Chapter 2. Science, matter, energy and
ecosystems: connections in nature
Geog415
Dr Hengchun Ye
Science: is an attempt to discover the order in the natural
world and use that knowledge to describe what is likely to
happen in nature.
Scientific hypothesis: an unconfirmed explanation of an
observed phenomenon that can be tested by further
research (peer review; reproducibility)
Scientific theory: a verified, credible, and widely accepted
scientific hypothesis or a related group of scientific
hypothesis
The real situation is more complicated because many
variables or factors influence most process. So scientists
conduct controlled experiment to isolate and study the
effect of a single variable.
Two Groups: (1) experimental group: the chosen variable is
changes in a known way. (2) control group: the chosen
variable is not changed. The difference between these
two groups is considered as the results of this single
variable impact.
If need to assess a huge number of interacting variable, then
use multivariable analysis, use mathematic models in
computers.
Outcome for scientific research (a) disprove things (2)
establish that a particular theory or law has a very high
probability or degree of certainty of being true.
Matter
Matter: is anything that has mass and
takes up space. It is made of elements
and compound.
Matter quality: how useful a form of matter
is to us as a resource.
High quality: concentrated, usually is found
near the earth’s surface and has great
potential for use as a matter resource.
Low quality matter: dilute, often in deep
underground or dispersed in the ocean
or the atmosphere. It has little potential
to use as a material resource.
Material efficiency (or resource
productivity): the total amount of
material needed to produce each unit of
goods or services. (will be greatly
improved by 75-90% within 2 decades
using existing technology.
Energy
Energy: the capacity to do work and transfer heat.
Kinetic energy: movement (wind, flowing water, electricity)
Potential energy: stored and potentially available for us (book held in your
hand, unlit match, chemical energy stored in gasoline molecules, etc)
Electromagnetic radiation: energy traveling in the form of a wave as a result
of the changes in electric and magnetic fields.
Energy-continue
High quality energy: concentrated and can perform
much useful work (electricity, chemical energy in
the coal and gasoline, concentrated sunlight,
nuclei of uranium-235-fule for nuclear power
plant).
Low-quality energy: dispersed and has little ability
to do useful work. (heat dispersed in the moving
molecules of a large amount of matter-air or
water, so the temperature is low)
Laws
The law of conservation of matter: in any physical and chemical change, matter is neither
created nor destroyed but merely changed from one form to another; existing atoms
are rearranged into different spatial patterns of different combinations.
Things we threw away are always still there. They may be changed into a less harmful
forms.
First law of thermal dynamics: energy can be changed from one form to another but can
never be crated or destroyed (we cannot get something from nothing)
Second law of thermal dynamics: when energy is changed from one form to another,
some of the useful energy is always degraded to lower-quality, more dispersed, less
useful energy. (cannot break even in terns of energy quality)
Energy efficiency (productivity): a
measure of how much useful
work is accomplished by a
particular input of energy into
system (about 43%
unnecessarily waste).
We can never recycle or reuse
high-quality energy to perform
useful work, but there are lots of
rooms to improve energy
efficiency (productivity)
Earth’s life support system
Ecology: the study of how organisms interact with one another and with their non-living
environment. (organisms made of cells and classified into species-a form of life)
Species: groups of organisms that resemble one another in appearance, behavior,
chemistry, and genetic makeup (under natural conditions, they can breed with one
another and produce live, fertile offspring)
Microbes (microorganism): a term for many thousands of species of bacteria, protozoa (a
group of unicell animals in different morphology present in most habitats including the
parasitic), fungi, and yeasts-most too small to be seen with the naked eye. Harmful
microbes are minority (3.6 million to 100 million species on the earth).
Examples: in soil to fix nitrogen from the air; in food such as bread, cheese, yogurt,
vinegar, tofu, soy sauce, beer, and wine.
Bacteria help purify water by breaking down the wastes, in intestinal track break down the
food you eat; control plant disease and insect species that attack food crops, help
clean toxic waste sites.
Insects: sustaining life on the earth by pollinating plants that provide food, and eating
insects that we classify as pests. Have been around for 400 million years, reproduce
at astounding rate and rapidly evolve new genetic traits (resistance to pesticides),
very resistance to extinction. They can survive without us, but we cannot live without
them.
Example. A single female housefly and her offspring can theoretically produce about 5.6
trillion flies in one year.
Earth’s life supporting systemcontinue
Population: a group of interacting
individual or organisms of the same
species occupying a specific area.
Population’s genetic diversity: individuals
vary slightly in their genetic makeup
and do not all look or act alike
Community (biological community):
consists of all the populations of the
different species living and interacting
in an area (network of plants, animals
ands microorganisms).
Ecosystem: is a community of different
species interacting with one another
and with their physical environment of
matter and energy. Example: a puddle
of water, a stream, a patch of woods,
forest, etc. Crop field, farm ponds and
reservoirs are artificial ecosystems.
Biosphere is made of ecosystem.
Four life supporting
systems:
atmosphere,
hydrosphere,
lithosphere, and
biosphere.
Two components in biosphere and its
ecosystem:
Abiotic: nonliving components such as
water, air, nutrients, and solar energy)
Biotic: plants, animals, and microbes
Law of tolerance: the existence, abundance, and distribution of a
species in an ecosystem are determined by whether the levels of
one or more physical or chemical factors fall within the range
tolerated by that species. A species may have a wide range of
tolerant to some factors but narrow to others. Most species are
least tolerant during juvenile or reproductive stages of their life
cycles.
Limiting factor principle: too much or too little of any abiotic factor can
limit or prevent growth of a population, even if all other factors are at
or near the optimum range of tolerance.
For land, limiting factor may be water, soil nutrients
For aquatic life: temperature, sunlight, nutrient availability, salinity and
dissolved oxygen content.
Solar energy
Albedo: the percentage of solar radiation
reflected by a surface