Section 3, Part D Flashcards
What are trophic relationships, & how do food chains & food webs relate to energy flow through an ecosystem?
Trophic relationships are the feeding relationships within a community; in other words, they describe what “level” an organism eats at. Energy flows up food chains/webs from producers up through primary/secondary/tertiary consumers and on.
Describe the feeding relationships among different species within a community.
Primary producers convert inorganic materials into organic materials (think: Photosynthesis) and Primary decomposers/consumers break down those producers. Secondary consumers eat primary consumers; tertiary consumers eat secondary consumers; etc. See 56.1 page 1150 for a nice picture.
Approximately how much energy is transferred from one trophic level to the next? What are the possible consequences of this pattern for top predators and the human population?
Only 10% of energy in one trophic level makes it to the next level up. This is an estimate; there is some variation. For instance, ectotherms (cold-blooded) are more efficient because they don’t spend energy to keep warm. Large mammals are more efficient at producing biomass because they lose less heat and have a smaller surface area to volume ratio. This means that only a tiny, tiny fraction of the sun’s energy ever makes it to top predators. Predators must expend energy to catch their prey, meaning energy is diverted from growth/reproduction (i.e. generation of biomass) to cell respiration.
What ecosystems have the highest and lowest net primary productivity per unit area? Explain your answer.
Considering terrestrial vs. aquatic ecosystems, terrestrial ecosystems likely have higher net primary productivity because light is much more readily available for photosynthesis. Among land environments, we might expect warm areas with lush plant life (tropical regions) to have high NPP due to the heavy producer presence (compared to, say, deserts). Productivity is highest near the equator, except for the Sahara.
Describe how carbon cycles through an ecosystem. What biological processes are involved?
-movement of carbon among terrestrial, ocean, and atmosphere –ocean largest store; atmosphere fastest (i.e., C can move most quickly in and out of atmosphere…think respiration and combustion) -photosynthesis takes C out of atmosphere and incorporates it into tissue in terrestrial/aquatic ecosystems -Cell resp releases carbon back as CO2
How have human activities impacted the carbon cycle? What are the possible consequences for ecosystems?
Deforestation - Cutting down trees for agriculture and settlements. Hampers CO2 processing/photosynthesis. Burning fossil fuels - fossil fuels are carbon stores that we artificially release CO2 is a greenhouse gas that traps heat on the earth and raises temperatures, leading to overall climate change
trophic levels
A “feeding” level. Organisms that get energy from the same type of source occupy the same trophic level.
primary consumers (herbivores)
Autotrophs – organisms that can synthesize their own food from inorganic sources. In most ecosystems, primary producers use solar energy + photosynthesis to manufacture food. In deep-sea hydrothermal vents, primary producers use methane and hydrogen sulfide
net primary production
The total amount of chemical potential energy stored in organic material, or biomass.
pyramid of productivity
Organisms are more productive (i.e. lose less energy to heat tax and respiration) than the trophic level above them, meaning that top consumers are not very productive
primary producers
Organisms that produce biomass from inorganic compounds (i.e. autotrophs)
secondary / tertiary / quaternary consumers (carnivores)
Organisms that eat the creatures below their trophic level
biomass
The total mass of all organisms in a given population or geographical area; usually expressed as total dry weight.
detritivores (decomposers)
Decomposers (detritivores) get energy by feeding on the remains of other organisms or waste products
greenhouse gas
A gas that traps heat radiated from earth and keeps it from being lost into space, a la CO2
