Biology 9th Class Biology

Chapter 1 Introduction to Biology – 9th Class Biology Notes



Question#1) Define Science and Biology?

Answer: Science: Word science is derived from scientia means knowledge. Science is the study in which observations are made, experiments are done and logical conclusions are drawn in order to understand the principles of nature.

“OR”  The knowledge obtained through observations and experiments is called science.

Biology: The word “biology” derived from two Greek words “Bios” meaning life and “Logos” meaning study, so the scientific study of life is called biology. OR “The study of living things is called biology”. Biology includes several branches. Three major branches of biology are given below.
Question#2) Write a note on major branches of Biology?

Answer: Botany –Greek: botane means plant.
“Branch of biology which deals with the scientific study of plants is called Botany”.
Zoology – Greek: Zoon means animals.
“ The branch of biology that deals with animals and animal life, including the study of the structure, physiology, development, and classification of animals”.
Microbiology – Greek: mikros means small.
“The branch of biology that deals with microorganisms and their effects on other living organisms”
Question#3) Write a note on specialized branches of biology?

Answer: Branches of Biology: Biology is further divided into several sub branches some of them are given below,
Morphology – Greek: Morph means structure
“A branch of biology which deals with the study of form and  structure of organisms is called morphology”.
Anatomy – Greek: Anatome means dissection / cutting
“A branch of biology which deals with the study of internal structure of organisms is called anatomy”
Physiology – Latin: Physiologia means function
“A branch of biology which deals with the study of the functions of living organisms and their parts is called physiology”
Embryology / Developmental Biology – Greek: Embryon means growth.
: It is the study of the development of an embryo to new individual.
Cell Biology/ Cytology – Greek: Cyto means cell
“The study of structure and function of the cell and cell organelles is called cell biology.”it also deal with cell division.
Histology – Greek: Histos means tissue
“A branch of biology which deals with the microscopic study of tissue is called histology”
Paleontology – Greek: Palaios means primitive/fossil/being ancient.
It is the study of fossils, which are the remains of extinct organisms. Paleontology has further two branches, a) paleobotany: Study of plants fossils, b) Paleozoology: study of animals fossils.
Immunobiology /Immunology – Latin: Immunis means body defence system/not affected by disease.
“A branch of biology which deals with the study of the immune system in body of organisms against diseases is called immunology.
Entomology – Greek: Entomon means Insect.
The study of insects is called entomology.
Genetics – Greek: Genos means race/kind/ancestry/heredity/origin.
The study of genes and their role in inheritance is called genetics.  OR  “Branch of biology which deals with the study of inheritance is called genetics.
Microbiology – Greek: mikros means small
“A branch of biology which deals with the study of small and microscopic organisms (microorganisms/microbes) and their interactions with other living things is called microbiology.
Biotechnology –It deals with the practical application of living organisms to make substances for the welfare of mankind.

Environmental Biology / Ecology – Greek: Oikos means house/habitation: It deals with the study of the interactions between the organisms and their environment.
Parisitology – Greek: Parasitos means some body that eats another’s food/grains
“A branch of biology which deals with the study of parasites is called parasItology. Parasites are the organisms that take food and shelter from living hosts and, in return, harm them. E.g: Cuscuta, bed bug, etc.
Social biology – Latin: Socialis means companion : This branch deals with the study of social behaviour of the animals that make societies.   OR
“A branch of biology which deals with the study of those organisms which are living together in a community and interact each other is called social biology, e.g. social insects (ants, bees, and termites), birds flock, humans and fishes living in groups.
Pharmacology – Greek: Pharmakon means drugs  ; It is the study of drugs and their effects on the systems of human body.

“A branch of biology which deals with the study and practical application of preparation, use, and effects of drugs and synthetic medicines is called pharmacology.

Molecular biology (biochemistry): deals with the study of the molecules of life; e.g. water, proteins, carbohydrates, lipids, and nucleic acids.


Useful words: Scientific knowledge is the common heritage of mankind.

Dr. Abdus Salam

Question#4) Write a note on relationship of Biology with other sciences? OR Give points to advocate that biology is linked with physics, chemistry, mathematics, geography and other sciences?

Answer: RELATIONSHIP OF BIOLOGY TO OTHER SCIENCES OR MULTIDESCIPLINARY APPROACH TO THE STUDY OF BIOLOGY: Biology is a very wast field and is related to other branches of science in some respects. It works in coordination with other branches of science. Due to this reason some new branches of biology arises. Some of them are as follows.1)

1) Biophysics: It deals with the study of the principles of physics, which are applicable to biological phenomena. For example there is a similarity between the working principles of lever in physics and limbs of animals in biology.

2) Biochemistry: It deals with the study of the chemistry of different compounds and processes occurring in living organisms. For example the study of basic metabolism of photosynthesis and respiration involves the knowledge of chemistry.

3) Biomathematics / Biometry: It deals with the study of biological processes using mathematical techniques and tools. For example to analyze the data gathered after experimental work, biologists have to apply the rules of mathematics.

4) Biogeography: It deals with study of the occurrence and distribution of different species of living organisms in different geographical regions of the world. It applies the knowledge of the characteristics of particular geographical regions to determine the characteristics of living organisms found there.

5) Bioeconomics: It deals with the study of organisms from economical point of view. For example the cost value and profit value of the yield of wheat can be calculated through bioeconomics and benefits or losses can be determined.


Question#5) If you study biology which career path will you prefer to choose and why?
Answer: As a Biologist there are several career paths one of them I will choose like;
1) Field of Medicine: “A substance used in the diagnosis, treatment, or prevention of a disease is called medicine”. While studying biology a student should prefer to choose medical line because it is one of the best among career paths, after completion of intermediate.
2) Fisheries: (As Ichthyologist) the study of fishes is called ichthyology. After selecting biology as a subject, next best field after medical, is fishery. As Ichthyologist, a man must know about fish habitats, breeding, diseases, food, population, fish farming or aquaculture etc. As a manager they may work in hatchery (place of hatching eggs) and prevention from diseases. And keep up to date with fish production and information.
3) Agriculture: The science of cultivating crops like wheat, maize, rice and farming of animals that gives milk and meat. Agriculture is one of the best fields so, after completion of intermediate a student of biology may join this line for their career.
4) Animal Science/ Animal husbandry: Animal science is related to breeding and veterinary (medical or surgical treatment) of animals. After completion of intermediate a student of biology has a choice to select D.V.M (Doctor of Veterinary Medicine) which makes his/ her future bright.
5) Horticulture: Latin hortus, garden. “The science of cultivating fruits, vegetables, flowers, or ornamental plants” Horticulture primarily differs from agriculture in two ways. First, it surrounds a smaller scale of cultivation. Secondly, horticultural cultivations include a wide variety of crops.
6) Forestry: Forestry is the scientific management of forest lands for wood water, wildlife, and recreation. Because the major economic importance of the forest lies in wood and wood products, forestry chiefly concerned with timber management, especially reforestation, maintenance of the forest, and fire control.
7) Farming: It deals with the development and maintenance of different types of farms. For example in some farms animal breeding technologies are used for the production of animals which are better protein and milk source. In poultry farms chicken and eggs are produced. Similarly in fruit farms, different fruit yielding plants are grown. A student who has gone through the professional course of agriculture, animal husbandry or fisheries etc. can adopt this profession.

Question#6) What does Quran teachs us about biology?


At many places in Holy Quran, Allah hints about the origin and characteristics of living organisms. In the same verses human beings have been instructed to expose the unknown aspects of life, after getting the hints. Here are few examples of such guidelines.

“We made every living thing from water.”

(Sura: Ambia, Verse: 30)

We know that water makes the 60-70% of the composition of protoplasm of all living things. The above Verse hints at the common origin of all living things in water. As Allah has ordered human beings to think at the hints given by Him, we should study living things so that the mysteries of their origin can be revealed.

“He made man from clay like the potter.”    (Sura: Rehman, Verse: 14)

In another verse, God says:

“Then fashioned We the drop a clot, then fashioned We the clot a little lump, then fashioned We the little lump bones, then clotted the bones with flesh”       (Sura: Al-Mominoon, Verse: 14)

When we think at the hints given in both these Verses, we find the events that occurred in the creation of human beings. Allah also hints at the method of the development of animals including human beings.

Biology introduction

“Allah hath created every animal from water. Then some of them creep up over their bellies, others walk on two legs, and others on four. Allah creates what He pleases.”    (Sura: Al-Nur, Verse: 45)

This Verse describes the common origin and modification of organisms and also supports the modern concepts of classification.

Thus, Quran hints not only at the origin and development of life but also at many characteristics of living organisms.

Question#7) Write a note on contribution of  Muslim scientists in the field of Biology?

MUSLIM SCIENTISTS: Muslim scientists have made great contributions to the study of science and we are aware of their success in different fields of science. Here we would summarize the work of Jabir Bin Hayan, Abdul Malik Asmai and Bu Ali Sina in the development of the present day knowledge of plants and animals.

Jabir Bin Hayan (721 – 815 AD): He was born in Iran and practiced medicine in Iraq. He introduced experimental investigation in chemistry and also wrote a number of books on plants and animals. His famous books are “Al-Nabatat” and “Al-Haywan”.

Abdul Malik Asmai (740 – 828 AD):He is considered the first Muslim scientist who studied animals in detail. His famous writings include “Al-Abil (camel)”, “Al-Khail (horse)”, “Al-Wahoosh (animal)”, and “Kalq al-ansan”.

Bu Ali Sina (980 – 1037 AD): He is honoured as the founder of medicine and called as Avicenna in the West. He was a physician, philosopher, astronomer and poet. One of his books “Al-Qanun-fi al-Tib” is known as the canon of medicine in West.

Question#8) Describe the levels of organization of life?


The hierarchy of complex biological structures and systems that define life is called level of biological organization. These levels are as follows.

  1. Subatomic and Atomic level: An Atom is the smallest entity of matter that can enter into a chemical reaction. An element is the substance that can not be further simplified into other substances by physical and chemical means. Atoms of same elements are alike. Atoms further consists of subatomic particles protons, neutrons and electrons.

BIOELEMENTS: The elements that make the body mass of living organisms are called bioelements.

NUMBER OF BIOELEMENTS: Out of 92 elements, 16 are called bioelements. Out of these bioelements;

Only six (O, C, H, N, Ca, & P) make 99% of the total mass. Other ten (K, S, Cl, Na, Mg, Fe, Cu, Mn, Zn, & I) collectively make 01% of the total mass.

Role of bioelements: Mainly carbon, hydrogen and oxygen make most structures such as, sugars, starches and other energy molecules while nitrogen, phosphorus and sulphur make proteins.
Other elements are needed in less quantity. E.g. Iron is essential for haemoglobin (red blood cells), calcium for teeth and bones. Sodium and potassium are important for sending messages along nerves. Zn work as a coenzyme. Magnessium help in photosynthesis, etc.
2) M0lecular level: Atoms combined to form molecules.

Biomolecules: molecules that are present in living organisms are called biomolecules. Biomolecules are of two types.

  1. Micromolecules: molecules with low molecular weight are called micromolecules. e.g. glucose, water etc.
  2. Macro molecules: Molecules with high molecular weights are called macromolecules. e.g. starch, proteins, lipids etc.

Criterion for classifying biological molecules: Biological molecules are classified on the basis of molecular size. The small sized molecules are placed in micromolecules while large sized molecules are placed in macromolecules. In short words the micro molecules combined to form macro molecules.

Difference between molecule and biomolecule:

              Molecule            Biomolecule
A molecule is the smallest unit of substance usually non living.Biomolecule is the smallest particle of a living substance.
Molecules may be organic or inorganic.Biomolecules are organic.
Molecule can consist of any element found in periodic table.Biomolecules consists of carbon, hydrogen, oxygen, nitrogen, sulphur, calcium and phosphorous mainly.
Molecules combined to form compounds. These may be ionic, covalent, dative, etc.Biomolecules may be categorized as monomers or polymers. These are organic in nature having covalent linkage.


  • Organelle level and Cell level:

Organelle level: The building blocks of a cell are called organelle. Biomolecules (Macro molecules) combined to form organelles. Organelles are basically sub cellular structures. Each and every organelle perform a specific function. For example, mitochondria is involved in respiration, chloroplast is responsible for photosynthesis, etc.

Cell level: Cell is the basic structural and functional unit of life. Organelles combined to form a cell. Some organisms consists of only one cell like bacteria, protists, etc. while other consists of many cells. E.g;Human.

4) Tissue level: Tissue a collections of similar cells working together to perform a specific job. E.g, epithelial tissues, connective tissues, etc.

5) Organ and Organ system level:

Organ: Two or more types of tissues work together to complete a specific task is called organ. E.g, heart, stomach, brain, etc.

Organ system (system) : several organs working in union to achieve a common goal is called organ system. E.g, digestive system, cardiovascular system, respiratory system, etc.

Protons and neutrons are located inside nucleus of atom while electrons orbit in energy levels (electrons shells) around the nucleus. The number of electrons in the outermost shell determines the manner in which atoms react with each other.
A molecule is the smallest part of a compound that retains the properties of that compound.


6) Organism level or Individual level :  several organ systems functioning together forms an organism. E.g, human, dog, tree, frog, mustard,etc.
7) Population level: A group of organisms of the same species located at the same place, in the same time and sharing the same resources is called population. Individual organisms of the same species working together to achieve a common goal. Examples: population of human, population of mustard, population of frogs, etc.

A species is defined as a group of organisms capable of interbreeding and producing fertile offspring.

8) Community level: A community is an assemblage of different populations, interacting with one another within the same environment. A forest may be considered as a community. It includes different plant, microorganisms, fungi and animal species.

Habitat means the area of the environment in which organism lives.

9) Biosphere level:

The part of the Earth inhabited by organisms’ communities is known as biosphere. It constitutes all ecosystems (areas where living organisms interact with the nonliving components of the environment) and is also called the zone of life on Earth.

Ecological or biological organization


Question#9) Write a note on cellular organization of life?

Answer? CELLULAR ORGANIZATIONS: The arrangement of cells in a specific passion to make an entire living organism is called Cellular organization. Cellular organization are of three types.

1) Unicellular Organization: In this type of organization an organism is composed of only one cell. Those type of organisms are called unicellular organisms. Examples: Amoeba, Paramecium, and Euglena, Bacteria, etc.

  • Colonial Organization: In colonial type of cellular organization, many unicellular organisms live together but do not have any division of labour among them. Each unicellular organism in a colony lives its own life and does not depend on other cells for its vital requirements. Volvox is a green alga found in water that shows colonial organization. Hundreds of Volvox cells make a colony.

3) Multicellular organization: In multicellular organization, cells are organized in the form of tissues, organs and organ systems. Frog and mustard are the familiar examples of multicellular organization.

Question#10) What do you know about Mustard plant?

Answer: Mustard plant: Mustard plant (scientific name: Brassica campestris) is sown in winter and it produces seeds at the end of winter. The plant body is used as vegetable and its seeds are used for extracting oil. The organs of the body can be divided into two groups on the basis of their functions. Root, stem, branches and leaves are the vegetative organs, which do not take part in the sexual reproduction of the plant. Flowers are the reproductive parts of the plant because they take part in sexual reproduction and produce fruits and seeds.


Mustard Plant Picture


  • Common name … Mustard
    KINGDOM … Plantae
    DIVISION … Tracheophyta
    CLASS … Dicotyledonae
    ORDER … Capparales
    FAMILY … Brassicaceae
    GENUS … Brassica
    SPECIES … Campestris
    SCIENTIFIC NAME … Brassica Campestris

Question#11) Write a detailed note on Frog?

Answer: Frog: Frog (scientific name: Rana tigrina) shows the multicellular organization. The body is made of organ systems and each organ system consists of related organs. All the organs are made of specific tissues (epithelial, glandular, muscular, nervous etc). Some organs and organ systems of frog have been described in the practical activity given next.

Frog image

Common name … Frog
KINGDOM … Animalia
PHYLUM … Chordata
CLASS … Amphibia
ORDER … Salientia (Anura)
FAMILY … Ranidae
SPECIES … Tigrina
SCIENTIFIC NAME … Rana tigrina.

2) Common name … Man
KINGDOM … Animalia
PHYLUM … Chordata
CLASS … Mammalia
ORDER … Primat
FAMILY … Hominidae
GENUS … Homo
SPECIES … Sapiens


Question#12) Arrange these structures in order of lower level of organization to upper level and write the level against each structure. Neuron, nervous system, electron, man, mass of neurons, carbon, mitochondria, brain, protein?

Answer: Electron ( sub-atomic level) → Carbon (atomic level) → Protein (molecular level) → Mitochondrion (organelle level) → Neuron (cell level) → Mass of neuron (tissue level) → Brain (organ level) → Nervous system (organ system level) → Man (individual or organism level).

Question#13) Is there any division of labour among the cells of a colony? If you find division of labour among the cells and tissue what level of cellular organization is it?

Answer: Colonial organization donot have any division of labour. Division of labour is at organelle level in unicellular organization . Division of labour is fully developed in multicellular organization. It may be at cellular, tissue, organ and organ system level.

Question#14) What do you mean by horticulture and how is it related to agriculture?

ANSWER: Horticulture: Field of Biology deals to the art of gardening is called horticulture.

Horticulture is a branch of agriculture that deals to the science, technology and buisniss of plant cultivation. It includes developments of the gardens, cultivation of fruits, vegetables, nuts, flowers seeds, mushrooms, etc.

Question#15) Define the following terms?

(i) Fossil (ii) Inheritance (iii) Colony (iv) Protist (v) Surgery (vi) Volvox

Answer: (i) Fossil: Dead remains of plants and animals burried in rocks are called fossils. Dead remains of plants are called plant fossils while dead remains of animals are called animal fossils.

(ii) Inheritance: Characters that are transmitting from parents to off-springs are called inheritance.

 (iii) Colony: In Biology a colony refers to individual organisms of the same species living closely together , usually for mutual benefit , such as stronger defence or the ability to attack bigger prey. E.g volvox is a green alga form spherical colonies of up to 50,000 cells.

(iv) Protist: Any of eukaryotic organism belong to kingdom protista that show characters both like plants and animals and are mostly unicellular or colonial. e.g, Amoeba.

(v) Surgery: The branch of medicines that employs operations in the treatment of diseases or injury.

(vi) Volvox: Volvox is a green alga from genus cholorophyta that form spherical colonies of upto 50,000 cells.

Solved Exercise

Understanding the concept – Introduction to Biology


Question#1. Arrange these structures in order of lower level of organization to upper level and write the level against each structure. Neuron, nervous system, electron, man, mass of neurons, carbon, mitochondria, brain, protein?

Answer: Please see question number 12.

Question#2. How would you define biology and relate it with its major divisions?

Answer: Please see question number 1, 2 and 3.

  1. Draw a table showing the branches of biology and the studies these deal with?

Answer: Please see question number 3.

Question#4. Give points to advocate that Biology is linked with physics, chemistry, mathematics, geography and economics?

Answer: See question number 4.

Question#5. How would you distinguish the biomolecules from other molecules? What is the criterion for classifying a biomolecule as micromolecule or macromolecule?

Answer: Please see question number 8.

Question#6. Describe the levels of organization of life.

Answer: Please see question number 8.

Question#7. Is there any division of labour among the cells of a colony? If you find division of labour among the cells and tissue what level of cellular organization is it?

Answer: Please see question number 13.

Introduction to Biology Short Answers Question


Question#1. Define biotechnology?

Answer: Biotechnology –It deals with the practical application of living organisms to make substances for the walfare of mankind.

Question#2. What do you mean by horticulture and how is it related to agriculture?

Answer: Please see question number 14.

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