2.1: Life on the Planet
pg. 29
Key Concepts:
1. Life on Earth exists in the atmosphere, lithosphere, and hydrosphere.
Evidence of Learning: Students can …
- Explain that although Earth is very large, Earth’s biosphere is very thin.
- Describe what Earth’s atmosphere, lithosphere, and hydrosphere are.
- Describe how Earth’s spheres overlap and relate to one another.
- Earth is the only planet supporting life, millions of species of organisms.
- Organisms live in habitats of different types throughout the world.
- Habitats: terrestrial, or aquatic.
The Spheres of Earth
- Earth orbits the Sun, 150 X 106 km. away from the Sun.
- Earth has a gaseous layer, and terrestrial, aquatic, and ice surfaces.
Atmosphere: the layer of gases surrounding the Earth.
Lithosphere: Earth’s solid outer layer.
Hydrosphere: all of the Earth’s water in solid, liquid, and gas form.
Biosphere: the zone around Earth where life can exist.
- The mass of Earth creates gravity, which holds the gaseous layer to the planet.
- Earth’s atmosphere consists of the following primary gases: Nitrogen (72%), Oxygen
(21%), and Carbon dioxide and other gases (1%).
- The atmosphere moderates the Earth’s temperature, controlling the temperature during
the day and night.
- The atmosphere prevents UV rays and other solar radiation which are harmful, skin
cancer.
- The Lithosphere is the terrestrial (land) portion of the planet. (rocks and minerals)
- The hydrosphere is the aquatic (water) portion of the planet. (oceans, seas, lakes, rivers,
streams, ice, etc.)
- Earth’s oceans contain 97% of the water on the planet.
Figure 3: Earth’s biosphere is found in regions of the atmosphere, lithosphere, and
hydrosphere.
Biosphere
- Are the locations where life can exist, including the atmosphere, lithosphere, and the
hydrosphere.
- All conditions of life are met and maintained within a thin layer of ground, water, and
lower atmosphere.
- Living things require, space, water, and nutrients to survive, but are only found in
limited areas, which limit the number of species that can survive.
The Gaia Hypothesis
- A hypothesis present by James Lovelock, in the 1960’s.
- A hypothesis is an educated guess based on previous scientific information.
- The Earth and its interactions of each of the four spheres behave like a living organism.
- The Earth will respond to changes in its environment. It also maintains a consistent
internal condition over time. (like a cell)
Check Your Learning
Questions 1 – 7, page 31
Summary:
- Earth’s atmosphere is made up of about 78% nitrogen, 21% oxygen gas, and other
gases.
- The atmosphere moderates surface temperatures and blocks some incoming solar
radiation.
- The lithosphere is Earth’s solid outer shell.
- The hydrosphere is Earth’s water in all its forms.
- The biosphere is the area where life can exist within the lithosphere, atmosphere, and
hydrosphere.
- The Gaia hypothesis proposes that Earth behaves like a living organism.