Topics
Reproduction in Organisms
Sexual Reproduction in Flowering Plants
- Flower - a Fascinating Organ of Angiosperms
- Pre-fertilisation in Flowering Plant: Structures and Events
- Structure and Development of Anther
- Microsporogenesis
- Structure and Development of Male Gametophyte
- Pollen Products
- Structure and Development of Ovule
- Megasporogenesis
- Development of Female Gametophyte or Embryo Sac
- Pollination
- Autogamy
- Geitonogamy
- Xenogamy
- Agents of Pollination
- Anemophily
- Hydrophily
- Animal-Mediated Pollination (Zoophily)
- Outbreeding Devices
- Pollen Pistil Interaction
- Artificial Hybridization or Artificial Fertilization
- Double Fertilization and Triple Fusion
- Post-fertilization Events
- Endosperm
- Embryo
- The Seed
- Apomixis
- Polyembryony
Reproduction
Genetics and Evolution
Human Reproduction
- Human Reproduction
- Overview of The Male Reproductive System
- Overview of The Female Reproductive System
- Overview of Gametogenesis
- Structure of Sperms
- Oogenesis
- Menstrual Cycle (Ovarian Cycle)
- Major Events of Menstrual Cycle
- Menstrual Hygiene
- Fertilization in Human
- Implantation in Human
- Pregnancy and Embryonic Development
- Parturition (Birth) in Human
- Lactation in Human
Reproductive Health
- Concept of Reproductive Health
- Population Explosion and Birth Control
- Methods of Birth Control and Contraceptive Devices
- Natural Contraceptive Methods
- Artificial Contraceptive Methods
- Induced Abortion or Medical Termination of Pregnancy (MTP)
- Sexually Transmitted Diseases (STD) or Sexually Transmitted Infections (STI)
- Infertility
- Assisted Reproductive Technology (ART)
- Amniocentesis
- Genetic Counselling
Biology and Human Welfare
Biotechnology
Principles of Inheritance and Variation
- Heredity and Variation
- Gregor Johann Mendel – Father of Genetics
- Mendel's Experiments on Inheritance
- Monohybrid Cross
- Punnett Square
- Back Cross and Test Cross
- Mendel's Laws > The Law of Dominance
- Mendel's Laws > The Law of Segregation (Law of Purity of Gametes)
- Exceptions to Mendel's Principles > Incomplete Dominance
- Exceptions to Mendel's Principles > Co-Dominance
- Dihybrid Cross
- Mendel's Laws > The Law of Independent Assortment
- Chromosomal Theory of Inheritance
- Linkage and Recombination
- Polygenic Inheritance
- Exceptions to Mendel's Principles > Pleiotropy
- Sex Determination
- Sex Determination in Humans
- Sex Determination in Honey Bees
- Mutations
- Pedigree Analysis
- Mendelian Disorders in Humans
- Chromosomal Disorders or Abnormalities
Environmental Issues
- Environmental Issues
- Controlling Vehicular Air Pollution: a Case Study of Delhi
- Effects of Domestic Sewage and Industrial Effluents on Water
- Solid Wastes
- Radioactive Wastes
- Greenhouse Effect and Climate Change
- Ozone Depletion in the Stratosphere
- Degradation by Improper Resource Utilisation and Maintenance
- Radioactive Waste Management and E-waste
- Environmental Issues
Molecular Basis of Inheritance
- Deoxyribonucleic Acid (DNA)
- Structure of Polynucleotide Chain
- Packaging of DNA Helix
- Search for Genetic Material
- Griffith’s Experiment
- Avery, McCarty and MacLeod’s Experiment
- The Hershey-Chase Experiment
- Properties of Genetic Material
- The RNA World
- DNA Replication
- Conservative Replication
- Dispersive Replication
- Semi-Conservative Replication
- Meselson and Stahl’s Experiment
- Enzymes used in DNA Replication
- Mechanism of DNA Replication
- Central Dogma
- Reverse Transcription (Teminism)
- Transcription
- Transcription Unit and the Gene
- Process of Transcription in Bacteria
- Process of Transcription in Eukaryotes
- Genetic Code
- Characterestic of the Genetic Code
- Mutations and Genetic Code
- tRNA – the Adapter Molecule
- Translation
- Regulation of Gene Expression
- The Lac Operon
- Human Genome Project
- DNA Fingerprinting
Ecology
Evolution
- Origin of Life on Earth
- Evolution of Life Forms - a Theory
- Evidences Supporting the Theory of Evolution
- Adaptive Radiation
- Biological Evolution
- Theories and Mechanism of Evolution
- Hardy Weinberg’s Principle
- Brief Account of Evolution
- Human Evolution
- Overview of Evolution
Human Health and Diseases
- Concept and Determinants of Health
- Modes of Transmission of Diseases through Pathogens
- Diseases Caused by Bacteria > Typhoid
- Diseases Caused by Bacteria > Pneumonia
- Diseases Caused by Viruses > Common Cold
- Diseases Caused by Protozoa > Malaria
- Diseases Caused by Protozoa > Amoebiasis (Amoeboic dysentery)
- Diseases Caused by Helminths > Ascariasis
- Diseases Caused by Helminths > Filariasis (Elephantiasis)
- Diseases Caused by Fungi > Ringworm
- Prevention and Control of Infectious Diseases
- Immunity
- Types of Immunity > Innate Immunity
- Types of Immunity > Acquired Immunity
- Active and Passive Immunity
- Vaccination and Immunization
- Allergies
- Autoimmunity
- The Immune System
- Acquired Immuno Deficiency Syndrome (AIDS)
- Cancer
- Causes of Cancer
- Symptoms and Diagnosis of Cancer
- Prevention/Treatment of Cancer
- Drugs and Alcohol Abuse
- Addiction and Dependence
- Effects of Drug and Alcohol
- Prevention and Control of Drugs and Alcohol Abuse
- Overview of Human Health and Diseases
Microbes in Human Welfare
Strategies for Enhancement in Food Production
Biotechnology - Principles and Processes
- Biotechnology
- Principles of Biotechnology
- Restriction Enzymes
- Cloning Vectors
- Competent Host (For Transformation with Recombinant DNA)
- Processes of Recombinant DNA Technology
- Overview of Biotechnology - Principles and Processes
Biotechnology and Its Application
- Biotechnology
- Biotechnological Application in Agriculture
- Biotechnological Application in Medicine
- Transgenic Animals
- Ethical Issues
- Overview of Biotechnology and Its Application
Organisms and Populations
- Organisms and Their Environment
- Ecology
- Population Attributes
- Population Growth
- Life History Variation
- Population Interactions
- Negative Interactions > Predation
- Negative Interactions > Competition
- Negative Interactions > Parasitism
- Positive Interactions > Commensalism
- Positive Interactions > Mutualism (Symbiosis)
- Overview of Organisms and Populations
Ecosystem
Biodiversity and Its Conservation
- Biodiversity
- Species on Earth and Species in India
- Patterns of Biodiversity
- Importance of Species Diversity to the Ecosystem
- Loss of Biodiversity
- Conservation of Biodiversity
- Biodiversity Conservation Methods
- Overview of Biodiversity and Its Conservation
CBSE: Class 12
Key Points: Origin of Life
- The universe originated about 13.8 billion years ago by the Big Bang, and Earth was formed about 4.5 billion years ago in the Milky Way galaxy.
- Early Earth had a reducing atmosphere with gases like methane, ammonia, hydrogen and water vapour; oceans formed as the Earth cooled.
- Life appeared about 4 billion years ago, initially in water, after the formation of oceans and the ozone layer.
- The theory of spontaneous generation was disproved by Louis Pasteur, who showed that life arises only from pre-existing life.
- Oparin–Haldane theory proposed chemical evolution of life; Miller’s experiment (1953) proved that organic molecules like amino acids could form from inorganic substances under early Earth conditions.
CBSE: Class 12
Theory: Evolution of Life Forms
- The theory of special creation claimed that all life forms were created as they are, diversity remained unchanged, and Earth was only about 4000 years old; these ideas were challenged in the 19th century.
- Charles Darwin, based on observations from the voyage of H.M.S. Beagle, proposed that life forms have evolved gradually, many became extinct, and all organisms share common ancestors.
- Darwin proposed natural selection as the mechanism of evolution, where organisms with better reproductive fitness survive and produce more offspring, leading to evolution over long geological time.
CBSE: Class 12
Key Points: Evidences Supporting the Theory of Evolution
| Evidence Type | Basis of Evidence | Key Observation | Example(s) | Conclusion |
|---|---|---|---|---|
| Palaeontological (Fossils) | Study of fossils in sedimentary rocks | Different fossils found in different geological layers | Dinosaurs, extinct organisms | Life forms existed at different times and evolved over time |
| Embryological Evidence | Study of embryos | Early embryos of vertebrates show similar features | Gill slits in vertebrate embryos | Indicates common ancestry |
| Comparative Anatomy (Homology) | Similar structure, different functions | Same basic structure adapted for different uses | Forelimbs of human, whale, bat, cheetah | Divergent evolution; common origin |
| Comparative Anatomy (Analogy) | Different structure, same function | Different organs evolved for same function | Wings of bird & butterfly; potato & sweet potato | Convergent evolution |
| Biochemical Evidence | Similarity in genes and proteins | Common molecular sequences in different organisms | Similar proteins/genes | Supports common ancestry |
CBSE: Class 12
Definition: Saltation
Evolution occurring due to sudden, large mutations leading to the formation of new species in a single step is called saltation.
