Science: Nature is beautifully ordered and coordinated in its activities and it operates under some principles. To understand these principles observations are made, experiments are done and logical conclusions are drawn. Such studies are called science. Scientific knowledge was then classified into different branches like biology, physics, chemistry, mathematics, etc.

Scientific knowledge is the common heritage of mankind - Dr Abdus Salam

Characteristics of living organisms: There are more than 2 million kinds of life on Earth that are known to scientists. All of these characteristics are found in each living thing, which is called an “organism”.

1. Living organisms are highly organized and complex entities having many complex chemical substances.
2. They are made up of cells, either one or more. A cell is the smallest unit, said to be alive.
3. They contain a genetic program that works for their characteristics.
4. They can acquire and use energy.
5. They carry out and control numerous chemical reactions, which become the basis of all of their characteristics.
6. They can grow and attain a definite form and size.
7. They maintain or try to maintain a constant internal environment of their bodies.
8. They respond to changes in the environment and so remain or try to remain adapted to their environment.
9. They produce offspring similar to themselves.
10. They are not eternal and have a limited life span.

Definition of Biology: Biology is the scientific study of life. Through this study, the scientists (biologists) do their best to understand, explain, integrate and describe the world of living things. The word "biology has been derived from two Greek words 'bios' meaning 'life' and 'logos' meaning ‘thought or reasoning’.

Relation of biology with its major divisions/Branches:

There are three major divisions of biology which study the different aspects of the lives of these groups.

Zoology: This division of biology deals with the study of animals.

Botany: This division of biology deals with the study of plants.

Microbiology: This division of biology deals with the study of microorganisms such as bacteria etc.

1. The unicellular organisms that do not have distinct nuclei are grouped as prokaryotes, for example, bacteria. The unicellular or simple multicellular organisms with distinct nuclei are called protists e.g. Euglena, Paramecium, Green algae, etc.
2. Fungi e.g. mushrooms are multicellular, heterotrophic, and absorptive in their mode of nutrition. Plants e.g. mustard are multicellular autotrophic organisms that develop from embryos. Animals e.g. frogs are multicellular heterotrophic organisms that ingest food.

Community.

Communal life means interactions within a community, while the community is defined as organisms of all species living in a particular habitat at a particular time.

The term biotechnology is only used when microorganisms, plants, or animals are used to produce something other than food. Therefore, the use of farm animals and crops for milk, meat, eggs, and cereals is not included in biotechnology. 

 Human population growth, infectious diseases, addictive drugs, and environmental pollution are the major biological issues today.

Relationship of biology to other sciences:

1. Biophysics:

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

1. Biochemistry:

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

1. Biomathematics:

It deals with the study of biological processes using mathematical techniques and tools. It has both practical and theoretical applications in biological research. For example, to analyze the data gathered after experimental work, biologists have to apply the rules of mathematics.

1. Biogeography:

It studies 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.

1. Bioeconomic:

It studies the organisms from an economical point of view. It includes the study of the cost-effectiveness and viability of biological projects. 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.

Careers in Biology:

The following are the careers that a student of biology can plan to adopt.

1. Medicine/Surgery:

The profession of medicine deals with the diagnosis and treatment of diseases in humans. In surgery, the parts of the body may be repaired, replaced, or removed, for example, the removal of stones through renal surgery, transplantation of kidney, liver, etc. Both these professions are studied in the same basic course (MBBS) and then students go for specializations.

1. Fisheries:

Fisheries is the professional study of fish production. There are departments in Pakistan where professionals in fisheries are employed. They serve for enhancing the quality and quantity of fish production. In Pakistan, this profession can be adopted after the bachelor's or master's level study of zoology and fisheries.

1. Agriculture:

This profession deals with the food crops and animals which are the source of food. An agriculturist works for the betterment of crops like wheat, rice, and animals from which we get food. In Pakistan, many universities offer professional courses in agriculture after the higher secondary education in biology.

1. Animal husbandry:

It is the professional study of the diagnosis and treatment of diseases in livestock. The livestock includes all the domestic animals. Professional courses in animal husbandry can be adopted after the higher secondary education in biology.

1. Horticulture:

This profession includes the art of gardening. A horticulturist works for the betterment of existing varieties and the production of new varieties of ornamental plants and fruit plants Biology students can adopt this profession after their higher secondary education.

1. Farming:

In this profession, different types of the farm are developed and maintained. For example, in some farms, animal breeding technologies are used for the production of animals that are better protein and milk sources. In poultry farms, chicken and eggs are produced. Similarly, in fruit farms, different fruit-yielding plants are grown. A student who has gone through a professional course in agriculture, animal husbandry or fisheries, etc can adopt this profession.

1. Forestry:

In forestry, professionals look after natural forests and advise the government on planting and growing artificial forests. Many universities offer professional courses in forestry after the higher secondary education in biology or after bachelor level study of zoology and botany.

1. Biotechnology:

It is the latest profession in the field of biology Biotechnologists study and works for the production of useful products through microorganisms Universities offer courses in biotechnology after the higher secondary education in biology and after bachelor level studies in botany or zoology.

Quran instructs us to reveal the study of life:

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

 ۖ وَجَعَلْنَا مِنَ ٱلْمَآءِ كُلَّ شَىْءٍ حَىٍّ ۖ

"We made every living thing from water."

(Surah: Ambia, Verse: 30)

We know that water makes 80-90% of the composition of the protoplasm of all living things. The above Verse hints at the common origin of all living things in the water. As Allah has ordered human beings to think about the hints given by Him, we should study living things so that the mysteries of their origin can be revealed.

خَلَقَ ٱلْإِنسَـٰنَ مِن صَلْصَـٰلٍۢ كَٱلْفَخَّارِ 

"He made man from clay like the potter."

(Sura. Rehman, Verse: 14)

When we think about 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.

ثُمَّ خَلَقْنَا ٱلنُّطْفَةَ عَلَقَةًۭ فَخَلَقْنَا ٱلْعَلَقَةَ مُضْغَةًۭ فَخَلَقْنَا ٱلْمُضْغَةَ عِظَـٰمًۭا فَكَسَوْنَا ٱلْعِظَـٰمَ لَحْمًۭا ثُمَّ أَنشَأْنَـٰهُ خَلْقًا ءَاخَرَ ۚ فَتَبَارَكَ ٱللَّهُ أَحْسَنُ ٱلْخَـٰلِقِينَ 

“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”

(Surah: Al-Mominoon, Verse: 14)

Now here is a Verse that describes the common origin and modification of organisms. This Verse also supports the modern concepts of classification,

وَٱللَّهُ خَلَقَ كُلَّ دَآبَّةٍۢ مِّن مَّآءٍۢ ۖ فَمِنْهُم مَّن يَمْشِى عَلَىٰ بَطْنِهِۦ وَمِنْهُم مَّن يَمْشِى عَلَىٰ رِجْلَيْنِ وَمِنْهُم مَّن يَمْشِى عَلَىٰٓ أَرْبَعٍۢ ۚ يَخْلُقُ ٱللَّهُ مَا يَشَآءُ ۚ إِنَّ ٱللَّهَ عَلَىٰ كُلِّ شَىْءٍۢ قَدِيرٌۭ

"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."

(Surah: Al-Nur, Verse: 45)

Quran hints not only at the origin and development of life but also at many characteristics of living organisms. Scientists reveal such mechanisms.

Muslim scientists:

1 - Jabir Bin Hayan (721 - 815):

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".

2 - Abdul Malik Asmai (740 - 828):

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 "Khalq-al-Ansan".

3 - Bu Ali Şina (980 - 1037):

He is honored as the founder of medicine and called 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 the west.

Structure of an atom:

Protons and neutrons are located inside nucleus of atom while electrons orbit in energy levels (electron shells) around the nucleus. The number of electrons in the outermost shell determines the manner in which atoms react with each other.

Molecule:

A molecule is the smallest part of a compound that retains the properties of that retains the properties of the compounds.

1. Subatomic and Atomic Level:
2. Molecular level:
3. Organelle and Cell level:
4. Tissue level:
5. Organ and Organ system level:
6. Individual level:
7. Population Level:
8. Community level:

Biologists study biological organization at different levels. The list goes from simpler to complex levels.

1. Subatomic and Atomic Level: All types of matter are made up of elements and there are about 92 kinds of elements, found in nature. Each element is made up of a single kind of atom (a": not, tom: cut).

These atoms are the structures formed by many subatomic particles. The most stable subatomic particles are electrons, protons, and neutrons. Each of these is found in a definite number, in a specific atom.

Bio elements:

Out of the 92 kinds of elements that occur in nature, 16 are called bioelements. These take part in making the body mass of a living organism.

Out of these elements; only six (O. C, H, N, Ca, & P) make up 99% of the total mass. The other ten (K, S, CI, Na, Mg, Fe, Cu, Mn, Zn, & I) collectively make 0.1% of the total mass.

2. Molecular level:

In organisms, bioelements usually do not occur in isolated forms. Rather, atoms of different bioelements combine through ionic or covalent bonding. The stable particle formed by the bonding between different elements is called a molecule. Bioelements share their atoms in making biomolecules or molecules of life.

3. Organelle and Cell level:

An enormous number of biomolecules become associated in a particular way and form organelles. The organelles are sub-cellular structures and when they assemble, cells are formed. Each type of organelle is specialized to perform a specific function. For example; mitochondria are specialized for cellular respiration and ribosomes are specialized for protein synthesis. In this way, the functions of the cell are accomplished by structures. It is an example of the division of labor within the cell.

4. Tissue level:

In multicellular organisms, similar cells (performing similar functions) are organized into groups, called tissues. We can define tissue as a group of similar cells specialized for the performance of a common function. Each cell in a tissue carries on its life processes (like cellular respiration, and protein synthesis), but it also carries on some special processes related to the function of the tissue There are four major types of animal tissues i.e. epithelial, connective, nervous and muscular tissues. Epithelial tissue acts as the covering and glandular tissue. Connective tissue acts as the connecting and supporting tissue. Nervous tissue conducts messages and muscular tissue acts as the contracting tissue.

There are four major types of animal tissues i.e. epithelial, connective, nervous, and muscular tissues. Epithelial tissue acts as the covering and glandular tissue. Connective tissue acts as the connecting and supporting tissue. Nervous tissue conducts messages and muscular tissue acts as the contracting tissue.

5. Organ and Organ system level:

In higher multicellular organisms, particularly in animals, more than one type of tissue having related functions are organized together and make a unit, called an organ. Different tissues of an organ perform their specific functions and these functions collectively become the function/s of that organ.

For example, the stomach is an organ specialized for the digestion of proteins and for storing food. Two major types of tissue are organized in their structure. Epithelial (glandular) tissue secretes the gastric juice and muscular tissue performs contractions of stomach walls for grinding of food, mixing enzymes with food, and moving food to the posterior end. So, two tissues perform their specific functions, which collectively become the function of the stomach.

Note:

The organ system level is less definite in plants as compared to animals. The complexity of organ and organ system levels in animals is associated with a far greater range of functions and activities than in plants.

6. Individual level:

Different organs (in plants) and organ systems (in animals) are organized together to form an individual/organism. In organisms, various organs and organ systems are organized in such a way that all the functions, processes, and activities are coordinated. For example, when a man is engaged in continuous and hard exercise, not only his muscles are working but also there is an increase in the rate of heartbeat. This accelerated rate of respiration and heartbeat supplies more oxygen and food to the muscles which they need for continuous work.

Note:

In animals, regulation of activities (coordination) is achieved by the nervous system and hormones while in plants, coordination is brought about only by hormones.

7. Population Level:

Biologists extend their studies to the population level where they study interactions among members of the same species living in the same habitat. A population is defined as a group of organisms of the same species located in the same place, at the same time. For example, the number of rats in a field of rice in 2002, the number of students in biology class in the semester of 2008, etc. Similarly, the human population comprises the number of human beings in a particular city or country at a particular time.

Note:

At the population level, biologists study life in several new parameters, which cannot be considered at the individual (organism) level. For example gene frequency gene flow, age distribution, population density, and population pressure.

8. Community level:

A community is an assemblage of different populations, interacting with one another within the same environment. A forest may be considered a community It includes different plant species e.g. oak trees, ash trees grasses, bushes, etc; different species of microorganisms and fungi, and different animal species. Communities are collections of organisms, in which one population may increase and others may decrease. Usually, populations change due to fluctuations in abiotic factors and changes in the size of other populations.

Complex Communities:

Some communities are complex e.g. a forest community, a pond community, etc. Other communities may be simple e.g. a fallen log with various populations under it.

Simple Community:

In a simple community number and size of populations is limited so any change in biotic or abiotic factors may have drastic and long-lasting effects.

Some notorious diseases damage vital organs for example kidneys, liver, lungs etc and lead to death. Kidney of some donor can be transplanted, if the kidney damage has been diagnosed well in time.

Functions of digestive organs and sum up processes of the digestive system:

Prokaryotes:

Prokaryotes have only a limited number and types of organelles in their cells. They are made up of simple cells which lack membrane-bounded organelles e.g. mitochondria, and the Golgi complex.

Eukaryotes:

Eukaryotes have a large number and types of organelles in their cells. They are made up of complex cells which have membrane-bounded organelles. A cell membrane (outer covering of cell) is however present in all cells, whether prokaryotic or eukaryotic.

In the case of bacteria and most protists, the entire organism consists of a single cell. In the case of most fungi, animals, and plants, the organism consists of up to trillions of cells.

The structures of many organelles e.g. mitochondria, Golgi complex ribosomes, etc. have been studied with the help of electron microscope and staining techniques. 

An organism is formed by an enormous number of biomolecules of hundreds of different types. These molecules are the building material and are themselves constructed in great variety and complexity due to specific bonding arrangements.

Classification of Biomolecules:

Biomolecules may be classified as micro molecules and macromolecules.

Micro molecules:

micro molecules are with low molecular weight e.g. glucose, amino acids, fatty acids, etc.

Macromolecules:

Macromolecules are with high molecular weights e.g. starch, proteins, lipids, etc.

Conjugated Molecules:

Two different molecules, belonging to different categories, usually combine to form a conjugated molecule e.g. glycoproteins, lipoproteins, nucleoproteins, etc.

Parameters of study at different levels of biological organization:

Yes, there is a division of labor among the cells of a colony. Such a type of division is found in multicellular organizations.

Division of labor among the plant tissues:

Based on their structures and functions, plant tissues are divided into two types i.e. meristematic tissues and permanent tissues.

Meristematic tissues:

Meristematic tissues are made of undifferentiated, small cells which can divide. These tissues are located at the tips of roots and shoots (apical meristem) and between the xylem and phloem tissues (lateral meristem).

Permanent tissues:

Permanent tissues are made of differentiated cells of different shapes and sizes. They are further divided into epidermal tissues (the outermost covering of leaf, stem, and root), ground tissue (or parenchyma: prepares food and stores food and water), supporting tissue (i.e. collenchyma/sclerenchyma: provides strength to the plant) and conducting tissue xylem and phloem (transports water and food).

Division of labor among the animal tissues:

There are four major types of animal tissues i.e. epithelial connective, nervous and muscular tissues. Epithelial tissue acts as the covering and glandular tissue. Connective tissue acts as the connecting and supporting tissue. Nervous tissue conducts messages and muscular tissue acts as the contracting tissue.

Arrangement of structures in order of lower level of organization to upper level:

Basic types of cells:

There are two basic types of cells i.e. prokaryotic and eukaryotic cells.

Organization of cell:

In living organisms, the cells organize in three ways to make the bodies of organisms Cells make unicellular, colonial, and multicellular organizations and the organisms formed through these organizations are unicellular, colonial organisms, and multicellular organisms.

Unicellular organization:

In unicellular organisms, only one cell makes the life of an organism. All the life activities are carried out by the only cell. We are familiar with Amoeba and Euglena etc.

Multicellular organization:

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

Colonial type of cellular organization:

In the colonial type of cellular organization, many unicellular organisms live together but do not have any division of labor 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. Sometimes a Volvox colony consists of daughter colonies. Each cell of the colony has two flagella at the anterior end, which are directed toward the surface of the colony. The colony moves in water by the combined action of the flagella of the cells.

The scientific name of the Mustard plant is Brassica campestris.

The scientific name of the frog is Rana tigrine.