methods
Reliability - Random sampling eliminates bias / Repetitions reduces affect of anomeles
Accuracy+precision - larger sample size
Control experiment shows whether result is due to another factor
Investigating populations cont. 2 Mark release rec
To measure the abundance of a more mobile species
Total Population size =
(Number caught in 1st sample X Number caught in 2nd sample) / (Number marked from 2nd sample)
Capture a sample (pitfall/pooter/beating tray)
Mark with paint & Release & redistribute
take 2nd sample and count the amount marked with paint
Requirements to be Accurate:
Marked sample has oppurtunity to mix
Marking hasn't affected chance of survival
No changes to population due to births/deaths/migration
Nitrogen cycle
[ Nitrogen gas ]--Nitrogen fixation--> [Nitrogen compounds in producers]--Digestion-->
[Nitrogen compounds in consumers]--death-->[Nitrogen compounds in decomposers]
Ammonification-->[Ammonium Ions]-Nitrification-->[Nitrites]--Nitrification>[Nitrates in soil]
-->Denitrification-->[Nitrogen in atmosphere]
Nitrogen cycle cont
Nitrogen fixation = Nitrogen gas into nitrogen compounds by nitrogen fixing bacteria on roots of leguminous plants. Bacteria gets sugars from plants to respire
Ammonia = nitrogen + hydrogen
Ammonification = decomposers turn nitrogen compounds in dead organisms and urea turned into ammonium compounds
Nitrification = Ammonium compounds changed into nitrogen compounds to be used by plants. so ammonia - nitrites - nitrates
Denitrification - only in anerobic conditions (waterlogged soil) Nitrates in soil converted to nitrogen gas by denitrifying bacteria which respire.
Carbon Cycle
Carbon cycle - how carbon moves through Biotic organisms and Abiotic environment
[Carbon Dioxide in air] --Photosynthesis-->[Carbon compounds in producer]--Digestion-->
[C-compounds in Consumer]--Death-->[C-compounds in Decomposers]--Respiration-->
[Carbon dioxide in air]...
Carbon compounds in Producers can also be converted to carbon dioxide in air by burning fossil fuels (combustion)
Carbon dioxide in atmosphere / Affects of Global w
Least carbon dioxide in air mid-day in summer, because increase in light intensity - increase in photosynthesis
more fossil fuels burnt = more Carbon dioxide + methane
More decomposers - more respiration - more Carbon dioxide
more cattle - more farting - more methane
higher temperature - frozen ground thaws - natural stores of methane released
Wild animals/plants less abundant - when ice melts polar bear loses surface to hunt on
more abundant - Boarfish , organisms with extreme phenotypes
Crop yield - Carbon Dioxide no longer limiting factor - increases rate
Insect Pests - Warmth speeds up larvae process so reach adulthood quicker
Warm/wet increases mosquitoes
Photosynthesis key words
Photosynthesis 6C02 + 6H20 --->C6H1206 + 602
Carbon dioxide + water ----> Glucose + Oxygen
Metabolic pathway - A series of small reactions controlled by enzymes
Photophosphorylation - Adding Phosphate using Light
Photolysis - Splitting of a molecule using light energy
Hydrolysis - Splitting of a molecule using water
Decarboxylation - Removal of Carbon Dioxide
Dehydrogenation - removal of Hydrogen
Redox reactions - involve oxidation (loss of electrions/hydrogens) & reduction (gain of e- & H+)
Thylakoid - site of dependent reaction Stroma - site of independent reaction
Photosynthesis Light Dependent
Light dependent - in Thylakoid which absorbs light energy
light energy excites electrons in cholorophyll
electrons move along electron carriers
energy released generates ATP from ADP + Pi
Electrons accepted by another chorophyl molecule and is excited by light
electrons move along and are accepted by NADP
Light energy splits water (photolysis) into electrons (restore chlorophyl) hydrogens ( reduce NADP) and Oxygen
Products: reduced NADP (NADPH), ATP, Oxygen
Photosynthesis - light independent (A.K.A calvin c
Light Independant occurs in the stroma which is within the inner membrane of chloroplast (contains enzymes, sugars and organic acids)
Ribulose Bisphosphate (RuBP) ( 5 Carbon)
combines with Carbon dioxide to make Glycerate 3 Phosphate (GP) (2 X 3C)
GP is reduced from the addition of electrons/hydrogens by Reduced Nadp (from Light dependent) converting to Nadp (returns to light dependent), and ATP ( from Light Dependent) converting into ADP+Pi (returns to light dependent)
Triose Phosphate is formed (TP/ GALP)
makes organice substances, amino acids, fatty acids, Glucose-starch/cellulose
Respiration Glycolysis
Aerobic - oxygen present Anerobic - Oxygen is not present
Anaerobic Glycolysis takes place in the Cytoplasm of a mitochondria
Glucose (6Carbon sugar)
energy released from splitting of 2ATP into 2ADP+Pi
Makes PG (unstable)
Converts into Triose Phosphate (TP/ GALP) (2 X 3C)
Oxidised by loss of hydrogens/electrons to reduce coenzyme NAD into NADH (goes to electron transport chain) and converts 4ADP+Pi into 4ATP
Pyruvate (2 X 3C) Net Gain 2ATP molecules
Products: Pyruvate, ATP, Reduced NADP (NADPH)
Respiration The Link reaction (aerobic)
2 link reactions take place: addition of Coenzyme A to Pyruvate (3C)
NAD reduced to NADH and Carbon Dioxide is released
Acetyl Coenzyme A (2C) is formed!
Krebs Cycle ( in Matrix)
Acetyl Coenzyme A combines with 4-carbon molecule = 6 Carbon molecule
NAD is reduced to NADH
2Carbon dioxides released
FAD reduced to FADH
ATP formed by Substrate- level Phosphorylation (formation of ATP by direct transfer of phosphate group)
Products: Acetyl CoenzymeA, NADH, FADH, Carbon dioxide
Respiration - Oxidative phosphorylation - electron
Oxidative Phosphorylation
NADH to NAD supplies Electron transport chain with electrons off hydrogen atom
Electrons decrease in energy making 3 ATP from 3 ADP+Pi
energy from electron transport chain pumps protons off Hydrogen atoms into inner membrane of Cristae in mitochondria
Protons diffuse out of ATP Synthase molecule on membrane into matrix and ATP from ADP+Pi is created
finally, when protons and electrons at end of electron transport chain combine and are accepted by oxygen to make water (H20)
Products: 3 ATP, water
Genetics terms
Gene - A sequence of bases on a DNA molecule that codes for a protein
Allele - A version of a gene. The order of bases are slightly different
Genotype - Genetic constitution BB
Phenotype - Expression of gene and interaction with enviroment
Co-dominant - neither is recessive or dominant (e.g. sickle-cell anaemia)
Locus - position of a gene on a chromosome
Homozygote - organism carries 2 copies of the same allele BB
test cross - When a plant or animal is crossed with homozygous/recessive to determine if an organism is homozygous or heterozygous for a particular allele
Sex-linked - gene carried on the X or Y chromosome. Y chromosome is shorter than X so alleles will be expressed in phenotype whether recessive or not
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