ecosystems and sampling biodiversity

• population - all the organisms belonging to one species that live together in the same area at the same time
• community - all the populations of different species that live in the same place at the same time and interact
• habitat - the place where the organism lives
• niche - the role of an organism within the ecosystem, two species cannot have the same niche
• trophic level - the stage at which an organism feeds in the food chain
• ecosystems - a relatively self contained unit of living organisms interacting with each other and their abiotic environment

  • dynamic `
  • biomass constantly flows through
  • mineral ions are cycled
• biotic factors

  • grazing
  • predations
  • parasitism
  • mutualism/symbiotic relationships
  • competition (interspecific/intraspecific)
• abiotic factors

  • temperature
  • light intensity
  • oxygen
  • humidity
  • rainfall
  • extreme values slow growth
• energy and biomass transfer through ecosystems

  all organisms need energy, plants use light energy in photosynthesis to produce organic compounds

  products of photosynthesis are used in respiration

  biomass can then be passed through food chain
• energy and biomass losses along food chains

  at each trophic level some energy and biomass is lost

  energy lost as heat

  biomass lost as carbon dioxide + water
• excretion - waste products form metabolic processes
• egestion - never digested
• efficiency of biomass energy transfer

  $biomassofhighertrophiclevel/biomassoflowertrophiclevel$
• primary producitivty

  • <3% of sunlight is converted to photosynthesis: light not hitting plants, light on non photosynthesising parts of the plant, light reflected from leaf surface, light transmitted through the leaf
• gross primary productivity = the light energy converted into chemical energy by photosynthesis

  • some is used for respiration, energy lost as heat
  • remaining energy and biomass transferred = NPP
• net primary productivity = the amount of energy converted in photosynthesis which remains as biomass in the plant after respiration
• Gross Primary Productivity =Net Primary Productivity +Respiration
• efficiency of biomass transfer from producers to consumers 5-10%

  • not all parts of plant are eaten (roots)
  • cannot digest all parts of the plant (cellulose cell wall)
  • energy lost as heat in consumers digestive system
• efficiency of biomass transfer from consumers to consumers 15-20%

  • some animals not eaten
  • some parts of animals not eaten (bones)
  • energy lost from food chain as heat due to respiration
• measuring efficiency of biomass and energy transfer - numbers

  • count organisms using random sampling with quadratic
  • camera traps or mammal traps collect animals
  • problems: change depending on time of year, traps aren't ethical, random sampling not always reliable
• measuring efficiency of biomass and energy transfer - biomass

  • weigh sample and multiply by proportion
  • must be dry biomass
  • kill the organisms and heat to remove water
  • problems: unethical, ecological issues associated with damage to environment, doesn't consider bones
• measuring efficiency of biomass and energy transfer - energy

  • using a bomb calorimeter set fire and see how much water heated by
  • more accurate than boiling tube
  • temperature change
  • burn in oxygen
  • problems: ecologically disruptive, large species cannot fit into calorimeter
• manipulating energy flow - primary productivity of an ecosystem will vary

  • climate; light intensity
  • seasonal variation
  • soil condition
  • plant density
  • age of plants, young plants put more energy into growth
• intensive agriculture

  • high crop density - more light hitting plants than soil
  • irrigation and drought resistant varieties - stomata open more
  • increasing temp and co2 - rate of photosynthesis increases
  • fertilisers - provide the plants with mineral ions for chlorophyll and amino acid production
  • insecticides - stops plant losses
  • gm - increases growth rate
• secondary productivity

  • use primary consumers, more energy efficient
  • restrict movement
  • artificial warmth, less co2 and water loss
  • high energy foods
  • selective breeding
  • antibiotics
  • killing animals just before adulthood
• decomposers - bacteria and fungi recycle nutrients from dead organisms and waste materials back into the ecosystem

  • feed saprotrophically
  • secrete enzymes onto dead matter, organic molecules are hydrolysed, small soluble ones are absorbed into organism.
  • decomposers release inorganic compounds and elemtns into environment
• detritivores - maggots, earthworms. Help speed up decay by feeding on dead and decaying matter and breaking it into smaller pieces, increases sa for decomposers
• recycling nitrogen

  plants get nitrogen from ammonium ions and nitrate ions from soil

  animals get nitrogen from amino acids breaking down
• nitrogen fixation - process of making nitrogen compounds from nitrogen gas

  • lightning strikes
  • haber process
  • nitrogen fixing bacteria
• free living nitrogen fixing bacteria

  • azotobacter
  • fix nitrogen gas from air spaces in soil
  • manufacture amino acids for growth
• nitrogen fixing bacteria in root nodules

  • live in root nodules of leguminous plants (peas and beans)
  • eg rhizobium
  • bacteria have mutualistic relationship with the plant, provide plant with fixed nitrogen in return for glucose
  • leghaemoglobin in nodules absorbs oxygen and maintains anaerobic conditions allowing the bacteria to use nitrogen reductase to reduce nitrogen gas to ammonium ions
• ammonification - from protein to nitrates in the soil

  • decomposition
  • saprotrophic fungi and bacteria break down amino acids from dead organisms and nitrogenous waste products
  • nitrogen compounds converted to ammonia and then ammonium ions
• nitrification

  • ammonium compounds are oxidised by bacteria in the soil into compounds that plants can use
  • nitrifying bacteria are chemoautotrophic (gain energy from reaction)
  • ammonium ions oxidised to nitrites by nitrosomonas bacteria
  • nitrites to nitrates by nitrobacter bacteria
• denitrification

  • some bacteria convert nitrates to nitrogen gas
  • bacteria present in water logged soil
  • nitrates used as a source of ox for respiration
• recycling carbon

  fluctuations

  • co2 levels change during the day and seasonally, dependent on rate of photosynthesis
  • combustion of fossil fuels and deforestation
  • positive feedback, less co2 dissolved in oceans at higher temps
• abundance - how many of the organisms are present
• distribution - where in the ecosystem the organism lives
• random sampling - used to avoid bias

  1. set axis in a representative area
  2. use random number generator to produce coordinates
  3. place quadrat at coordinate
  4. repeat
  5. use ID card to identify species
• limitations of random sampling

  • seasonal variation subjected to
  • difficulty identifying plants
• non random sampling - useful to ensure all areas of a habitat where there is lots of variation are studied and look at the distribution of organisms