The document discusses the factors that make Earth habitable for life, including its temperature, atmosphere, available energy from sunlight, and nutrient cycles. It also explains that Earth has four interconnected subsystems: the atmosphere, biosphere, geosphere, and hydrosphere. The atmosphere is composed primarily of nitrogen and oxygen gases. The biosphere encompasses all living things on Earth. The geosphere refers to the solid parts of the planet. And the hydrosphere includes all water on the planet, which covers 70% of Earth's surface.

1. The Earth and
Its
Subsystems

2.  Recognize the uniqueness of Earth, being the
only planet in the solar system with properties
necessary to support life.
 Explain that the Earth consists of four
subsystems, across whose boundaries matter
and energy flow.

3. Concepts to ponder:
Earth is the only place in the known
universe confirmed to host life and is the
only one known for sure to have liquid
water in the surface. It has the right
distance from the sun.

4. Concepts to ponder:
Science Trivia
The name Earth is at least 1,000 years old.
All of the planets, except for Earth, were
named after Greek and Roman gods and
goddesses. However, the name Earth is a
Germanic word, which simply means “the
ground.”

5. Concepts to ponder:
Planetary Habitability -ability to harbor life.
Factors that make a planet habitable.
 Temperature- It influences how quickly atoms, molecules or
organisms move. Low temperature slows down chemical reaction
and produces ice that makes liquid water unavailable. High
temperature can cause break down of important biological
molecules. In Earth’s condition, temperature is just right to
support life. Negative 15 degrees to 115 degrees Celsius is the
ideal temperature.

6. Concepts to ponder:
 Atmosphere- The Earth’s blanket that shields the surface
from the harmful radiation and provides chemical needed
for life. The size of the planet and its distance from the
sun affects its ability to hold significant amount of
atmosphere. Earth has a right size and distance from the
sun that permits it to have a right amount of atmosphere.
The presence of gravity also helps in sustaining its
atmosphere.

7. Concepts to ponder:
 Energy- Earth has available energy- rich sunlight
to support life. Living organisms like plants and
photosynthetic bacteria use light as the source of
their energy. Some chemosynthetic organisms rely
on chemical energy to support various biological
processes.

8. Concepts to ponder:
 Nutrients- It is an essential factor used to build
and maintain organism’s body structure.
Insufficient or absence of nutrients can impede
synthesis of the different biological molecules. In
our planet, there are processes that recycle
nutrients. Water, carbon and oxygen, phosphate
and nitrogen cycles are some of the examples.
Volcanism also helps in cycling the nutrients.

9. Subsystems of the Earth
1. Atmosphere –from the Greek word “atmos”
meaning air. It is the gaseous layer above the
Earth’s surface primarily composed of different
gases such as 78% nitrogen and 21% oxygen, 1%
other gases.

10. Subsystems of the Earth
2. Biosphere – “bio” means life. It is the zone of
the Earth where all forms of life exist. This serves
as the ecosystem of all living and non- living
organisms.

11. Subsystems of the Earth
3. Geosphere – the solid part of the Earth that
consists of the entire planet from the center of the
core to the outer crust. It includes core, mantle, and
crust of the Earth. It includes only the non-living
things.

12. Subsystems of the Earth
4. Hydrosphere – “hydro” means water. The water
part of the Earth that includes oceans, rivers,
glaciers etc.. The total amount of water on a planet.
About 70% of the surface of the Earth is covered by
liquid or frozen water. Because of this, Earth is
sometimes called “blue planet.”

14. Interconnection between the four spheres