Chapter One: Definition of Biology Notes For Medical
College Entrance Test MCAT & 1st Year
DEFINITION
OF BIOLOGY
Biology is the study of living organisms. It is
derived from Greek words.
CLASSIFICATION
OF LIVING ORGANIZATION
According
to the modern classification given by R.H.Whittaker in 1969, living organisms
are divided into five major kingdoms, which are:
KINGDOM MONERA
It
includes all prokaryotes, unicellular organisms. For example Bacteria and Cyan
bacteria.
KINGDOM PROTOCTISTA(PROTISTA)
It
includes unicellular Eukaryotic organisms, which are in between plants and
animals. e.g. Chlamydomonas, Euglena, Paramecium. etc
1. KINGDOM FUNGI
It includes non-chlorophyllus multi-cellular, thallophytic organisms having
cell wall. For example all types of fungi, unicellular to multi-cellular like
Mushrooms and Yeast etc.
2. KINGDOM PLANTAE
It includes all chlorophyllus multi-cellular Eukaryotic living organisms having
cellulose cell wall. For example apple, red wood etc.
3. KINGDOM ANIMALIA
It includes all Eukaryotic multi-cellular, non-chlorophyllus organisms having
no cell wall. For example Hydra, Earthworm, Human Beings etc.
EUKARYOTIC ORGANISMS
Those
organisms, which have true membranous structure in their cells, like
mitochondria, golgi bodies, endoplasmic reticulum. e.g. All plants, Higher
animals.
PROKARYOTES
Those
living organisms, which do not have true membranous structure in their cells.
e.g. Bacteria, Blue green algae.
PHYLETIC LINEAGE
All
living organisms of today belong to a common ancestor and each specie of
organism arranged no ancestor to descendent order with rest of the group
evolved from one that immediately preceded.
BRANCHES
OF BIOLOGY
1. MOLECULAR BIOLOGY
It is a recent branch of biological science that deals with the structure and
function of the molecules that form structure of cell and organelles that take
part in the biological processes of a living organism (Nucleic acid – Protein
molecule)
2. MICRO BIOLOGY
It deals with the study of micro-organisms (viruses, bacteria, protozoan etc)
3. ENVIRONMENTAL BIOLOGY
It deals with the study of environment and its effect on organisms.
4. MARINE BIOLOGY
It deals with the study of organisms inhabiting the sea an ocean, and the
physical and chemical characteristics of their environment.
5. FRESH WATER BIOLOGY
It deals with the life dwelling in fresh waters, physical and chemical
characteristics of fresh water bodies affecting it.
6. PARASITOLOGY
It deals with the study of parasitic organisms, their life cycles, mode of
transmission and interaction with their hosts.
7. HUMAN BIOLOGY
The branch of biology deals with all biological aspects of man regarding
evolution, anatomy physiology, health, inheritance etc.
8. SOCIAL BIOLOGY
Social biology is concerned with the social interactions with in a population
of a given species, especially in human beings focuses on such issue as whether
certain behavior are inherited or culturally induced.
9. BIOTECHNOLOGY
This is a very recent branch introduce in biological sciences. It deals with
the use of data and techniques of engineering and technology for the study and
solution of problems concerning living organisms particularly the human beings.
BIOLOGICAL METHOD
In
order to solve the biological problems (any animal or plant disease or
environmental hazard), following steps are necessary.
1. HYPOTHESIS
An
educated guess or fact regarding the biological problem.
INDUCTIVE REASONING
Isolated facts to reach a general idea that explain the biological problem.
DEDUCTIVE REASONING
Accurate experimentation, true conclusions or results regarding the biological
problems.
2. OBSERVATION/EXPERIMENTS
The
given hypothesis is checked with the help of observation and experiments and
then on the basis of it a theory or rule is established.
3. THEORY
If
observations and experiments come true then hypothesis is taken true, other
wise it is rejected. Only on the basis of true hypothesis a theory is
established.
4. LAW/PRINCIPLE
When
theory is proved to be true under all tested circumstances then it is accepted
as a law.
MALARIA
§ Malaria
means disease cause by bad air.
§ Actual
Causative agent is plasmodium (Vector Female, Anopheles Mosquito)
§ Leveran
first discover plasmodium in human R.B.C.
§ Ronald
Ross discovered plasmodium in the stomach of female Anopheles Mosquito.
§ Grassi
discover the complete life cycle of Plasmodium in human being and mosquito.
ANTIBIOTICS
Substances
or chemicals, which are required in small quantity to inhibit the growth of
Microorganisms. The first antibiotic was penicillin discovered by Fleming.
Other examples are: Erythrosine, Rythocin, Gentamycin, Ampicillin etc.
CHEMOTHERAPY
Treatment
with drug or chemical.
RADIOTHERAPY
Treatment
with radiations, like α, β, γ or X-rays.
HYDROPONICS
It
is the science of terrestrial plants growing in aerated solutions (add CO2
under pressure, in any liquid also known as aerated water). This technique is
also known as soil less or water culture.
ADVANTAGES
1.
Control weeds and soil disease problems.
2. Area required for cultivation is minimum.
3. Can be applied on any part of the world.
4. Main purpose is to fulfill the food requirements of rapidly increasing world
population.
CLONING
Production
of duplicate copies of genetic material, cells or entire multi cellular living
organisms, occurring naturally in plants or animals. Duplicate copies are known
as clones.
NATURAL CLONING
§ Identical
twin, triplet in humans.
§ Asexual
reproduction in plants and animal.
§ Regeneration
and wound healing.
§ Growth
of tumor cells or cancers.
ARTIFICIAL CLONING
§ Cloning
of human cells such as liver cells, skin cells, blood cells are quite helpful
to develop human organs in laboratories.
§ There
are also enormous advantages of cloning in the field of medicine and
agriculture. Examples are vegetative reproduction of fruits and nuts by
grafting.
§ Artificial
cloning is also used for treating disease, production of medically significant
substances such as Insulin, growth hormones, interferon and anti-thrombin etc.
LEVEL
OF BIOLOGICAL ORGANIZATION
Life
is built on chemical foundation and the life of all living organisms emerges on
the level of cell. The foundation of cell is based on elements. Atoms of
different elements unite to form molecules. Living organism usually form
extremely large and complex molecules by living matter which is present in
their bodies. The molecules of living organisms are mostly composed of carbon
and provide building blocks of living matter. Mostly living matter of an
organism is composed of organic molecules along with inorganic compounds
(minerals) are also associated for e.g. Human blood. Simple organic molecules
present in living organisms are sugar, glycerol and fatty acids, amino acids,
purine and pyramidines. Similar types of cells form-tissues, similar tissues
form organs, different organs coordinating with each other form system and
different systems combine to form a living organism.
Cell → Tissues → organs → System → An Individual
Biological organization can be divided into the following levels:
SUB-ATOMIC PARTICLES
“Particles that make up an atom are
called sub-atomic particles”.
For e.g. electron, proton and Neutron.
ATOM
“The smallest particle of an element
that retains the property of that element”.For example: Hydrogen, carbon
and oxygen etc.
MOLECULE
“The combination of similar and
different atoms are called molecules”.
For example Hydrogen and oxygen combines to form water molecules.
ORGANELLE
“A structure with in a cell that
performs a specific function”.
For example: Mitochondria, chloroplast etc.
CELL
“The smallest structural and
functional unit of life”.
For example: A nerve cell
TISSUE
“A group of similar cells that
performs a specific function”.
For example: Nervous tissue.
ORGAN
“A structure with in an organism
usually compose of several tissue types that forms a functional unit”.For
example: The brain
ORGAN SYSTEM
“Two or more organs working together
in the execution of a specific bodily function”.For example: The nervous
system.
MULTICELLULAR ORGANISM
“An individual living thing composed
of many cells are called Multicellular organisms”.For example: Pronghom
antelope.
SPECIE
“A group of very similar inter
breeding organisms constitutes a species”.For example Herd of pronghom
antelope.
POPULATION
“Members of same species inhabiting
the same area are considered as population”.For example: Herd of
pronghom antelope.
COMMUNITY
“Population of several species living
and interacting in the same area form a community”.For example: Snake,
antelope and hawk.
ECO-SYSTEM
“A community with its environment
including land, water and atmosphere, constitute an eco-system”.
BIOSPHERE
“The part of earth inhibited by living
organisms, both living and non-living components.”
