its a presentation on environmental science

1. INTRODUCTION TO
ENVIRONMENTAL SCIENCE
Week 1

2. The Environment
 Surroundings of an organism.
 Consists of: -
i. The physical environment
ii. The biological environment
iii. The social environment

3. The
Biological Environment:
 The living part of the environment
consisting of plants & animals.
 Everything that has life that affects a living
organism.

4. The
Physical Environment
 The non-living part of the environment.
 May be:
 Climatic - pertaining to climate.
 Edaphic – pertaining to soils.
 Physiographic – pertaining to landforms.

5. The
Social Environment
 Developed as a result of human
interactions with one another and also with
the physical environment.
 It includes historical, economic, political,
cultural, moral and aesthetic aspects of
human life.

6. COMPOSITION OF THE EARTH
 The earth can be divided into 2 parts:
i) Internal structure (Solid earth)
 Comprises: the core, the mantle & the crust
ii) External structure (above the earth’s surface)
Has been sub-divided into:
a) The atmosphere
b) The hydrosphere
c) The biosphere
d) The Lithosphere

7. THE
EARTH’S LIFE – SUPPORT SYSTEMS
The earth is made up of air, water, soil, minerals and life,
all interconnected and occurring as spherical layers.
v v v v v v v v v v
Atmosphere
Vegetation/ Animals
Soil, Water
Rock
v v v v v v v v

8. A. The Atmosphere
 The gaseous envelop that surrounds the planet
earth
 Is estimated to extend many kilometres into the
sky
 Atmosphere exists largely in gaseous state
 But, varying amounts of substances in liquid &
solid form also exist
 The density of the gases is highest at sea level

9. Sub-divisions of the Atmosphere
Has been sub-divided into 2 main layers:
I) Homosphere
 Is the lower layer of the atmosphere extending
upto about 80 kilometre
 Homosphere is further sub-divided into 3 layers
based on: altitude, temperatures and zones of
temperature changes

10. Troposphere
 Extends from the surface of the earth to about 18
kilometres
Stratosphere
 This is the layer where the temperature first holds
constant with increased altitude
Mesosphere
 Is a transitional zone between the homosphere &
heterosphere

12. Composition of the Homosphere
Is largely composed of:
 Nitrogen (78%)
 Oxygen (21%)
 Argon (0.9%)
 Carbon-dioxide (0.03%)
 Other rare gases in extremely minute

13. Note:
 That the proportions of these gases don’t vary,
thus its often known as the homogeneous
atmosphere
 As opposed to nitrogen, oxygen is chemically
highly active and enters into chemical unions with
other substances
 It readily combines with other elements in the
process of oxidation leading to combustion of
fuels & decay

14. Carbon-dioxide is useful in the absorption of heat enabling
the lower atmosphere to be warmed by heat radiation
coming from the sun and from the earth’s surface
 It is important that these proportions are maintained,
otherwise we are the danger of increased global warming
 The stratosphere & higher layers of the atmosphere are
almost free of water vapour, dust particles & clouds, but
winds of high speed are observable

15. b). The Lithosphere
 Refers to the solid state of the earth’s crust that
constitutes the continents
 It is basically composed of mineral matter
 The soil and other vital elements such as salt are
part of the lithosphere
 Most abundant elements are: silicon, aluminium
and magnesium

16. c). The Hydrosphere
 A term used to refer to all the free water of the
earth – in gaseous, liquid or solid form
 Covers 71% of earth’s surface
 It is the earth’s global reserve of water in the form
of vapour, liquid and ice
 The bulk of the hydrosphere is found in the
world’s oceans
 Oceans play a major role in the modification of
climate

17. Diagram of hydrological cycle

18. d). The Biosphere
 Is the zone of organic matter on the earth’s
surface where life exists
 It is at the interfaces or zones of contact of the
‘life layers’ of the atmosphere and the lithosphere
 Man interacts with his environment very much
within this zone
 The zone experiences intense activity in the form
of exchanges of energy & matter from one
environmental system to another

19.  From his physical environment, man receives
necessary for life process
 Man not only responds to the forces of the
physical environment, but also acts upon them &
modifies them in the process
 NOTE: that although the four environmental
systems have been looked at separately, they
relate to one another & should studied in an
integrated way

20. Environmental Sustainability
Satisfying the needs of the current population
without depleting or degrading the natural
resources and thereby preventing the future
generations from meeting their needs