Populations & Ecosystems- Unit 3.5 Flashcards
What is a population?
All the members of one species in an area that can breed with each other
What is a community?
All the members of all species in an area
How is a population different to a community?
A population describes the number of one species, whereas a community describes the number of many different species in an area
What is a habitat?
The place in an ecosystem where an organism lives
What is a niche?
The role of an organism in an ecosystem, generally a feeding role
What is an abiotic factor?
All the non-living parts of an ecosystem
What is a biotic factor?
All the living and organic components of an ecosystem
What is interspecific competition?
Occurs between individuals of the different species
What is intraspecific competition?
Occurs between individuals of the same species
What is a density depenent factor?
Has varying impacts depending on population size. (intraspecific competition)
What is a density independent factor?
The effect it has is not influenced by the population size. (tornado, tsunami)
What is carrying capacity?
Carrying capacity is the maximum number of individuals that can be sustained in a population
Name two sampling techniques:
Abundance- a measure of how many individuals exist in a habitat
Distribution- describes area or volume in which a species is distributed
What is biotic potential?
The maximum rate at which the population can reproduce, given it had all the resources necessary.
(environmental resistance makes this practically unachievable)
What is environmental resistance?
All factors limiting population growth:
•Accumulation of waste products.
•Lack of food/space/resources.
•Adverse climate.
•Predators/parasites/competitors.
What is percentage frequency in sampling?
The number of times a plant appears in a square.
(if a plant is in 25 squares, percentage frequency is 25)
What is succession?
The change in structure and species composition of a community over time. It is one directional.
Seres meaning:
The different stages in a succession when particular communities dominate.
What is a climax community?
When succession continues until the community reaches equilibrium with its environment and no further changes occur.
What is primary succession?
Introduction of organisms into an area where they haven’t been colonised before.
What is secondary succession?
Occurs at sites that have previously supported a community after a major disturbance.
What factors affect a populations size/growth?
Birth rate
Death rate
Immigration
Emigration
What is an ecosystem
A characteristic community of interdependent species interacting with the abiotic components of their habitat.
What is ecology?
The study of living things and their interactions with each other and their environment
What is the main source of energy for an ecosystem?
The sun
What is the lag phase for animals and bacteria?
Animal- first arrives there
Bacteria- synthesis of enzymes & replicating DNA
What is the log phase for animals and bacteria?
Animal- Food availability is high, competition low
Bacteria- Cells divide rapidly due to high food availability
What is the stationary phase for bacteria?
Nutrients deplete, reproduction & death rate stabalise.
What is the death phase for bacteria?
Toxins build up so death exceeds reproduction rate
What would the antilog10 (5) be?
10 to the power of 5 so
100,000
How do you calculate rate of growth in exponential phase for bacteria?
no. of bacteria at day x - no. of bacteria at day y / (divided by) x - y
What methods are used to measure animal abundance?
Capture- mark- recapture
Kick sampling in aquatic environments
What methods are used to measure plant abundance?
Quadrats to calculate population density
Estimating percentage cover
Estimating percentage frequency
What techniques are used to measure plant distribution?
Line transects- lay tape across sample area, record any species touching tape.
Belt transects- Quadrat at set intervals along tape and estimate species in it
What techniques are used to measure animal distribution?
Direct observation (they are mobile so quadrats/transects unsuitable)
What is a possible problem with using quadrats? How is this overcome?
Some plants form clumps so it is difficult to count individual plants. Plant density/percentage cover is calculated instead.
How is percentage cover estimated?
Using a gridded quadrat, it is divided into 10x10 squares so each square is 1%. Each square covered with plants is counted (more than half of square) which gives the percentage.
How is plant density calculated?
Use 10 quadrats
Count number of species and calculate mean (gives per 0.25m2)
Change this to per m(2) by x4
This is the density.
When are RANDOM transects deemed unsuitable?
When there is a change in environmental gradient. (light intensity/altitude)
Belt transect would be used instead as it is systematic
How is population estimated using capture- mark- recapture technique? (Lincoln Index)
no. captured first x no. captured second/ no. of recaptured
What is a micro-habitat?
An area of a habitat with specific conditions.
What is an ecological niche?
The place which a species occupies, resources it uses, role it carries out, etc. Two species cannot occupy same niche at same time in a specific habitat.
What is a decomposer?
Microbes which get their nutrients from dead organisms
What is a detritivore?
Organism feeding on organic debris from plants and animals
Why is 60% of light energy that falls on a plant not absorbed?
-The wavelength is wrong (has to be within 380nm and 720nm)
-Lost by reflection
-Transmitted straight through the leaf
What is photosynthetic efficiency? (PE) What factors make it differ?
Measures ability of plant to trap light energy
-Selective breeding
-Genotype
-Light intensity
-Temperature
How is PE measured?
Light energy incorporated into product / energy falling onto plant x100
What is gross primary productivity? (GPP)
Rate of production of chemical energy in organic molecules via photosynthesis in a given area in a given time.
What is net primary production? (NPP)
Energy in plants biomass that is available to the primary consumers
What is the mini word equation involving GPP & NPP?
GPP - respiration = NPP
What is primary productivity?
Rate that producers convert energy into biomass
What is secondary productivity?
Rate which consumers convert chemical energy from food into biomass within their cells/tissue
Why do herbivores have less secondary productivity than carnivores?
-Do not eat all of the plant, meaning only part of NPP of ecosystem is transferred.
-Cannot digest cellulose so remains undigested within faeces.
How is efficiency of energy transfer calculated between trophic levels?
Energy made into biomass after transfer / energy available in biomass before transfer x100
What factors affect succession?
Migration
Competition
Facilitation
What is commensalism?
One species benefits from relationship, one does not. (almost opposite of mutualism)
What is the only way that plants can uptake nitrogen?
Active transport and facilitated diffusion through their roots in the form of nitrate and ammonium
What are the 4 main processes of the nitrogen cycle?
Putrefaction
Nitrification
Nitrogen fixation
Denitrification
What is putrefaction? (1st)
Bacteria/fungi convert organic nitrogen from dead organisms protein into ammonia
What is nitrification? (2nd)
Nitrifying bacteria convert the ammonia into nitrItes, then into nitrAtes.
This is the absorbable form of nitrogen.
What is nitrogen fixation? (3rd)
Free living bacteria & nitrogen fixing bacteria in root nodules of LEGUMES convert atmospheric nitrogen into nitrogen compounds.
What is denitrification? (4th)
Denitrifying bacteria within soil reduce nitrates to molecular nitrogen.
Why is waterlogged soil bad?
Denitrifying bacteria are anaerobic so are present in this soil. Anaerobic competes with aerobic bacteria and denitrification occurs, losing nitrogen from the soil.
How do legumes have a mutualistic relationship with nitrogen fixing bacteria?
Bacteria convert nitrogen into ammonia. Since they have provided a nitrogen source, the bacteria receive carbohydrates and nodules in the root in which they can exist in a moist environment.
What is eutrophication?
Natural process in which concentration of salts (nitrates & phosphates) build up in bodies of water.
Sewage & fertiliser add to this.
Why is eutrophication bad when it is the result of fertilisers/nitrates. (humans)
Algal blooms build up along the surface of the water, making it inpenetratable to light. Deeper parts of the body of water cannot photosynthesise. Eventually the top of the water becomes deoxygenated so fish die as the microbes have respired and used all the oxygen after decomposing dead plants.
Anaerobic bacteria also reduces nitrate to nitrite which are toxic compounds.
Why do plants actually need nitrates?
For protein synthesis. (amino acids)
