Ecosystems Flashcards
Define ecosystem
All the living organisms that interact with each other and the physical factors in a defined area
Define and give examples of biotic factors
Living factors. Food, space, breeding partners, size of populations
Define and give examples of abiotic factors
Non living factors. Light, temperature, water availability, oxygen availability
Define trophic level
Each stage in a food chain
Define producer
An organism that converts light energy into chemical energy by photosynthesis
Define consumer
Organisms that obtain energy by feeding on other organisms
Define primary consumer
An animal that eats a producer
Define biomass
Mass of living material present in a particular place or in particular organisms
How do you calculate biomass at each trophic level?
Biomass present in each organism x total number of organisms in that trophic level
How do you measure biomass?
Burn a sample of the organism in a calorimeter. This energy is used to heat a known volume of water. Calculate the change in temperature of the water. This can be used to calculate the energy in the sample. Should be measured in J or Kj
Explain efficiency at producer level
○ 1-3% of sunlight converted
○ 90% reflected, some is transmitted through the leaf and some is of unusable wave length
○ Other limiting factors
○ A proportion is lost as it is used for photosynthetic reactions
How do you calculate the energy available to the next trophic level?
Net production = gross production - respiratory losses
Explain efficiency at consumer levels
○ 10% of biomass is converted to their own organic tissue
○ Not all food is consumed
○ Transferred as metabolic heat
○ Indigestible parts
○ Excretion
How do humans manipulate biomass through ecosystems
○ Suitable abiotic conditions (warmth, watering, shelter)
○ Competition is removed
○ Threat of predators is removed
○ Reduction of trophic levels
○ Selective breeding
Define a decomposer
An organism that feeds on dead matter and breaks down organic compounds into inorganic compounds
Define saprobiotic nutrition
Obtaining nutrition from dead/waste organic material. Secreting enzymes onto dead matter which breaks down complex organic molecules into more soluble molecules.
Define detritivores
They speed up decay process by feeding on detritus which breaks down organic matter into smaller pieces (increasing the surface area)
Explain the roles of Azotobacter and Rhizobium
Combines nitrogen with hydrogen to form ammonia - nitrogen fixation
Azotobacter : free living soil bacterium
Rhizobium : live inside root nodules (which grow on leguminous plants)
Why is the relationship between bacteria and plants described as mutualistic?
Plants gain amino acids from Rhizobium and bacteria gains carbohydrates from the plant during photosynthesis
How does nitrification occur?
It occurs in well aerated soil
Nitrosomanas oxidises compounds into nitrites
* Nitrobacter* oxidises nitrites into nitrates
Nitrate ions are highly soluble therefore can enter plants
What condition does denitrification happen under?
Anaerobic condition
Nitrogen Cycle
Nitrogen gas -> Nitrogen fixation -> Organic Nitrogen -> Ammonification -> Ammonium -> Nitrification -> Nitrite/Nitrate -> Denitrification -> Nitrogen Gas
Why do levels of carbon dioxide fluctuate?
Plants only photosynthesise during the day whereas respiration is constant
Higher in the winter than in the summer as photosynthesis happens less
Define primary succession
Development of organisms on a newly formed area of land
Define secondary succession
Development of organisms on an area of land with soil present but no species
What causes primary succession to occur?
Volcanic eruption
Sand blown by wind
Silt and mud are deposited at river estuaries
Glaciers retreating
Define seral stage
Each step in succession
Describe the first stage of succession
Pioneer species - arrive by wind or droppings by birds
○ seeds germinate rapidly
○ produce large quantities of seeds or spores
○ photosynthesise rapidly
○ tolerance to extreme conditions
○ nitrogen fixation
Define humus
Organic products released by decomposition of pioneer species
Describe the intermediate community
Secondary colonisers use soil to dominate the area
As the conditions improve, new species arrive (Tertiary colonisers). At each stage, the soil becomes more nutrient rich
What is the final seral stage called?
Climax community
Describe the climax community
Few species will dominate, little changes over time, stable state
Define plagioclimax
The final stage when succession is stopped artificially
How to measure distribution of plants
Line transect - laying measuring tape down and taking samples at regular intervals
Belt transect - two parallel lines arenarked and samples are taken from the area in between
How to measure plant abundance
Using a quadrat placed randomly
How to measure animal abundance
Capture-mark-release-recapture
