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

• 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

• 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.

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.
• Following are the three types of cell division −
  --> Amitosis
  --> Mitosis &
  --> Meiosis

Let’s discuss each of them in brief −

Amitosis

• 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.

Mitosis

• 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 −

Prophase

• 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.

Prometaphase

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

Metaphase

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

Anaphase

• In this phase two identical daughter chromosomes are formed.

Telophase

• 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

• 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

• 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

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

CViral 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)

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.

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

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 −

Arteries

• 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.

Veins

• 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.