Not on Exams Flashcards
Describe how energy flows through ecosystems.
Energy enters an ecosystem through photosynthetic
primary producers. Some is passed on to primary
consumers, then to secondary consumers. At each trophic level, some energy is used for
respiration. Some is used for growth. It is eventually
dissipated from the ecosystem as heat.
Describe how the following materials cycle in ecosystems: H2O, CO2, minerals, O2.
H2O: From atmosphere, Consumers and Decomposers to Producers.
CO2: From Consumers to Producers.
O2: From Producers to Consumers and Decomposers.
Which of the above materials do the primary producers (the photoautotrophs) use, and what
for? Which materials do they produce as byproducts/waste?
Primary producers use H2O and CO2 for photosynthesis to produce O2 for the ecosystem.
Which are used as materials by heterotrophs, and what for?
Heterotrophs eat producers and consume O2 for cellular respiration.
What is the role of decomposers/detritivores in ecosystems?
Decomposers break down the producers and consumers into nutrient soil for the producers to use later.
What is meant by the terms Gross Primary Production, Net Primary Production and Net
Ecosystem Production?
GPP: The total amount of
energy captured and converted to chemical form by
photosynthesis per unit time.
NPP: (biomass) equals gross primary
production less respiration by the autotrophs (RA) NPP = GPP – RA. It represents the amount of energy captured by photosynthesis that can be passed on to higher
trophic levels. (That was not used for respiration.)
NEP: equals gross primary
production less respiration by all organisms of the
ecosystem (RT). NEP = GPP – RT An ecosystem can be gaining total biomass (NEP > 0). It can be losing biomass (NEP
Which parameter indicates whether the ecosystem is acting as a carbon source or a carbon
sink?
NEP
What factors limit primary production in aquatic ecosystems?
Nitrogen and iron.
In terrestrial ecosystems?
Sunlight, water, nitrogen, and phosphorous.
Define and explain secondary production
The amount of energy in food that
is converted to consumer biomass per unit time. At each consumer trophic level, some energy is used for movement, metabolism, etc. Only a part is incorporated into biomass—this part is the
secondary production.
The new biomass.
Do different species significantly differ in the efficiency of their secondary production? Why?
Production Efficiency (%): Production Efficiency expresses the ratio of secondary production to total energy assimilated. Secondary production Total energy assimilatedX 100. In mammals, birds: 1-3%. Much energy used for
movement, regulation of body temperature
(homeotherms). In fishes ~10%. No energy expenditure for body temp regulation. In insects, microorganisms, up to 40%.
Describe the carbon cycle. By what routes is CO2 removed from the atmosphere? Is it stored
in living organisms, and what for?
CO2 in the atmosphere goes towards photosynthesis. The consumers eat photosynthesizers and use that C to carry out cellular respiration, resulting in CO2 emission into the atmosphere. CO2 is also released from consumers via decomposition.
By what routes does CO2 enter the atmosphere?
Cellular Respiration and burning of fossil fuels.
Are the rates of CO2 removal from the atmosphere and entry into the atmosphere in balance?
Why or why not?
No, at this moment more CO2 is entering than is being removed. The burning of fossil fuels is too much for the depleting photosyntesizers to keep up with.
What is an “extinction vortex,” and why are small populations particularly susceptible?
Extinction Vortex: Small population to smaller population.
Small population size subject to inbreeding and genetic
drift.
• Average fitness may decline due to homozygosity of
deleterious recessive alleles.
• Genetic diversity of population may decline.
• Population less able to adapt to changes.
