MPPCS Paper III- Biology

Organism and Types of organisms

  Each organism is different from other organisms. The total number of species living on the planet is imprecisely known and published estimates vary from 12 million to over 100 million. This is because there are large numbers of species yet undiscovered and undescribed, and there is not always agreement on whether certain organisms should be regarded as separate species. The total number of known species including all animals, plants and micro-organisms is about 1.4 million, and over half of these are insects! Taxonomists have fairly complete records for the best known groups (e.g. birds with 9, 881 species world-wide). ... Read more


Tissues Tissue, in physiology, a level of organization in multicellular organisms; it consists of a group of structurally and functionally similar cells and their intercellular material. Tissues are absent from unicellular organisms. Even among the simplest multicellular species, such as sponges, tissues are lacking or are poorly differentiated. But multicellular animals and plants that are more advanced have specialized tissues that can organize and regulate an organism’s response to its environment. Tissues in plants Bryophytes (liverworts, hornworts, and mosses) are nonvascular plants; i.e., they lack vascular tissues (phloem and xylem) as well as true leaves, stems, and roots. Instead bryophytes ... Read more

Fundamental unit of life-Cell

  Objects having characteristics of cellular organization, growth, reproduction, ability to sense environment and give response are living organisms. There are some important features of living organisms: It should grow, which means its structure changes as time goes by in an advantageous manner. It should show adaptation to the environment. It should maintain some balanced conditions in its inner structure. This is called Homeostasis. Its structure is highly organized. It should be able to break down or build up nutrients to release or store energy based on need. This is called Metabolism. It should be able to reproduce itself. Classification ... Read more


Metabolism  is the set of life-sustaining chemical transformations within the cells of organisms. The three main purposes of metabolism are the conversion of food/fuel to energy to run cellular processes, the conversion of food/fuel to building blocks for proteins, lipids, nucleic acids, and some carbohydrates, and the elimination of nitrogenous wastes. These enzyme-catalyzed reactions allow organisms to grow and reproduce, maintain their structures, and respond to their environments. The word metabolism can also refer to the sum of all chemical reactions that occur in living organisms, including digestion and the transport of substances into and between different cells, in which ... Read more

Control And Coordination

Plants and animals All the living organisms respond and react to changes in the environment around them. The changes in the environment to which the organisms respond and react are called stimuli such as light, heat, cold, sound, smell, touch etc. Coordination in plants Coordination refers to ordered working of different but interrelated parts to perform one or more activities smoothly. Since the nervous system doesn’t exist in plants, they use a chemical system. Plants coordinate their behavior against environmental changes with the help of Hormones. Plants have various hormones that help them to coordinate growth and response to the ... Read more


Reproductive systems The reproductive system in both males and females consists of structures that produce reproductive cells, or gametes, and secrete sex hormones. A gamete is a haploid cell that combines with another haploid gamete during fertilization. Sex hormones are chemical messengers that control sexual development and reproduction. The male reproductive system consists of structures that produce male gametes called sperm and secrete the male sex hormone testosterone The reproductive system is a collection of internal and external organs in both males and females that work together for the purpose of procreating. Due to its vital role in the survival ... Read more

Heredity and Evolution

Evolution, simply put, is descent with modification. This definition encompasses small-scale evolution (changes in gene frequency in a population from one generation to the next) and large-scale evolution (the descent of different species from a common ancestor over many generations). Evolution helps us to understand the history of life. Evolution is not simply a matter of change over time. Lots of things change over time: trees lose their leaves, mountain ranges rise and erode, but they aren’t examples of biological evolution because they don’t involve descent through genetic inheritance.  The central idea of biological evolution is that all life on ... Read more