Biology, an immensely important area of science, plays a
variety of crucial roles in ensuring protection and welfare of all living
beings on earth. With the progress of scientific development, humans are
enjoying a much more comfortable life, but side by side many more problems are
viciously emerging and causing a serious threat to all forms of life and their
environment. In that case, biology can
help human to face some critical challenges of the century, and some of these
are the production of food, development of medical science and conservation of
organisms in their hostile environment. In this chapter, the definition of
biology, names of its branches and naming
system of organisms have been discussed.
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| Introduction to Biology |
Concept of Biology
In nature, we generally find two types of objects, nonliving
things and living organisms. The characteristics of nonliving things are
usually discussed in Physics and Chemistry.
Biology is a branch of scientific knowledge concerning life and characteristics
of organisms. It is one of the oldest branches of natural science. Its
background was even created before the origin of life on the earth.
By studying biology, one can acquire interesting knowledge
of different plants and animals and human life. In the realm of living
creation, the presence of life in a living cell is remarkable. This is why a
good command of biology plays an important role in knowing more about the
different parts and organ structure of organisms, different chemical activities
in them, their adaptation with their environment, their intake of nutrition and
reproduction. The roles of a cell or cells in all steps of life are
indisputable. Science has a great contribution in our everyday activities and
developing our experience. For our living survival, the fundamental base of
biology is inherent in the components of our environment. At the time of
walking, our muscles conduct our legs, our nerves move our muscles and the
blood circulation in our muscles provides them with oxygen, nutrition and
strength. A single celled organism also survives in the same way using oxygen,
nutrition and energy. For the maintenance of biological existence, all living
organisms require oxygen and energy. An animal derives this energy from food
produced by plants themselves and other sources.
Biology is one of the fundamental branches of science. The
term biology is derived from the Greek word “bios” (life) and the suffix “logia” (study of). Greek philosopher
Aristotle (384BC – 322BC) is called the father of biology. Biology is the
branch of science concerned with the study of life and living organisms,
including their structure, function, growth, reproduction, classification,
origin and evolution.
Branches of Biology
Based on the type of organism, biology is divided into two branches – Botany and Zoology. Grounded
on the aspect of consideration, there are also two other divisions of biology -
physical biology and applied biology.
Physical Biology
In the field of physical biology, theoretical concepts are
usually discussed. The following subjects are the general fields of its
concern.
1.
Morphology: The field deals with the
form and structure of organisms. It is usually divided into two branches
– external and internal morphology. The external description of the body is
called external morphology and the internal description of the body is called
internal morphology.
2.
Taxonomy: Classification of organisms
and the principles related to this task are discussed in the field.
3.
Physiology: This branch of biology
deals with the biochemical activities of different organs of organisms.
Besides, detailed description of all the physiological process of organisms is
found in it.
4.
Histology: The microscopic structure,
arrangement and function of plant and animal tissues are studied in this
subject.
5.
Embryology: The branch of biology
discusses the development of embryo of organisms.
6.
Cytology: The structure, function and
division of an individual cell in a body of organisms are studied in
this field of biology.
7.
Genetics: The branch of biology deals
with genes and heredity.
8.
Evolution: The gradual development of
life and organisms over successive generations on earth is studied in
this subject.
9.
Ecology: It is the science of
reciprocal relationship between organisms and their environment.
10.
Endocrinology: The field of science
deals with the study of endocrine glands and hormones secreted by them
in a body of organisms.
11.
Biogeography: The branch of biology
studies the geographical distribution of organisms, past and present,
throughout the landscape of planet earth including the knowledge of classifying
bio-geographical patterns.
Applied Biology
Applied subjects related to life are included in this
category, and some of them are mentioned below:
1.
Paleontology: Science of the
prehistoric life forms and fossils;
2.
Biostatistics: Science of statistics
of organisms;
3.
Parasitology: Science related to parasitism,
life process of parasitic organisms and diseases caused by them;
4.
Fisheries: Science dealing with fish,
harvesting of fish, management and conservation of fish assets;
5.
Entomology: Science related to the
study of life, merit, demerit, and control of insects including the
losses caused by them;
6.
Microbiology: Science related to
virus, bacteria, fungi and other microorganisms;
7.
Agriculture: Science concerning
agriculture;
8.
Medical Science: Science related to
human life, disease, treatment etc.;
9.
Genetic Engineering: Science
associated with gene technology and its utilities;
10.
Biochemistry: Science connected to
biochemical process and diseases of organisms;
11.
Soil science: Science related to
soil, soil structure and soil environment;
12.
Environmental Science: Science
related to environment;
13.
Oceanography: Science related to
ocean and its resources;
14.
Forestry: Science related to forest,
management and conservation of its resources;
15.
Biotechnology: Science associated
with the technology of utilizing of organisms for the benefit of
mankind;
16.
Pharmacy: Science dealing with
technology and industry of medicine;
17.
Wildlife: Science related to wild
animals;
18.
Bioinformatics: Biological
information based on computer technology, information on the analysis of
cancer, for example.
Biological Classification
About four million of different plant species and thirteen millions
of animal species have been named and described till today. The number is not
yet final because the description of more and more new species is being added
to it almost every day. It is assumed that the number will reach a crore in
future when the description of all the organisms will be ended. A large number
of organisms are needed to be grouped systematically for the convenience to
know, understand and learn them. Many years back natural scientists felt the
necessity to classify living world following a natural system. From this very
necessity, a distinct branch of biology, taxonomy had emerged. The aim of
classification is only one to know the vast and diverse living world accurately
and classify them with little effort in a short period of time.
The contribution of Swedish botanist, physician and
zoologist Carolus Linnaeus (1707-1778) in the field of taxonomy is more worth
mentioning. In 1735 at the age of 28, he took his doctoral degree in medicine
at the University of Harderwijk, and in 1741 he was appointed Professor of
Medicine at Uppsala University. Though he was first responsible for
medicine-related matters, soon he changed his position with the other Professor
of Medicine to become responsible for the Botanical Garden, botany and natural
history instead. He thoroughly reconstructed and expanded the Botanical Garden.
It was the main field of his intense interest to classify organisms from his
botanical and zoological observations that he assembled from his many
expeditions. He classified living world into two kingdoms – Plant and Animal.
In 1953 Linnaeus published his book Species Plantarum
which is internationally accepted as the starting point of modern botanical
nomenclature and in 1958 he released the tenth edition of his book Systema
Naturae which established itself as the starting point for
zoological nomenclature. He first defined the term genus and species in his
book. Based on the observations of size, structure and characteristic, plants
and animals are named. On the basis of each other’s similarity and
dissimilarity, grouping organisms is called classification.
Aim of Classification
The aim of classification is to acquire knowledge of every
group and subgroup of each organism. To document the accumulated information
systematically focusing on the diversity of living organisms, introduce the
total knowledge concisely and take proper steps after identifying organisms to
conserve them or increase the number of species for the well-being of human
beings and the living world are the objectives of classification.
Living World
Until recently, from the age of Carolus Linnaeus up to the
middle of the twentieth century, all living organisms were classified in one of
two kingdoms: Animals and Plants. With the progress of science, on the basis of
data collected from time to time, for instance, the type of DNA or RNA in a
cell, features and number of cell in a living body and mode of nutrition that a
cell adopts, a five-kingdom classification was proposed by R.H.Whittaker in
1969. Then Margulis introduced a modified and expanded form of Whittaker’s
classification in 1974. She divided the whole living world into two
super-kingdoms and grouped the five kingdoms under these two super-kingdoms.
Superkingdom-1:
Prokaryota
They are microscopic, prokaryotic and one celled organisms.
Kingdom-1: Monera
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a) Bacteria b) Nostoc (Blue green
algae)
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Characteristics: They
are mostly unicellular, filamentous, colonial or mycelial. Though chromatin
material is present in every cell, there is no nuclear membrane and nucleolus
in their cells. No plastids, mitochondria, endoplasmic reticuli are there in
their cells but ribosome is present in them. Cell divides through the process
of binary fission. Their chief mode of nutrition is absorption though some of
them produce their food through the process of photosynthesis or
chemosynthesis.
Example:
Bacteria, Blue green algae;
Superkingdom-2:
Eukaryota
They are eukaryotic and unicellular or multicellular and
live induvidually or in a colonial form.
Kingdom-2: Protista
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a) Amoeba and b) Diatom
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Characteristics: They
are unicellular or multicellular, individual or colonial or filamentous and the
nuclei in their cells are well structured. Their cells contain nuclear
materials bounded by a nuclear membrane. In chromatin material, there are DNA,
RNA and protein. All types of cell organelles are there in their cells. Their
modes of nutrition are absorption, ingestion or photosynthesis. They accomplish
their asexual and sexual reproduction by the process of mitosis and conjugation
respectively. No embryo is developed in them.
Example: Protozoa
(Amoeba, Paramecium) and unicellular algae, diatom for example;
Kingdom-3: Fungi
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a) Penicillium and b) Mushroom
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Characteristics: Most
of them are terrestrial, saprophytic or parasitic. Their body is constituted
with a single cell or mycelium. Nucleus is well organized. Cell wall is
composed of chitin. Their mode of nutrition is absorption. The photosynthetic
apparatus chloroplast is absent in them. They reproduce by haploid spores.
Their cells divide through mitotic cell division.
Example: Yeast,
Penicillium, Mushroom etc.
Kingdom-4: Plantae
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a) Spirogyra Multicellular algae and
b) Jackfruit tree
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Characteristics:
They are photosynthetic and prokaryotic. Advanced tissue systems are found in
them. They develop embryo and diploid stage is started from it. They are mostly
terrestrial but there are also many aquatic species under this kingdom. Their
sexual reproduction is of anisogamous type. They are archegoniate and flowering
plants.
Example: Advanced
green plants, multicellular algae;
Kingdom-5: Animalia
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Royal Bengal Tiger
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Characteristics:
They are eukaryotic and multicellular animals. Their cells possess non-living
cell wall, plastid and vacuole in them. Because of having no plastid in their
cells, they are heterotrophs, and so they depend on other organisms for their
food. After ingestion, they digest their food. They have advanced and complex
type of tissue systems. Sexual reproduction is their usual way of reproduction.
Haploid gametes are usually produced in the reproductive organs of mature and
diploid male and female. Embryonic layers are developed at the time of their
embryonic development.
Example: The
entire invertebrate (except protozoa) and vertebrate animals.
Thomas Cavlier-Smith from Oxford
University divided the kingdom Protista of living world into two groups, and
renamed the kingdom Monera as the Kingdom of Bacteria in 2004. In this way, he
grouped the living world into six kingdoms. You will learn more about it at
your higher level of education.
Taxonomy classification
In classifying the organisms, some units or ranks are used
in taxonomy. The largest classification rank is kingdom, and the smallest
classification rank is species.
Kingdom →
Phylum / Division → Class
→ Order → Family → Genus → Species
In modern classifications, the ranks are divided into
sub-groups as the necessity demands.
End
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