Ecology : unit 1. Ecosystems

Habitat, population, community, ecosystems

environment in which an organism lives (e.g. elephants in the grasslands of Africa)

total number of organisms of the same species living in the same geographical area (elephants) at the same time

the populations of all of the different species that live in the same habitat (e.g. zebras, giraffes) → contains all biotic parts of the environment

how both biotic and abiotic factors of an environment interact

competition caused by requirements for materials

organisms require a supply of materials from surroundings e.g. water and other organisms but bc of being short in supply they have to compete with each other.

plants : light and space, water and soil min+aq

animals: food+water , mates, territory

interdependence, plants on animals, animals on plants,

all different species in a community depend on eachother

every animal depends on other living organisms for food e.g. plants or other animals

some living organisms provide shelter e.g. trees from the sun

plants depend on animals e.g. bees to transfer pollen and seed dispersal

consequences if a species disappears, and a stable community

if a species disappears from a community, this can disrupt the whole community

(e.g. if a pollinator species dies lots of flowers cannot reproduce and animals that feed on these plants pop wil ↓)

in most communities the populations of the different species remain fairly constant.

In a stable community the populations of organisms are in balance with each other and with the abiotic resources

biotic factors : Availability of food, new predators

all animals eat other living organisms for food, all sources of food whether plants or animals are biotic factors and if the availability falls then no of organisms in that community will also fall

can cause population of prey species to fall and can affect existing predators e.g. if they are competing for the same prey,

biotic factors : competition, and infectious diseases

if a species is outcompeted then its population can fall so much that numbers aren’t sufficient to breed ∴ local extinction

if an infectious disease emerges (pathon) then spreads it can wipe out a population of a species

abiotic factors : lux, temp, water

all plants need light to conduct p.synth but if lux is too low then p.synth rate ↓ and plants will grow more slowly → if less plant biomass then primary consumers will not be in a large population ∴ the rest of the food chain affected

if temp of an envir changes then this can cause species distribution to change e.g. animal migration and plants can disappear

both plants and animals need water to survive ∴ a major abiotic factor

abiotic factors : pH and soil mineral content, gas levels

important for plants and many have an optimum pH and so cannot grow if conditions are too acidic or alkaline and need specific minerals e.g. nitrates

wind intensity and direction is another abiotic factor that can affect plants e.g. strong wind from land to see can cause plant water loss

CO2 and O2 concs / availabilty in air, needed for p.synth and aer resp

{[(in air stays relatively constant, but can decrease in water when hot affecting marine )]}

Adaptations (feature that helps an organism survive and reproduce in its habitat) - divided into structural - functional - behavioural

structural is concerned with body shape, structure and composition {[(e.g. camels having more fat in a singular hump so that less insulation around the body to allow heat loss)]}

functional concerned with the internal bodily functions [{(e.g. camels produce concentrated urine and dry faeces to reduce water loss)}]

behavioural concerned with lifestyle / behaviour {[(e.g. kangaroo rat nocturnal to avoid day heat)]}

general adaptations of animals

ear size - small or large to give favoured SA:V for heat loss

fur or concentration of fat in one place to insulate - prevent insulation of whole body

camouflage - hunt or hide for prey better by making it hard to see

teeth - sharp for meat in carnivores, herbivores more molars

hibernation - avoid energy wastage in cold migration - more favourable conditions

General plant adaptations

leaf chlorophyll composition / size → ↑ light absorption

long deep roots, shallow for water absorption

ability to shed leaves or reduce to spines for water loss + protection from eating

thick waxy cuticle and fleshy leaf store and reduce water loss

flower and fruit - seed dispersal

Extremophiles

Organisms that are adapted to live in extreme conditions, including extreme heat and freezing cold and high pressure and salt concentrations

e.g. bacteria living in deep sea vents have enzymes that do not denature at high temps

food chains - trophic levels, pri sec ter, preds prey

shows the direction of E and biomass flow

the first trophic (feeding) level is called the producer and it accounts for all the mass of the food chain - synthesises complex bio molecules from gluc from p.synth

then the chain goes prim, sec tertiary consumer, each one eats the one before

(prim is herbivore and sec ter are usually carnivores)

animal attacking is predator and being eaten is prey

decomposers and apex predators in food chains

apex predators are carnivores at the top of the food chain and have no predators

decomposers are needed as they release Min+aq into the soil (to be taken up by plants) by digesting dead organic matter + waste and small soluble food molecules diff into the MG done by secreting enzymes into the envir

Predator prey cycles - only true in a stable community without e.g. extreme conditions or competition

number of predator and prey rise and fall in cycles, with a small latency for reproduction (predator peak lags behind prey)

because if prey ↑ e.g. because lots of food, they reproduce and their pop ↑ , and so the pred has more prey to kill and eat ∴ their rate of reproduction and population also starts to ↑,

but at this time they have eaten too many prey, so prey pop starts to ↓ to which pred pop starts to ↓ as less food ∴ lower RO reproduction and because less hunting and eating of prey, their pop starts to ↑ and the cycle repeats

Random sampling - avoids experimental bias - how to compare abundance of species in diff areas

a quadrat of a certain area is used and this will be placed many times in an area

• take two tape measures to cover a good distance of a field to form axes

• random no gen to gen 2 random numbers used as coords to place the quadrat

• count no of organisms of the desired species in the quadrat

we need a large number of quadrats for the sample to be representative - gives valid results

Random sampling equation - and limitations with sampling methods and technique

area sampled is the number of samples x quadrat area

counted in the sample is the total number of organisms of species

if we are sampling for a specific effect on an abiotic factor, it is possible there are multiple factors are affecting abundance or distribution

others can be small sample, counting error, uneven distribution

Transect sampling - investigate abiotic factors on distribution of a species in areas

take a tape measure (transect) so it runs across the habitat looking at a specific abiotic factor e.g. distance from a tree

then use quadrats to count the number of organisms of the species at specific intervals along the transect

repeat again to find mean and multiple transects along the area or at diff directions from e.g. a tree for representative ∴ validity

Carbon Cycle, how carbon enters and exits the cycle, and within the cycle

begins with atm CO2 - main way is to enter the cycle through p.synth of plants and can return through aer resp / combus

• used to synth complex bio molecules carbs lipids proteins (CBMs) that make up cells - they also respire so some CO2 is released back into atm

• plants eaten by animals and food chains → becomes animal CBMs

  • they respire ∴ CO2

• animal faeces and dead organic matter are decomposed by bacteria and fungi which releases atm CO2

importance of decomposers and fossil fuels

decomposers are needed as they cycle materials through an ecosys, returns CO2 to the atm as O2, they release Min+aq into the soil

in conditions like low pH and low O2, decomposers cannot function effectively ∴ the organic matter is not broken down, and so the C here is converted into fossil fuels over millions of years under extreme heat and pressure

combusting fossil fuels is releasing CO2 back into the atm

Conditions needed for optimum decay rate

temp - warm temp - not hot because needed for optimum enzyme ROR, not denaturing - tend to be quite warm anyway bc aer resp is exo

water - work faster if moist, bc many of the decay reactions require water

O2 availability - aeration and mixing allows for O2 for aer resp - also breaks clumps ↑ SA for decomposers to act on

compost + anaerobic decay

dead plant material is placed with soil in a compost heap and MGs decompose. This is then used as a natural fertiliser as it is very rich in the minerals that the plants need to grow

absence of O2, producing methane (biogas) that can be used for fuel - anaerobic resp and diges of dead plant matter

RP : rate of decay of fresh milk

invar : temp , devar : time taken for phenol to go colourless control : conc, vol, type milk and solutions and washing glass to prevent contamination

take 5cm milk and add 5 drops phenol, 7cm3 Na2CO3 to make it alkaline and then place in a water bath with 1cm3 lipase in a separate tube w a tmeter to get to temp, then pour lipase into milk, start stopwatch and stop when goes from pink to pale occasionally swirling

repeat at same temp for mean and then repeat at other temps

have multiple ppl decide when the solution goes pale

Explanation of milk decay rp explanation

the phenol goes from pink to colourless when acid is produces → lipids broken down into glycerol + fatty acids reducing pH

at low temps lipase ROR is slow bc less Ke for active site substrate collisions

optimum temp is highest freq of successful active site substrate collisions

passing opt lipase denatures

ROR = 1/t

Pyramids of Biomass, how to find biomass, drawing and efficiency of biomass transfer calcs

Biomass is mass of all living tissue in an organism

to find of an organism in a food chain would be killed and dried for dried biomass - more accurate than wet bc water levels can vary - published data should contain necessary info to avoid killing

plotting pyramids should have a central line of 0 and mass should branch out on either side equally

each trophic level should be the same height

efficiency of biomass transfer = biomass gain / total biomass intake x100

why only 1% of light E incident on producers is absorbed and used in p.synth , and reasons for biomass loss between trophic levels

because reflection, obstruction, wrong wavelengths and limiting factors

only around 10% of the biomass is transferred between trophic levels , because :

• not all of the animal is eaten e.g. bones

• some biomass lost from aer resp for (movement warmth) and metabolic waste as CO2 urea

• not all of the animal is digested - egested as faeces

this means that no of organisms at ↑ trophic lvls ↓ and there are v few chains more than than 5 lvls