6.5 Ecosystems Flashcards
What is an ecosystem ?
An ecosystem is made up of all the living organisms that interact with one another in a defined area.
What are biotic factors ?
Living factors. Eg competition, food, predator-prey relationships.
What are abiotic factors ?
Non-living or physical factors. Eg, rainfall, light intensity, temperature, o2 availability.
What are edaphic factors ?
Different soil types.
What is clay soil ?
Fine particles, easily waterlogged and forms clumps.
What is loam soil ?
Different size particles, retains water but doesn’t become water logged.
What is sandy soil ?
Coarse, well separated particles that allow free draining.
What is a trophic level ?
Each stage in chain is known as a trophic level.
What is a producer ?
Organism that converts light energy into chemical energy by photosynthesis.
What are consumers ?
Subsequent levels after producer. Organisms that obtain enerrgy by feeding on other organisms.
What are decomposers ?
Break down dead organisms, releasing nutrients back into the ecosystem.
What is biomass ?
Mass of living material present in a particular place or organisms. Can be equated to energy content.
How to calculate biomass at each trophic level ?
Multiply biomass in each organism by total number of organisms in that trophic level.
Why is biomass less than in trophic level before ?
When animals eat, only a small portion of food they ingest is converted into new tissue.
What is ecological efficiency ?
Efficiency in which biomass or energy is transferred from one trophic level to the next.
Why do producers only produce 1-3% of sunlight they receive ?
Not all solar energy available is used for photosynthesis.
Other factors may limit photosynthesis.
Energy is lost during photosynthetic reactions.
How to calculate energy available to next trophic level ?
net production = gross production - respiratory loss.
How to calculate ecological efficiency ?
Energy available after transfer / energy available before transfer x 100.
What is decomposition ?
Chemical process in which a compound is broken down into smaller molecules or its constituent molecules.
Why are decomposers saprotrophs ?
They obtain their energy from dead or waste organic material. They digest food externally by secreting enzymes.
What are detritivores ?
Another class of organism involved in decomposition. They help to speed up decay process by feeding on detritus (dead and decaying material).
How do animals obtain nitrogen ?
Animals obtain it by the food they eat.
How do plants take in nitrogen ?
They take it in from the environment.
What is nitrogen-fixing bacteria ?
Contain enzyme nitrogenase, which combines atmospheric nitrogen with hydrogen to produce ammonia. This can then be used by plants.
How does this bacteria and plant have a symbiotic relationship ?
Plant gains amino acids from bacteria, which are produced by nitrogen fixation.
Bacteria gain carbohydrates produced by plant during photosynthesis.
What is nitrification ?
Process by which ammonia compounds in the soil are converted into nitrogen-containing molecules that can be used by plants.
What is process of nitrification ?
Nitrifying bacteria oxidise ammonium compounds into nitrites.
Another type of nitrifying bacteria oxide nitrites into nitrates. These are highly soluble so can enter a plant.
What is denitrification ?
Denitrifying bacteria converts nitrates in soil into nitrogen gas. Only happens under anaerobic conditions.
What is ammonification ?
Name given to process by which decomposers convert nitrogen containing molecules in dead organisms into ammonium compounds.
What is the nitrogen cycle ?
The processes of nitrogen fixation, nitrification, denitrification and ammonification all form this cycle.
Why do levels of CO2 in atmosphere fluctuate during day?
Higher at night than in day. Photosynthesis takes place in day but repsiration takes place day and night.
Why do levels of CO2 in atmosphere fluctuate seasonally?
CO2 levels are lower on summers day than in winter as photosynthesis rates are higher.
Why has levels of CO2 increased over recent years ?
Combustion of fossil fuels and deforestation.
What is succession ?
Process by which ecosystems change over time.
Why does succession occur ?
Due to changes in the environment, causing plant and animals species to change.
What is primary succession ?
This occurs on an area of land that has been newly formed or exposed. There is no soil or organic material to begin with.
What is secondary succession ?
Occurs on areas of land where soil has been present but contains no plant or animals species. An example would be an bare earth that remains after a forest fire.
When does primary succession occur ?
Volcanoes erupt, sand is blown by wind, silt and mud are deposited, glaciers retreat.
What are the stages of succession known as ?
Known as a seral stage.
What are the main seral stages ?
Pioneer community, intermediate community and climax community.
What is pioneer community ?
Colonisation of inhospitable environment. Species arrive as spores or seeds carried by wind from nearby land masses.
What is intermediate community ?
Weather of bare rock produces particles that form basis of soil. When organisms of pioneer species die, small organic products are released into soil.
What is organic component of soil known as ?
Known as humus.
What is climax community ?
Community is stable. Few dominant plant and animals. Depends on climate. Not most biodiverse as it peaks in mid-succession.
What is animal succession ?
Primary consumers are first to colonise. Secondary consumers arrive once suitable food source has been established. Eventually larger organisms such as mammals will colonise the area.
What is deflected succession ?
When succession is stopped artificially. Eg, grazing from animals, removing vegetation, burning as a means of forest clearance.
What is plagioclimax ?
Final stage of succession when it has been artificially stopped.
What is the distribution of organisms ?
Refers to where individual organisms are found within an ecosystem. Usually uneven.
How to measure distribution ?
Use belt or line transect
What is abundance of organisms ?
Refers to number of individuals of a species present in an area at any given time.
Measure abundance of plants
Measure abundance of plants, quadrats are placed randomly.
Number of individuals in sample / area of sample.
What is name of nitrogen fixing bacteria ?
Azobacter and rhizobium
What is mutualistic bacteria ?
Live in root nodules and obtain carbohydrates from plants and plant gets amino acids from bacteria.
What is name of nitrifying bacteria that converts ammonium to nitride ?
Nitrosomonas
