Biology DSM 52

why are changes in the global carbon cycle important

carbon dioxide is a greenhouse gas

soil organic matter?

soil organic matter is rich in humic acid

why is the term cycling used to describe material transfer, whereas the term flow is used for energy exchange?

materials are repeatedly used, but energy flows through and out of ecosystems

natural nitrogen cycle

nitrogen-fixing bacteria in roots and soil fix atmospheric nitrogen to ammonia and nitrate, decomposers convert detritus into ammonia

which country is per capita the highest producer of carbon dioxide (CO2) emission?

canada

in a typical grassland community, which of the following is the primary consumer?

grasshopper (eats the grass)

the global carbon cycle involves the movement of carbon among ecosystems, largest reservoir of carbon?

ocean

net primary productivity

marine productivity is highest along coasts and in areas where water wells up from the ocean floor to the surface

components of ecosystems?

primary producers are autotrophs or “self-feeders”

biogeochemical cycles

if a plant dies, the nutrients and the plant biomass become plant litter

the energy invested in the production of new tissue by autotrophic organisms is …

net primary productivity

to recycle nutrients, an ecosystem must have, at a minimum, …

producers and decomposers

of the many links in a nutrients cycle, which one most often limits the overalls rate at which nutrients move through an ecosystem?

decomposition of detritus

biomagnification

the concentration of toxin can more than double at each level of the food chain

human impacts on the global water cycle

the water table is dropping on every continent

how does net primary productivity (NPP) differ from gross primary productivity (GPP)

NPP is the amount of energy available for primary consumers, whereas GPP is the amount of energy produced by plants and others producers

example of ecosystem studies

how the energy in sunlight dissipates as it flows thriugh an ecosystem

which of the following has (have) beeb presented as a cause for sudden irreversible shifts, such as those seen in the forested area converting to a grassland?

forest fires, invasive species, climate change

productivity

energy can be converted to tissue

major human impacts on ecosystems include farming, logging, and burning. These processes all result in accelerated nutrients export by what common mechanism?

vegetation removal

which of the following statements is an example of a negative feedback loop?

warmer conditions lead to increased photosynthetic reates and, hence, an increase in uptake of carbon dioxide (CO2), which could decrease the temperature

human have substantially altered the global nitrogen cycle over the past century. How?

humans are responsible for almost doubling the amount of nitrogen available by natural means

which trophic level is most vulnerable to extinction?

tertiary consumer level