Ecosystems and Earth's Life-Support Systems

Flashcards covering the components of Earth's life-support systems, atmospheric layers, ecosystem organization, energy flow, and primary productivity.

What are the four major components of the Earth's life-support system?

The four major components are the atmosphere, hydrosphere, geosphere, and biosphere.

What are the altitude range and major characteristics of the troposphere?

The troposphere extends 7-18 km above the equator (with an average thickness of 10 km), contains almost 80% of the total mass of air and practically all atmospheric water vapor, and is the active region where weather events occur.

Why does air temperature increase with altitude in the stratosphere?

Air temperature increases with altitude (19-50 km above the equator) due to exothermic reactions triggered by UV radiation from the sun, which produce ozone ($O_3$) that protects Earth from harmful UV rays.

What are the characteristics of the mesosphere?

Located 30-50 km above the equator, the mesosphere has low concentrations of ozone and other gases, and its temperature decreases with increasing altitude.

What process causes temperature to increase with altitude in the thermosphere?

In the thermosphere (50-400 km above the equator), energetic particles like electrons and protons from the sun bombard molecular $O_2$ and $N_2$ and atomic species, liberating energy mostly as heat.

What is the exosphere and what are its features?

The exosphere is the outermost atmospheric layer (~400 km above the equator, 10,000 km thick) that separates the atmosphere from space, containing widely spread-out hydrogen and helium gases, no breathable air, and very cold temperatures.

How are the hydrosphere, geosphere, and biosphere defined?

The hydrosphere is Earth's aqueous envelope (liquid water, water vapor, and ice); the geosphere includes the interior, rocks, minerals, and landforms (core, mantle, crust); and the biosphere comprises parts of all three where life is found.

What optimum temperature range on Earth supports life and chemical processes?

$-18\text{ }^\text{o}\text{C}$ to $38\text{ }^\text{o}\text{C}$.

Who defined ecology, and what are the five levels of organization studied by ecologists?

Ernst Haeckel defined ecology as the study of interactions of living things with each other and their physical environment. The five levels are organisms, populations, communities, ecosystems, and the biosphere.

What two requirements must be met for an ecosystem to be self-sustaining?

1. A constant source of energy and a living system capable of incorporating this energy into organic molecules. 2. A cycling of materials between organisms and their environment.

What is the difference between producers, consumers, detritivores, and decomposers?

Producers (autotrophs) make nutrients via photosynthesis; Consumers (heterotrophs) eat other organisms; Detritivores feed on dead wastes (detritus); and Decomposers (saprotrophs) cause decay by releasing nutrients from organic wastes back into soil, water, and air.

What is the difference between a habitat and an ecological niche?

A habitat is the place where a particular population of a species lives, whereas an ecological niche is the functional role of a species in an ecosystem.

What are the First and Second Laws of Thermodynamics?

First Law: Energy cannot be created or destroyed, only changed in form. Second Law: Usable energy decreases over time as energy is transformed into disorganized heat (entropy).

What percentage of the sun's energy is reflected back into space?

About 30%.

What is the chemical equation for photosynthesis?

$$6CO_2 + 12H_2O + \text{radiant energy} \rightarrow C_6H_{12}O_6 + 6H_2O + 6O_2$$

What is the chemical equation for cellular respiration?

$$C_6H_{12}O_6 + 6O_2 + 6H_2O \rightarrow 6CO_2 + 12H_2O + \text{energy}$$

What is ecological efficiency, and what energy loss occurs between trophic levels?

Ecological efficiency is the percentage of usable chemical energy transferred as biomass from one trophic level to the next (1.3% to 56%), resulting in an energy loss of 44% to 98.7% at each step.

How do Gross Primary Productivity (GPP) and Net Primary Productivity (NPP) differ?

GPP is the rate at which producers convert solar energy into chemical biomass. NPP is GPP minus the rate at which producers use energy for respiration, given by the formula $\text{NPP} = \text{GPP} - \text{R}$.