Chapter 3 notes (#'s 1, 4, 5, and 6)

Distinguish among the following ecological levels: population, community, ecosystem, landscape, and biosphere.

A population is a group of organisms of the same species that live together in the same area at the same time. A community is a natural association that consists of all the populations of different species that live and interact together within an are at the same time. An ecosystem is a community ant its physical environment. A landscape is a spatially heterogeneous region that includes several interacting ecosystems. the biosphere is the layer of earth containing all living organisms.

State the first and second laws of thermodynamics, and discuss the implications of these laws as they relate to organisms.

According to the first law of thermodynamics, energy cannot be create or destroyed, although it can change from one form to another. the second law of thermodynamics states that when energy is converted from one form to another, some of it is degraded into heat, a less usable form that disperses into the environment. The first law explains why organisms cannot produce energy but must continuously capture it from the surroundings. The second law explains why no process require energy is ever 100% efficient. In every energy transaction, some energy is dissipated as heat, which contributes to entropy.

Photosynthesis:

6CO₂ + 12H₂O + radiant energy → C₆H₁₂O₆ + 6H₂O + 6O₂

Cellular respiration:

C₆H₁₂O₆ + 6O₂ + 6H₂O → 6CO₂ + 12H₂O + energy

Distinguish between gross primary productivity and net primary productivity, and discuss human impact on the latter.

Gross primary productivity (GPP) is the total amount of photosynthetic energy that plants capture and assimilate in a given period. Net primary productivity (NPP) is productivity after respiration losses are subtracted. Scientists have estimated how much of the global NP is appropriated for the human economy and therefore not transferred to other organisms. when both direct and indirect human impacts are considered, humans are conservatively estimated to use 32% of the annual NPP of land-based ecosystems.