Unit B: Sustainable Ecosystems and Human Activity
Chapter 2: Understanding Ecosystems
Key Question: How are organisms affected by living and nonliving things in their environment?
Key Concepts:
- Energy passes through ecosystems, but matter cycles within
ecosystems.
- Photosynthesis and respiration are processes that work together.
- Aquatic and terrestrial ecosystems are strongly influenced by
their abiotic environment.
- Human activities disturb the natural cycles.
2.1: Life on Earth
pg. 28
Habitat: the environment where an organism lives.
Atmosphere: the thin layer of gases that surrounds the
Earth.
Biosphere: the zone in, on, and around Earth where life can
exist.
Diversity of Life on Earth
The area in which an organism lives is known as its habitat.
There are terrestrial and aquatic habitats. Terrestrial
habitats are those that are found on land and contain
different types of ecosystems. Aquatic habitats are found in
water, there are different types; freshwater, estuaries, and
marine ecosystems.
Earth’s Spheres
The Atmosphere
The earth is surrounded by a layer of gases known as the
atmosphere, which can also b subdivided into different
layers; Troposphere, Stratosphere, Mesosphere,
Thermosphere, and the exosphere, which are responsible
for controlling the Earth’s temperature, block harmful UV
rays, and climate. The atmosphere contains gases: Nitrogen
(78 %), Oxygen (21 %), and Carbon dioxide and other
gases (water vapour) (1 %), which are necessary to keep
organisms alive.
Lithosphere and Hydrosphere
The lithosphere is the terrestrial land forms; the mountains,
grasslands, and the ocean floor; that make up the shell of
the Earth. The Hydrosphere is the aquatic environment
made up of; oceans, lakes, rivers, creeks, swamps, ponds,
ice, and clouds above and below the Earth’s surface.
The Biosphere
The biosphere is the areas where living organisms may
exist, which include the atmosphere, lithosphere, and
hydrosphere.
Figure 3: The biosphere is a thin layer that includes land, water, and air.
Check You Your Learning;
Questions 1 – 4, pg. 29
Wrap Up:
- Earth has a variety of organisms living in habitats on land
and in water.
- Earth’s spheres include the atmosphere, lithosphere, and
hydrosphere.
- The atmosphere moderates the temperature and amount of
radiation that reaches Earth.
- The biosphere is where life can exist in the atmosphere,
lithosphere, and hydrosphere.