Main concepts of life Science Tnpsc

Main Concepts of Life Science

Life science definition

The life sciences or biological sciences comprise the branches of science that involve the scientific study of life and organisms – such as microorganisms, plants, and animals including human beings.

Concepts of life science

Life science is one of the two major branches of natural science, the other being physical science, which is concerned with non-living matter.

Some life sciences focus on a specific type of organism. For example, zoology is the study of animals, while botany is the study of plants.

Other life sciences focus on aspects common to all or many life forms, such as anatomy and genetics.

Some focus on the micro-scale (e.g. molecular biology, biochemistry) others on large scales (e.g. cytology immunology, ethology, ecology). Another major, branch of life sciences involves understanding the mind’s neuroscience.

Life sciences discoveries are helpful in improving the quality and standard of life and have applications in health, agriculture, medicine, and the pharmaceutical and food science industries.

List of life sciences

Different branches of Life science


Study of form and function, in plants, animals, and other organisms specifically in humans


The study of the formation and presence of life in the universe


Study of the chemical reactions required for life to exist and function usually focuses on the cellular level.


Development of methods or software tools for storing, retrieving, organizing

and analyzing biological data to generate useful biological knowledge.


Study of the biology and evolution of language.

Biological anthropology

The study of humans, non-human primates, and hominids. Also as physical anthropology

Evolutionary biology

Study of the origin and descent of species over time.

Evolutionary Developmental Biology

Study of the evolution of development including its molecular control.


The study of the mechanics of living beings.


Study of biological processes by applying the theories and methods that

have been traditionally used in the physical sciences.


Study of plants.

Cell biology

Study of the cell as a complete unit, and the molecular and chemical interactions that occur within a living cell. Also known as cytology.

Developmental biology

Study of the processes through which an organism forms, from zygote to full structure.


Study of the interactions of living organisms with one another and with the non-living elements of their environment.


The study of behavior.

Evolutionary Biology

It is the study of the origin and descent of species over a period of time.

Evolutionary Development Biology

It is the study of the evolution of development including its molecular control.


It is the study of genes and heredity


It is the study of tissues.


It is the study of the immune system.


It is the study of microbes and their interactions with other living organisms.

Molecular Biology

It is the study of biology and biological functions at the molecular level and with cross-over with chemistry related to biology (biochemistry), genetic study, and microbiology.


It is the study of the Nervous system of living organisms.


It is the study of the action of the drug in living organisms.


It is the study of the organs and parts of living organisms.

Population Biology

It is the study of conspecific organisms.

Structural Biology

It is a branch of molecular biology, with chemistry and physicals concerned with the molecular structure of biological macromolecules.

Synthetic Biology

It is the development of artificial biological entities such as enzymes, genetic circuits, and cells or the creation of new biological systems.

System Biology

It is the study of integration and dependencies of various components of a biological system, with particular focus upon the role of metabolic pathways and cell signaling strategies.

Theoretical Biology

The use of the scientific and mathematical model to study the biological phenomenon.


It is the study of the effect of chemicals on living organisms


It is the study of animals

Cell and cell structure

The structure and functional unit of all living things are cells. The basic building blocks of organisms are cells. The study about the structure and function of the cell is called Cytology or Cell Biology.

An organism that is made up of only one cell is called a unicellular organism. An example of unicellular organisms is Chlamydomonas. Organisms that are made of many cells are called multicellular organisms. Example – Plants and Animals.

The shape of the plant cell may be spherical or rectangular or hexagonal. Plant cell consists of a cell wall and protoplasm. The cell wall is absent in animals cells.

Protoplasm consists of the plasma membrane, nucleus, cytoplasm, and vacuoles. The cell organelles embedded in the cytoplasm are the endoplasmic reticulum, mitochondria, chloroplast, Golgi bodies, and ribosomes.

Plant Tissues

In unicellular organisms, all the body functions are performed by a single cell.

In multicellular organisms, different functions are performed by different groups of cells. The group of cells having a common origin and performing similar functions is called tissues.

Several tissues are organized to form Tissue systems. Various tissue systems are organized to form organs.

Several organs are organized to form an organism. The two types of plants tissue are Meristematic tissue and Permanent tissue.

The immature cells capable of division are known as Meristematic tissues. The mature cells incapable of division are known as Permanent tissues.

The three types of Meristematic tissue are apical meristem, lateral meristem, and intercalary meristem. The two types of permanent tissue are simple permanent tissue, and complex permanent tissue.

The protecting and supporting tissue are known as simple permanent tissues. The conducting tissue is known as complex permanent tissues.

The three types of simple permanent tissue are parenchyma, collenchyma, and sclerenchyma. The two types of complex permanent tissue are xylem and phloem.

Plant Functions

The physiology that deals with the plant’s function are known as plant physiology. The universal solvent, essential for the physiological activities of the plant as water.

The universal solvent plays a vital role in photosynthesis, respiration, transpiration, transportation, from root to leaf, etc are water.

Soil water contains minerals in the dissolved state. The process of absorbing water and minerals by plants are imbibition, diffusion, and osmosis.

The three forces of absorption in plants are imbibition, diffusion, and osmosis.


The uptake of water or other solvents by substances that do not dissolve in water results in swelling of these substances known as imbibition.

The substances used for imbibition are called imbibants. An example of imbibants is wood and seeds.

In-plant cells, the imbibants is the cell wall. The imbibants absorb water and form a channel for movement of water into the cell, by diffusion and osmosis in plants is the cell wall.

The force which plays a very important role in seed germination, swelling, and rupture of the radicle and plumule is imbibition.

The dissolved molecules move from a region of higher concentration to the region of lower concentration until the molecules are evenly distributed throughout the available space known as diffusion.

Gases such as oxygen, carbon-di-oxide, and nutrients like minerals move into or between the cells by diffusion.

The movement of a solvent from a region of its higher concentration to the region of its lower concentration through a semi-permeable membrane is called osmosis.

The two mechanisms involved in helping the soil water to enter into the root hairs is passive absorption and active absorption.

The absorption of mineral ions without the use of metabolic energy is called passive absorption. The uptake of mineral ions by using metabolic energy is called active absorption.

The water along with mineral salts, is absorbed by the root through its roots hairs reaches the xylem vessels, and finally reaches the leaves and this movement is known as the ascent of sap.

Synthesizing carbohydrates using light energy, carbon dioxide, and water is known as photosynthesis. Intake of oxygen and giving carbon dioxide known as respiration.

Giving out excess water as water vapor by leaf is known as transpiration. The buds that develop into new plants are known as vegetative reproduction.


Photo means light and synthesis means to build. Photosynthesis means ‘building up by light’. Green plants are autotrophic and synthesize their own food by the process of photosynthesis.

The green leaves prepare food by combining CO2 and water in presence of sunlight and chlorophyll known as photosynthesis. Carbon dioxide from the atmosphere enters the leaves through tiny pores called stomata.

The green pigment present in leaves absorbs light energy called Chlorophyll.

The gas released during photosynthesis is oxygen. The materials required for photosynthesis are light, chlorophyll, CO2, and water.

The main photosynthetic organelles of the plant present in the leaves are chloroplasts. The pigments present in the chloroplasts which are necessary for the synthesis of food are chlorophyll pigments.

The two phases of photosynthesis are light reaction and dark reaction. The reaction involving pigments, solar energy, and water that produces ATP and NADP is called a Light reaction.

ATP means Adenosine Triphosphate. NADPH2 means Nicotinamide Adenine Dinucleotide Phosphate reduced form.

The reaction in which CO2 is reduced to carbohydrates by making use of ATP and NADPH2 generated by the light reaction is called the Dark reaction.

Light is not required for the Dark reaction. The factors influencing photosynthesis are light, temperature, CO2, Chlorophyll distribution, water, mineral salts, and age of the leaf.

The loss of water through the aerial parts of the plant such as leaves and green short is known as transpiration.

The three types of transpiration are stomatal transpiration, cuticular transpiration, and lenticular transpiration.

The tiny pores in the epidermis of leaves and other aerial parts of the plant-like stem are called stomata.

Stomata are surrounded by two kidney-shaped cells called guard cells. Each guard cell has an elastic outer thin wall and a thick inner wall.

The guard cell has an elastic outer thin wall and a thick inner wall.

The guard cells are turgid(full of water), the outer wall is stretched and the stomata remain open during the daytime. The guard cell becomes flaccid by losing water to the surrounding cells during nighttime.

The transpiration of water through stomata is called stomatal transpiration. A large quantity of water is lost through the stomata during transpiration.

The waxy layer lying over the epidermis of the leaf is known as the cuticle. Only a small amount of transpiration that occurs through the cuticle is known as cuticular transpiration.

The minute pores are found on the banks of woody plants are known as lenticel. A small amount of transpiration occurs through lenticel known as lenticular transpiration.

The factors affecting transpiration are light, temperature, wind, the quantity of water in the soil, the number of stomata, and the surface area of the leaf.

All the energy required for the life process is obtained by the oxidation of food. The seats of biological oxidation which furnish energy for the various activities of the cell are mitochondria.

The process by which food (carbohydrate) is broken down and the energy is released is called oxidation. The Bio-Chemical process of oxidation and degradation of food with the release of energy is known as respiration.

The energy released during respiration is stored in the cells in the form of Adenosine Triphosphate (ATP).

ATP has a high energy content. The energy currency of the cell is ATP. The two types of respiration are Aerobic and Anaerobic respiration.

The respiration in which glucose is completely oxidized in presence of oxygen, releasing CO2 water and energy known as Aerobic respiration.

Aerobic means with the help of air. The four steps of Aerobic oxidation of glucose are Glycolysis, Oxidation of Pyruvic acid, Krebs cycle, and electron transport chain.

Organisms like bacteria and Yeast undergo respiration in the absence of oxygen is called anaerobic respiration. The common for both Aerobic and Anaerobic organisms is Glycolysis.

The factors which affect respiration are oxygen, temperature, water, light, CO2, and glucose. To carry things from one place to another is known as transport.

The process of a substance absorbed or made in one part of the body of an organism is carried to other parts of the body known as transportation. The two transport systems of the plants are the xylem and phloem.

The two parts of the transport of materials in a plant are 1) water and minerals and 2) food and other substances like hormones.

The two kinds of xylem cells are xylem vessels and tracheids. The only water-conducting tissue in pteridophytes and gymnosperms are Tracheids.

The transport of water that occurs in angiosperms through phloem depends on the action of living cells called sieve tubes.

The food is made in the mesophyll cells of a leaf.

The food made by the mesophyll cells of a leaf enters into the sieve tubes of the phloem.

The food, transported to all the other parts of the plant body by the network of sieve tubes of stem and roots. The movements of water and dissolved salts in the xylem are always upwards.

Main Concepts of Life Science tnpsc pdf

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* * All the Notes in this blog, are referred from Tamil Nadu State Board Books and Samacheer Kalvi Books. Kindly check with the original Tamil Nadu state board books and Ncert Books.
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