Chapter 3 Ecosystems: What Are They and How Do They Work? Section 3-1: What Keeps Us and Other Organisms Alive?
Earth’s life support system has four major components:
The atmosphere (air)
The hydrosphere (water)
The geosphere (rock, soil, and sediment)
The biosphere (living things)
The atmosphere can be divided into two layers:
The troposphere extends about 17 km above sea level at the tropics and about 7 km above the north and south poles. It contains the air we breathe: 78% Nitrogen
1% Greenhouse gases (H2O, CO2, CH4) that absorb and release energy that warms the lower atmosphere The stratosphere stretches 17-50 km above the earth’s surface. Its lower portion holds enough ozone gas (O3) to filter out 95% of the sun’s harmful UV rays.
The hydrosphere consists of all of the water on or near earth’s surface. It is found as: Water vapor in the atmosphere.
Liquid water on the surface and underground.
Ice in polar ice, icebergs, glaciers and frozen soil layers, called permafrost.
The oceans, which cover about 71% of the globe, contain about 97% of the earth’s water.
Most of the geosphere is located in the earth’s interior. It contains: An intensely hot core
A thick mantle made mostly of rock
The thin outer crust
The geosphere’s upper portion contains nonrenewable fossil fuels and minerals that we use, as well as renewable soil chemicals (nutrients) that organisms need in order to live, grow, and reproduce.
The biosphere consists of all living things and the places in the atmosphere, hydrosphere, and geosphere where life can be found.
One goal of environmental science is to understand the interactions that occur within this thin layer of air, water, soil, and organisms.
Three Factors Sustain Earth’s Life
1. The one way flow of high-quality energy from the sun, through living things in their feeding interactions, into the environment as low-quality energy...
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