Evolution -NEET NOTES

1. Origin of Life

1.1 Origin of Universe

The Big Bang Theory explains the origin of the universe.
Around 13.7 billion years ago, all matter and energy were concentrated at a single point.
A massive explosion (Big Bang) caused the universe to expand.
The explosion released subatomic particles and radiation, forming stars, galaxies, and planets over time.
Formation Timeline:
First few seconds: Formation of protons, neutrons, and electrons.
Few minutes later: Hydrogen and helium nuclei formed.
Millions of years later: Atoms formed, leading to the formation of stars and galaxies.
The Earth formed around 4.5 billion years ago.

1.2 Conditions of Early Earth

The early Earth was drastically different from its current form.
🌫️ Atmospheric Conditions:
Earth’s atmosphere lacked free oxygen (O₂).
It was a reducing atmosphere composed of:
- Water vapour (H₂O)
- Methane (CH₄)
- Ammonia (NH₃)
- Hydrogen (H₂)
The surface was extremely hot and volcanic.
🌩️ Environmental Conditions:
Frequent lightning, UV radiation, and volcanic eruptions were common.
The temperature was too high for water to remain in liquid form.
As the Earth cooled, water vapour condensed into oceans.
These conditions created a favourable environment for the origin of life.

1.3 Theory of Panspermia

Panspermia is a hypothesis suggesting that life originated from extraterrestrial sources.
It proposes that:
Life or its building blocks (like bacteria or spores) came to Earth through comets, meteors, or cosmic dust.
This theory lacks direct evidence but suggests that life is universal and spread across space.

1.4 Theory of Spontaneous Generation

This theory suggests that living organisms arise from non-living matter spontaneously.
Popular belief in ancient times:
Aristotle proposed that insects, worms, and mice could spontaneously arise from rotting matter.
Examples of belief:
Frogs from muddy water.
Flies from decaying meat.
This theory was later disproved by scientific experiments.

2. Louis Pasteur’s Experiment

Louis Pasteur (1861) conclusively disproved the theory of spontaneous generation.
Experimental Setup:
He used two flasks:
- Flask 1: With a curved “swan-neck” that allowed air in but trapped dust and microbes.
- Flask 2: With a broken neck, allowing dust and microbes to enter.
Both flasks contained a nutrient broth.
Observations:
Flask 1 (swan-neck): No microbial growth → The broth remained sterile.
Flask 2 (broken-neck): Microbial growth occurred due to contamination.
Conclusion:
Microbes come from pre-existing life (biogenesis), not from spontaneous generation.
This experiment supported the biogenesis theory.

3. Theory of Chemical Origin of Life

3.1 Oparin-Haldane Theory of Origin of Life

Proposed independently by:
Alexander Oparin (1924) → Russian biochemist.
J.B.S. Haldane (1929) → British scientist.
Their theory suggested that:
Life originated through a slow chemical process from simple inorganic molecules.
Steps Involved:

Formation of Simple Organic Molecules:

In the early reducing atmosphere, simple compounds like CH₄, NH₃, H₂, and H₂O interacted under UV radiation and lightning.
This resulted in the formation of organic molecules such as amino acids, sugars, and nitrogenous bases.

Polymerization:

Organic monomers combined to form complex polymers like proteins, nucleic acids, and carbohydrates.

Formation of Protobionts:

Polymers aggregated into protobionts (pre-cell structures) surrounded by a membrane-like layer.
These could carry out basic metabolic functions.

Formation of First Living Cell:

Over millions of years, protobionts evolved into the first primitive cells capable of self-replication and metabolism.

3.2 Urey and Miller Experiment

In 1953, Stanley Miller and Harold Urey tested the Oparin-Haldane hypothesis.
Experimental Setup:
They simulated the early Earth’s atmosphere:
- A mixture of CH₄, NH₃, H₂, and H₂O vapour.
- Subjected it to continuous sparks of electricity (to simulate lightning).
The system was cooled, and the resulting condensate was collected.
Observations:
After a week, they found organic compounds, including:
- Amino acids (glycine, alanine).
- Sugars and other biomolecules.
Conclusion:
Organic molecules, the building blocks of life, could be formed under prebiotic conditions.
This provided experimental support for the chemical origin of life.

4. Evolution of Life Forms – A Theory

4.1 Natural Selection

Proposed by Charles Darwin in his book “On the Origin of Species” (1859).
It is the driving force of evolution, explaining how species evolve over time.
Principles of Natural Selection:

Variation:

Individuals in a population exhibit differences in traits (size, colour, speed).

Overproduction:

Organisms produce more offspring than can survive.

Struggle for Existence:

Due to limited resources, individuals compete for survival.

Survival of the Fittest:

Individuals with favourable traits are more likely to survive and reproduce.
Those with less favourable traits are eliminated.

Inheritance of Favorable Traits:

Offspring inherit beneficial traits, making them more likely to survive.

Speciation:

Over generations, accumulated variations lead to the formation of new species.

Example of Natural Selection:

Industrial Melanism in Peppered Moths:
Before the Industrial Revolution:
- Light-coloured moths were common as they blended with lichen-covered trees.
After the Revolution:
- Dark-coloured moths increased due to industrial pollution darkening tree bark.
Conclusion: Dark moths survived better due to camouflage, proving natural selection.

5. Evidences for Evolution

5.1 Paleontological Evidences

Paleontology is the study of fossils.
Fossils provide direct evidence of evolution by showing the gradual changes in organisms over millions of years.
Fossil:
A preserved remnant or impression of an organism from the past.
Found in sedimentary rocks.
Types of Fossils:
Impression fossils: Imprints or outlines of organisms (e.g., leaf imprints).
Mold and cast fossils: Negative and positive imprints of an organism.
Petrified fossils: Organic matter replaced by minerals, turning into stone.
Amber fossils: Organisms trapped in tree resin.

Fossil Evidence Examples:

Archaeopteryx:

A transitional fossil between reptiles and birds.
Shows both reptilian and avian features:
- Reptilian traits: Teeth, tail, clawed fingers.
- Avian traits: Feathers and wings.

Horse Evolution:

Fossil records show the gradual evolution of horses:
- Eohippus → Small, multiple toes, forest-dwelling.
- Mesohippus → Larger, fewer toes.
- Equus → Modern horse with single hoof and larger size.

Hominid Fossils:

Fossils of Australopithecus, Homo habilis, Homo erectus, and Homo sapiens show the gradual evolution of humans.

5.2 Comparative Anatomy and Morphological Evidences

Comparative anatomy shows similarities and differences in the structure of organisms, providing evidence of common ancestry.
The study reveals:
Homologous structures → Common origin, different function.
Analogous structures → Different origin, similar function.
Vestigial organs → Reduced or non-functional remnants of ancestral organs.

Comparison Table:

Type of Evidence	Definition	Examples	Significance
Homologous organs	Same origin, different function	Forelimbs of humans, bats, whales	Evidence of divergent evolution
Analogous organs	Different origin, similar function	Wings of bats and insects	Evidence of convergent evolution
Vestigial organs	Non-functional remnants of ancestral organs	Appendix in humans, pelvic bones in whales	Evidence of common ancestry

5.3 Embryological Support for Evolution

Embryology: The study of development of embryos.
Proposed by Ernst Haeckel → Stated that “ontogeny recapitulates phylogeny”.
This means:
The embryonic development of an organism repeats ancestral forms.
Evidence from Embryos:

Early embryos of different vertebrates (fish, amphibians, reptiles, birds, and mammals) appear similar.
Similarities in:

Gill slits in all vertebrate embryos (even in mammals) suggest common aquatic ancestry.
Tail in human embryo indicates a reptilian-like ancestor.
Significance:
Similarities in embryonic stages indicate common evolutionary origins.
Gradual divergence during later stages shows species differentiation.

5.4 Biochemical Evidences

Biochemical similarities in different organisms provide evidence for common ancestry.
Key Biochemical Evidences:

DNA and Genetic Code:

All living organisms have DNA as their genetic material.
The universal genetic code (triplet codons) is identical across species.

Proteins and Enzymes:

Similarities in protein structure (e.g., haemoglobin, cytochrome C) suggest common ancestry.
Cytochrome C in humans and chimpanzees is almost identical.

Molecular Homology:

Similarities in DNA and protein sequences reveal evolutionary relationships.
Example: Human and chimpanzee DNA share 98-99% similarity.

Metabolic Pathways:

All living organisms share common metabolic pathways:
- Glycolysis, respiration, and protein synthesis occur in a similar way.

Immunological Evidence:

The closer the species, the more similar their immune proteins.
Example: Human and monkey blood serum shows strong immune reactions.

6. Evolution by Natural Selection

Charles Darwin proposed Natural Selection as the main mechanism of evolution.
Key Principles of Natural Selection:

Overproduction:

Organisms produce more offspring than can survive.

Variation:

Individuals within a population vary in their traits.

Struggle for Existence:

Competition for limited resources.

Survival of the Fittest:

Individuals with favourable traits survive and reproduce.

Inheritance of Favourable Traits:

Beneficial traits are passed to the next generation.

Speciation:

Over time, accumulated changes lead to the formation of new species.

Examples:

Peppered Moth (Biston betularia):

Before industrialisation:
- Light-coloured moths were more common due to better camouflage.
After industrialisation:
- Dark-coloured moths became more frequent due to industrial melanism.

Darwin’s Finches:

On the Galápagos Islands:
- Finches had different beak shapes based on their diet.
- This was due to adaptive radiation caused by natural selection.

7. Evolution by Anthropogenic (Human) Action

Humans influence the evolution of species through:
Artificial selection
Environmental changes
Pollution and genetic modifications

Examples of Human-Driven Evolution:

Antibiotic Resistance:

Overuse of antibiotics leads to the evolution of drug-resistant bacteria.
Bacteria with resistant genes survive and reproduce.

Pesticide Resistance:

Insects exposed to pesticides develop resistance through natural selection.

Industrial Melanism:

Moths adapted to industrial pollution by darkening their colour.

Selective Breeding:

Humans selectively breed plants and animals for desired traits.
Example: Cabbage, broccoli, and cauliflower are all derived from a single wild plant.

Climate Change and Evolution:

Climate change forces species to adapt or face extinction.
Example: Polar bears face habitat loss, causing evolutionary pressure.

8. Adaptive Radiation

Adaptive radiation is the evolution of different species from a common ancestor in a specific habitat.
It occurs when:
Species diversify to exploit different ecological niches.
Key Features:

Rapid Speciation:

Multiple species evolve in a short period.

Ecological Diversity:

Species adapt to different environments and resources.

Morphological Diversity:

Physical traits evolve based on the environment.

Examples of Adaptive Radiation:

Darwin’s Finches:

On the Galápagos Islands:
- Finches diversified into 13 different species.
- Each species had a unique beak shape suited to its food source.

Australian Marsupials:

From a common ancestor:
- They evolved into diverse forms such as:
- Kangaroos → Grazers.
- Koalas → Tree dwellers.
- Tasmanian devils → Carnivores.

Placental Mammals:

From a common ancestor, they radiated into:
- Herbivores (deer)
- Carnivores (tigers)
- Aerial mammals (bats)
- Aquatic mammals (whales)

9. Biological Evolution

9.1 Darwinian Theory of Evolution

Proposed by Charles Darwin in his book “On the Origin of Species” (1859).
It explains how species evolve over time through natural selection.
Key Principles:

Overproduction:

Organisms produce more offspring than the environment can support.

Variation:

Individuals within a species show variations in traits.
Variations occur due to genetic differences.

Struggle for Existence:

Individuals compete for limited resources.
Competition leads to differential survival.

Survival of the Fittest:

Individuals with favourable variations have a higher chance of survival.
They reproduce and pass on their traits to the next generation.

Inheritance of Favorable Traits:

Favourable traits become more common in future generations.

Speciation:

Gradual accumulation of variations over generations leads to the formation of new species.

Evidence Supporting Darwinian Theory:

Industrial Melanism:
Peppered moths during the Industrial Revolution.
Dark-coloured moths had a survival advantage due to camouflage.
Galápagos Finches:
Different beak shapes in finches due to adaptation to different food sources.
Antibiotic Resistance:
Bacteria evolving resistance to antibiotics due to natural selection.

9.2 Lamarck’s Theory of Evolution (Theory of Inheritance of Acquired Characters)

Proposed by Jean-Baptiste Lamarck in 1809.
It suggests that:
Organisms can acquire traits during their lifetime due to use or disuse of organs.
These acquired traits are inherited by offspring.

Key Principles:

Use and Disuse of Organs:

Organs that are frequently used become stronger and more developed.
Organs that are not used deteriorate over time.

Inheritance of Acquired Traits:

Acquired characteristics during an organism’s lifetime are passed on to the next generation.

Continuous Use Leads to Development:

Continuous use of a specific trait results in its enhancement.

Disuse Causes Degeneration:

Lack of use causes the organ to weaken and eventually disappear.

Examples:

Giraffe’s Long Neck:
According to Lamarck, giraffes stretched their necks to reach taller branches.
This acquired trait was passed to future generations, leading to long-necked giraffes.
Webbed Feet in Ducks:
Ducks that frequently swam developed webbed feet.

Criticism of Lamarckism:

Weismann’s Experiment:
August Weismann cut the tails of rats for 22 generations.
The offspring were still born with normal tails, disproving Lamarck’s theory.

10. Mechanism of Evolution

10.1 Hugo de Vries’ Mutation Theory

Proposed by Hugo de Vries in 1901.
Suggested that:
Evolution occurs due to sudden and large variations called mutations.
Mutations cause discontinuous variations that lead to new species.

Key Principles:

Mutation:

Sudden, inheritable changes in the genetic material.

Large Effect of Mutation:

Even a single mutation can create significant changes.

Discontinuous Variations:

Mutations cause abrupt changes, unlike Darwin’s gradual changes.

Role in Speciation:

Accumulation of mutations over generations can lead to the formation of new species.

Example:

Evening Primrose (Oenothera lamarckiana):
Hugo de Vries observed sudden variations in evening primrose plants.
This led to the formation of new varieties, supporting the mutation theory.

10.2 Comparison of Darwinian Theory and De Vries’ Mutation Theory

Feature	Darwinian Theory	De Vries’ Mutation Theory
Nature of Variations	Gradual and continuous	Sudden and discontinuous
Rate of Evolution	Slow and gradual	Rapid and abrupt
Cause of Variations	Small variations due to natural selection	Large mutations
Effect of Changes	Small changes over a long period	Large changes in a short period
Example	Evolution of giraffe’s neck	Mutation in evening primrose
Speciation	Occurs slowly through natural selection	Occurs quickly due to major mutations

10.3 Modern Synthetic Theory of Evolution

Developed by Dobzhansky, Huxley, and Mayr in the 1930s and 1940s.
Combines Darwin’s natural selection with genetics, population genetics, and mutation theory.
Describes evolution as a gradual process resulting from:
Mutation
Natural selection
Genetic drift
Gene flow
Recombination

Key Factors:

Genetic Variations:

Variations arise due to mutations, recombination, and gene flow.

Natural Selection:

Favourable variations are selected over time.

Gene Flow:

Movement of genes between populations increases genetic diversity.

Genetic Drift:

Random changes in allele frequency, especially in small populations.

Reproductive Isolation:

New species arise due to reproductive barriers.

11. Hardy-Weinberg Principle

Proposed by G.H. Hardy and Wilhelm Weinberg in 1908.
States that:
Allele and genotype frequencies in a population remain constant from generation to generation in the absence of external factors.
Represents a genetic equilibrium.

Mathematical Expression:

(p+q)²= p²+2pq+q²=1 and p+q=1
Where:

(p) = Frequency of dominant allele.
(q) = Frequency of recessive allele.
(p^2) = Frequency of homozygous dominant genotype.
(q^2) = Frequency of homozygous recessive genotype.
(2pq) = Frequency of heterozygous genotype.

Factors Affecting Hardy-Weinberg Equilibrium:

Mutation:

Introduction of new alleles disrupts the equilibrium.

Gene Flow (Migration):

Movement of individuals alters allele frequency.

Genetic Drift:

Random changes in allele frequency due to chance events.

Non-Random Mating:

Selective mating changes genotypic frequencies.

Natural Selection:

Favourable traits increase in frequency, altering the equilibrium.

12. Types of Natural Selection

Type of Selection	Definition	Effect on Population	Example
Stabilizing Selection	Favors average phenotypes	Reduces extreme variations	Human birth weight
Directional Selection	Favors one extreme phenotype	Shifts population towards that extreme	Peppered moths (melanism)
Disruptive Selection	Favors both extreme phenotypes	Splits population into two groups	Beak size in finches

13. Evolution of Man

Human evolution began around 7 million years ago in Africa.
Gradual evolution led to the emergence of Homo sapiens.

Key Stages of Human Evolution:

Australopithecus (4-2 MYA) → Bipedal, small brain, used basic tools.
Homo habilis (2.4-1.5 MYA) → Larger brain, used crude tools.
Homo erectus (1.9-0.3 MYA) → Larger brain, used fire, migrated.
Homo neanderthalensis (0.4-0.04 MYA) → Robust build, complex tools, buried dead.
Homo sapiens (300,000 years ago) → Modern humans, developed language, culture.

14. Stages of Human Evolution

14.1. Dryopithecus

Period: Around 20-25 million years ago (MYA).
Location: Africa and Eurasia.
Physical Features:
- Ape-like appearance with long arms.
- Quadrupedal locomotion (moved on four limbs).
- Lived in tropical forests.
Diet:
- Mainly herbivorous (fruits and leaves).
Significance:
- Considered an ancestor of both apes and humans.

14.2. Ramapithecus

Period: Around 14-15 MYA.
Location: Africa and Asia.
Physical Features:
- More human-like jaw compared to Dryopithecus.
- Walked partially upright.
- Smaller canines and thick enamel.
Diet:
- Omnivorous (fruits, leaves, and small animals).
Significance:
- Believed to be one of the earliest hominids.
- Showed early adaptations toward bipedalism.

14.3. Australopithecus (4 – 2 MYA)

Period: Around 4 – 2 million years ago.
Location: Africa (Ethiopia, Tanzania, Kenya).
Physical Features:
- Bipedal locomotion → Walked on two legs.
- Short stature (4-5 feet tall).
- Small brain size (350-600 cm³).
- Protruding jaw and brow ridges.
Diet:
- Omnivorous, consumed fruits, leaves, and small animals.
Tools:
- Used simple tools made of stone and wood.
Significance:
- First definite hominid to show bipedalism.
- Marked a major step in human evolution.

Australopithecus species:

Australopithecus afarensis → Best-known species (Lucy fossil).
Australopithecus africanus → Slightly larger brain.

14.4. Homo habilis (2.4 – 1.5 MYA)

Period: Around 2.4 – 1.5 MYA.
Location: Eastern and Southern Africa.
Physical Features:
- Bipedal with long arms.
- Brain size: 600-750 cm³.
- Smaller face and teeth compared to Australopithecus.
Diet:
- Omnivorous → Ate plants, small animals, and scavenged meat.
Tools:
- Used simple stone tools (Oldowan tools).
Significance:
- Known as “handy man” due to tool-making skills.
- First hominid with evidence of primitive culture.

14.5. Homo erectus (1.9 – 0.3 MYA)

Period: Around 1.9 – 0.3 MYA.
Location: Africa, Asia, and Europe.
Physical Features:
- Fully bipedal.
- Taller stature (5-6 feet).
- Brain size: 900-1100 cm³.
- Thick skull bones and prominent brow ridges.
Diet:
- Omnivorous, including meat.
Tools and Fire Use:
- Used Acheulean stone tools (hand axes).
- First hominid to use fire for cooking and protection.
Significance:
- First species to migrate out of Africa.
- Showed early signs of social organization and cooperation.

14.6. Homo neanderthalensis (0.4 – 0.04 MYA)

Period: Around 400,000 – 40,000 years ago.
Location: Europe and western Asia.
Physical Features:
- Robust build with short limbs.
- Brain size: 1200-1700 cm³.
- Stocky and muscular to survive cold climates.
- Large nasal passages for cold adaptation.
Diet:
- Omnivorous → Consumed meat, plants, and nuts.
Tools and Culture:
- Used Mousterian tools.
- Buried their dead → Indicated early cultural practices.
Significance:
- First hominid with ritualistic burial practices.
- Demonstrated complex social behaviour.

14.7. Homo sapiens (300,000 years ago – present)

Period: Around 300,000 years ago – present.
Location: Originated in Africa, later migrated worldwide.
Physical Features:
- Fully upright posture.
- Brain size: 1300-1600 cm³.
- Flat face, smaller jaw, and prominent chin.
- Taller and slender build.
Diet:
- Omnivorous → Developed agriculture and domestication of animals.
Tools and Culture:
- Advanced stone tools, spears, and bows.
- Developed art, language, and culture.
- Complex societies and agriculture.
Significance:
- First hominid with advanced language and culture.
- Created civilizations, art, and religion.

15. Key Trends in Human Evolution

Bipedalism:
- Evolution of upright walking for efficient locomotion.
Increased Brain Size:
- Gradual increase in brain volume for better cognition.
Reduction in Jaw and Teeth Size:
- Evolution towards a flatter face and smaller teeth.
Cultural Evolution:
- Development of art, language, and tools.
Social Organization:
- Formation of family structures and early societies.
Technological Advancement:
- From stone tools to metal tools and eventually modern technology.

Comprehensive Comparison Table of Key Concepts in Evolution

Topic	Definition	Key Features	Example(s)
Darwinian Evolution	Theory of evolution by natural selection.	– Gradual changes over time. – Survival of the fittest.	Galápagos finches, peppered moths.
Lamarckian Evolution	Evolution by inheritance of acquired traits.	– Use and disuse of organs. – Traits passed on.	Giraffe’s long neck (hypothetical).
Hugo de Vries Mutation Theory	Evolution occurs through sudden mutations.	– Discontinuous changes. – Speciation through large mutations.	Evening primrose mutations.
Modern Synthetic Theory	Combination of natural selection and genetics.	– Includes mutation, recombination, and drift. – Gradual changes over time.	Evolution of antibiotic resistance.
Natural Selection	Process where fittest individuals survive.	– Gradual and continuous. – Selective advantage.	Evolution of industrial melanism.
Artificial Selection	Human-driven selection of desirable traits.	– Faster than natural selection. – Controlled breeding.	Dog breeds, cattle breeding.
Stabilizing Selection	Favors average phenotypes.	– Reduces extremes. – Increases intermediate traits.	Human birth weight.
Directional Selection	Favors one extreme phenotype.	– Shifts population towards one extreme.	Peppered moths during the Industrial Revolution.
Disruptive Selection	Favors both extremes over the average.	– Leads to two divergent populations.	Beak size in Darwin’s finches.
Paleontological Evidence	Fossils showing transitional forms.	– Proof of species’ gradual evolution.	Archaeopteryx (link between reptiles and birds).
Comparative Anatomy	Study of similarities in body structures.	– Shows common ancestry. – Homologous and analogous organs.	Forelimbs of vertebrates.
Embryological Evidence	Similarities in embryonic development.	– Common embryonic stages. – Similar gene expression.	Fish and human embryos have gill slits.
Biochemical Evidence	Similarities in DNA, RNA, and proteins.	– Common amino acid sequences. – Similar genetic code.	Insulin in humans and pigs.
Anthropogenic Evolution	Evolution due to human activities.	– Rapid changes in species. – Decreased genetic diversity.	Antibiotic-resistant bacteria.
Adaptive Radiation	Divergence of species from a common ancestor.	– Species adapt to new niches. – Divergent evolution.	Darwin’s finches.
Convergent Evolution	Unrelated species evolve similar traits.	– Similar environmental pressures.	Wings in bats and birds.
Divergent Evolution	Species diverge from a common ancestor.	– Results in homologous structures.	Forelimbs of vertebrates.
Parallel Evolution	Two related species evolve similarly.	– Similar adaptations over time.	Marsupial and placental mammals.
Co-Evolution	Two species influence each other’s evolution.	– Reciprocal adaptations.	Pollinators and flowering plants.
Homologous Organs	Similar structure, different functions.	– Common ancestry. – Divergent evolution.	Forelimbs of mammals.
Analogous Organs	Different structure, similar functions.	– No common ancestry. – Convergent evolution.	Wings of insects and birds.
Vestigial Organs	Reduced/unused structures.	– Remnants of ancestral functions.	Human appendix, wisdom teeth.
Gene Flow	Movement of genes between populations.	– Increases genetic diversity.	Migration of humans introducing new genes.
Genetic Drift	Random changes in allele frequency.	– Stronger in small populations. – Reduces genetic diversity.	Founder effect and bottleneck effect.
Hardy-Weinberg Principle	Genetic equilibrium in a population.	– Allele frequency remains constant.	No evolution occurs in a stable population.
Evolution of Man	Gradual transition from ape-like ancestors.	– Increased brain size. – Bipedalism.	Australopithecus → Homo sapiens.
Australopithecus	Early hominid, first bipedal ape.	– Small brain. – Used simple tools.	“Lucy” fossil.
Homo habilis	Known as “Handy man”, used stone tools.	– Larger brain. – Omnivorous diet.	Oldowan stone tools.
Homo erectus	First hominid to use fire and migrate.	– Taller, stronger build. – Large brain.	Acheulean tools.
Homo neanderthalensis	Stocky, strong hominid with cultural practices.	– Buried their dead. – Complex tools.	Neanderthal fossils.
Homo sapiens	Modern humans with advanced cognitive skills.	– Language, art, and technology.	Cro-Magnon man, early humans.

💡 Tips for NEET:

High-weightage topics:
- Origin of life and Miller-Urey experiment.
- Natural selection and evolutionary evidence.
- Hardy-Weinberg principle and factors affecting it.
- Human evolution stages and features.
Frequent question types:
- Direct factual questions on concepts and definitions.
- Application-based questions (Hardy-Weinberg, natural selection).
- Diagram-based questions on evolutionary stages.