topic 10

• a biosphere is the parts of Earth where life occurs, including land, sea, and air
• an ecosystem is a reasonably self - contained area with all its living organisms
• a biome is a region of the world with a particular climate and organisms
• a habitat is the physical or abiotic part of an ecosystem with specific characteristics where the organisms live

  ~ most ecosystems have multiple habitats
• a microhabitat is a localised specific habitat within a larger habitat
• a terrestrial is an ecosystem on dry land
• an aquatic is an ecosystem in water
• a marine is an ecosystem in the sea
• a community is a living or biotic part of an ecosystem
• a population is the members of the same species in one habitat
• a random sample is when you want a representative sample of a whole area to study

  • there should be a large number of samples - at least 10, preferably 100
  • you should sample at least 2 % of the area
• a systematic sample is where you investigate a specific pattern in the ecosystem and often uses a transect

  ~ it requires both biotic and abiotic factors to be measured at each sampling site to test for correlation
• transects can either be:

  ~continuous -> measures across the whole transect

  or

  ~interrupted -> has gaps between each sample

  and

  ~line -> only measures the organisms touching the transect

  or

  ~belt -> places quadrats along the transect and measures organisms in the quadrat
• abiotic factors should be measured several times at each sampling site over the course of a day or a year, to account for daily or seasonal variations
• biotic factors are identified using identification keys and measured through their:

  ~ abundance -> use a capture mark recapture method for animals + often calculate the density

  -> cannot use this if measuring something like grass - impossible to distinguish separate organisms

  ~ distribution -> clumped, form, random

  ~ diversity

  ~ growth

  ~ biomass
• there are three types of distribution:

  ~ clumped -> most common distribution, could be clumped for defence against predators, in hunting packs, social groups, or due to localised resources e.g. a water hole

  ~ uniform -> when individuals are as spread out as possible for territorial reasons or due to competition for scarce, thinly - spread resources

  ~ random -> least common distribution, occurs when dispersal of young is random and the location of each individual is independent of others - can only happen when resources are abundant and even, so little competition
• to measure biomass, we measure dry mass as water doesn't contain energy -> the organism needs to be warmed in an oven at around 80 C so the water is evaporated but the organic matter isn't burnt, and weighed in intervals until the mass doesnt change

  ~ this technique is called drying to constant mass
• to find the best size quadrat for sampling, you need to place quadrats inside eachother in the area to be studied and count the number of species found. then, plot a species - area graph - where the line begins to plateau should be the most efficient size as it is likely to catch all the species without unnecessary effort
• there are different ways to measure using quadrats:

  ~ density -> count abundance then divide by total quadrat area - innapropriate when species are hard to identify from eachother

  ~ species frequency -> record the number of quadrats a species was found, or use a quadrat with a grid and record the number of small squares where the species were found

  ~ percentage cover -> for species such as grass where it's hard to identify separate organisms - can be subjective but more accurate if quadrat with a grid is used

  ~ abundance scale -> e.g. ACFOR - quick but subjective and not quantitative
• ACFOR is used to categorise species by abundance quickly, and can be paired with percentage cover to make semi - quantitative

  A - abundant

  C - common

  F - frequent

  O - occasional

  R - rare
• DAFOR is used to categorise species by abundance quickly - a verion of ACFOR

  D - dominant

  A - abundant

  F - frequent

  O - occasional

  R - rare
• a point quadrat is a small quadrat where a needle is dropped through a hole in a frame and whatever the needle hits is recorded - the number of hits is divided by the total number of repeats to give percentage cover

  ~ this is less subjective than a quadrat, and can be quick with practice
• animals that are sessile (dont move e.g. limpets) or sedentary (move slowly e.g. snails) can be measured using quadrats
• different ways to catch animals

  ~ nets e.g. sweep nets for insects on plants, d - nets for invertebrates dislodged from the mud and stones on river beds (aka kick sampling) which are then emptied onto trays for sampling

  ~ traps e.g. pitfall traps for invertebrates moving on the ground, longworth traps for small mammals, light traps for flying insects - theyre left overnight + should not harm the animal

  ~ sighting methods - also counts evidence for animals such as nests, burrows, or faecal pellets
• capture mark recapture works by

  ~ capturing a sample of animals using a trap / net

  ~ counting all the animals caught then marking them in a way that doesn't harm them e.g. a spot of paint

  ~ release the animals where they were caught + give time for them to assimilate with population

  ~ capture a second sample of animals in the same place with same trapping technique

  ~ count animals in second sample and number of recaptured animals

  ~ se these to calculate a population estimate using e.g. the lincoln - petersen index
• there are two main ethical considerations for an investigation

  ~ the work should not harm the environment

  ~ the organisms should be treated with respect + not harmed / moved from habitat if possible
• the t-test is used like binomial distributions where we look for a difference between the two sets of data, whilst spearmans rank is used like PMCC to test that the two sets of data are related to eachother
• the p-value should be 0.05, andthe critical values will be based on the degrees of freedom ( total number of organisms - the number of samples taken )in a t - test or the number of pairs of data in a spearmans rank
• detritus is dead waste and matter not eated by consumers

  ~ also can be called carrion
• detritivore is an animal that eats detritus
• a saprobiont is a microbe that lives on detritus

  ~ also can be called a saprotroph
• ~ matter cycles between living and non living, but no new matter reaches earth and none leaves

  ~ energy is constantly arriving from the sun, passing through living organisms, then leaving the earth as heat
• pyramids of numbers can be almost any shape, but pyramids of biomass are mostly pyramid shaped
• typically, only some biomass absorbed by a consumer is passed on because

  ~ it is used in respiration and converted to carbon dioxide and water, which are excreted

  ~ some biomass is not eaten by consumers, or cannot be absorbed by the organism - this becomes detritus and is used by decomposers
• a pyramid of biomass can be inverted if the measurements were in specific seasons ( often happens with aquatic ecosystems ) e.g. winter

  ~ if average biomass was recorded throughout a year, the pyramid of biomass would be normal
• pyramids of energy are always pyramid shaped as energy cannot be created, and are always very shallow as the transfer of energy between trophic levels is very inefficient - the 'missing' energy is eventually lost as heat
• in food chains, matter is lost as

  ~ carbon dioxide and water through respiration

  ~ uneaten parts

  ~ waste e.g. faeces, urine

  energy is lost as

  ~ chemical energy in uneated parts

  ~ movement energy of consumers

  ~ heat energy, especially in homeothermic animals
• the carbon cycle

  A) photosynthesis

  B) respiration

  C) respiration

  D) respiration

  E) combustion

  F) death

  G) death

  H) decay

  I) no decay

  J) producers

  K) consumers

  L) decomposers

  M) fossil fuels

  N) atmosphere

  O) ocean

  P) detritus

  
• photosynthesis is the only route that fixes inorganic carbon to organic

  ~ terrestrial producers e.g. forests account for around half of carbon fixation

  ~ marine microbial producers e.g. phytoplankton accounts for the other half
• ~ a carbon source releases more carbon as carbon dioxide than it accumulates in biomass long term e.g. farmland and deforestated areas ( due to decay )

  ~ a carbon neutral ecosystem balances the release of carbon dioxide and carbon fixation e.g. mature forests

  ~ a carbon sink accumulates more carbon in biomass than it releases as carbon dioxide long term - this happens when the conditions are not suitable for decomposers ( too cold, too dry, too acidic, etc.) .g. peat bogs (too acidic), ocean floor (too cold + anaerobic), growing forests (carbon incorporated into biomass)