Ecosystems and sustainability Flashcards
what is an ecosystem?
a stable self-maintaining unit consisting of the community of populations (biotic factors) and the physical habitat (abiotic factors) and their reactions
what is meant by the fact that ecosystems are dynamic?
they are constantly fluctuating e.g. a population size can rise or fall, affecting other populations via food chains - e.g. nitrogen-fixing plants increase nitrate soil level, and other plants take up nitrates decreasing the level
What are biotic factors? name some biotic factors in an ecosystem
Factors that involve other living organisms including:
- feeding of herbivores on plants
- predation of predators on prey
- competition between species for shared resources
- parasites living on hosts
- mutualistic relationships where 2 species benefit from each other
What are abiotic factors? name some abiotic factors in an ecosystem and how they affect the organisms in the environment
Factors involving the non-living physical habitat such as:
- temperature: rate of reactions in endotherms and ectotherms
- light intensity: rate of photosynthesis (plants) and behaviour (animals)
- O2 concentration in water: aerobic respiration
- water supply
- wind speed: plant transpiration, lowers temperatures
- atmospheric humidity: water loss by sweating/transpiration
- ion availability: nitrates affect plant growth
- soil type: drainage and water content for plants
what is the energy input into an ecosystem? why is it needed
light energy from the sun. Ecosystems need a flow of energy through it to be self-maintaining
What is a producer? e.g.
autotrophic organisms - e.g. plants convert light energy into chemical energy in photosynthesis
a few convert chemical energy into usable chemical energy
What are consumers
organisms that obtain energy feeding on other organisms
what are decomposers
organisms which obtain their energy feeding on dead matter/animal waste
What is a trophic level?
what do arrows in food chains represent
each step in a food chain is called a trophic level. Arrows represent flow of energy from one trophic level to another
What is the number of organisms in an ecosystem fundamentally determined by?
The efficiency of energy flow through the ecosystem
What are some reasons for energy lost to the environment at each step in a food chain? (4)
- respiration of molecules to produce ATP for life processes such as protein synthesis
- heat loss from respiration and other chemical reactions
- loss of plant parts which die/shed (this energy is available only to decomposers)
- plants parts - cellulose - that cannot be digested
- energy lost in animal waste e.g. urine, faces (this energy is available only to decomposers)
What are 3 ways to measure the efficiency of energy transfers in an environment?
- pyramids of biomass: dry mass of all organisms at a trophic level
- pyramids of energy: calorimetry used to measure energy released
- productivity: energy available in a particular trophic level per square metre per year
How do you work out the net primary productivity (NPP) available to a consumer in a habitat?
gross primary productivity (the rate at which plants convert light energy into chemical energy) take away respiratory losses
GPP - respiratory losses
what are the problems associated with measuring efficiency of energy transfers using pyramids of biomass, pyramids of energy, and NPP?
pyramids of biomass: destructive to the ecosystems when organisms are dried in an oven at 80 degrees, and the alternative method of collecting wet mass and converting it to dry mass using published data is also unreliable because different species may contain different amount of energy per unit mass.
pyramids of energy: destructive, time-consuming, doesnt take into account fluctuation in population sizes over time
NPP: varies in different habitats and even areas of the same habitat according to factors affecting rate of photosynthesis
How can humans manipulate environmental factors to increase primary productivity (i.e. plant crops)?
- light intensity: artificial light in greenhouses/planting erlier in the year
- water: irrigation/development of drought-resistant crops
- temperature: higher in glasshouses
- ion availability: nitrate levels increased by crop rotation, use of nitrogen-fixing plants, inorganic fertilisers
- pests: use of pesticides, selective breeding/genetic modification to create pest-resistant strains
- competition reduced: use of herbicides
How can humans manipulate energy transfer from producers to consumers to increase secondary productivity (i.e animals)?
- slaughtered before adulthood so less energy used in growth
- selective breeding can produce breeds with faster growth rates, increased egg production or higher milk yields
- antibiotics can be given to prevent energy losses to combat diseases
- animals can be kept indoors to minimise heat loss and restrict energy losses due to movement
- increased food availability e.g. protein supplements to increase muscle growth
describe primary succession
the sequence of plant and animal populations that colonise a new area over a period of time. Each population changes the physical conditions, making it possible for other species to colonise the area and out-compete and replace the previous community
why is nitrogen so important for living organisms?
involved in many important biological molecules such as nucleic acids, proteins, ATP and are required in the form of nitrates
what is the only way nitrogen in the atmosphere can be accessed? what type of bacteria are involved anywhere might they be found?
NITROGEN-FIXATION: nitrogen-fixing bacteria such as Rhizobium convert N2 gas into ammonium compounds. Can be found free living in the soil or inside root nodules of leguminous plants
describe ammonification
Nitrogen containing compounds e.g. proteins in dead animals are converted to amino acids then ammonia compounds by decomposer bacteria/fungi
describe the process by which ammonium compounds are converted into materials which are accessible to plants. Bacteria involved?
NITRIFICATION: ammonium compounds –> nitrites (uses Nitrosomonas) –> nitrates (uses Nitrobacter)
Requires oxygen, so aerated soil required.
Plants can take up the nitrates from the soil by active transport
what is denitrification?
conversion of nitrates in the soil to N2 gas by denitrifying bacteria. Occurs in anaerobic soils and makes the soil less fertile as fewer nitrates are available for plant growth
Discuss the efficiency of energy transfers between trophic levels
At each step in a food chain, some enegry is lost to the environment and so is not available to the next trophic level.
This means there are rarely more than 5 trophic levels in a food chain.
Reasons for energy losses:
- respiration of molecules to produce ATP for life processes e.g. protein synthesis
- heat loss from respiration and other chemical reactions
- loss of plant parts e.g leaves/flowers - energy available to decomposers only
- indigestible plant parts such as cellulose
- excreted energy in urine, faeces only available to decomposers
how can the distribution and abundance of organisms in a habitat be measured?
using sampling techniques such as line transects, belt transects, quadrats and point quadrats
