Biology
What is Biology?
Biology is the branch of science in which living organisms are studied.
Biology can be divided into two parts:
Bio = Living
Logy = Study
In other words, biology includes the study of living life.
Branches of Biology
The father of biology was Aristotle, who first studied it scientifically. Biology mainly has two branches:
- Zoology
- Botany
- Zoology: Under zoology, the life of animals and their lifestyle are studied. Its father was Aristotle.
- Botany: In botany, plants and vegetation are studied. Its father was Theophrastus.
Characteristics of Living Organisms
Living organisms have the following characteristics:
- Growth: A definite increase in the number of cells and mass is called growth.
In other words, growth always occurs in an increasing order. - Reproduction: When a cell or organism produces another cell or organism similar to itself, it is called reproduction.
- Sensitivity: The ability to adapt according to the environment is called sensitivity.
- Metabolism: Through this, all biological and chemical processes of the body are carried out.
- Self-replication: Making carbon copies of oneself through asexual reproduction is called self-replication; it is also called cloning.
Based on cells, organisms can be classified into three parts:
- Acellular
- Unicellular
- Multicellular
- Acellular: No cells are present, only DNA and RNA are present.
Example – Vishnu - Unicellular: Cells are present, DNA and RNA are present.
Examples: Amoeba, Paramecium, Euglena, etc. - Multicellular: Cells are present.
Example – Human
Nomenclature of Organisms
Nomenclature is a system to identify organisms with the same name worldwide.
ICZN – International Code of Zoological Nomenclature
Naming of animals
Example: Human → Homo sapiens
ICBN – International Code of Botanical Nomenclature
Naming of plants
Example: Mango → Mangifera indica
Fundamentals of Biology
Father of Biology: Aristotle
Father of Zoology: Aristotle
Father of Botany: Theophrastus
Biodiversity:
The total number of known species on Earth is approximately 1.7 to 1.8 million, in which animal species are the highest.
Need and Organizations of Nomenclature
Why is a scientific name needed?
Different languages and regions have different names for organisms (e.g., Mango, Aam, Amra).
To avoid confusion, a universal scientific name is needed so that organisms can be identified worldwide.
Main international organizations:
- ICZN – for animals
- ICBN – for plants
Rules of Binomial Nomenclature
Founder: Carolus Linnaeus (Father of Nomenclature)
Main rules:
- One organism has only one scientific name.
- No one name can be given to two different organisms.
- All names are written in Latin (dead language, no changes).
- Scientific names have two parts:
- First word: Genus
- Second word: Species
- Letter rule:
- Genus starts with a capital letter
- Species starts with a small letter
- Printed form: written in italics
- Handwritten: both words underlined separately
- Author’s name is written in short form at the end (e.g., Linn.)
Examples:
Mango → Mangifera indica Linn.
Human → Homo sapiens
Cellular Classification
Classification based on cells:
Acellular
No cell, only DNA/RNA and protein coat
Example: Virus
Unicellular
Prokaryotic
Example: Bacteria
Eukaryotic
Acellular Organisms: Virus
Key Features:
- No cells present
- No cell organelles (like mitochondria, Golgi body)
- Made of genetic material (DNA or RNA) and protein coat
Example: HIV Virus
Full name: Human Immunodeficiency Virus
Genetic material: RNA (2 copies)
Outer covering: lipid + protein (lipoprotein)
Structure of HIV:
- Knob – helps in attachment
- Bi-lipid layer – outer layer
- Capsid – protein coat
- Central core – inner part
- RNA (2) – genetic material
- Enzymes – Protease and Integrase
Karyology and Cell Types
Karyon = Nucleus
Logy = Study
Karyology: Study of nucleus
Types of cells based on nucleus:
- Prokaryotic
No true nucleus (example: bacteria) - Eukaryotic
True nucleus present
Prokaryotic Cell: Bacteria
Main features:
- No true nucleus
- Nucleoid present (DNA)
- Extra circular DNA called plasmid
- Ribosomes for protein synthesis
- Mesosomes for respiration
Classification
Classification means dividing organisms into groups based on characteristics, behavior, habitat, etc.
Purpose: To make study easier
Father: Carolus Linnaeus
Systems of Classification
Two Kingdom (Linnaeus):
- Plants
- Animals
Five Kingdom (R.H. Whittaker):
- Monera
- Protista
- Fungi
- Plantae
- Animalia
Taxonomy
Taxa: Scientific term used in classification
Definition: Dividing organisms into groups based on characteristics
Taxonomic Hierarchy
Trick: K-PCOFGS
Kingdom
Phylum
Class
Order
Family
Genus
Species
Species is the smallest unit
Species
A group of organisms with similar characteristics
Example: Homo sapiens
Rules:
- Homo = Genus
- sapiens = Species
- Species written in small letters
- Written in Latin and underlined
Basis of Study of Species
- Morphology: Study of external structure
- Anatomy: Study of internal structure
Conclusion: Both should be similar for classification
Recap
Biology = Study of living organisms
Botany – Theophrastus
Zoology – Aristotle
Characteristics:
Growth, Reproduction, Sensitivity, Metabolism, Diversity
Types of Organisms
Acellular: Virus
Unicellular: Bacteria
Multicellular: Human
Nomenclature and Classification Systems
ICZN – Animals
ICBN – Plants
Classification Systems
2 Kingdom – Linnaeus
5 Kingdom – Whittaker
Taxonomic Hierarchy
Kingdom
Phylum
Class
Order
Family
Genus
Species
Genus
Group of similar species
Example:
Potato → Solanum tuberosum
Genus = Solanum
Family
Group of similar genera
Examples:
Solanaceae
Panthera
Includes:
Potato, Petunia, Datura
Cheetah, Leopard, Tiger
Class
Example: Mammalia (milk-producing animals)
Carnivora: tiger, cat, dog
Phylum
Examples:
Amphibia – lives on land and water
Reptilia – crawling animals
Aves – birds
Mammalia – mammals
Kingdom
Highest category
Monera
Protista
Fungi
Plantae
Animalia
Quick Revision
Kingdom → highest
Species → smallest
Important Points (VVI)
- Father of Classification: Carolus Linnaeus
- Purpose: Easy study
- Smallest unit: Species
- Largest unit: Kingdom
- Taxa: Scientific term used in classification
