topic 5 revision notes ecology o biosphere o population · 2018-08-30 · topic 5 revision notes...

Topic 5 Revision Notes

Ecology

Ecology is the study of living things within their environment.

o Biosphere: “part of the earth inhabited by living organisms”, within Biospheres there are

different ecosystems.

o Ecosystem: “All the organisms living in a particular area as well as the non-living features of their

environment”. Ecosystems are self-sufficient i.e. organisms spend most of their lives there and

their essential nutrients will be endlessly recycled around and through them. All ecosystems have

distinctive features that affect the organisms living there.

o Habitat: is defined as “the place where an organism lives”.’ Example within a pond ecosystem

some organisms may live in the pond, beside the pond or others floating on top, all of these 3

different sites are the habitat.

o Community: “Populations of different species in a habitat make up a community”. Population ‘is

the number of individuals of one species in a particular area’; various populations sharing a

habitat/ecosystem make up a community. If two different species in a community share similar niches i.e. eat the

same prey (or any other similar biological interaction) then there will be inter-specific competition and the

species better adapted to the abiotic and biotic conditions of the habitat will survive and the other less adapted

species would be forced out the habitat. It is important to note that two species are able to occupy the same

habitat as long as they have different niches, this means niches as well as biotic and abiotic factors affect

distribution and abundance of species present in a habitat.

Abiotic Factors

Abiotic and biotic factors both determine which species appear in which habitat as well as its abundance and distribution.

Abiotic factors defined as ‘Non-living features of an ecosystem.’Examples of Abiotic factors are as follows:

o Solar energy input: energy source for photosynthesis has a role in initiating flowering and required for seed

germination and in many animals affects behaviour such as reproduction as length of day is longer. Solar energy

input itself is affected by latitude, season, cloud cover, and changes in earth’s orbits.

o Climate: Rainfall, Wind exposure and temperature all affect plants and animals e.g. increase rainfall could mean

more plants, increase wind exposure could mean increase in seed dispersal and increase temperature could mean

increases in enzyme activity which would also affect animal metabolism, decrease in sunlight could adversely

affect plants growth.

o Topography: Gradient, slope and aspect (which direction land faces the sun) and drainage. Gradient, slope and

aspect affects which plants can grow on a particular place and what animals might graze there.

o Oxygen Availability: important in aquatic systems. Faster flow of water increases oxygen whereas in stagnant

water oxygen availability is low.

o Edaphic factors (relating to soil): Soil pH, mineral content, salt availability, soil texture all affect the plants that

grow in a certain area and the distribution of plants and the animals that eat it.

o Pollution: Can be air, water or land. Poor air pollution may favour those lichen that can survive and thrive in areas

with poor air pollution.

o Catastrophes: Infrequent events e.g. Earthquakes, volcanic eruptions and fires.

Biotic Factors


Biotic Factors defined as “Living features of an ecosystem”.

o Competition: for resources such as food, light, mate and space this can be

intra specific competition which is when organisms of the same species

compete with each other for the same niche or inter specific competition

which is when organisms of different species compete for the same

resources.

1) Population of a species (e.g. polar bear) increases when resources are rife,

increase population means increase in competition for resources.

2) Resources such as food and space become scarce as a result population

falls.

3) Smaller population means less competition for resources which will instigate growth and reproduction of species.

4) Maximum stable population size is called carrying capacity

this type of competition often leads to competition for resources though the degree of competition is dependent

on the niche the animals occupies in the habitat, if two different species occupies same niche then only one

animal will survive in that particular habitat.

o Disease –Is fatal not just to animals but humans. It could

potentially affect population sizes

o Predation: This is very clearly a biotic interaction between the

predators that eats the prey. Populations of both parties are

linked in what are called predator-prey cycles. The snowshoe

hare (prey) and Lynx (predator) is a classic example in which

the prey population rises followed by an increase in

population of the predator this would result in fall of the prey

population and the predator population would also fall, there

are lags between increases and decreases in population this

is due to lengthy reproduction cycles of organisms involved.

o Predation, Grazing and Parasitism are all relationships between two organisms where one benefits at the others

expense.

o Mutualism/Symbiotic: Relationship where both parties benefit.

o *Biotic factors are density dependent i.e. if size of population is big relative to the area then competition for

resources (light, space, mates et cetera) is also greater.

Abundance and distribution of organisms are governed by Abiotic and biotic factors; this involves a complex interaction

between both sets of factors. Example, poor weather results in reduction in survival rate of a species; this will then have a

knock on effect on its predator. An Abiotic example being, if the pH of soil changes, this may affect rate of decomposition

and recycling of material and in turn the time it takes for the site to reach climax community and be able to support other

animals and plants.

Anthropogenic Factors

These arise from human activities and can be biotic or abiotic. For example much of the woodlands in Britain may still

been here today if it was not deforestation, moor burning and grazing. Grazing is strictly a biotic factor in addition humans


have introduced animals into new environments which place an extra strain on the existing animals, examples being

sheep, goat and cattle. The following abiotic and biotic factors arise due to human activity:

Abiotic Factors

o Water availability– use of water, which is normally used by other organisms puts an extra strain on the existing

animals

o Topography–Humans may alter gradients of a natural site, example making a gradient less steep, this in turn may

affect drainage which will have an adverse effect on plants whose supply of water is reduced and does not meet

there demands to survive and reproduce (asexually or seed dispersal/germination).

o Climate – Global warming (see said section for more details)

o Soil and mineral content– Fertilisers such as NPK increase the levels of different mineral contents which would

increase growth of plants however, when excessive fertiliser is used, the excess fertiliser gets washed up by rain

and could end up going into lakes potentially killing aquatic organisms and marine plants as the solar energy is

blocked due to unnatural growth of plants on top of the lake not allowing solar energy to reach the depths of

ponds and thus plants do not grow fully e.t.c.

Biotic Factors

o Introduce animals into an environment– Farm animals

o Predation/Hunting -

o Grazing – Introduced animals graze leaving less

behind for those who were already present in the

habitat.

o Deforestation – Cutting/burning down forests

means animals that were settled and had the

correct adaptations to survive in said forest die or

are forced to migrate elsewhere.

Adapted for survival

Species survive in a habitat because they have adaptations

that enable them to cope with both the biotic and abiotic

conditions in their niche. (fig5.7 shows the adaptations of a

polar bear)

Sampling methods

o Rationale: To find the distribution: “Where a particular species is within the area being investigated”

o Abundance: “Number of individuals of one species in a particular area i.e. population size of species in a habitat”.

Random sampling

o Map the area and computer generates and assigns numbers to the areas and then computer randomly picks an

area. Then pick a technique to take a sample of the population (line transect or belt transect). Repeat process to

increase reliability and validation of results.

Calculations


o To find number of organisms present in the whole area you have to: Average number of specific species

multiplied by size of the area. This will give an estimate of population of the specific species and the figure will be

closer to the true value if one takes lots of samples from different areas.

o Percentage cover: Count number of squares a specific species occupies in the quadrat, most quadrats will have 100 squares thus the number of squares occupied by squares is = the % cover, 1 square = 1%

Systematic sampling

o Systematic sampling is when samples are taken at different intervals, usually along a line. This involves doing

transects, where a sample line is set up across areas where there are clear gradients e.g. could be used to see

difference and change in species when moving from grassland to woodland. Systematic sampling can be

conducted in two different ways: line and belt transects.

Line Transect

o Line transects are used to measure distribution of plants across an area.

o Ranging poles parallel to each other set up at a known distance using a tape measure. The species that touch the

tape measure are recorded. Line transects can be used in any ecosystem not just a beach e.t.c.

o A specific distance is used. Species touching the line may be recorded along the whole length of the line

(continuous sampling). Alternatively presence or absence of species at each marked point is recorded according

to which plants touch the line. (systematic sampling).

Belt transect

o Unlike Line transects this technique gives us more information like, abundance, % cover and presence or absence

of species also a quadrat is used.

o Area chosen, ranging poles set up at a known distance parallel to each e.g. 32 metres, predetermined intervals

chosen example placing quadrat every 4 metres this would give 8 samples. Plant/animal abundance and

distribution calculated abundance by counting up how many species present and distribution calculated by %

cover.

Succession

o Succession is the “process by which an ecosystem changes over time”.

o Biotic conditions (plant and animal communities) change as abiotic conditions change (e.g. water availability).

Primary succession

Primary succession starts in newly formed habitats where there never has been a community before e.g. bare rock. Below

shows the steps to go from primary succession to a climax community.

1) Newly formed land (e.g. post volcano eruption) or exposed land (e.g. sea levels drop = new land) present, it is

important to note that new land must have the minimum requirements to allow it grow plants i.e. land must be

fertile. Land formed from volcano eruption is very fertile due the minerals in the lava.

2) Seeds and spores are transported to the land by wind or by humans, the plants then begin to grow, these plants

are called Pioneer species they are named so because they are the 1st species to colonise a new habitat e.g.

include algae and lichen which colonise bare rock. Pioneer species can cope with extreme conditions such as low


soil nutrients and water content and different temperature extremes, pioneer species are specialised species e.g.

marram grass which grows on sand dunes as it has deep roots to retrieve water and other nutrients and is

tolerant to very saline conditions.

3) Pioneer species like any species dies and microorganisms decompose the dead organic material which in turn

over a long time period results in accumulation of basic soil.

4) Accumulation of soil makes the abiotic conditions such as water and mineral availability in soil more prominent

this in turn makes the conditions less hostile for new organisms to grow, they out compete the plants present as

abiotic conditions favour the larger plants. These plants then die and decompose increasing the amount of soil

making it deeper and richer in minerals, this in turn allows larger plants to grow whose demands of minerals,

water and solar energy e.t.c. are greater e.g. shrubs.

5) Like this more larger and complex plants move and grow in the habitat as current plants die and decompose

making soil richer in minerals and deeper, the dead plants die as they’re are out competed by the plant species

moving in as abiotic conditions(edaphic factors) & biotic conditions (out competing other species) suit them.

6) As succession continues the ecosystem becomes more complex as animals move in to the community benefiting

from the plants (as they have food & space).

7) Eventually the ecosystem will be in a

state of stability while being complex

with a varying amount of different

species present, Trees would be the

dominant species, the roots are very

deep and minerals are rife and the

sheer height of trees allows it to

benefit from increase solar input

compared to the less dominant plant

species which may have a height of

just a few centimetres of the ground

and thus not benefit from the solar

energy as much as trees in addition

trees roots would allow it to tap into

untapped minerals not usually

reachable to other plant species. This is called climax community – “largest and most complex community of

plants and animals”. Biodiversity increases as succession continues though may fall slightly in climax community

as ecosystem is dominated a few dominant species e.g. Trees.

8) Different ecosystems have different climax communities, moderate temperate climate = Large trees. Polar

climate = herbs and shrubs, this is because less water meaning no trees can grow and abiotic

factors(temperature/climate) do not support trees inhabiting these areas.

Secondary succession

o This occurs when an existing community has been cleared by things such as forest fires, deforestation and

ploughed fields by farmers. The soil would allow plants to grow if there is no human intervention the ecosystem

would reach climax community e.g. Oak forest.

Deflected Succession

o Defined as “When human interference prevents succession” e.g. grazing by cattle, deforestation and fruit

plantations, these examples are all anthropogenic biotic factors.


Productivity

o Primary productivity is the “rate at which energy is converted by photosynthetic and chemosynthetic autotrophs

to organic substances”. The total amount of productivity in a region or system is gross primary productivity

(GPP).

o Producers/Autotrophs – “Organisms make their own organic compound from inorganic compounds” e.g. include

plants, green algae and bacteria which are all photosynthetic autotrophs. Chemosynthetic

autotrophs “Make organic molecules using energy released from chemical reactions”, e.g.

chemosynthetic bacteria in deep ocean vents.

Energy transfer

o Most energy enters an ecosystem via solar energy, plants utilise this energy via photosynthesis

(or chemosynthesis dependent on ecosystem). Autotrophs then pass on a partial amount of the

energy to the next trophic level to heterotrophs, they obtain readymade organic matter by

ingesting material from other organisms i.e.cattle. All animals, all fungi, most bacteria and some

protoctists are heterotrophs. They are consumers which can be primary, secondary or tertiary.

o Primary consumer/Herbivores – Are heterotrophs that eat plant material

o Secondary consumer/Carnivores – Feed on primary consumer

o Tertiary Consumer/also Carnivores – Eat other consumers. The carnivores

at the top of the food chain is sometimes called “Top Carnivore”

o Omnivores – Animals that eat plants and animals

o Food chain/Food web –A sequence of interactions that represents the way in which energy is transferred from one organism in a community to another. It is important to note that in some food chains end after secondary consumer as the amount of energy available for the next trophic level (NPP) is minuscule hence a 3rd trophic level may not exist. Some chains may go on and include more than 3 trophic levels as energy available to next trophic level is sufficient enough to support it.

o Food chain–Defined as “Arrows that represent energy transfer” and clearly

show which species is Top carnivore.

o Food web- Defined as “shows lots of food chains and how consumption

overlaps”.

o Trophic level – “The position a species occupies in a food chain”. Energy is lost through each trophic level (see

below for more details)

Decomposers and Detritivores

Not all energy is passed onto the next consumer, some

energy is locked in bones and faeces which through

detritivores and decomposers are recycled back into the

ecosystem. Nitrogen cycle -------------->


o Detritivores– primary consumers that feed on dead organic material e.g. Detritus, woodlice, earthworms and

freshwater shrimps

o Decomposers – species of bacteria and fungi that feed on dead remains of organisms and on animals faeces,

they are heterotrophs. Decomposers and detritivores are part of the Nitrogen cycle.

Efficiency of energy transfer o Not all the energy is passed onto the next consumer

Inefficiency of energy transfer in plants

o Some solar energy is at the wrong wavelength for

chlorophyll of plant and thus cannot be utilised by it but

could be used by other species of plants

o Solar energy may hit a non photosynthesising part of a plant

e.g. bark of a tree, hence available solar energy not used.

o Light energy could be reflected from plant hence not used.

Inefficiency of energy transfer in animals

o Some parts of food are not edible for certain animals and

thus energy available is not utilised e.g. bones and roots.

o Indigestible part of food pass through organisms and come

out as waste i.e. faeces

o 40% of available energy is absorbed (GPP) but not all of this is available to the next trophic level

o 30% of GPP is lost through movement, photosynthesis, heat loss, active transport

o 10% is the NPP, it becomes biomass (stored or used for growth), and this energy is then available to the

next trophic level. (% above are not accurate and will depend up every food chain)

Productivity and energy transfer calculations

Trophic level productivity

o Gross primary productivity (GPP) – Rate at which energy is incorporated into organic molecules by an ecosystem

expressed by the following units - kJ m-2y-1

o Net primary productivity (NPP) – The rate which energy is transferred into the organic molecules that make up

the new plant biomass and Energy available for the next trophic level.

o Respiration loss (R)– 6O2 + C6H12O6 6CO2 + 6H2O

o To find the productivity of a trophic level one has to work out NPP, equations is as follows NPP=GPP-R

o Working out respiration loss, R=GPP-NPP

o Working out Gross primary productivity, GPP=NPP+R

Percentage efficiency of photosynthesis

o GPP/amount of light energy striking plant x 100


Energy transfer between trophic levels

o % efficiency of energy transfer between trophic levels = NPP of a level/NPP of a previous level

Photosynthesis

o Plants need energy for photosynthesis, active transport, DNA replication, cell division and protein synthesis

o Animals need energy for muscle contraction, maintenance of body temperature, active transport, DNA

replication, cell division and protein synthesis

o Photosynthesis is process by which energy from light is used to break apart the strong bonds in H2O, this is called

photolysis. Hydrogen reacts with CO2 to store it to form carbohydrate fuel glucose which is stored or converted to

other organic molecules and O2 is released.

o 6CO2 +6H2O ->C6H12O6 + 6O2 overall photosynthesis reaction.

o Photosynthesis is different from respiration, there are two types: aerobic and anaerobic, with and without O2 .

o Phosphoroylation – Add phosphate to a molecule

o Photophosphoroylation(Cyclic & Non Cyclic) – adding phosphate to a molecule using light

o Photolysis – Splitting of a molecule using light energy

o Hydrolysis – Splitting of a molecule using water e.g. ATP hydrolysed to ADP + Pi

o Redox Reactions – Reactions that involve reduction and oxidation (OILRIG)

o Co-enzyme – A molecule that aids the function of an enzyme. Photosynthesis utilises this type of molecule

ATP

o Adenosine Triphosphate (ATP) is composed of adenine (organic base), ribose (5-carbon

sugar) and 3 phosphate groups; the 3rd phosphate attached to the 2nd carbon is loosely bonded and

easily removed. ATP is the most important energy transfer molecule, it transfers energy to wherever

it is needed in the cells.

o Glucose cannot be directly used as a source of fuel instead in respiration when glucose is

released this energy is used to make ATP

Formation of ADP and Pi

o The 3rd phosphate on ATP is loosely bonded which means the reverse reaction of the formation of ATP is possible

i.e. ADP and Pi can be reformed.

o ATP in water -> ADP + hydrated Pi+ energy: When the 3rd phosphate is removed from ATP, ADP is formed, once

removed the inorganic phosphate group becomes hydrated, which then bonds with the surrounding water

molecules releasing energy which then drives processes in the cell, this breakdown reaction is catalysed by

ATPase. This is a hydrolysis reaction which provides an immediate energy for biological processes.

Formation of ATP

o ADP + Pi -> ATP: The formation of ATP is a

Phosphoroylation reaction as inorganic phosphate is

added onto ADP which only has two Phosphate groups. In


order to make ATP, phosphate must be separated from Water molecules which require energy, this reaction is

powered by an energy releasing reaction such as the breakdown of glucose in respiration, and the energy is

stored in the phosphate bond as chemical energy. ATP synthase is the catalyst. ATP then diffuses to where it is

needed in the cell; the stored chemical energy is what fuels the processes in the cells such as protein synthesis.

Structure of Chloroplast

Two stages of photosynthesis

Photosynthesis is not a single reaction but a series of reactions controlled by enzymes; there are two main stages, shown

below

1) Light dependent reaction–Uses energy from light and hydrogen from photolysis of water to produce reduced

NADP, ATP (created via photophosphoroylation) and waste product Oxygen, The oxygen is then used in

respiration or released into the

atmosphere through the

stomata. Takes place in the

thykaloid membrane, light

energy is absorbed by the

Photo systems

2) Light independent

reaction/Calvin cycle – Uses

reduced NADP and ATP from

Light dependent reaction to

reduce CO2 to carbohydrates.

Light Dependent Reaction

1) Light energy is absorbed by PSII (680nm), this excites the electrons, the electron

move to a higher energy level. The excited electrons move along the electron

transport chain.


2) The Electrons that have left must be replaced thusly light energy splits water (photolysis)

into H+ (protons), Electrons and Oxygen, the equation H2O ->2H+ + 0.5O2

3) Excited electrons loose energy as they move through the electron transport chain, this

lost energy allows the transport of protons into the thykaloid, which now has a high

concentration of them creating a proton gradient, H+ (which comes from photolysis of

water) then move down their concentration gradient into the stroma via an enzyme

called ATP Synthase (facilitated diffusion). This means ADP is re-phosphorolated into

ATP as shown in the equation ADP + Pi -> ATP

4) Light energy is absorbed PSI (700nm), which excites the electrons to a higher energy

level. These electrons then are transferred to co enzyme NADP along with a proton

from the stroma to form reduced NADP (remember oxidation is loss, reduction is

gain of e- hence reduced NADP)

5) The products of LDR are Reduced NADP and ATP

Light independent reaction/Calvin Cycle

o Takes place in the stroma of the chloroplast using reduced NADP and ATP from the LDR.

o CO2 from the air is reduced during a series of reactions to make 2 x Triose -3- Phosphate, this molecule then goes

on to make glucose and other important substances.

o This reaction requires energy provided by reduced NADP which provides the H+ and the ATP provides the energy.

o It is a cycle hence some of the products are used to continue the cycle

1) CO2 enters leaf via the stomata and diffuses

into the stroma of the chloroplast. 6CO2

combines with 6RuBP (5C) which is catalysed

by Ribulosebisphosphate carboxylase

(RuBISCO).

2) An unstable 6-Carbon compound is formed

which quickly breaks down into 12 x 3

Glycerate Phosphate (GP)


3) GP (3C) is then reduced to a 12 x 3 Glyceralaldehyde -phosphate (GALP aka TP) which is also a 3 carbon

compound though it is a sugar , this reduction is done by the H+ from the reduced NADP and ATP (also from LDR)

powers the reaction by providing energy.

4) 2/12 GALPs formed are then involved in the creation of a 6-carbon sugar (hexose) i.e glucose which is used for

biological processes in the plant.

5) 10/12 GALPs are involved in the recreation of RuBP to form 6 5C compounds (30C)

6) Carbohydrates, amino acids, lipids and nucleic acids all use the glucose to make their respective products.

7) To summarise there are 3 overarching phases of the Calvin cycle:

o Phase 1– CO2 ->RuBP (RuBISCO) (Carbon fixation)

o Phase 2 – GP reduced to GALP/TP

o Phase 3 – Regeneration of RuBP via GALP/TP

Structure of chloroplasts in relation to their role in photosynthesis

1) Chloroplast envelope/ Double membrane - Keeps the reactants for

photosynthesis to their reaction site

2) Thykaloid membrane –They have a larger surface to allow as much light

energy to be absorbed as possible. Used in the LDR. e- transfer chain present on

this membrane

3) ATP Synthase –Lots of these molecules are present in the thykaloid

membranes to produce ATP in the LDR and allow H+ reach stroma where it would

give energy for the phosphorolation of ADP into ATP

4) Stroma–Used in LIR & contains all enzymes, sugars and organic acids for the LIR to take place.

Causes of global warming

o Reliable data suggests that changes in the atmosphere are linked to climate change. Atmosphere is very

important as without it temperatures would hugely fluctuate making life almost impossible on earth.

o The increase in global temperate leading to global warming and sometimes temperature decreases is natural,

though human activity has lead to and still is increasing global temperatures as such global warming has also

increased through the greenhouse effect

Greenhouse Effect

o The sun radiates energy mostly visible light, the earth’s surface absorbs this

energy and radiates this back as ultra violet light to the atmosphere where

greenhouse gases absorb and retain this energy, essentially warming up the

atmosphere and earth. More greenhouse gases = more heat.

o Greenhouse gases such as CO2, CH4 and CFCs stop the reflection of IR radiation,

trapping the energy and the heat.

Greenhouse Gases


o These gases increase the

greenhouse effect, these include: CO2,

CH4 and CFCs

o This table allows one to

quantify the global warming potential of

different gases

o GWP: “gives an indication of

the effect over a 100 years period,

effect of releasing 1 kg of the gas into

the atmosphere compared with 1 kg of CO2”.

o E.g. of GWP of CO2: 3.8X10-2 X 1 = 3.8X10-2

o It is important to note that some gases such as the CFCs that have a very high GWP have little overall effect on

global warming due to its miniscule abundance and equally small average lifetime in the troposphere.

Methane CH4, how it contributes to GW and its effect

o CH4 concentration has increased rapidly since the mid 19th century from 700ppb to 1700ppb in 2000.

Methane concentration is increasing because of the following point

o Methane is produced by anaerobic decay of organic matter in water logged conditions e.g. Bogs and rice

paddy fields, decay of domestic waste, produced by animals when they belch, fart and when there faeces

decomposes and is also produced in incomplete combustion of fossil fuels. An increase in all of these

activities has increased the concentration of greenhouse gas CH4 leading to an increase greenhouse gas

Carbon Dioxide CO2, how it contributes to GW and its effect

o CO2 concentration has increased from the mid 19th century from 280ppb to

380 ppb in the 2000s. The concentration has increased due to the following

reasons.

o Natural reasons for GW to increase due to an increase in CO2 is as follows

changes in earth’s orbit around the sun, changes in solar radiation

(Milankovitch cycles) and volcanic eruptions, though human activity has lead

to a disruption in this natural process, activities such as burning fossil fuels

and deforestation which has lead to a decrease in the number of natural carbon sinks, trees.

Analysis and interpretation of global warming evidence

o There is anecdotal evidence from elders which suggest that the climate was different in past, though this

type of information is unreliable and thusly useless to interpret and analyse hence other methods of are

used to gather evidence for GW, they include: Carbon Dioxide levels (analysed above), Pollen in peat bogs

and dendrochronology (tree rings) and temperature records

Temperature Records and interpreting, analysing the graph.

o Temperatures have been recorded in central England from 1659 to 2000, shown in the graph. In the time

period there is a gradual increase in average temperature. The average in 1659 being 8.5oC to 10.2oC in

2000.


o This temperature increase is evidence of global warming, some scientists may suggest no causal link exists

between human activities and global warming but the

evidence and studies are overwhelmingly suggest

global warming does exist in addition most of the

scientists who suggest otherwise have other agendas

backed by cooperation’s who would adversely be

affected by the emergence of the notion of global

warming to the masses

Peat bogs and interpreting and analysing the graph.

o Thermometers were used to measure temperature records from 1659 upwards though peat bogs allow

scientists to measure temperature change from many thousands of years ago.

o A peat bog is an accumulation of partially decayed organic matter, mainly dead remains of dead plants. In

anaerobic and often acidic conditions the rate of decay is slowed or stopped.

o Pollen grains are well preserved in peat and it is the pollen that allows scientists to determine climate

change over a certain period of time. Pollen from peat is useful for reconstructing past climate because:

o Plants produce vast amounts of pollen throughout all seasons and every plant species produces a different

type of pollen grain which helps distinguish different species of plant.

o Peat bogs form in layers the deeper the layer the older the peat, Carbon dating allows age of a particular

peat to be identified.

o Before identifying the peat bog with C-14 dating one must know the ecological conditions a certain plants

peats like to grow in, e.g. if plant A’s peat was very prevalent and we knew with prior knowledge that this

species prefers warmer conditions we can infer from the quantity of peat bog that plant A preferred warmer

conditions , though one must use C-14 dating on the pollen grains to identify whether the pollen grain in

question is in fact from peat bog of species A

o It is important to note that the peat bogs present would only be the ones who suited the ecological

conditions hence peat bogs of less successful species may not be prevalent

Depth of samples (M) Approximate age of sample (years)

Num of pollen grains in sample of oak

Num of pollen grains in sample of fir

0.5 3100 253 28

1.0 4200 194 121

1.5 5700 138 167

2.0 7100 51 231

o Between 7100 and 3100 the number of oak pollen grains increased from 51 to 253 which suggests that the

climate favoured growth of oak tree, in the same time fir pollen grain decreased from 231 in 7100 to 28 in

3100 this suggest that the climate did not favour the growth of fir, fewer fir trees reached maturity and

produced pollen grains where as the reverse is true for oak trees.

Dendrochronology (tree rings)


o Dendrochronology allows one to determine the age and more about a tree, the tree produces one ring per

year the thicker the ring the warmer/wetter the conditions which favoured the growth of the tree and

reverse is true for less warmer climates.

o Scientists can take cross sectional samples from the bark of a tree to identify and then count how many rings

they are identifying how old the tree is and then measuring the thickness of the rings

o One could be asked to analyse and interpret a graph contains information about tree ring width

o Another method of measuring climate change which allows one to retrieve information about climate

change even past 20,000 years which is achievable with pollen grains is drilling for ice cores, when water

freezes bubbles of air become trapped within the ice, the ratio of different isotopes of Oxygen is measured

and this gives an estimate for average air temperature.

o Scientist could combine data from all of these methods to have information about the climate dating many

thousands of years.

o It is important to note just because there is a correlation between two factors that does not imply a causal

link exists between the factors.

Predicting future climates

o Scientists can use the data we have on different factors which have been identified as a contributor to GW to

make predictions about the future climate e.g. Using current CO2 data to make predictions about the future

CO2 data and its effect on the climate.

o The IPCC have put together a 5 scenarios using current data on how the climate may be in a 100 years time

the scenarios are as follows

o S1: maximum emissions

o S2: emissions increasing but not being managed as well

o S3: emissions increasing but being managed better than S2

o S4: Emissions staying on today's level

o S5: huge crackdown on emissions and there is minimum emissions being produced

Limitations of making predictions

o Accuracy of the scenarios are unknown

o The degree to which climate will change quantitatively by each scenario is unknown

o There may be natural events which may cause CO2 to rise e.g. Huge volcanic eruption

o There may be hugely successful yet unknown measures to tackle certain climate changing factors e.g. CO2

reduction

Controversial conclusions about different facets of global warming

o There is consensus in the scientific community that GW is happening and humans are contributing to it by

e.g. human activity such as burning fossil fuels increasing CO2 emissions.


o Some scientists with financial motives may come up with different conclusions on climate change data e.g. A

scientist working for a oil company may conclude CO2 does not have a big of a impact on the climate change

as previously thought, some may even claim that global warming is entirely due to the workings of nature.

These conclusions are not based on pure scientific evidence but motivated by financial rewards.

o Similarly scientist from green/alternative energy firms may heighten the true impact of CO2 and other factors

that contribute to GW in an attempt to promote and hopefully sell their products.

o This is why it is important for the scientific community to see what background other scientists arise from to

debunk any conclusions made by those with altierier motives.

Effects of global warming

o GW directly affects plants and animals as well as indirectly affecting animals and plants by changes in global

rainfall patterns and timing of seasonal cycles.

Effect of increasing temperature on enzyme activity of plants, animals and micro-organisms

o Increasing temperate would increase the rate of enzyme-catalysed reactions as more enzyme and substrate

are colliding and forming complexes as the increased temperate has increased the momentum of said

particles, this increases the RofR and metabolism of some animals.

o This increase in temperature may help those species who had a high optimum temperate but could not

reach it due to surrounding cooler temperate, however this increase in temperature may adversely affect

those species whose optimum temperature matched/nearly matched the previous temperature as the

increase in temperature would have meant that metabolic reactions would have slowed down, rate of

growth decrease as well as progressing through the life cycle slower and the onset of denaturing of enzymes

which would further affect rate of growth, the reverse is true when a species who hasn't reached their

optimum temperature is in question.

Changing rainfall patterns

o GW changes the level of rainfall in certain areas of the world

o Changing rainfall patterns will affect the life cycles of certain organisms e.g. Some organism lie dormant

when dry but come out of hibernation when it starts to rain and environment becomes more moist, reduced

rainfall may mean a longer hibernation period which may affect its predators who may be reliant on the

certain species coming out of hibernation this would have a domino effect on all the other animals and

plants linked in the food web.

o Distribution of species will also be affected as those species who are less adapted to live in the area may

migrate to another area or run the risks of death conversely conditions in the desert may suit certain species

to migrate in the desert, which could negatively affect those species who are present in the habitat already.

Seasonal cycles

o GW warming affects the transition time of changing from one season to another as such this then effects

plants and animals life cycle, development and distribution.

o Some species mate at a certain time of the year e.g. In summer where they may be more food availability but

changes in timing of food availability means that sometimes for species to stay successful and pass on their

genes to the offspring they have mate quicker to take advantage of food availability this is the case with red

squirrels


o Changing seasonal cycles also could affect distribution of some species e.g. Some birds spend their time in

warmer climates and then migrate to colder ones to mate, the timing of this could be affected by seasonal

changes which could affect the birds while they are still in the warmer climates and also affect those who are

dependent upon their arrival in the colder climate.

Carbon cycle and reducing atmospheric CO2levels

o The carbon cycle is nature’s way of maintaining a balance between processes that remove CO2 and those

that add CO2 to it. Carbon cycle shows a movement of carbon between organisms and the atmosphere

o Atmospheric CO2 is absorbed by plants when they carry out respiration, this then become carbon

compounds in the plants tissue as organic

molecules (biomass)

o Carbon compounds are then eaten by animals

and when the animal dies, decomposers then

decompose the organic matter (Carbon

compounds)

o Carbon is returned to the environment via

respiration in the form of CO2

o There are no decomposers in some parts of the

ocean hence Carbon compounds over millions

of years becomes fossil fuel which could be then

used in combustion

o All of these processes have a reverse process which keeps carbon levels in check, however human activity

has disrupted Carbon neutrality.

Imbalance in atmospheric carbon levels

o CO2 levels have been rising for over 100 years this indicates an imbalance in CO2 level. The two main factors

that have caused this is the combustion of fossil fuels & deforestation

Combustion of fossil fuels

o Coal represents a Carbon sink, coal was formed from dead trees millions of years ago this would have been

decomposed if this happens today but millions of years ago the inability of fungi and bacteria to decompose

meant that it never happened.

o This Carbon sink in the form of coal means we are essentially adding Carbon into the environment which was

never balanced by decomposition, this places an imbalance on Carbon neutrality.

Deforestation

o Deforestation results in destruction of trees which are then unable to take up atmospheric CO2 in

photosynthesis which creates an imbalance, they are not respiring which would also widen the gap between

CO2 and O2

o Most of the time only the best timber is used and taken the other parts of a tree are burned which increases

the level of CO2 in the atmosphere rather if they let it be this would enable decomposers to decompose the

rest of the tree and release O2


Other factors that create an imbalance

o Volcanic eruption/ other natural events

o Acid rain = Erosion of Calcium Carbonate = CO2 levels increase

Maintaining the balance

Biofuels

o Biofuels are produced from biomass which is recently living dead material.

o Biofuels are a renewable source of energy as well as being a carbon neutral source of energy. It is neutral e.g.

Tree photosynthesises adds Carbon containing tissues on the tree, this process removes Carbon from the

environment, which is then added when part of the tree is burnt hence there is no net increase in Carbon in

the atmosphere

o Some biofuels have the ability to replace fossil fuels

Reforestation

o This concept requires the growing of more trees in existing and depleted forests

o More trees results in more CO2 intake from the environment which allows balance to start to re balance

again as more CO2 is stored as Carbon containing tissue.

Problems with alternative measures of generating energy

o Biofuel: farmers may protest that they are not making crops for food rather for fuel purposes, those who

drive cars may like this idea as biofuel would place competition on traditional oil which drives down prices,

there may be food shortages as more plants are used for biofuels rather than food

Evolution through change in gene mutation and natural selection

o Evolution is defined as a change in allele frequency and it could be achieved through gene mutation and

natural selection.

Evolution by change in allele frequency

o Alleles present in a population are called its gene pool, new alleles are formed by changes in the base sequence of

alleles.

o Allele frequency tells one how often an allele appears in a population. When the frequency of an allele changes

evolution has took place.

Evolution by natural selection

o Individuals within a population vary due to different alleles, those who have alleles that allow them to better

adapt to the environment are more likely to survive, reproduce and pass on their successful alleles to the next

generation who would have the beneficial allele and thus will be able to survive, reproduce and pass on the

beneficial allele this process increases the frequency of the allele in the population, this is called natural selection

Speciation


o This is when environmental conditions resulting from climate change provide a selection pressure which leads to

evolution of species which could sometimes mean on a molecular level the two subjects are very different and

hence two different species.

How are species formed

o For a species to evolve into another species it must be

reproductively isolated, the most common isolation is

geographical isolation e.g. Pangea resulting in an island

being split and the group of species being reproductively

isolated.

o Species become different as they respond to the different

selection pressures presented to them in different ways e.g.

Island A cold climate and those with the ability to survive will

and reproduce and pass on genetic material. Island B may

have a warmer climate and those adapted will, survive and

pass on genes to next generation eventually two species

would have been formed

o As random mutations accumulate, when the two species

meet they wouldn't be able to interbreed to form reproductive species

o There are other methods of reproductive isolation such as:

Role of the scientific community in validating new evidence & evidence for evolution

Molecular biology

o Molecular biology is the study of molecules such as DNA and protein

DNA Evidence

o Theory of evolution suggests that all organisms have evolved from a shared common ancestors, they then

diverged through speciation


o This results in scientists being able to find how similar DNA is between two organisms, the more common the

DNA means less time has passed since speciation between the two groups occurred

Proteomics

o This is the study of proteins in particular its size, shape and amino acid sequence of proteins

o The more common the DNA sequences in the base between two species less time has passed since speciation

The scientific method of validating evidence about evolution

o Scientists propose hypothesises and collect data via experiment, this then proves there idea correct or disproves

its validity. Once the idea has been proved by data it is a theory, this is then tested by scientists for its validity

o Scientists share and discuss their work in 3 mainstream manners:

1) Scientific Journals

o They are academic magazines where articles are published concerning new ideas, theories, experiments and

conclusions. This information should allow other scientists to conduct the same experiment to test the validity of

the conclusions

o If the results as stated are replicated many times by different scientists then the scientific community accepts the

theory

2) Peer review

o Before work is published in a journal it must be peer reviewed, scientist who work in the same area read and

review the work and they check if conclusions made supports the evidence this allows those experiments to be

published that are valid and carried with the highest standards.

3) Conferences

o Scientists who are interested in your work and or have an interest in the same field as the work conducted are

invited

o This presents a great opportunity for a scientist to present their work this would allow other scientists to ask

questions and discuss their work

o This also allows scientist to stay up to date with the latest theories and experimental evidence

topic 5 revision notes ecology o biosphere o population · 2018-08-30 · topic 5 revision notes...

Documents