Ecosystems ✅ Flashcards
What are biotic factors affecting ecosystems
Competition and consumption, Eg Living organisms
What are abiotic factors affecting ecosystems
Temperature: Enzyme activity, thermoregulation, leaf-fall and flowering (in plants)
Photosynthetic rate (in plant) eg light
What is a trophic level
A stage in a food chain
List the names of a food chain with 5 stages
Producer-primary consumer-secondary consumer-tertiary consumer-quaternary consumer
What is a producer
An organism (eg a plant) that converts light energy to chemical energy (ie autotrophic nutrition)
What is a consumer
An organism that gains energy by feeding in other organisms (ie heterotrophic nutrition)
What is procedure, adv and disadv of measure of fresh (wet) biomass
Procedure: living organisms measured
Adv: no organisms are killed
Disadv: presence of water reduces accuracy
What is procedure, adv, disadv of measure of dry biomass
Procedure: organisms are killed and heated at 80^C until all water removed
Adv: estimates of mass are more accurate
Disadv: organisms must be removed from ecosystem and killed
When might a pyramid of biomass not be a pyramid
When the consumer is usually large but in small number Eg trees may be few in number within an ecosystem, but their total biomass will still be greater then that of primary consumers
What transfer occurs at producer level and consumer level
Producer: light energy conveyed to chemical energy in producers
Consumer: stored energy in biomass of one trophic level is transferred to next trophic level by consumption
What is some energy not transferred at producer and consumer level
Producer: most light energy (90%) cannot be absorbed by plants. Some energy used in reactions of respiration and bud not converted to chemical energy in biomass
Consumer: some parts of organism (eg bones, roots, feathers) are inedible or indigestible. Some energy lost from food chain as heat, through movement or urine
What is the calculation formula for producer and consumer levels
Producer: net production=gross production - respiratory losses
Consumer: ecological efficiency= (energy available after transfer/ energy available before transfer) X100
How can humans manipulate factors in the production of plants
Light: plants grown in greenhouses under optimal light intensity and duration, seed sowing times to maximize leaf area present for photosynthesis during brightest months of year
Temperature: greenhouses provide regulates optimal temps
Water: irrigation, genetically engineered to drought resistant crops
Nutrient levels: fertilizer
Pests: pesticides
How do humans manipulate the efficiency of energy transfers to primary consumers
Movement: movement of farm animals limited. More energy channeled into growth
Disease: antibiotic use reduces energy expenditure in immune systems
What is decomposition
Process of large organic molecules (in dead animals and plants) being broken down into smaller inorganic molecules
What can decomposes be classed as
Bacteria
Fungi
Or can be referred to as saprotrophs
What is decomposition in the nitrogen cycle called
Ammonification- breakdown of proteins, nucleic acids, vitamins in dead organisms, faeces, iron to form ammonia and ammonium compounds
What are the 3 processes to re enter nitrogen into food chain
Nitrification
Nitrogen fixation
Denitrification
What is the reaction of nitrification and name of bacteria
NH3/NH4+ ions to NO2- (nitrosomonas)
NO2- to NO3- (nitrobacter)
What is the reaction for nitrogen fixation and what bacteria is used
N2 (in atmosphere) converted to NH4+ions/NH3
rhizobium (which lives in roots of some plants)
Azotobacter (free living in soil)
What is the reaction for denitrification and what bacteria is used
NO3- to N2 gas
Denitrifying bacteria (required anaerobic conditions)
Describe nitrogen cycle
Ammoinium ions—>nitrite ions—> nitrate ions (all by nitrification)
Nitrate ions to N2 in atmosphere (denitrification) or nitrogen containing molecules in producers (absorption)
Nitrogen containing molecules in producers to consumers by feeding and digestion
Both nitrogen containing molecules go to ammoinium containing molecules in decomposes which go to ammonium ions by ammonification
Describe carbon cycle
Photosynthesis converts CO2 to organic molecules in organisms
Respiration, decomposition, combustion return CO2 to atmosphere
What is succession
Composition of an ecosystem gradually alters as abiotic factors in environmental changes, progression from bare ground to stable complex community of organism
Describe the process of primary succession from bare rock to stable community
Only pioneer species can colonise bare rock eg lichen and algae which can fix nitrogen from atmosphere. Pioneer species represent the fist seral stage
Erosion of rock produces basic soil
Death and decomposition of pioneer organism adds nutrients to soil
Soil development enables secondary colonizers eg mosses
Improved environmental conditions enable more species to colonise
Climax community forms which is stable and relatively biodiverse
What is deflected succession
Human activities can prevent climax community from forming
What is the result of deflected succession and give examples
Plagioclimax
Found on agricultural land and in managed forests
Describe the stages from barren land to climatic climax
Barren land
Primary colonizers (lichen)
Secondary colonizers (mosses)
Tertiary colonizers (grasses)
Scrubland (shrubs)
Climatic climax (woodland)
Last 3 can go to plagioclimax Eg farmland
What is used to analyze how distribution of organisms varies in an ecosystem, what type of sampling is this
Transect, systematic
What can be uses to estimate abundance of plant species per area
Quadrats
What technique is used to estimate animal abundance
Capture-mark-release-recapture
describe the factors that reduce the efficiency of energy transfer between trophic levels (3 marks)
inedible/ indigestible parts
energy used in respiration/ to produce heat
energy used for movement
some energy lost in excretion
explain how farmers can increase the proportion of consumed energy that is used for growth in cattle (3 marks)
restrict movement
use antibiotics to reduce amount of energy used by the immune system
maintain optimal environmental temperature
more energy is converted to biomass
explain how human activity has upset the natural balance of the carbon cycle (3 marks)
deforestation
reduces photosynthesis
more combustion
in industry/vehicles/as fuel
higher CO2 concentrations in the atmosphere
suggest why farmers may try to prevent their soils becoming waterlogged (3 marks)
anaerobic conditions
increased denitrification
reduced nitrification
lower concentrations of nitrates for crop plants to absorb
explain what is meant by a plagioclimax, and identify one example resulting from land management (2 marks)
a community resulting from deflected succession, where human influence gas prevented succession from producing s climax community
(examples include) managed forests, grazing grassland, arable crop fields
describe 3 important characteristics of a pioneer species (3 marks)
tolerance of extreme conditions/ environments
ability to fix nitrogen from the atmosphere
ability to photosynthesise
production of many seeds/ spores that can be carried by the wind
rapid germination of seeds
describe the difference between primary succession and deflected succession, and explain why primary succession is likely to result in greater biodiversity (3 marks)
primary succession is the natural development of an ecosystem to form a climax community
deflected succession is when human activity interrupts succession, producing a plagioclimax
primary succession tends to produce greater biodiversity because deflected succession reduces the number of ecological niches available
explain why the measurement of distribution should be systematic (2 marks)
different areas within an ecosystem are identified
