Biology Part 2 - Quick Guide

Biology - Classification of Organisms


  • The technique of classifying organisms is known as Taxonomy.

  • Taxonomy is made up of two words i.e. ‘Taxis,’ which means ‘arrangement’ and ‘Nomos,’ which means ‘method.’

  • The Swedish botanist Carolus (Carl) Linneaeus has developed the modern taxonomic system.

  • Linneaeus has developed the following hierarchy of groups to explain the taxonomy −

  • In this hierarchy, Domain is the highest order and the broadest category and Species is the lowest order category.

  • Further based on the difference between eukaryotes and prokaryotes (cells) ‘Domains’ classified into three broad categories namely −

  • Archea(Archeabacteria) − It comprises the bacteria that live in extreme environments.

    • Eubacteria − It comprises the bacteria that found in everyday life.

    • Eukaryote − It comprises almost all the world's visible living things.

  • The above given three domains are further categorized into Five following Kingdoms

  • Let’s discuss each kingdom in brief −

    • Monera − It comprises the unicellular organisms, e.g. bacteria.

    • Protista − Similar to monera (unicellular), but more developed and complex. It contains nucleus.

    • Plantae − All plants from smallest (such as algae) to the largest (such as Pine, Eucalyptus trees, etc.) are studied under this kingdom.

    • Fungi − It is a group of eukaryotic organisms that comprises microorganisms such as yeasts, molds, and mushrooms. The organisms of this kingdom do not make their food, they are basically parasites.

    • Animalia − It includes all the multicellular and eukaryotic organisms (of animal group). It is also known as Metazoa.

Binomial Nomenclature

  • The naming culture (of different organisms) practiced uniformly across the world is known as binomial nomenclature.

  • Binomial Nomenclature largely consists of two words – the first word beginning with a capital letter and known as genus (of the organism) and the second word begins with lower case letter and defines the species of the organism.

  • Binomial Nomenclature must be written in italic and also known as scientific name.

  • For example, the binomial nomenclature of human is - Homo sapiens; tiger - Panthera tigris, etc.

Eukaryotes and Prokaryotes

  • Cells are fundamentally categorized by prokaryotes and eukaryotes.


  • Prokaryotes are the smallest and simplest type of cells.

  • Prokaryotes have no true nucleus and no membrane-bound organelles. E.g. Bacteria.

  • Prokaryotes’ Genome consists of single chromosome.

  • Reproduction is asexual; basically mitosis type.


  • Eukaryotes are complex in structure.

  • Eukaryotes have nuclei and membrane-bound organelles.

  • Eukaryotes’ Genome consists of numerous chromosomes.

  • Reproduction is sexual; by mitosis and meiosis.

Biology - Cell Division


  • The process of division of parent cell into two or more daughter cells is known as cell division.

  • In early 1880s, Flemming first observed the process of cell division.

Cell Division
  • Following are the three types of cell division −

    • Amitosis

    • Mitosis &

    • Meiosis

  • Let’s discuss each of them in brief −


  • Parent cell gets divided into two parts, and each of them grows as a new complete organism.

  • Amitosis can be seen in less developed organisms. E.g. bacteria

  • Amitosis is also known as binary fission.

  • There is no stage of division, cell directly gets divided into two new organisms.


  • The process of division of parent cell into two new identical cells is known as mitosis.

  • In both the new cells, the number of chromosomes remain same.

  • Mitosis (cell division) occurs only in eukaryotic cells.

  • In mitosis, the division of the nucleus is preceded by the S stage (i.e. interphase - during this phase, the DNA is replicated).

  • After the interphase, the cytokinesis process begins, which divides the cytoplasm, cell organelles, and cell membrane into two new cells.

  • The process of mitosis is divided into the following stages −

    • Prophase

    • Prometaphase

    • Metaphase

    • Anaphase

    • Telophase

  • The stages of mitosis are described in the following image −

  • Let’s discuss each of them in brief −


  • During the prophase, cell prepares to get divided.

  • The prophase process is also known as chromosome condensation, as chromatin fibers condense into discrete chromosomes.

  • Each chromosome has two chromatids and these two chromatids are joined at a place known as centromere.


  • In this phase, the nuclear envelope gets disintegrated into small membrane vesicles.


  • In this phase, the two centrosomes start pulling the chromosomes towards opposite ends of the cell and ensure the equitable distribution of chromosomes.


  • In this phase two identical daughter chromosomes are formed.


  • Telo is a Greek word meaning ‘end’.

  • In this phase, the nuclear envelop gets broken and a new nuclear envelop forms.

  • The new envelope gets formed around each set of separated daughter chromosomes; parallel, the nucleolus reappears.

  • Likewise, the mitosis is complete.


  • Cytokinesis, technically, is not a phase of mitosis, but rather a distinct process, essential for completing the cell division.

  • In this phase, cytoplasm begins to divide and completed with the development of two new identical cells.


  • Meiosis is a typical type of cell division in which the chromosome number gets reduced by half, creating four haploid cells. Each cell is genetically distinct from the parent cell.

  • Meiosis cell division process occurs in all sexually reproducing single-celled and multicellular eukaryotes, including plants, animals, and fungi.

  • Meiosis cell division is primarily categorized as Meiosis I and Meiosis II.

Biology - Virus


  • A virus is a micro infectious agent, which is found as parasite in the living cells of other organisms.

  • Virus replicates swiftly inside the living cells of other organisms.

  • Virus is a Latin term meaning ‘poison’ and other ‘noxious’ liquids.

  • Viruses can infect any type of life forms, ranging from animals and plants to microorganisms, including bacteria and archaea.

  • The study of viruses is known as virology.

  • Virus is first discovered by Dmitri Ivanovsky in 1892.

  • Virus has the properties of living as well non-living.

  • One of the living properties is – virus has either DNA or RNA (never both).

  • One of the non-living properties is – virus has no protoplasm.

Types of Virus

  • Based on parasitic nature, virus is categorized as −

    • Animal Virus

    • Plant Virus

    • Bacterial Virus

    • Archaeal Virus

Viral Diseases in Human Being

  • Following are the list of diseases caused by virus in Human beings −

    • Chickenpox

    • Encephalitis

    • Influenza (or Flu)

    • Herpes (skin disease)

    • Human immunodeficiency virus (HIV/AIDS)

    • Human papillomavirus (HPV)

    • Infectious mononucleosis

    • Mumps (measles and rubella)

    • Shingles

    • Viral gastroenteritis (stomach flu)

    • Viral hepatitis

    • Viral meningitis

    • Viral pneumonia

Viral Diseases in Plants

  • Following are the list of diseases caused by virus in plants −

    • Peanut - Stunt Virus

    • Maize - Mosaic Virus

    • Lettuce - Mosaic Virus

    • Cauliflower - Mosaic Virus

    • Sugarcane - Mosaic Virus

    • Cucumber - Mosaic Virus

    • Tobacco - Mosaic Virus

    • Tomato - Twisted leaf disease

    • Lady finger - Yellow vein mosaic

Viral Diseases in Animals

  • Following are the list of diseases caused by virus in animals −

    • Cow – Herpes (Herpes virus)

    • Buffalo – Small pox (Poxverdi orthopox)

    • Dog – Rabies (Stereit virus)

Biology - Bacteria


  • Bacteria normally comprises a large number of prokaryotic microorganisms.

  • Bacteria most probably were among the first life that formed to appear on the Earth.

  • Bacteria belong to Monera kingdom.

  • Bacteria usually inhabit in all range of environments, such as soil, water, acidic hot springs, radioactive waste, and the deep portions of Earth's crust.

  • The study of bacteria is known as bacteriology.

  • Bacteria play an important role in many stages of the nutrient cycle by recycling nutrients including the fixation of nitrogen from the atmosphere.

  • Bacteria grow to a fixed size and after maturity reproduce through asexual reproduction i.e. basically binary fission.

  • Under favorable conditions, bacteria can grow and divide very swiftly, and the bacterial populations can double merely in every 9.8 minutes.

  • When viruses that infect bacteria is known as Bacteriophages.

  • In order to modify themselves (to survive in the adverse environment), Bacteria frequently secrete chemicals into their environment.

Advantages of Bacteria

  • Bacteria are advantageous in many ways, such as −

    • Bacteria help in atmospheric nitrogen fixation.

    • Bacteria decompose dead plants and animals and clean the environment.

    • Bacteria are the major element that convert milk into curd and wine into vinegar.

    • Some specific types of bacteria are used in making proteins.

    • Some types of bacteria are also used as pesticides.

Disadvantages of Bacteria

  • Bacteria cause many diseases and infection to living organisms.

Bacterial Diseases

  • Bacteria cause many diseases, significant of them are −

    • Anthrax - caused by Bacillus anthracis

    • Brucellosis - caused by Brucella abortus

    • Botulism - caused by Clostridium botulinum

    • Coliform diseases - caused by Escherichia coli

    • Leprosy - caused by Mycobacterium leprae

    • Plague - caused by Yersinia pestis

    • Typhoid fever - caused by Salmonella typhi

    • Trachoma - caused by Chlamydia trachomatis

    • Diphtheria - caused by Corynebacterium diphtheria

    • Tetanus - caused by Clostridium tetani

    • Tuberculosis - caused by Mycobacterium bovis

    • Cholera - caused by Vibrio cholera

    • Syphilis - caused by Treponema pallidum

    • Whooping cough - caused by Bordetella pertussis

    • Gonrhoea - caused by Gonococcus

    • Potato wilt - caused by Pseudomonas solanacearum

    • Blight of rice - caused by Xanthomonas orzae

    • Fire blight of apple - caused by Invenia

Biology - Fungi


  • Fungi are the members of eukaryotic organisms, which includes microorganisms such as molds, yeasts, and mushrooms.

  • Fungi do not photosynthesize rather they obtain their food by absorbing the dissolved molecules, usually by secreting digestive enzymes into their environment.

  • Fungi are found in almost every part of the world, and they can grow in a wide range of habitats, ranging from extreme environments (such as deserts) to mild (such as temperate region).

  • Fungi are the primary decomposers in most of the ecological systems.

  • The study of fungi is known as mycology.

  • Fungi have membrane-bound cytoplasmic organelles, for example mitochondria, sterol-containing membranes, and ribosomes.

  • Fungi have also a cell wall and vacuoles (property of plants).

  • Fungi have no chloroplast and they are heterotrophic organisms (property of animals); likewise, fungi have both the properties of plants and animals.

Advantages of Fungi

  • Fungi have medicinal advantages, as they have been used for the manufacturing of antibiotics and various enzymes.

  • One of the most popular antibiotic drug penicillin is manufactured from the fungus Penicillium.

  • The ‘shiitake,’ one of the types of mushroom is a source of a clinical drug known as Lentinan.

  • Fungi are also used as the biological pesticides to control plant diseases, weeds, and insect pests.

  • In Japan, Lentinan is used to treat in cancer disease.

  • As they feed the dead organic matters, fungi recycle about 85 percent of the carbon from dead organic matter; likewise, fungi release the locked-up nutrients so that they can be used by other organisms.

  • Many varieties of fungi such as oyster mushrooms, straw mushrooms, shiitakes, milk mushrooms, truffles, and black trumpets are edible.

  • Portobello mushrooms and Button mushrooms are usually used in soups and salads.

  • Fungi are also used to produce industrial chemicals, including citric, malic and lactic acids.

  • Fungi are frequently used to produce industrial chemicals, such as citric, malic and lactic acids.

Disadvantages of Fungi

  • Some mushrooms, though they look like edible mushrooms, but they are poisonous that may cause even death to the person who ate.

  • Some Fungi can infiltrate the external layers of the human bodies and cause itching and rashes problems.

  • Certain fungi appear on food stuffs and destroy them shortly.

  • Fungi also cause various diseases to animals (including humans) as well as plants.

Fungal Diseases

  • Fungi cause many diseases, significant of them are −

    • Athlete’s foot - Taenia pedis

    • Asthma - Aspergillus fumigatus

    • Ring work - Trichophyton

    • Meningitis - Cryptococcus neoformans

    • Baldness - Taenia captis

    • Dermatophilosis - Dermatophilus congolensis

    • Wart disease of potato - Synchytrium endobioticum

    • Rhinosporidiosis - Rhinosporidium seeberi

    • Rust of wheat - Puccinia graminis tritici

    • Red rot of sugarcane - Colletotrichurn falcatum

Biology - The Roots


  • Root is the most essential part of a plant that grows down to the soil and water.

  • Root avoid the sunlight, as it grows down to soil and water, and absorbs mineral salt and water from the soil.

  • However, some typical roots are also aerial or aerating, that grow up above the ground or especially above the water.

  • Roots do not have leaves, buds, and nodes.

Functions of the Roots

  • The roots absorb mineral salts and water from the soil then supply them to other parts of the plants.

  • Roots provide foundation to plants and keep them static.

  • Some roots absorb foods for the contingency period; e.g. radish, carrot, etc.

Types of Roots

  • Primarily, roots are classified as −

    • Tap Root

    • Fibrous Root

    • Adventitious Root

    • Let’s discuss them in brief −

Tap Root

  • There is a main root (see the image given below) that grows faster and it has many branches. Usually, it occurs in dicotyledon plants.


Fibrous Roots

  • There is as such no primary root rather there are numerous roots of similar shape, thickness, and size.

Fibrous Root
  • It is typical feature of monocots (plant).

Adventitious Root

  • A typical root that grows from any part of a plant except the primary root part.

Adventitious Root
  • Adventitious root may be underground or may aerial.

Modified Taproots

  • The following table illustrates some typical examples of modified taproots −

Taproots Examples
Conical shape Carrot
Napiform Beet root
Fusiform Radish
Pneumatophores Sundari plants
Pneumatophores Sundari plants

Modified Adventitious Roots

  • The following table illustrates some typical examples of modified adventitious roots −

Adventitious Roots Examples
Aerial root Orcede
Parasitic root Kascutta
Moniliform root Grapes
Prop root Banyan tree
Stilt root Sugarcane, maize, etc.
  • Note − Tuber is a stem that grow horizontally under the soil and develop roots on their lower surfaces. Major function of this swollen stem is to store food and nutrients. E.g. potato, onion, etc.

Biology - The Plant Stem


  • A stem is one of the main structural axes of a vascular plant.

  • The stem, structurally, is categorized into nodes and internodes (see the image given below).

  • The other term used for the stem is shoot, but there is difference between stem and shoot, i.e. stem includes only stem part, whereas, shoot includes stem, leaf, flower, etc. (shoot term basically used for new plant growth).

Functions of Stem

  • Following are the significant functions of a stem −

    • Stems keep plant upright and support leaves, flowers, and fruits.

    • Stems comprise xylem and phloem (tissues) that transport fluids and nutrients between root and shoot.

    • Stems store nutrients and produce new cells and tissues.

Types of Stems

  • Stems are usually categorized as −

Underground Stem

  • The stem that grows inside the soil is known as underground stem. E.g. Potato.

  • Such type of stems store food for contingency period.

Subaerial Stem

  • The stem, which partial remains inside the soil and partial above (i.e. in the air), is known as subaerial stem. E.g. Cynodon


Aerial Stem

  • The stem, which entirely remains in the air (i.e. out-side of soil or water), is known as aerial stem. E.g. passiflora, grapes, etc.


Modification of Stems

  • Sometimes, stems perform some specific task (other than their regular task), for which they change their shapes and sizes.

  • The following table illustrates some of the examples that modified stems −

Location Type Example
Underground Modified Stem Bulb Garlic, Onion, etc.
Corm Saffron, Crocus, etc.
Stem tuber Potato
Rhizome Ginger
Subaerial Modified Stem Stolon Jasmin, Straberi, etc.
Offset Water plant, Pistia, etc.
Sucker Roses, Musa, etc.
Runner Mereilia, Cynodon, etc.
Aerial Modified Stem Stem thorn Lemon, Citrus
Stem tendril Grape
Phylloclade Cactus, Opuntia
Bulbils Ruscus, Agave
Tendril Passiflora

Biology - The Plant Leaf


  • Leaves, usually, are thin and flattened organs, borne above ground.

  • There are varieties of leaves in terms of shapes, sizes, and textures. Likewise, different species of plants have different shapes, sizes, and textures of leaves.

  • Some varieties of leaves are thick and juicy (especially of succulent plants).

  • Leaves are usually of green color because of the presence of chloroplast.

  • However, some show plants have colorful leaves (see image given below) −

Colorful Leaves
  • Succulent plants often have thick juicy leaves, but some leaves are without major photosynthetic function and may be dead at maturity, as in some cataphylls and spines (see image given below).

Thick Leaves

Functions of Leaves

  • Following are the major functions of leaves −

    • Leaves prepare food through photosynthesis.

    • Leaves are the most important parts through which plants respire.

    • Some leaves also store foods for the contingency period.

    • Leaves assist in reproduction and pollination.

    • Some leaves (especially of succulents plants – shown above), store chemical energy and water.

Modified Leaves

  • To survive in an adverse environment, some of the plant species (especially leaves) modified themselves. Following are the list of such leaves −

  • Spine leaves − Such leaves are look like spines, e.g. cactus plants (see image below).

  • Bract leaves − Also known as pseudanthia (or false flowers), they are colorful leaves (see image below).

  • Succulent leaves − These leaves store water and organic acids (see image below).

  • Tendril leaves − Such leaves take the form of tendril and support plant to climb, e.g. pea plants (see image below).

  • Scaly leaves − Some leaves modify themselves to protect buds known as scaly leaves, e.g. onion, garlic, etc. (see image below).

  • Hook leaves − Such leaves modified as nails known as hook leaves, e.g. Bignonia (see image below).

Modified Leaves
  • Pitcher leaves − Such leaves trap insects, e.g. pitcher plant. This is known as carnivorous plant (see image given below).

Pitcher Leaves

Biology - The Flowers


  • Flowers, as all of us interpret, are the beautiful parts of the plants, which beautify the environment by their enthralling colors and decisive fragrance.

  • But flower is biologically the reproductive part of the plant.


Functions of Flower

  • Following are the major functions of a flower −

    • The primary function of a flower is reproduction by the process of the union of sperm with eggs.

    • Depending upon the inherent property, flowers may facilitate selfing, which means fusion of sperm and egg from the same flower OR it may facilitate outcrossing, which means fusion of sperm and eggs from different individuals in the respective population.

    • The flowers produce diaspores (consisting of a seed or spore) without fertilization.

    • The flower is the site where gametophytes (is the sexual phase) develop.

    • Some of the flowers fascinate animals, birds, and other insects, so as to cause them to be vectors for the transfer of pollen.

    • After sometime of fertilization, the ovary of the flower develops into fruit that contains seeds.

Parts of Flower

  • Primarily, the parts of a flower are categorized as −

    • The Vegetative Part and

    • The Reproductive Part

  • Let’s discuss them in brief −

Vegetative Part

  • Calyx − Calyx is the outermost part that consists of some units known as sepals. It is typically of green color (see the image given below).

  • Corolla − Corolla is the second (next to calyx) coil towards the apex, composed of units known as petals. Petals are usually thin, soft, and colored. It attracts insets and birds that ultimately help in pollination.

Parts of Flower

Reproductive Part

  • Androecium − It consists stamens (the male sex organ). Every stamen has three parts namely Filament, Anther, and Connective.

  • Gynoecium − It is the inner most part of the flower and consists of carpels (female sex organ).

  • Carpels consist of ovary, style and stigma, collectively known as a pistil.

Reproductive Parts Flower


  • Pollination is basically the process of movement of pollen from the anthers to the stigma.

  • When the pollens move to stigma of the same flower, it is known as self-pollination; on the other hand, if pollen move to stigma of other flower, it is known as cross-pollination.

Pollination Process

  • Pollination process occurs through different mediums (see the table) −

Process (Pollination) Medium (Pollination)
Anemophilous By air
Entomophilous By insects
Hydrophilous By water
Chiropteriphilous By bats
Malacophilous By shells
Ornithophilous By birds
Zoophilous By animals

Biology - The Fruit


  • For the common people, fruits are nutritious and delicious edible things, but for a botanist, fruits are the seed-bearing structure found in flowering plants.

  • During the ancient period or even today, many of the animals including human beings are dependent on fruits (for their survival).

  • Likewise, fruit is usually fleshy seed-associated structures of a plant, which is edible in the raw state (not all types of fruits are edible, as some are poisonous) and tastes sweet or sour.

Structure of the Fruit

  • The layer, usually, surrounding the seeds, is known as ‘pericarp.’

  • Formed of ovary, pericarp is the edible part of fruit.

  • The pericarp further classified as epicarp, mesocarp, and endocarp.

Seedless Fruits

  • Some fruits are seedless (such as banana), which have pretty high commercial importance.

  • Further, some fruits are scientifically developed seedless such as pineapples, grapes, etc.

Types of Fruits

  • Based on the fertilization of the flowers, fruit is classified as −

  • True Fruits − When the fruit forms in the ovary (of the flower) through fertilization is known as true fruit. E.g. strawberry.

  • False Fruits − The fruits formed some other means (other than ovary), such as calyx, thalamus, corolla, etc. known as false fruits. E.g. pear, apple, etc.

  • Further, because of verities and diversities, fruits are classified as −

  • Simple fruit − It can be either dry fruit (such as coconut, walnut, etc.) or fleshy (such as gooseberry, tomato, etc.).

  • Aggregate fruit − It is formed from single flowers, which have multiple carpels. E.g. raspberry.

  • Multiple fruit − It is formed from a cluster of flowers, e.g. pineapple, mulberry, etc.

Fruits and their Edible Parts

  • Following table illustrates the name of fruits and their edible parts −

Fruits Edible Parts
Apple Thalamus
Banana Mesocarp
Coconut Endosperm
Coriander Thalamus
Chinese date Epicarp & Mesocarp
Custurd apple Pericarp
Guava Pericarp
Grape Pericarp
Ground nut Seed leaves
Jack fruit Sepals
Lemon Juicy pore
Litchi Pulpy aerial
Mango Mesocarp
Mulberry Bract, sepals
Orange Juicy hair
Pear Thalamus
Papaya Pericarp
Tomato Pericarp
Wood apple Mesocarp

Biology - Plant Diseases


  • Like animals, plants also suffer from verities of diseases.

  • The biological agents that causing diseases to plants are known as pathogens.

Plant Disease
  • Some of the common plant pathogens are −

    • Viruses

    • Bacteria

    • Fungi

    • Nematodes

  • However, some non-pathogenic diseases (in plants) may also occur when the pH value, moisture, humidity, soil, etc. of soil change.

Viral Diseases in Plants

  • The following table illustrates the major plant diseases caused by virus −

Disease Plants Affected
Bud Blight Soy beans
Curly top Beans, tomato, sugar beets, etc.
Mosaic leaf Tomato, tobacco, corn, legume, potato, pea, sugar beet, cucumber, maize, cauliflower, sugarcane, bean, etc.
Yellowing of leaf Barley, sugar beet, potato, etc.
Spotted Wilt Virus Tomato, capsicum, etc.
Chlorosis Virus Tomato, capsicum, etc.

Bacterial Diseases in Plants

  • The following table illustrates the major plant diseases caused by Bacteria −

Disease Plants Affected
Blights Vegetable crops, fruit trees, etc.
Bacterial wilts Corn, tobacco, potatoes, alfalfa, tomatoes, etc.
Bacterial speck Fruits and leaves of different plants
Cankers Woody plants
Leaf spot Cotton, beans, peas, etc.
Soft rots Fleshy or succulent plant parts
Fire Bligh Rosebushes, pome fruit trees, etc.

Fungal Diseases in Plants

  • The following table illustrates the major plant diseases caused by Fungi −

Disease Plants Affected
Cankers Largely woody plants
Downy mildew Grains, onions, cucumbers, alfalfa, etc.
Ergot Rye, barley, wheat and other grasses
Powdery mildew Grains, legumes
Tuber diseases Potato, sweet potato, etc.
Rusts Wheat, barley, rye, oats, etc.
Root rots All types of plants
Scab Wheat, barley, rye, potato, etc.
Smuts Oats, barley, corn, wheat, grasses, etc.
Wilts Potatoes, alfalfa, etc.
Cavity spot Carrot
Leaf blight Carrot
Ring spot Brassicas

Diseases by Nematodes in Plants

  • The following table illustrates the major plant diseases caused by Nematodes −

Disease Plants Affected
Hairy root Sugar beets, potatoes, soybeans, etc.
Root lesions Different species of plants get affected
Root-knot Tomatoes, peanuts, etc.

Biology - The Blood


  • The body fluid, found in almost all multicellular fauna (animals, birds, reptiles, etc.), and responsible for transporting necessary substances such as oxygen and nutrients to different parts of the body, is known as blood.

  • Blood is basically connective tissue in the liquid form.

  • Blood is largely composed of blood cells and plasma.

  • Plasma constitutes about 55 percent of blood fluid.

  • The pH value of blood pH is ranging between 7.35 and 7.45, i.e. slightly basic.

  • Plasma is mostly water (i.e. 92% by volume) and contains dissipated proteins, glucose, hormones, mineral ions, and carbon dioxide.

  • The blood of vertebrate (animals) appears bright red when its hemoglobin is oxygenated; when it is deoxygenated, it (blood) appears dark red.

  • The blood accounts about 7 percent of the human body weight.

Functions of Blood

  • Following are the significant functions of blood in the body −

    • Transports oxygen to tissues and cells located in different parts of the body

    • Supplies nutrients (e.g. glucose, fatty acids, amino acids, etc.) to tissues and cells located in different parts of the body

    • Removes waste products (e.g. carbon dioxide, urea, etc.) and help to throw outside the body

    • Also strengthens the immune system of the body

    • Regulates the body temperature.

Blood Terminologies

  • Following are the significant terminologies that help to understand the blood −

  • Blood Cells − based on color and function blood cells are classified as Red Blood Cells (RBC) and White Blood Cells (WBC).

  • Red Blood Cells (see the image given below) consist of red pigments, known as haemoglobin, helps in oxygen transportation.

  • White Blood Cells − (WBC) increase the immune system of the body, as it fights with the harmful germs that enter in your body.

  • Platelets − Blood platelets have very important function i.e. it helps in blood clotting.

  • Lymph − Lymph is a colorless fluid, which contains specialized lymphocytes; lymphocytes are accountable for the immune responses of the body.

Blood Vessels

  • Following are the two major types of blood vessels −

    • Arteries and

    • Veins

  • Let’s discuss them in brief −


  • The blood vessels that carry oxygen-rich blood (i.e. pure blood) from heart to all different parts of the body is known as arteries.

  • Arteries usually have thick (vessels) wall because of having high blood pressure.

  • All types of arteries transport oxygen rich blood from heart to different parts of the body except ‘Pulmonary Artery.’

  • Pulmonary Artery carries carbon dioxide rich blood from heart to the lung for the oxygenation purpose.

  • The tiny networks of blood vessels are known as capillaries. Capillaries are very thin structure.


  • The blood vessels that carry carbon dioxide rich blood (i.e. impure blood) from different parts of the body back to heart are known as veins.

  • Veins usually have comparatively thin (vessels) wall.

  • The pulmonary vein carries oxygen rich blood from lung to the heart.

Biology - Blood Group


  • Based on the presence and absence of antibodies, the blood is classified into different groups.

  • Further, while classification, the presence and absence of the inherited antigenic substances also considered.

Blood Group
  • The types of blood groups are inherited and represent contributions from both the father and the mother.

ABO Blood Group System

  • In human blood, usually, there are two antigens and antibodies.

  • The two antigens are antigen A and antigen B.

  • The two antibodies are antibody A and antibody B.

  • The antigens are remaining in the red blood cells, whereas the antibodies are found in the serum.

  • Based on the antigen property, the blood group of all human beings can be classified as −

    • Blood Group A − antigen A and antibody B

    • Blood Group B − antigen B and antibody A

    • Blood Group AB − antigen A and antigen B and no antibody

    • Blood Group O − no antigen, but antigen A as well as antibody B

  • Consideration of the ABO system is the most imperative while transfusion of human blood.

  • The ABO blood group systems were first discovered by Karl Landsteiner in 1901.

Rh Blood Group System

  • The Rh system (the meaning of Rh is Rhesus) is another significant blood-group system. It is very important to match Rh system while blood transfusion.

  • Rh antigen first studied in Rhesus monkeys; therefore, its name is given Rh factor/system.

  • The person who does not have Rh antigen is known as Rh negative (Rh-ve) and the person who has the Rh antigen is known as Rh positive (Rh+ve).

Blood Transfusion

  • Based on the above discussed two blood grouping system (i.e. ABO and Rh), the following table illustrates the possibilities of blood transfusion among different blood groups −

Recipient Donor
O- O+ A- A+ B- B+ AB- AB+
O- Yes No No No No No No No
O+ Yes Yes No No No No No No
A- Yes No Yes No No No No No
A+ Yes Yes Yes Yes No No No NO
B- Yes No No No Yes No No No
B+ Yes Yes No No Yes Yes No No
AB- Yes No Yes No Yes No Yes No
AB+ Yes Yes Yes Yes Yes Yes Yes Yes


  • Based on the blood transfusion table given above the blood group O- is the universal donor, which can give blood to the person of any blood group.

  • Secondly, the blood group AB+ is the universal recipient, as it can accept blood from the person of any blood group.

Biology - Human Brain


  • The brain of a human being is the central organ of the nervous system.

  • The human brain consists of three parts namely the cerebrum, the brainstem and the cerebellum.

Human Brain
  • The brain of a human being plays significant role, as it controls most of the activities of the human body.

  • The brain is located inside the head, and protected by the skull bones.

  • The brain consists of more than 86 billion neurons and almost equal number of other cells as well.

  • Brain activity is made possible because of the interconnections of all the neurons that are linked together.

  • The study of brain functions is known as neuroscience.

  • An adult human brain weighs about 1.2 to 1.4 kg (i.e. average weight); which is about 2% of the total body weight.

Parts of Human Brain

  • A human brain is primarily classified as the −

    • Forebrain

    • Midbrain

    • Hindbrain

  • Forebrain is largely made up of cerebrum, thalamus, hypothalamus and pineal gland.

  • Midbrain is largely made up of a portion of the brainstem.

  • Hindbrain largely made up of the remaining brainstem, cerebellum and pons.

  • Further, the (brain) hemisphere is conventionally classified into four lobes namely −

    • Frontal lobe

    • Parietal lobe

    • Temporal lobe

    • Occipital lobe

  • The naming is done according to the skull bones that overlie them.

Parts of Brain


  • Divided into nearly symmetrical left and right hemispheres by a deep groove, the cerebrum is the largest part of the human brain.

  • Cerebrum normally controls higher brain functions including language, logic, reasoning, and creativity.

Functions of Human Brain

  • Major functions of human brain are −

    • Perceive or sense the signal coming from the (external) environment

    • Giving sense of feelings and emotion

    • Regulating and controlling the human behaviors

    • Regulating and controlling the physical action

    • Regulating the memory function

    • Process of thinking (and other cognitive process)

Biology - Skeleton System


  • The human Skeleton system is an internal structure that provides support and strength to human body.

  • At the birth, there are about 300 bones, but over period time, specifically at maturity, the number of bones is 206.

Humans Skeleton

Classification of Bones

  • Human Skeleton system broadly classified into −

    • Axial skeleton and

    • Appendicular skeleton

  • Let’s discuss them in brief −

Axial Skeleton

  • With the total 80 bones, the axial skeleton consists of −

    • Vertebral column

    • Rib cage

    • Skull and other associated bones

Appendicular Skeleton

  • With total 126 bones, the appendicular skeleton consists of −

    • Pectoral girdles

    • Upper limbs

    • Pelvic girdle

    • Pelvis

    • Lower limbs

  • The image given below illustrates the names of the major bones of a human body.

Human Skeleton

Functions of Bones

  • Following are the major functions of skeleton system −

    • It provides support to the body

    • It protects many parts of the body, e.g. the skull protects brain; the vertebrae protect spinal cord; the rib cage protects lungs; the spine protects heart, and the sternum protects blood vessels

    • The skeleton system helps in movement

    • The skeleton system helps in the production of blood cells

    • The skeleton system stores minerals

    • The skeleton system helps in endocrine regulation

Biology - Endocrine System


  • The endocrine system is study of the glands of an organism that secrete hormones directly into the circulatory system.

  • The organs through which the life running hormones are secreted are known as endocrine glands or simply ductless glands.

  • The hormone secreting glands are located in different parts of a human body (see the image given below).

Endocrine System
  • The scientific study of the endocrine system and its disorders is known as endocrinology.


  • The hormone is a complex but very important chemical substance released by the different glands in the body.

  • The hormone is mainly made up of amino acid, catecholemines, and steroids.

  • It is the hormone which is responsible for the overall growth and development; safety and security; behavior, sexual characteristics, and reproductive activities of a human body.

Types of Endocrine System

  • Following are the major types of endocrine system −

    • Hypothalamus

    • Pineal Gland

    • Pituitary Gland

    • Thyroid Gland

    • Parathyroid Gland

    • Adrenal Gland

    • Pancreas Gland

    • Reproductive Gland (Ovaries & Testes Glands)

  • Let’s discuss these glands in brief −


  • It is located at the base of the brain.

  • It releases Growth hormone-releasing hormone, Somatostatin hormone, etc., important for the growth.

Pineal Gland

  • It is located at the base of the brain.

  • It releases melatonin hormone helpful in lowering the core body temperature.

Pituitary Gland

  • With the size of a pea, the pituitary gland is found at the base of the human brain.

  • The average weight of pituitary gland is about 0.5 grams.

  • It is also known as hypophysis.

  • Following are the hormones secreted by the pituitary gland −

    • Growth hormone (somatotropin) − It is abbreviated as GH and it stimulates growth and cell reproduction.

    • Thyroid-stimulating hormone (thyrotropin) − It is abbreviated as THS and it stimulates iodine absorption by thyroid gland.

    • Adrenocorticotropic hormone (corticotropin) − It is abbreviated as ACTH and it stimulates corticosteroid and androgen.

    • Beta-endorphin − it inhibits perception of pain.

    • Prolactin − it stimulates milk synthesis and release from mammary glands.

Thyroid Gland

  • Thyroid gland is located just below the larynx in the throat (pharynx).

  • The hormone secreted by the thyroid gland is known as thyroxine.

  • Following are the important hormones secreted by the thyroid gland −

    • Triiodothyronine(T3) − It stimulated body oxygen and energy consumption. It also promotes protein synthesis.

    • Thyroxine − It increases the basal metabolic rate.

    • Calcitonin − It stimulates osteoblasts and bone construction.

Parathyroid Gland

  • It is located in the neck of a human body.

  • It releases parathyroid hormone that helps in regulating the amount of calcium in the blood as well as within the bones.

Adrenal Gland

  • Adrenal gland is found above the kidneys.

  • It releases the following major hormones −

    • Glucocorticoids − It stimulates gluconeogenesis and fat-breakdown in adipose tissue.

    • Mineralocorticoids − It stimulates active sodium reabsorption in kidneys.

    • Adrenaline − It increases the supply of oxygen and glucose to the brain and muscles.

    • Dopamine − It increases heart rate and blood pressure.

    • Enkephalin − It regulates pain.

Pancreas Gland

  • Pancreas gland is located in the abdominal cavity (behind the stomach).

  • Pancreas is a mixocrine gland, as it releases both enzymes and hormones.

  • It releases the following major hormones −

    • Insulin − It regulates the metabolism of carbohydrates, proteins, and fats.

    • Glucagon − It raises the concentration of glucose in the bloodstream.

    • Somatostatin − It inhibits release of insulin and glucagon.

Reproductive Gland

  • The reproductive gland is classified as Testes in Male and Ovary in Female.

  • Testes releases androgens (hormone) that help in strengthening muscle, increasing bone density, maturation of sex organs.

  • Ovary releases progesterone hormone that helps during pregnancy period.

Biology - Endocrine Diseases


  • The diseases caused by either the deficiency or excessive of hormones is known as endocrine diseases.

  • The branch of medicine that studies the endocrine disorders is known as endocrinology.

The List of Endocrine Diseases

  • The following table illustrates the endocrine diseases −

Glucose Homeostasis Disorders
Diseases Types Result
Diabetes Mellitus Type 1 Diabetes Increases sugar levels
Type 2 Diabetes
Gestational Diabetes
Hypoglycemia Idiopathic hypoglycemia Decreases sugar level (below normal)
Glucagonoma Cause: Because of the overproduction of glucagon hormone tumor of the pancreas
Thyroid Disorders
Goiter Cause: deficiency of iodine swelling of the neck or larynx
Hyperthyroidism (excessive production of thyroid hormone) Graves-Basedow disease Muscle weakness, sleeping problems, diarrhea, weight loss, etc.
Toxic multinodular goitre
(low release of thyroid hormone) Poor ability to tolerate cold, a feeling of tiredness, constipation, depression, and weight gain
Thyroiditis Hashimoto’s thyroiditis Inflammation of the thyroid gland
Thyroid cancer Nodule in the thyroid region of the neck
Metabolic Bone Disease
Parathyroid gland disorders Primary hyperparathyroidism Alterations in the blood calcium levels and bone metabolism
Secondary hyperparathyroidism
Tertiary hyperparathyroidism
Osteoporosis Bone weakness
Paget's disease of bone Weakening of bones
Rickets and Osteomalacia Child disease (because of vitamin D deficiency)
Pituitary Gland Disorders
Diabetes insipidus Excessive thirst and excretion of large amounts of severely dilute urine
Pituitary tumors Pituitary adenomas
Cushing's disease
Sex Hormone Disorders
Intersex disorders Hermaphroditism
Gonadal dysgenesis
Androgen insensitivity syndromes
Genetic and chromosomal disorders Kallmann syndrome
Klinefelter syndrome
Turner syndrome
Acquired disorders Ovarian failure
Testicular failure
Disorders of Puberty Delayed puberty
Precocious puberty
Menstrual function or fertility disorders Amenorrhea
Polycystic ovary syndrome

Biology - Carbohydrate


  • Consisting of oxygen (O), carbon (C), and hydrogen (H), carbohydrate is a biological molecule.

  • Carbohydrate is one of the essential elements for the living organisms, as it plays various important roles.

  • Carbohydrate is the main source of energy, as about two-third energy requirement of living beings is fulfilled by it.

  • Glucose, sugar, and starch are the important examples of carbohydrate.

Source of Carbohydrate

  • Carbohydrates naturally are occurring in wide variety of foods, such as −

    • Wheat

    • Maize

    • Rice

    • Potatoes

    • Sugarcane

    • Fruits

    • Table sugar

    • Bread

    • Milk

  • Sugar that we eat in our everyday life is mainly sucrose (table sugar).

  • Sucrose is added in many food items while preparing, e.g. jam, biscuits, cakes, energy drinks, etc.

  • Further, many fruits naturally contain glucose and fructose.

  • Glycogen is another type of carbohydrate that found in the liver and muscle.

  • Cellulose found in the cell wall of plant cells is carbohydrate.

Types of Carbohydrate

  • The following table illustrates major categories and sub-categories of carbohydrate −

Class Subgroup Components
Sugar Monosaccharides Glucose, fructose, xylose, galactose
Disaccharides Sucrose, lactose, maltose, trehalose
Polyols Sorbitol, mannitol
Oligosaccharides Malto-oligosaccharides Maltodextrins
Other oligosaccharides Raffinose, stachyose, fructo-oligosaccharides
Polysaccharides Starch Amylose, amylopectin, modified starches
Non-starch polysaccharides Cellulose, hemicellulose, pectins, hydrocolloids

Functions of Carbohydrate

  • Following are the major functions of carbohydrates −

    • Carbohydrates provide energy required for the proper function of the body.

    • Carbohydrates also store food in the body for the contingency period.

    • Carbohydrates form nucleic acids.

    • Carbohydrates also support skeleton system of animals.

    • Carbohydrates provide sweetness and flavor.

    • Carbohydrates break down the fatty acid.

Biology - Proteins


  • Proteins, which are basically biomolecules, play wide range of functions in the body of a living organism.

  • Proteins are made up of tiny elements of different types of amino acids.

  • A sequence of amino acid residues in a protein is known particularly by the sequence of a gene; gene is encoded in the genetic code.

  • After formation, proteins exist for a fixed period of time and are then degraded and recycled.

  • The proteins get recycled by the cell's machinery by the process of protein turnover.

  • Most of the proteins contain linear polymers made up of series of up to 20 different L-α-amino acids.

  • The amino acids in a polypeptide chain are connected by peptide bonds (see the image given below).

Peptide Bond
  • The peptide bond, usually, has two resonance forms, which contribute some double-bond characters.

Protein Structure

  • Most of the proteins illustrate unique 3-dimensional structures (see image given below).

Protein Structure
  • However, proteins have not a rigid structure, but rather, proteins may vary between several related structures especially when they perform their functions.

Functions of Proteins

  • Following are the major functions of proteins −

    • In the cell, proteins are the chief actors that carry out the duties defined by the information encoded in genes.

    • Proteins are essential for the overall body growth.

    • Proteins play a role of bio-catalyst and biotic regulator.

    • Proteins provide instant energy especially during the emergency period.

    • Proteins help in catalyzing the metabolic reactions.

    • Proteins are the essential elements in DNA replication.

    • Proteins actively help in transporting molecules from one location to another in the body.

Types of Protein

  • Following are the major types of protein −

    • Enzymes − enzymes play important role especially during the breakdown of molecules. Enzymes are also required for the digestion and growth of the cell.

    • Structural Proteins − such type of proteins provide strength to cells, tissues, and organs.

    • Signaling Proteins − Such proteins facilitate cells to communicate with each other by providing signals.

    • Defensive Proteins − Such proteins help organisms to fight with infection and support damaged tissue in healing fast.

    • Hormone − Some hormones are proteins that help in metabolic activities.

Biology - Fats


  • Fat is a significant foodstuff for many forms of life.

  • Fats serve structural as well as metabolic functions.

  • The fats are molecules made up of glycerol and fatty acid.

  • Fat is an organic compound of hydrogen, carbon, oxygen.

  • Based on the number and bonding of the carbon atoms, fats and oils, are categorized in the aliphatic chain.


Functions of Fats

  • Following are the major functions of Fats −

    • Fat is a vital dietary requirement.

    • The fat is usually the stored source of energy in the body that remained store beneath the skin.

    • Fat acts a protective layer especially in the human body and provide protection.

    • Some of the vitamins such as vitamin A, vitamin D, vitamin E, and vitamin K are fat-soluble, which means they can only be absorbed, digested, and transported in conjunction with the fats.

    • Fats actively help in maintaining the healthy skin and hair.

    • Fats insulate body organs against external shock.

    • Fats also maintain body temperature.

    • Fats promote healthy cell function.

Types of Fats

  • Following are the major types of Fats −

Unsaturated Fats

  • The fats that remain in the liquid form at room temperature are known as unsaturated fats.

  • Unsaturated fats are beneficial for health, as it improves blood cholesterol levels, stabilize heart beats, etc.

  • Unsaturated fats are commonly found in vegetable oils, nuts, and many seeds.

Saturated Fats

  • Saturated fats have no double bonds between the carbons found in its chain.

  • Saturated fats can easily solidify and typically found in solid form at room temperature.

  • Saturated fats are found in animals’ meat, cheese, ice cream, etc.

Biology - Vitamins


  • Vitamin is one of the most essential organic compounds that organisms require for the growth and maintenance of the body.

  • Unlike other nutrients, vitamins are classified by their biological and chemical activity, instead of their structure.

  • The term vitamin was derived from a compound word namely "vitamin."

  • The Polish biochemist Kazimierz Funk, first used the compound word ‘vitamin’ in 1912.

  • Usually, vitamins are represented by the English capital letters, e.g. A, B, C, E, etc.

  • The body of a human being stores different vitamins widely; the vitamins A, D, and B12 are stored in substantial amounts, generally in the liver.

  • Deficiency of vitamins causes disease.

  • Based on solubility, vitamins are classified as water soluble vitamins and fat soluble vitamins.

  • Water-soluble vitamins can dissolve easily in water.

  • On the other hand, fat-soluble vitamins can be dissolved easily in fat.

  • Further, fat-soluble vitamins get absorbed easily through the intestinal tract.

List of Vitamins

  • By the time, thirteen vitamins are comprehensively recognized.

  • The following table illustrates the list of vitamins with their properties −

Vitamins Chemical Name Solubility Deficiency disease
Vitamin A Retinol Fat Night blindness, keratomalacia, etc.
Vitamin B1 Thiamine Water Beriberi
Vitamin B2 Riboflavin Water Ariboflavinosis, glossitis, etc.
Vitamin B3 Niacin Water Pellagra
Vitamin B5 Pantothenic acid Water Paresthesia
Vitamin B6 Pyridoxine Water Anemia
Vitamin B7 Biotin Water Dermatitis
Vitamin B9 Folic acid Water Megaloblastic anemia
Vitamin B12 Cyanocobalamin Water Pernicious anemia
Vitamin C Ascorbic acid Water Scurvy
Vitamin D Cholecalciferol Fat Rickets
Vitamin E Tocopherols Fat Hemolytic anemia (in children)
Vitamin K Phylloquinone Fat Bleeding diathesis

Functions of Vitamins

  • Vitamins have different biochemical functions, significant of them are −

    • Like hormone, vitamin D regulates and helps in mineral metabolism

    • Vitamin D also regulates and helps cells and tissue growth

    • Vitamin C and vitamin E act as antioxidants

    • Vitamin B complex acts as co-enzymes or the precursors of enzymes and helps them as catalysts in metabolic activities.

Biology - Minerals


  • Mineral is a chemical element essentially required as nutrient for the proper functioning of the body and healthy life.

  • Minerals cannot be made by living organisms, rather it occurs in the Earth naturally.

  • Most of the minerals that required for the proper function of a human life come from green plants, animals, and from drinking water.

  • Calcium, phosphorus, potassium, sodium, and magnesium are the five major minerals in the human body.

  • Minerals are present in the blood of a healthy human being at certain mass.

Major Minerals

  • The following table illustrates the list of major minerals along with their salient features −

Minerals Deficiency disease Sources
Potassium Hypokalemia Sweet potato, potato, tomato, lentils, banana, carrot, orange, etc.
Chlorine Hypochloremia Table salt
Sodium Hyponatremia Table salt, sea vegetable, milk, etc.
Calcium Hypocalcaemia Eggs, canned fish, dairy products, nuts, etc.
Phosphorus Hypophosphatemia Red meat, fish, bread, dairy products, rice, oats, etc.
Magnesium Hypomagnesemia Legumes, nuts, seeds, spinach, peanut butter, etc.
Iron Anaemia Meat, seafood, beans, nuts, etc.
Zinc Hair loss, diarrhea Red meat, nuts, dairy products, etc.
Manganese Osteoporosis Grains, nuts, leafy vegetables, legumes, seeds, tea, coffee
Copper Copper deficiency Seafood, oysters, nuts, seeds
Iodine Goitre Grains, eggs, iodized salt
Chromium Chromium deficiency Broccoli, grape juice, meat, etc.
Molybdenum Molybdenum deficiency Legumes, whole grains, nuts
Selenium Selenium deficiency Brazil nuts, meat, seafoods, grains, dairy products, etc.

Biology - Genetic Terminology

  • The following table illustrates the major Genetic Terminologies along with their brief explanations −

Sr.No. Terminology & Definition/Description


An alternative form of a gene



A silent gene


Angelman syndrome

a rare genetically inherited form of mental retardation



Synonymous with somatic chromosomes



An exceptionally rare person composed of the cells derived from different zygotes



Rod-shaped or thread-like structures located within the cell nucleus that carry genes encoded by DNA


Cloned gene

A recombinant DNA molecule along with the gene of interest



Having a common ancestor, i.e., blood relations


Crossing over

The exchange of genetic material between a pair of homologous chromosomes



Mating of two genetically different plants (but of the same species).


Dizygotic twins

Twins produced from two separate ova, which are separately fertilized


Deoxyribonucleic acid (DNA)

Composed of nucleic acids, DNA encodes the genes that facilitate genetic information to be passed to offspring.



Genetic change in a population of organisms over period of time



A reproductive sex cell (i.e. ovum or sperm)



Units of inheritance typically occurring at specific locations (a chromosome)


Gene Pool

All of the genes in all of the individuals in a breeding population


Gene Flow

The transference of genes from one population to another


Genetic Drift

Evolution, or change in gene pool frequencies, resulting from a random chance



Study of gene structure, action, and the patterns of inheritance of traits from parent to offspring



The full genetic complement of a species


Genomic imprinting

The epigenetic phenomenon by which certain genes are expressed in a parent-of-origin-specific manner



Genetic constitution of a cell (of an individual organism)



Genetically inherited metabolic disorder (or a type of arthritis)



Genetic disorder (largely inherited), problem in blood clotting



A cell containing two different alleles of a gene


Huntington's disease

An inherited disorder that results into death of brain cells



Combining the qualities of two animals or plants of different breeds, varieties, species (also known as crossbreed)



Change that occurs in DNA sequence


Observable characteristics or traits of an individual resulting from the interaction between genotype and the environment



When one gene influences two or more apparently unrelated phenotypic traits



An inherited disease categorized by recurring thick, reddish patches on skin



Genes occurring on the same chromosome



The fertilized egg is known as zygote

Organisms & their Chromosome Counts

  • The following table illustrates the number of chromosomes present in respective organisms −

Organism Scientific Name No. of Chromosomes
Carp 104
Red viscacha rat Tympanoctomys barrerae 102
Shrimp Penaeus semisulcatus 86-92
Great white shark Carcharodon carcharias 82
Pigeon Columbidae 80
Turkey Meleagris 80
African wild dog Lycaon pictus 78
Chicken Gallus gallus domesticus 78
Coyote Canis latrans 78
Dhole Cuon alpinus 78
Dingo Canis lupus dingo 78
Dog Canis lupus familiaris 78
Dove Columbidae 78
Golden Jackal Canis aureus 78
Gray wolf Canis lupus 78
Maned wolf Chrysocyon brachyurus 76
American black bear Ursus americanus 74
Asiatic black bear Ursus thibetanus 74
Brown bear Ursus arctos 74
Polar bear Ursus maritimus 74
Sloth bear Melursus ursinus 74
Sun bear Helarctos malayanus 74
Bat-eared fox Otocyon megalotis 72
Black nightshade Solanum nigrum 72
White-tailed deer Odocoileus virginianus 70
Elk (Wapiti) Cervus canadensis 68
Red deer Cervus elaphus 68
Gray fox Urocyon cinereoargenteus 66
Raccoon dog Nyctereutes procyonoides 66
Chinchilla Chinchilla lanigera 64
Echidna 63/64
Fennec fox Vulpes zerda 64
Horse Equus ferus caballus 64
Spotted spunk Spilogale x 64
Mule 63
Donkey Equus africanus asinus 62
Giraffe Giraffa camelopardalis 62
Gypsy moth Lymantria dispar dispar 62
Bengal fox Vulpes bengalensis 62
American bison Bison bison 60
Cow Bos primigenius 60
Goat Capra aegagrus hircus 60
Yak Bos mutus 60
Elephant Elephantidae 56
Gaur Bos gaurus 56
Capuchin monkey Cebus x 54
Sheep Ovis orientalis aries 54
Water buffalo Bubalus bubalis 50
Chimpanzee Pan troglodytes 48
Gorilla Gorilla 48
Orangutan Pongo x 48
Human Homo sapiens 46
Sable antelope Hippotragus niger 46
Dolphin Delphinidae Delphi 44
European rabbit Oryctolagus cuniculus 44
Giant panda Ailuropoda melanoleuca 42
Rat Rattus norvegicus 42
Rhesus monkey Macaca mulatta 42
Lion Panthera leo 38
Pig Sus 38
Tiger Panthera tigris 38
Kangaroo 16
Yellowfever mosquito Aedes aegypti 6
Spider mite 4-14
Jack jumper ant Myrmecia pilosula 2
Honeybee Apis mellifera 32

Biology - Viral Diseases

  • The following table illustrates the diseases caused by virus −

Disease Name Organs Affected Transmission
Influenza Respiratory Tract Droplets
Adenovirus Infections Lungs, Eyes Droplets, Contact Droplets
Respiratory Syncytial Disease Respiratory Tract Droplets
Rhinovirus Infections Upper Respiratory Tract Droplets, Contact
Herpes Simplex Skin, Pharynx, Genital organs Contact
Chicken pox ( Varicella) Skin, Nervous System Droplets, Contact
Measles (Rubeola) Respiratory Tract, Skin Droplets, Contact
German Measles ( Rubella) Skin Droplets, Contact
Mumps (Epidemic Parotitis) Salivary Glands, Blood Droplets
Viral meningitis Headache
Small Pox (Variola) Skin, Blood Contact, Droplets
Warts Kawasaki Disease Skin
Yellow Fever Liver, Blood Mosquito
Dengue Fever Blood, Muscles Mosquito
Hepatitis A Liver Food, Water, Contact
Hepatitis B Liver Contact with body Fluids
NANB Hepatitis Liver Contact with body Fluids
Viral Gastroenteritis Intestine Food, Water
Viral Fevers Blood Contact, arthropods
Cytomegalovirus Disease Blood, Lungs Contact, Congenital transfer
Shingles (varicella zoster virus) Skin
AIDS T-lymphocytes Contact with body Fluids
Rabies Brain, Spinal cord Contact with body Fluids
Polio Intestine, Brain, Spinal Cord Food, Water, Contact
Slow Virus Disease Brain
Viral pneumonia infection in lung
Arboviral Enephalitis Brain Arthropods
Ebola Whole body bodily fluids

Biology - Bacterial Diseases

  • The following table illustrates the diseases caused by bacteria −

Disease Name Bacteria Name Affected organs
Cholera Vibrio cholerae Small intestine
Anthrax Bacillus Anthrasis Skin, lung, and bowel disease
Diphtheria Corynebacterium diphtheriae Mucous membranes of your nose and throat
Leprosy Mycobacterium leprae Skin
Botulism Clostridium botulinum
Syphilis Treponema pallidum Genital part, lips, mouth, or anus
Tetanus Clostridium tetani Muscle (affected), nervous system
Trachoma Chlamydia trachomatis Eye
Tuberculosis Mycobacterium tuberculosis Lungs
Typhoid fever Salmonella typhi Almost of whole part of the body
Whooping cough Bordetella pertussis

Some Other Diseases

Disease Name Caused by Affected organs
Athlete’s foot Epidermophyton floccosum (fungi) Skin on the feet
Malaria Plasmodium vivax (Protozoa)
Amoebic dysentery Entamoeba histolytica Intestine
Filariasis Roundworms Lymph vessels
Hookworm disease Ancylostoma duodenale Intestine and lungs
Roundworm disease Ascaris lumbricoides Intestine
Blood fluke disease Schistossoma mansoni Skin, lymph, liver, and spleen

Biology - Branches of Biology

  • The following table illustrates the different branches of biology with their brief description −

Branch Studies
Anatomy Study of the internal structure of an organism
Aerobiology Study of airborne microorganisms
Agronomy Study of soil management and crop production
Agrostology Study of grasses
Araneology Study of spiders
Actinobiology Study of the effects of radiation upon living organisms
Angiology Study of the diseases of the circulatory system and of the lymphatic system
Bioinformatics of collecting and analyzing complex biological data including genetic codes through computer technology
Biotechnology Use of cellular and biomolecular processes to develop technologies and products, which ultimately help to improve human lives and the health of the planet.
Biochemistry Study of chemical and physio-chemical processes and substances, which occur within the living organisms.
Batrachology Study of amphibians including frogs and toads
Bioclimatology Study of the interactions between the biosphere and the Earth's atmosphere on time scales
Botany Study of plants
Bryology Study of mosses and liverworts
Cytology Study of the structure and function of plant and animal cells.
Cryobiology Study of biological material or systems at temperatures below normal
Chromatology Study of colors
Cetology Study of whales, dolphins, and porpoises
Chronobiology Study of periodic (cyclic) phenomena in living organisms
Conchology Study of mollusc shells
Chondrology Study of the cartilage
Craniology Study of the shape and size of the skulls of different human races
Cardiology Study of the diseases and abnormalities of the heart
Dendrology Study of trees
Dermatology Study of skin
Desmology Study of structures and anatomy of ligaments
Embryology Study of the prenatal development of gametes (sex cells), fertilization, and development of embryos and fetuses.
Ecology Study of interactions among organisms and their environment
Ethology Study of animal behaviors
Entomology Study of insects
Etiology study of causation, or origination (largely of diseases)
Epigenetics Study of the changes in a chromosome that affect gene activity and expression (specifically phenotype change and NOT genotype changes)
Ethnobotany Study of a geographic region's plants and their possible uses through the traditional knowledge
Forestry Study creating, managing, using, conserving, and repairing forests
Gynaecology Study of medical practice that deals with the health of the female reproductive systems
Gerontology Study of the process of ageing and old age problems
Genetics Study of genes, genetic variation, and heredity
Genecology Study of genetic variation of species and communities in comparison to their population
Genetic engineering Study of developing technique of direct manipulation of an organism's genome by using biotechnology
Horticulture Study of practice of garden cultivation
Helminthology Study of parasitic worms
Herpetology Study of reptiles (including amphibians)
Hepatology Study of liver
Haematology Study of blood, its problems and treatments
Histology Study of tissue
Ichthyology Study of fishes
Ichnology Study of traces of organismal behavior
Kalology Study of beauty
Lepidopterology Study of moths and the butterflies
Limnology Study of inland waters (emphasizing of biological, physical, and chemical features)
Limnobiology Study of animals and plants of fresh water
Molecular biology Study of the structure and function of the macromolecules (such as proteins and nucleic acids)
Malacology Study of the Mollusca
Mycology Study of fungi
Nephrology Study of kidney
Neurology Study of nervous system
Ornithology Study of birds
Ophthalmology Study of eye
Osteology Study of skeleton system
Palaeozoology Study of animal fossils
Physiology Study of normal functioning of living organisms
Pathology Study of disease and a major field in modern medicine and diagnosis
Palaeobotany Study of plant fossils
Phycology Study of algae
Pomology Study of fruits
Phrenology Study of specific functions of brain
Sedimentology Study of sand, silt, clay, etc.
Serpentology Study of snakes
Saurology Study of lizards
Sitology Study of food, diet, and nutrition
Spelaeology Study of caves
Taxonomy Study of nomenclature (classification) of animals
Trophology Study of nutrition (for healthy health)
Traumatology Study of wounds and injuries caused by accidents (or violence)
Zoogeography Study of distribution of animals
Zymology Study of the biochemical process of fermentation and its practical uses
Zootechny Study of domestication of animals (includes breeding, genetics, nutrition, and housing)
Zoonosology Study of animal diseases'
Zoology Study of animals

Biology - Inventions & Discoveries in Biology

  • The following table illustrates important inventions and discoveries in Biology −

Name of inventions/discoveries Discoverers & Inventors
Systemic circulation of blood William Harvey
Observation of microorganisms Antony van Leeuwenhoek
Sex hormones Eugen Stainak
Simple microscope Anton van Leeuwenhoek
Stethoscope René Laennec
First test tube baby Robert Edward and Patrick Steptoe
Vaccination Edward Jenner
Vitamin Casimir Funk
CT scan Godfrey Hounsfield & Allan Cormack
DNA Rosalind Franklin and Maurice Wilkins
DNA Structure James Watson and Francis Crick
DNA Fingerprinting Alec Jeffreys
Electrocardiogram (ECG) Willem Einthoven
5 kingdom classification R. H. Whittaker
Genetic code Marshall Nirenberg and Heinrich J. Matthaei
Genetic drift Sewall Wright
Father of heart transplantation Norman Shumway
Heart transplantation first performed Christiaan Barnard
Hormone William Bayliss
Insulin Frederick Banting and Charles H. Best
Malaria Parasite Charles Louis Alphonse Laveran
Magnetic Resonance Imaging (MRI) Damadian
Open heart surgery Dr. Daniel Hale Williams. And Dr. Daniel Williams
Penicillin Alexander Fleming
Polio vaccine Jonas Salk and a team
Rh factor in human blood Dr. Alexander S. Wiener and Karl Landsteiner
Cancer Hippocrates
Blood group (ABO group) Karl Landsteiner
Binomial nomenclature Carl Linnaeus
Bacteria (& protozoa) Van Leeuwenhoek
Aspirin Felix Hoffmann at Bayer in Germany
Jarvik-7 (first artificial heart) Willem Johan Kolff and Robert Jarvik
Anthrax vaccine Pasteur
Amoeba August Johann Rösel von Rosenhof
Oxygen in respiration and photosynthesis Joseph Priestley, Antoine Lavoisier and Jan Ingenhousz
Animal electricity Luigi Galvani
Cell Robert Hooke
Cell Theory Schleiden and Schwann
Chromosomes Hofmeister
Chioroplast Schimper
Mitochondria Kolliker
Nucleus Robert Brown
Nucleoplasm Strasburger
Enzyme Anselme Payen
Mitosis Walther Flemming
Meiosis Oscar Hertwig
Mutations Thomas Hunt Morgan and Lilian Vaughan Morgan
Virus Dmitri Ivanovsky & Martinus Beijerinck

Nobel Prize in Biology


Gerty Cori

  • Cori, a Czech-American biochemist, was the first woman to be awarded the Prize in Physiology or Medicine.

  • She received the prize in 1947.

  • She was the third woman and first American woman who won a Nobel Prize in science.

Gerty Theresa Cori
  • She received the award for her work namely “the mechanism by which glycogen—a derivative of glucose—is broken down in muscle tissue into lactic acid and then resynthesized in the body and stored as a source of energy (known as the Cori cycle).”

  • The following table illustrates some of the eminent Nobel Prize winners −

Name Country/Year Work
Emil Adolf von Behring Germany (1901) Serum therapy
Sir Ronald Ross UK (1902) Worked on malaria
Ivan Petrovich Pavlov Russia (1904) Physiology of digestion
Albrecht Kossel Germany (1910) Cell Chemistry
Allvar Gullstrand Sweden (1911) Dioptrics of the eye
Alexis Carrel France (1912) Vascular suture and the transplantation of blood vessels and organs
Archibald Vivian Hill UK (1922) Production of heat in the muscle
Sir Frederick Grant Banting & John James Rickard Macleod Canada & UK (1923) Discovery of insulin
Karl Landsteiner Austria (1930) Discovery of human blood groups
Thomas Hunt Morgan US (1933) Role played by the chromosome in heredity
Carl Peter Henrik Dam Denmark (1943) Discovery of vitamin K
Sir Alexander Fleming UK (1945) Discovery of penicillin and its curative effect in various infectious diseases
Sir Ernst Boris Chain UK (1945)
Howard Walter Florey Austria (1945)
Carl Ferdinand Cori US (1947) Discovery of the course of the catalytic conversion of glycogen
Gerty Theresa Cori, née Radnitz
Max Theiler South Africa (1951) Yellow fever
Selman Abraham Waksman US (1952) Discovery of streptomycin, the first antibiotic effective against tuberculosis
Joshua Lederberg US (1958) Genetic recombination
Peyton Rous US (1966) Discovery of tumor-inducing viruses
Charles Brenton Huggins US (1966) Hormonal treatment of prostatic cancer
Har Gobind Khorana India & US (1968) Interpretation of the genetic code and its function in protein synthesis
Marshall W. Nirenberg US (1968)
Robert W. Holley US (1968)
Albert Claude Belgium (1974) Structural and functional organization of the cell
Christian de Duve
George E. Palade Romania (1974)
Baruch S. Blumberg US (1976) Origin and dissemination of infectious diseases
D. Carleton Gajdusek
Michael S. Brown US (1985) Regulation of cholesterol metabolism
Joseph L. Goldstein
Sir Richard J. Roberts UK (1993) Discovery of split genes
Phillip A. Sharp US (1993)
Paul Lauterbur US (2003) Magnetic resonance imaging
Sir Peter Mansfield UK (2003)
Andrew Z. Fire US (2006) Discovery of RNA interference
Craig C. Mello
Harald zur Hausen Germany (2008) Human papilloma viruses causing cervical cancer
Françoise Barré-Sinoussi France (2008) Discovery of human immunodeficiency virus
Luc Montagnier
Sir Robert G. Edwards UK (2010) Development of in vitro fertilization
Tu Youyou China (2015) Discovery of a novel therapy against Malaria
Yoshinori Ohsumi Japan (2016) Mechanisms for autophagy