Grade 9 Biology
CHAPTER 2.1 - LIFE ON EARTH
Earth’s Systems
The Earth is a system consisting of four major interacting components:
● The atmosphere
● The lithosphere
● The hydrosphere
● The biosphere
Atmosphere - Earth System
A blanket of air that surrounds the Earth.
● Consists of four unique layers in order:
○ the troposphere
○ the stratosphere
○ the mesosphere
○ the thermosphere
● The atmosphere reaches over 560km up from the surface of the Earth.
● The atmosphere is primarily composed of nitrogen (about 78%) and oxygen (about 21%)
Other components exist in small quantities: O2, argon, ozone, etc.
The Troposphere - Atmosphere
The troposphere ends about 12-20 km above the surface. It is the densest layer of
the atmosphere. Almost all weather occurs in the troposphere.
,The Stratosphere - Atmosphere
The stratosphere is the next layer. The ozone layer, which absorbs and scatters the
Sun’s UV rays, is in the stratosphere.
The Mesosphere - Atmosphere
The mesosphere is directly above the stratosphere and below the thermosphere. It
extends from about 50 to 85 km above our planet.
The Thermosphere - Atmosphere
The outermost layer, the thermosphere, extends to 600 km. Temperatures in this
layer can reach 1727 degrees celsius and therefore chemical reactions occur much
faster in the thermosphere than on Earth.
The Lithosphere - Earth System
● The solid part of the Earth
● It consists of three layers:
○ Crust
○ Mantle
○ Core
● 4. The 6-35 km thick lithosphere, Earth’s crust.
● 3. The 2900 km thick mantle layer formed from
rapidly flowing magma.
● 2. The 2000 km thick outer core contains such
molten heavy metals as nickel and iron.
, ● 1. The 1370 km thick inner core, which is in a crystalline state because of the influence of
heat and high pressure.
Two Crusts
● Continental crust
○ It is about 32 km thick, made mainly of granite rocks
○ The elevated portion of the crust
● Oceanic crust
○ The ocean bed. It is about 7 km thick and made mainly of basalt.
The Hydrosphere - Earth’s System
Contains all water found on our planet.
● Water found on the surface of our planet includes the ocean as well as water from lakes
and rivers, streams, and creeks.
● Water found under the surface of our planet includes water trapped in the soil and
groundwater
● Water found in our atmosphere includes water vapour.
● Frozen water on our planets includes ice caps and glaciers.
● Only about 3% of the water on Earth is “fresh” water, and about 70% of the fresh water is
frozen in the form of glacial ice.
● Our Earth is mostly water.
● Approximately 70% of the Earth surface is water
● 30% of the Earth’s surface is land.
● 97% salt water, 2% ice, and 1% freshwater in bodies of water.
, ● Water of Earth is a unique feature that clearly distinguishes our “Blue Planet” from others
in the solar system.
● Not a drop of liquid can be found anywhere else in the solar system. Earth has just the
right mass, the right chemical composition, the right atmosphere, and the right distance
from the sun that permits water to exist mainly as a liquid.
● Water is the universal solvent and the basis of all life on our planet.
● Water circulates through the crust, oceans, and atmosphere, in what is known as the water
cycle.
The Biosphere - Earth’s System
Is the “life-zone” of the Earth, and includes all living organisms (including
humans), and all organic matter that has not yet decomposed.
● The biosphere is structured into a hierarchy known as the food chain (all life is dependent
on the first tier—mainly the primary producers that are capable of photosynthesis.)
● Energy and mass is transferred from one level of the food chain to another.
Earth System Science
Is the study of how the four spheres of the Earth system interact continually, each
affecting the others.
The Gaia Hypothesis
● Gaia is Greek mythology. She is the goddess of earth, mother of living things, sustainer
of life,
● An idea proposed by James Lovelock (published in 1979)
CHAPTER 2.1 - LIFE ON EARTH
Earth’s Systems
The Earth is a system consisting of four major interacting components:
● The atmosphere
● The lithosphere
● The hydrosphere
● The biosphere
Atmosphere - Earth System
A blanket of air that surrounds the Earth.
● Consists of four unique layers in order:
○ the troposphere
○ the stratosphere
○ the mesosphere
○ the thermosphere
● The atmosphere reaches over 560km up from the surface of the Earth.
● The atmosphere is primarily composed of nitrogen (about 78%) and oxygen (about 21%)
Other components exist in small quantities: O2, argon, ozone, etc.
The Troposphere - Atmosphere
The troposphere ends about 12-20 km above the surface. It is the densest layer of
the atmosphere. Almost all weather occurs in the troposphere.
,The Stratosphere - Atmosphere
The stratosphere is the next layer. The ozone layer, which absorbs and scatters the
Sun’s UV rays, is in the stratosphere.
The Mesosphere - Atmosphere
The mesosphere is directly above the stratosphere and below the thermosphere. It
extends from about 50 to 85 km above our planet.
The Thermosphere - Atmosphere
The outermost layer, the thermosphere, extends to 600 km. Temperatures in this
layer can reach 1727 degrees celsius and therefore chemical reactions occur much
faster in the thermosphere than on Earth.
The Lithosphere - Earth System
● The solid part of the Earth
● It consists of three layers:
○ Crust
○ Mantle
○ Core
● 4. The 6-35 km thick lithosphere, Earth’s crust.
● 3. The 2900 km thick mantle layer formed from
rapidly flowing magma.
● 2. The 2000 km thick outer core contains such
molten heavy metals as nickel and iron.
, ● 1. The 1370 km thick inner core, which is in a crystalline state because of the influence of
heat and high pressure.
Two Crusts
● Continental crust
○ It is about 32 km thick, made mainly of granite rocks
○ The elevated portion of the crust
● Oceanic crust
○ The ocean bed. It is about 7 km thick and made mainly of basalt.
The Hydrosphere - Earth’s System
Contains all water found on our planet.
● Water found on the surface of our planet includes the ocean as well as water from lakes
and rivers, streams, and creeks.
● Water found under the surface of our planet includes water trapped in the soil and
groundwater
● Water found in our atmosphere includes water vapour.
● Frozen water on our planets includes ice caps and glaciers.
● Only about 3% of the water on Earth is “fresh” water, and about 70% of the fresh water is
frozen in the form of glacial ice.
● Our Earth is mostly water.
● Approximately 70% of the Earth surface is water
● 30% of the Earth’s surface is land.
● 97% salt water, 2% ice, and 1% freshwater in bodies of water.
, ● Water of Earth is a unique feature that clearly distinguishes our “Blue Planet” from others
in the solar system.
● Not a drop of liquid can be found anywhere else in the solar system. Earth has just the
right mass, the right chemical composition, the right atmosphere, and the right distance
from the sun that permits water to exist mainly as a liquid.
● Water is the universal solvent and the basis of all life on our planet.
● Water circulates through the crust, oceans, and atmosphere, in what is known as the water
cycle.
The Biosphere - Earth’s System
Is the “life-zone” of the Earth, and includes all living organisms (including
humans), and all organic matter that has not yet decomposed.
● The biosphere is structured into a hierarchy known as the food chain (all life is dependent
on the first tier—mainly the primary producers that are capable of photosynthesis.)
● Energy and mass is transferred from one level of the food chain to another.
Earth System Science
Is the study of how the four spheres of the Earth system interact continually, each
affecting the others.
The Gaia Hypothesis
● Gaia is Greek mythology. She is the goddess of earth, mother of living things, sustainer
of life,
● An idea proposed by James Lovelock (published in 1979)
