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Biology Unit 4

Terms in this set (101)

What is an abiotic factor ?
Non-living
What is a biotic factor ?
Living
What is an ecosystem ?
Interacting biotic and abiotic features of a specific area
What is a population ?
All the interbreeding organisms of one species in a habitat (boundaries can be hard to define)
What is a community ?
All the different populations of different species living and interacting in a given place at a given time
What is a habitat ?
Where a community of organisms live
What is an ecological niche ?
How an organism fits into its environment, includes all biotic and abiotic requirements, no two species will occupy the same niche
What types of sampling is there ?
Random (Quadrat) and Systematic (Transect)
What factors do we have to consider when using a quadrat ?
Size (larger quadrats for larger species), Number (greater number of species, greater number of quadrats), Position (random)
Why use a line transect ?
To illustrate a transition along which communities of plants/animals change, clearly visualise the changes taking place, any organism which the line passes over is recorded
Why use a belt transect ?
To provide information of the density of a species
How do we estimate population ?
(no. individuals caught in the first sample x no. caught in second sample) / no. recaptured
Why do we estimate percentage cover ?
To estimate the area within a quadrat that a species occupies
What is the frequency ?
Chance of a particular species occurring within a quadrat
What can we assume when estimating population size ?
- Proportion os mared/unmarked in the second sample is the same as the whole population
- Individuals in the first sample distribute themselves evenly
- No migration/immigration
- Birth/death rate is low
- Marking is not toxic/conspicuous
- Marking not lost
What are the 3 main phases of population growth curves ?
1) slow growth - limited number of interbreeding species
2) rapid growth - increase in organisms that are able to reproduce
3) level off as there are limiting factors
What abiotic factors limit population size ?
- Temperature
- Light
- pH
- Water and humidity
What is intraspecific competition ?
Competition between members of the same species
- water
- minerals
- light
- mates
What is interspecific competition ?
Competition between members of different species
- two species competing for limited resources
What is predation ?
When one organism is consumed by another
What is the effect of predator-prey relationship on population size ?
- Predators eat prey, population of prey decreases
- Fewer prey, more predator competition, population of predators decrease
- Fewer predators, fewer prey consumed, population of prey increases
- more prey available, predator population increases
(more than one food source, size fluctuations rarely severe)
What 2 major factors have increased population size ?
1) Development of agriculture
2) Development of manufacturing (industrial revolution)
How do we calculate population growth ?
(Births+immigration)-(deaths+emigration)
How do we calculate %growth rate in a given period ?
(Population change during a period/ population at the start) x 100
What factors effect Birth rate ?
- Economic conditions
- Cultural/religious backgrounds
- Social pressures
- Birth control
- Political factors
How do we calculate Birth rate ?
(number of births per year x1000 /total population in the same year)
What factors effect Death rate ?
- Age profile
- Life expectancy at birth
- Food supply
- Safe drinking water
- Medical care
- Natural disasters
- War
How do we calculate average life expectancy ?
Age at which 50% of the population are still alive
What is energy ?
The ability to do work, can only be changed from one form to another, not created or destroyed
Why do organisms need energy ?
- Metabolism
- Movement
- Active Transport
- Production of enzymes/hormones
- Maintaining body temp
How does ATP store energy ?
The bonds between phosphate groups, water is used to convert ATP to ADP (ATP + H20 = ADP + Pi + Energy), which is a hydrolysis reaction (reversible reaction condensation)
What is the role of ATP ?
Immediate energy substance used to transfer energy
Better immediate source of energy than glucose because it is more manageable in small quantities and the hydrolysis of ATP is a single step
What adaptations can we find in a leaf ?
Air spaces, waxy cuticle, xylem, stomata, thin upper epidermis, palisade layer
What are the 3 main stages of photosynthesis ?
Capturing light energy, Light Dependent and Light independent phases
How is ATP made in a plant ?
Light Dependent Stage
- Chlorophyll absorbs light energy
- 2electrons move to higher energy levels and leave the chlorophyll molecule
- Electrons taken up by electron carriers and transferred along the electron transport chain
- Electrons loose energy at each stage, which is used to make ATP (ADP + Pi = ATP)
- At the end of the ETC, NADP accepts electrons and H+ from the thylakoid space, becoming reduced
What happen during photolysis ?
Electrons lost from the chlorophyll are replaced by electrons released when light breaks down water (oxygen is released as a bi-product) H2O = 2H+ + 1/2O2
What are the products of the Light dependent stage ?
ATP and reduced NADP, which are used to reduce carbon in the Light independent stage, and O2 from photolysis
What is photophosphorylation ?
Using light to attach a phosphate group
How is light energy converted to chemical energy ?
- Electrons raised to a higher energy level
- Pass through the ETC, losing energy
- This energy is used in the production of ATP
What is the advantage of having the ETC in the membrane ?
Allows rapid transfer of electrons from chlorophyll along the ETC in the right sequence
What is the role of Chlorophyll in photolysis ?
- Pigment that absorbs light energy
- Loses electrons and becomes positively charged
- Absorbs electrons from water
What happens in the Calvin cycle (Light independent stage) ?
- CO2 diffuses in through the stomata and into the chloroplast stroma
- There is combines with a 5 C compound called RuBP
- Produces two 3C compounds of GP
- ATP and reduced NADP from light dependent stage are used to activate production of TP
- some TP converted to useful organic substances, most are used to regenerate RuBP using ATP from the light dependent reaction
How is the chloroplast adapted to carrying out the light independent stage ?
- Fluid in stroma contains all necessary enzymes
- Fluid surrounds the grana, so products of the light dependent stage in the grana can readily diffuse into the stroma
- Contains DNA and ribosomes, so can quickly and easily manufacture proteins for the light independent stage
What are limiting factors in photosynthesis ?
Light intensity
Carbon dioxide concentration
Temperature
What is the effect of carbon dioxide on photosynthesis ?
High carbon dioxide can effect the enzyme catalysed reaction that combine RuBP with CO2
What is the effect of temperature on photosynthesis ?
Higher temperatures (above 25 degrees) causes the rate to decrease since enzymes become denautred
What are the 4 stages of glycolysis ?
1) Glucose is activated by phosphorylation (2ATP molecules used), addition of phosphate makes the glucose more reactive

2) Phosphorylated glucose splits into two 3C trios phosphate

3) Trios phosphate is oxidised, hydrogen is removed to the hydrogen carrier NAD to make NADH

4) Production of ATP, trios phosphate converted to pyruvate, 2 molecules of ATP produced
What is the energy yield from Glycolysis ?
2ATP
What is the links reaction ?
Pyruvate + NAD + CoA --> Acetyl CoA + NADH + CO2

Pyruvate actively transported into matrix of mitochondria, it is oxidised
What happens in the Krebs cycle ?
- A series of oxidation and reduction reations
- Acetyl CoA (2C) reactions with a 4C molecule to form a 6C molecule that loses CO2 and H to produce ATP
- (6C) deNA (5C) deNA (4C) A (4C) FA (4C) NA (4C)
What is the significance of the Krebs cycle ?
- Produces H atoms (NADH) used in the ETC for oxidative phosphorylation
- Regenerates 4C molecule, preventing an accumulation of acetyl CoA
- Source of immediate compounds used by cells to manufacture important substances such as fatty acids, amino acids and chlorophyll
What is needed from the Krebs cycle for the ETC ?
NADH & FADH, which are oxidised and release a proton and an electron
What happens in oxidative phosphorylation ?
1) NADH and FADH are oxidised and release a proton and an electron
2) Protons AT into inter membranous space
3) Electron taken up by electron carrier, which is therefore reduced
4) It is then oxidised as the electron passes to the next carrier
5) Through a series of redox reactions, electrons lose energy, which is combined with ADP and Pi
6) Protons accumulate in inter membranous space and diffuse back into the cell through special protein channels
7) Electrons combine with a proton and oxygen at the end of the chain to form water
8) Oxygen is the final acceptor of electrons
Why does anaerobic respiration occur ?
Oxygen is the final acceptor of electrons, so when it's not present, ATP cannot be produced in this way
How do plants respire anaerobically ?
Pyruvate + NADH --> ethanol + CO2 + NAD
How do animals respire anaerobically ?
Pyruvate + NADH --> lactate + NAD
NADH needs to be converted back to NAD for the process to continue
How is lactate removed ?
Oxidising with 02 to release more energy / back to pyruvate
What is a producer ?
A photosynthetic organism that obtains their energy through the photosynthesis of sunlight
What is a consumer ?
Organisms that feed off other organisms, they do not produce their own food
What is a decomposer ?
When a producer/consumer dies, the energy that they contain can be accessed by decomposers that break down the larger more complex molecules into smaller simpler components, which are recycled and taken up again by plants
Why is only a small amount of energy available to plants converted into organic matter ?
- 90% of suns energy reflected by the atmosphere
- Not all wavelengths can be absorbed
- Light might not fall on the chlorophyll molecule
- Limiting factors
How do we calculate net production ?
gross production - respiratory loss
Why is a low amount of energy absorbed at each stage?
- Organism is not fully eaten
- Organism eaten but not fully digested
- Lost in excretion
- Lost via respiration used to maintain a high body temperature
How do we calculate the efficiency of energy transfer ?
(Energy available after the transfer/ energy available before the transfer) x100
How do pyramids of number work ?
Higher up in the trophic level, the fewer the organism
What are the problems with pyramids of number ?
No account taken for size and the number of individuals can be so great that it would be impossible to count them all (e.g grass in a field)
How do pyramids of biomass work ?
The total mass of plants/animals of species in a given place, measured in gm-2
What are the problems with pyramids of biomass ?
Biomass unreliable as there are different amounts of water, dry mass recorded instead, but the organism must be killed and does not account for seasonal differences
How do pyramids of energy work ?
Data collected in a given area for a given period of time, more accurate since different organisms may have the same mass but one may have more fat and so will have more energy, measured in kjm-2 year-1
What is an agricultural ecosystem ?
An ecosystem made up of plants/animals used to make food for humans, used to ensure the most amount of energy available from the sun is transferred to humans as possible
What is productivity ?
The rate at which something is produced
What is gross productivity ?
The rate at which plants assimilate energy from the sun into chemical energy, measured in kjm-2 year-1
What is net productivity affected by ?
- Efficiency to carry out photosynthesis (limiting factors etc)
- Area of ground covered by the leaves of the crop
How do we maintain an agricultural ecosystem ?
- Prevent the climax community from forming by excluding other species in the community
- Removing pests diseases, feeding animals and removing weeds
Where does the energy required to maintain an agricultural ecosystem come from ?
1) Food - Farmers use energy to do work on the farm, which is from the food we eat
2) Fossil fuels - For different machines used to plough, transport and distribute pesticides
How is productivity different in a natural ecosystem ?
Productivity is low, energy input in agricultural ecosystems removes limiting factors, other species are removed to reduce competition, and fertiliser is added to reduce limiting factor of nitrate
What is a pest ?
An organism that competes with humans for food/space
What makes a pesticide effective ?
- Being specific
- Biodegradable
- Cost effective
- Does not accumulate
What is a biological control ?
The use of other organisms to control pests, If the pest was eradicated, the predator would starve and die
What as the disadvantages of a biological control ?
- Acts slowly
- Control organism may itself become a pest
What are the advantages of a biological control ?
- Pests do not become resistant
- Very specific and cost effective
What is an integrated pest-control system ?
All forms of pest control with the aim to determine an accepted level of the pest rather than trying to eradicate it
How do you manage pest-control systems ?
- Choosing an animal/plant that is as pest resilient as possible
- Manage the environment by ensuring the are nearby habitats for predators
- Regulating crops so early action can be taken
- Removing the pest mechanically
- Using biological agents
- Using pesticides as a last resoty
How does controlling pests effectively increase productivity ?
Pests compete for light and nutrients and is therefore a limiting factor. Some pests may also directly compete with humans by eating the crop
How is intensive rearing used to save energy ?
- Movement restricted (muscle contraction)
- Environment kept warm (body temperature)
- Nutrition carefully controlled (max growth and little wastage)
- Predators excluded
- Selectively breeding animals that are more efficient in converting food to biomass
- Hormones to increase growth rate
Why has CO2 concentration increased in recent years ?
- Combustion of fossil fuels
- Deforestation
- Global warming (sea releasing CO2)
What greenhouse gases are there ?
- CO2
- Methane
What are the consequences of global warming ?
- Affects niches available so there is an alteration in the distribution of species
- Melting ice caps, increasing sea levels
- High temperature leads to crop failure
What benefits come rom global warming ?
- Increased rate of photosynthesis
- Greater rain fall
- Possible twice year harvest
What are the stages of the nitrogen cycle ?
1) Ammonification
2) Nitrification / denitrification
3) Nitrogen fixing
What happens in the process of ammonification ?
- Production of ammonia from organic ammonium containing compounds
- Saprobiotic bacteria feed on the materials releasing ammonia, which converts to ammonium in the soil
What happens in the process of Nitrification ?
- Carried out by saprobiotic bacteria
- Convert ammonium ions into nitrite ions and then into nitrate ions
- Oxygen in required
What happens in the process of Nitrogen fixation ?
- Nitrogen gas converted into nitrogen containing compounds
What is nitrogen fixing carried out by ?
- Free living bacteria (reduces gaseous nitrogen into ammonia)
- Mutualistic nitrogen fixing bacteria (bacteria requires carbohydrates from the plant and provide the plant with amino acids)
When does denitrification take place ?
When there is little oxygen, so fewer aerobically respiring nitrogen fixing and more denitrifying anaerobically respiring bacteria
This bacteria converts soil nitrates into gaseous nitrogen
Why do we use fertilisers ?
- Plants need mineral ions (nitrogen)
- Plants use up nitrogen in soil to create amino acids
- Plants harvested, so nitrogen not recycled and replaced
- Nitrates in soil decrease
What types of fertiliser are there ?
- Natural (decaying/dead organisms + animal waste)
- Artificial (Minerals from rocks, nitrogen, potassium, phosphorus)
How do fertilisers increase productivity ?
- Nitrogen needed to make proteins and DNA
- More nitrates available, more developed the plants will get, grow quicker, taller and cover a greater area with their leaves
- Increases the rate of photosynthesis and therefore productivity
What are the negative effects of using a nitrogen fertiliser ?
- Reduce species diversity (favours growth of rapidly growing species, which would grow quicker and out compete others)
- Leaching (leads to pollution of watercourses)
- Eutrophication (algae bloom)
What adaptations do Pioneer species have ?
- Tolerance to extreme conditions
- ability to fix nitrogen from the air
- Photosynthesise
- Easily disperse seeds
What do pioneer species do ?
Change the abiotic environment by dying and releasing nutrients, changing the environment, making it less hostile
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