evolution

🧬 What is Evolutionary Biology?

It's the study of the history and changes in life forms (flora and fauna) on Earth over millions of years.
It connects:

• Origin of Life

• Changes in Biodiversity

• Evolution of Earth & Universe

🌌 Understanding Evolution: A Cosmic Perspective

1. Big Bang Theory (~13.7 billion years ago)
   🔹 Universe began as a singularity
   🔹 Rapid expansion → Stars & galaxies formed

2. Formation of Earth (~4.5 billion years ago)
   🔸 Gaseous cloud condensed
   🔸 Formation of planets around Sun
   🔸 Early Earth: No atmosphere, volcanic activity, hot, hostile

3. Conditions for Life
   🔹 Primitive atmosphere: CH₄, NH₃, H₂, Water vapour
   🔹 No free O₂
   🔹 Energy from UV rays, lightning → formation of organic molecules

Q3. Which theory attempts to explain the origin of the universe?

A) Lamarckism
B) Big Bang Theory
C) Oparin-Haldane Theory
D) Theory of Relativity

✅ Answer: B
📘 Explanation: The Big Bang Theory explains the origin of the universe as a huge explosion.

🔭 Q4. What formed first after the Big Bang according to NCERT?

A) Stars
B) Earth
C) Hydrogen and Helium
D) Galaxies

✅ Answer: C
📘 Explanation: After expansion and cooling, Hydrogen and Helium formed first before galaxies.

Q5. The Earth was formed approximately:

A) 20 billion years ago
B) 10 billion years ago
C) 5 billion years ago
D) 4.5 billion years ago

✅ Answer: D
📘 Explanation: Earth is believed to have formed about 4.5 billion years ago in the Milky Way galaxy.

Q1. What gases were present in the early Earth’s atmosphere according to NCERT?

A) Oxygen, nitrogen, methane, carbon dioxide
B) Water vapour, methane, carbon dioxide, ammonia
C) Oxygen, hydrogen, carbon monoxide
D) Only carbon dioxide and oxygen

✅ Answer: B
📘 Explanation: NCERT states water vapour, methane, carbon dioxide, and ammonia were released from the molten mass of early Earth.

🔆 Q2. Why did Hydrogen escape from the early Earth's atmosphere?

A) It combined with methane
B) It was too dense
C) It was light and escaped due to UV radiation
D) It reacted with nitrogen

✅ Answer: C
📘 Explanation: UV rays broke up water and light hydrogen (H₂) escaped into space due to its low molecular weight.

🛡 Q3. The ozone layer formed due to:

A) Methane oxidation
B) Oxygen released from plants
C) UV rays acting on oxygen molecules
D) Cooling of Earth

✅ Answer: C
📘 Explanation: Free oxygen (O₂) formed from UV-splitting of water later contributed to ozone (O₃) formation.

🌧 Q4. Oceans on early Earth formed because:

A) Volcanic eruptions released water
B) Comets hit Earth
C) Water vapour condensed and fell as rain
D) Life required water

✅ Answer: C
📘 Explanation: As Earth cooled, water vapour condensed into rain, filling depressions and forming oceans.

🌌 Q5. The theory that life came from outer space is called:

A) Abiogenesis
B) Panspermia
C) Biogenesis
D) Extraterrestrial origin theory

✅ Answer: B
📘 Explanation: Panspermia suggests life originated elsewhere and spores were transferred to Earth.

🧫 Q6. Louis Pasteur disproved the theory of:

A) Biogenesis
B) Natural selection
C) Spontaneous generation
D) Panspermia

✅ Answer: C
📘 Explanation: Pasteur’s experiments disproved spontaneous generation, showing life arises from pre-existing life only.

🧪 Origin of Life: A Hypothesis

• Oparin-Haldane Hypothesis:
  Life began in the “primordial soup” – organic molecules formed spontaneously.

• Miller-Urey Experiment (1953):
  🔬 Simulated early Earth in a lab
  🌩 After a week → formation of amino acids (building blocks of life)

Q1. Which of the following gases were used by Miller in his experiment?

A) CO₂, O₂, H₂
B) H₂, CH₄, NH₃, H₂O vapour
C) O₂, CH₄, NH₃
D) CO, NH₃, H₂, O₂

✅ Answer: B
📘 Explanation: Miller used H₂ (hydrogen), CH₄ (methane), NH₃ (ammonia) and water vapour, simulating primitive Earth.

Q2. Which of the following was NOT formed in Miller's experiment?

A) Amino acids
B) Sugars
C) DNA
D) Pigments

✅ Answer: C
📘 Explanation: DNA was not formed. Amino acids, sugars, nitrogen bases, pigments, fats were observed.

Q3. According to Oparin and Haldane, life originated from:

A) Meteorites
B) Non-living organic molecules
C) Existing prokaryotes
D) Deep sea vents only

✅ Answer: B
📘 Explanation: They proposed that life came from non-living organic molecules via chemical evolution.

Q4. What was the nature of the early Earth's atmosphere during chemical evolution?

A) Oxidizing
B) Neutral
C) Reducing
D) Fully oxygenated

✅ Answer: C
📘 Explanation: The early atmosphere was reducing (rich in CH₄, NH₃, H₂, etc.), not oxidizing.

Assertion (A): Miller's experiment supports the theory of chemical evolution.
Reason (R): He observed the formation of DNA in a reducing atmosphere.

A) Both A and R are true and R is the correct explanation of A
B) Both A and R are true but R is not the correct explanation of A
C) A is true but R is false
D) A is false but R is true

✅ Answer: C
📘 Explanation: Miller's experiment did support chemical evolution, but he did not observe DNA formation.

Assertion (A): According to the modern theory, life originated in water.
Reason (R): Early Earth had abundant water vapor that condensed to form oceans.

✅ Answer: A
📘 Explanation: Life originated in aqueous environments, supported by formation of oceans from water vapour.

The earliest forms of life were multicellular and photosynthetic.

❌ Incorrect
📘 They were most likely non-photosynthetic single-celled organisms.

Chemical evolution involves formation of organic molecules from inorganic molecules.

✅ Correct

the first cellular forms of life appeared 4.5 billion years ago.

❌ Incorrect
📘 They appeared around 2 billion years ago, while Earth formed 4.5 billion years ago.

🌍 From Molecules to Biodiversity

➡ Organic Molecules
➡ Coacervates
➡ Protocells
➡ First Cells (Prokaryotes)
➡ Photosynthetic Organisms
➡ Eukaryotes
➡ Multicellular life
➡ Explosion of Biodiversity

🔥 Remember This Flow:

Big Bang → Earth → Atmosphere → Organic Molecules → First Cell → Evolution of Species

🌌 Origin of Life – NEET Visual Notes

🔭 Peeking into the Past with Stars

• Light from distant stars takes millions of years to reach us.

• So, when we look at stars, we are looking into the past.

• Objects near us = seen in real-time ✨

💥 Big Bang Theory – Birth of Universe

• ~20 billion years ago – one massive explosion → 💥

• Universe started expanding → temperature dropped

• Formation of Hydrogen (H) and Helium (He) 🌌

🌌 Galaxies & Stars Formation

• Gases → clumped by gravity → galaxies & stars ☀

• Our galaxy: Milky Way

• Our solar system (with 🌍 Earth) formed ~4.5 billion years ago

🌍 Conditions on Early Earth

Aspect	Description
Atmosphere	❌ No oxygen initially
Gases Present	🌫 Methane (CH₄), Ammonia (NH₃), CO₂, Water vapour
Surface	🌋 Molten with volcanic eruptions
UV Rays	🌞 Broke water into H₂ & O₂ → H₂ escaped
Cooling	🌧 Water vapour condensed → rains filled depressions → Oceans formed 🌊

🧪 Chemical Evolution to Biological Life

• UV + lightning + gases → complex organic compounds (Amino acids etc.)

• Gradually → Coacervates / Protocells 🧫

• Then → First life form (simple, unicellular)

• Life appeared ~ 3.5 to 4 billion years ago

☂ Ozone Formation

• Oxygen (O₂) from photolysis → formed O₃ (ozone)

• Protected early life from UV radiation ☀🛡

🔁 Quick Recap Mnemonic

“Bang → Gases → Earth → Atmosphere → Oceans → Life”

🧬🌌 ORIGIN OF LIFE – NEET-STYLE VISUAL NOTES

☄ 1. Did Life Come From Space?

• 🌟 Panspermia Hypothesis: Life came from outer space via spores or microbes on meteorites.

• Still a popular theory among astronomers — but no proof!

💡 Mnemonic: “Panspermia – space bacteria mania!” 🪐

Which of the following statements is NOT a part of the theory of special creation?

A) All species were created as such.
B) Diversity has remained the same since creation.
C) Earth is only about 4000 years old.
D) New species arise from common ancestors.

✅ Answer: D
📘 Explanation: The theory of special creation does not support common ancestry or evolution.

Q2. Charles Darwin’s concept of fitness in the context of natural selection refers to:

A) Physical strength and power
B) Ability to adapt quickly
C) Reproductive success
D) Resistance to diseases only

✅ Answer: C
📘 Explanation: Fitness, according to Darwin, is about reproductive fitness, i.e., producing more offspring.

Q3. Darwin's observations during his voyage on H.M.S. Beagle led him to conclude that:

A) All species were created a few thousand years ago
B) Evolution is sudden and dramatic
C) Existing species show similarities with extinct species
D) Extinct species can come back

✅ Answer: C
📘 Explanation: Darwin noticed existing species resemble extinct ones, suggesting common ancestry and gradual evolution

Q4.

Assertion (A): Darwin considered natural selection as the mechanism for evolution.
Reason (R): Nature selects the individuals who are reproductively more fit.

A) Both A and R are true, and R is the correct explanation of A
B) Both A and R are true, but R is not the correct explanation of A
C) A is true, but R is false
D) A is false, but R is true

✅ Answer: A
📘 Explanation: Darwin’s theory of natural selection is based on differential reproductive success.

Assertion (A): According to the theory of special creation, diversity remains the same over time.
Reason (R): The theory supports evolutionary change over millions of years.

✅ Answer: C
📘 Explanation: A is true for special creation theory, but R is false—it contradicts the idea of evolution.

Darwin’s theory suggests that new forms of life arose through sudden creation.

---

❌ Incorrect
📘 Evolution is gradual over long periods.

Q7. Individuals with characteristics better suited to their environment are more likely to reproduce.

✅ Correct

the concept of fitness according to Darwin includes physical strength.

❌ Incorrect
📘 It refers to reproductive fitness, not necessarily strength.

Q9. According to Darwin, nature plays a role in selecting organisms through the process of natural selection.

✅ Correct

🧫 2. Spontaneous Generation (DISPROVED)

• Belief: Life came from rotting things like mud, straw etc.

• 🧪 Louis Pasteur → DISPROVED it using a swan-neck flask experiment

• Life arises from pre-existing life only ✅

🧠 Trick: “Pasteur killed the myth with yeast!”

🧪 3. Chemical Evolution (Oparin-Haldane Hypothesis)

• 🧬 Life came from non-living organic molecules

• Pre-life molecules like proteins, RNA formed first

• Earth had:

  • High 🌋 temperature

  • ⚡ Volcanic lightning

  • Reducing atmosphere (CH₄, NH₃, H₂, no O₂)

🧠 Trick: "Opa-Rin stirred the life soup in a reducing bin!"

Q1. Which naturalist is known to have arrived at a theory of natural selection independently of Charles Darwin?

A) Lamarck
B) Alfred Wallace
C) Haldane
D) Oparin

✅ Answer: B
📘 Explanation: Alfred Wallace developed a theory of natural selection similar to Darwin's while working in the Malay Archipelago.

The geological history of Earth is important in understanding evolution because:

A) Earth is only a few thousand years old.
B) Fossils are irrelevant to evolution.
C) Biological history is closely related to geological history.
D) New organisms do not appear over time.

✅ Answer: C
📘 Explanation: Biological evolution is deeply connected with geological time scales (eras, periods, epochs).

What conclusion can be drawn from the geological and biological history of Earth?

A) All organisms evolved at the same time.
B) Life on Earth is only a few thousand years old.
C) Earth and life on it are billions of years old.
D) All life forms have unique ancestors.

✅ Answer: C
📘 Explanation: Geological and fossil evidence show that Earth is billions of years old.

Assertion (A): Alfred Wallace independently proposed the concept of natural selection.
Reason (R): He was working in the tropical regions of Africa.

A) Both A and R are true, and R is the correct explanation
B) Both A and R are true, but R is not the correct explanation
C) A is true, but R is false
D) A is false, but R is true

✅ Answer: C
📘 Explanation: Wallace worked in the Malay Archipelago, not Africa.

---

Assertion (A): The Earth is only a few thousand years old.
Reason (R): Geological evidence does not support the theory of evolution.

✅ Answer: D
📘 Explanation: Both A and R are false. Earth is billions of years old, and geological evidence strongly supports evolution.

Q6. Alfred Wallace collaborated with Darwin to publish the theory of natural selection.

✅ Correct
📘 Note: They jointly presented their ideas in 1858.

According to current scientific understanding, Earth is only 10,000 years old.

x

According to current scientific understanding, Earth is only 10,000 years old.

❌ Incorrect
📘 Earth is approximately 4.5 billion years old.

Q8. All living organisms have no ancestral connection with each other.

❌ Incorrect
📘 Life forms show common ancestry, even if at different points in history.

⚗ 4. Miller-Urey Experiment (1953)

• S.L. Miller recreated primitive Earth’s atmosphere in a lab

• In a closed flask:

  • CH₄, NH₃, H₂ + H₂O

  • Electric discharge ⚡ at 800°C

• Result? ✅ Amino acids formed!

• 🧪 Proof of chemical evolution in lab

💡 Mnemonic: “Miller cooked life with gas and lightning”

🪐 5. Meteorites Also Contain Life Molecules

• Sugars, nitrogen bases, pigments etc. also found in meteorites

• Chemical evolution may not be Earth-only

🧫 6. First Life Form – How?

• 🌊 First non-cellular forms: Giant molecules (RNA, proteins etc.)

• 🧫 They could self-replicate

• 🌱 First cellular life formed ~2 billion years ago

• All life was aquatic initially 💧

🧠 Trick: “First life = Self-replicating soup in water loop”

📚 NEET Quick Revision Table:

Concept	Scientist/Details
Life from space	Panspermia
Disproved Spontaneous Gen.	Louis Pasteur – Swan-neck flask
Chemical evolution idea	Oparin (Russia) + Haldane (England)
Experimental proof	S.L. Miller → Amino acids formed ⚡
First non-cellular molecules	RNA, proteins, polysaccharides
First cellular life	~2 BYA, aquatic origin 🌊

🧬✨ EVOLUTION OF LIFE FORMS – NEET STYLE

📖 1. Theory of Special Creation (REJECTED!)

According to religious literature:

• All species were created as they are ✝

• No evolution, no change in diversity over time 🚫

• Earth is only ~4000 years old 🕰

❌ Rejected because:

• Fossil records & geological dating prove Earth is ~4.5 billion years old 🌍

• Extinct species found 🦕

• Evolutionary patterns noticed

🧠 Trick: “Special Creation = Static Creation” — but fossils said ‘Nope!’

🌊🛳 2. Darwin’s Voyage & Observations

• Sailed on H.M.S. Beagle ⛵

• Visited Galápagos Islands 🐢, studied finches and fossils

• Found that organisms resemble past forms ➤ evolution happened!

🧠 3. Darwin's Big Ideas 🔁 Gradual Evolution:

• Species evolved slowly over time

🎯 Natural Selection (Survival of the Fittest):

• Every population has variation 🌱

• Traits that help survival = favorable

• Individuals with such traits = more likely to reproduce ➤ pass on traits

• Over generations ➤ better adapted species form

💡 Mnemonic for Natural Selection: VOSF → Variation → Overproduction → Struggle → Fitness

Q1. The remains or impressions of ancient life-forms preserved in rocks are called:

A) Minerals
B) Fossils
C) Embryos
D) Isotopes

✅ Answer: B
📘 Explanation: Fossils are the preserved remains or traces of organisms from the remote past, usually found in sedimentary rocks

Q2. What do fossils found in different sediment layers indicate?

A) The same life forms existed forever
B) All species were created at the same time
C) Life forms have changed and evolved over time
D) Fossils are randomly distributed in rock layers

✅ Answer: C
📘 Explanation: Fossil evidence shows that different organisms lived at different times, proving evolution over time.

Q3. Which of the following is not true about embryological evidence?

A) Ernst Haeckel proposed it
B) All vertebrate embryos show gill slits
C) Embryos pass through adult stages of other species
D) Embryological features suggest common ancestry

✅ Answer: C
📘 Explanation: Karl Ernst von Baer rejected the idea that embryos pass through adult stages of other animals.

Q4.

Assertion (A): Fossils are considered strong evidence of evolution.
Reason (R): They help trace the changes in organisms over geological time.

A) Both A and R are true, and R is the correct explanation
B) Both A and R are true, but R is not the correct explanation
C) A is true, but R is false
D) A is false, but R is true

✅ Answer: A
📘 Explanation: Fossils show a chronological sequence of life forms and evolutionary transitions.

Assertion (A): Embryos of all vertebrates develop gill slits.
Reason (R): All vertebrates breathe through gills throughout their life.

x

✅ Answer: C
📘 Explanation: Gill slits are seen in embryos, but only fish use them for breathing. The reason is false.

Fossils found in deeper layers are older than those found in upper layers.

✅ Correct

Fossils found in deeper layers are older than those found in upper layers.

✅ Correct

According to Haeckel, embryonic stages of different vertebrates are dissimilar from each other.

❌ Incorrect
📘 Explanation: Haeckel proposed that embryonic stages are similar, not dissimilar.

x

❌ Incorrect
📘 Explanation: Haeckel proposed that embryonic stages are similar, not dissimilar.

Karl Ernst von Baer supported Haeckel’s theory of embryonic recapitulation.

---

❌ Incorrect
📘 Explanation: Von Baer disapproved Haeckel’s theory by showing embryos do not pass through adult forms of other species.

🧬 4. Fitness = Reproductive Success

• Fitness doesn't mean being strong or smart…

• It means leaving more babies 👶 = your genes survive

🧠 Fit = Fertile!

🌴 5. Alfred Wallace

• Worked in Malay Archipelago

• Came up with same ideas as Darwin independently

• Both presented the theory together 📜

💡 Mnemonic: “Darwin & Wallace – Evolution’s Power Palace!”

🌎🧪 6. Geological + Biological History = MATCH!

• Fossil records show gradual evolution over eras, epochs, and periods

• Earth is billions of years old (~4.5 BYA)

• Extinctions + emergence of new species observed

📝 NEET Quick Recap Table

Theory/Scientist	Key Point
Special Creation	No evolution, fixed species – rejected
Charles Darwin	Evolution by natural selection
Alfred Wallace	Co-proposed natural selection
Fitness (Darwinian)	Reproductive success 🍼
Geological Record	Matches with biological evolution

Soup ➤ Cell ➤ Swim ➤ Survive ➤ Select ➤ Species"

(From chemical soup → single cells → aquatic life → survival → natural selection → biodiversity)

🔍✨ EVIDENCES FOR EVOLUTION – NEET NOTES

---

🦴 1. Paleontological Evidence (Fossils)

• Fossils = preserved remains of organisms in sedimentary rocks

• Fossils of different ages are found in different rock layers (strata)

• Shows how life-forms have changed over time

• Proves extinct organisms once existed (e.g., dinosaurs)

Mnemonic:
"Paleo = Past Life Proof"

➡ Fossils tell us who lived when and how life evolved.

✅ NEET TIP:
Know how fossil age is determined using radioactive dating (like Carbon-14).

👶 2. Embryological Evidence

• Ernst Haeckel: Proposed vertebrate embryos look similar early on

• Gill slits appear in embryos of all vertebrates, even humans!
  ➤ Functional only in fishes, vestigial in others

⛔ BUT:
Karl Ernst von Baer disproved the idea that embryos pass through adult stages of other animals.

✅ NEET TIP:
Remember embryos show evolutionary history, not literal transformations.

🦴🦇👨‍🦱 3. Comparative Anatomy & Morphology a. Homologous Structures (Divergent Evolution)

Same structure, different function

• Indicates common ancestry

• E.g.: Forelimbs of:

  • Human (tools)

  • Whale (swimming)

  • Bat (flying)

  • Cheetah (running)

Which of the following is an example of homologous structures?

A) Wings of butterfly and bird
B) Eyes of octopus and mammals
C) Forelimbs of whale, bat, cheetah and human
D) Flippers of penguin and dolphin

✅ Answer: C
📘 Explanation: Despite different functions, the forelimbs of these mammals share the same anatomical structure, indicating

🧠 Mnemonic: "HOme Base"

Homologous = Origin same, Behaviour (function) Altered = Same structure
➡ Divergent evolution

b. Analogous Structures (Convergent Evolution)

• Different structure, same function

• NO common ancestry

• E.g.:

  • Wings of butterfly 🦋 (exoskeleton)

  • Wings of bat 🦇 (bones + skin)

🧠 Mnemonic:
“ANA – not related, but act alike!”

➡ Convergent evolution

Q2. Which of the following pairs is analogous but not homologous?

A) Thorn of Bougainvillea and tendril of Cucurbita
B) Wings of bat and forelimb of human
C) Sweet potato and potato
D) Forelimb of whale and leg of frog

✅ Answer: C
📘 Explanation: Both are underground storage organs, but sweet potato is a root, while potato is a stem – they have different origins, hence analogous.

---

Q3. The wings of birds and insects are:

A) Homologous organs showing divergent evolution
B) Analogous organs showing convergent evolution
C) Vestigial organs
D) Non-functional organs

✅ Answer: B
📘 Explanation: Wings of birds (vertebrate) and insects (arthropods) perform similar functions but have different structures.

Assertion (A): Thorn of Bougainvillea and tendril of Cucurbita are homologous organs.
Reason (R): Both are modifications of the stem and share a common origin.

A) Both A and R are true, and R is the correct explanation
B) Both A and R are true, but R is not the correct explanation
C) A is true, but R is false
D) A is false, but R is true

✅ Answer: A

Assertion (A): Wings of birds and bats are homologous organs.
Reason (R): Both evolved from a common vertebrate ancestor and have similar bone structure.

✅ Answer: A
📘 Explanation: Wings of both birds and bats are modifications of forelimbs, thus homologous.

⚠ Note: Wings of bat and bird = homologous,
Wings of bird and insect = analogous

---

Q6. Divergent evolution leads to homologous organs.

✅ Correct

analogous organs indicate close ancestry.

❌ Incorrect
📘 Explanation: Analogous organs perform similar functions but arise from different origins, so no common ancestry.

Eyes of octopus and mammals are analogous organs.

✅ Correct
📘 Explanation: Both are used for vision, but have different embryonic origins and structures.

Summary Table – NEET Focus

🧠

Evidence Type	Key Point	NEET Keywords
Paleontological (Fossils)	Fossils show changes in life over time	Radioactive dating, Dinosaurs
Embryological	Vertebrate embryos look similar early on	Gill slits, Ernst Haeckel, von Baer
Homologous Structures	Same structure, different function	Divergent evolution, common origin
Analogous Structures	Different structure, same function	Convergent evolution, no ancestry

• Wings of birds and bats are:

  • a) Homologous

  • b) Analogous ✅

  • c) Vestigial

  • d) Adaptive

• b) Analogous ✅

• Which structure is NOT homologous?

  • a) Hand of man

  • b) Flipper of whale

  • c) Wing of insect ✅

  • d) Wing of bat

• c) Wing of insect ✅

• Fossils are found in:

  • a) Igneous rocks

  • b) Sedimentary rocks ✅

  • c) Metamorphic rocks

  • d) Glacial rocks

• b) Sedimentary rocks ✅

🦠 1. Homologous Structures (Same Origin, Different Use)

➡ Definition: Structures that have the same anatomical origin but are modified for different functions
➡ Result of divergent evolution (diverging from a common ancestor)

📌 Examples (NEET favorites):

• Thorn of Bougainvillea 🌹 & Tendril of Cucurbita 🍈 → both are modified stems!

• Forelimbs of:

  • Human 👨 (tools)

  • Bat 🦇 (flying)

  • Whale 🐳 (swimming)

  • Cheetah 🐆 (running)

🧠 Mnemonic:
“Same Origin, Many Missions = HOMO”
➡ "They split from the same ancestor, but took different jobs!"

🦋 2. Analogous Structures (Different Origin, Same Use)

➡ Definition: Structures that look similar & perform the same function, but different origin
➡ Result of convergent evolution (unrelated organisms evolve similar traits due to similar environments)

📌 Examples:

• Wings of Butterfly 🦋 (exoskeleton) & Bird 🐦 (bones)

• Flippers of Penguin 🐧 & Dolphin 🐬

• Eye of Octopus 🐙 & Mammals 👁

• Sweet potato (modified root) & Potato (modified stem) 🥔

🧠 Mnemonic:
"ANAlogous = ANAther way to same function"
➡ "Different structure, same job – no family link!"

🔬 3. Biochemical Evidence

• Similar proteins (e.g., cytochrome c) and genes across species

• DNA and protein sequence similarities = evidence of common ancestry

🧬 NEET often asks:
➡ Which molecule shows common ancestry best?
✅ Answer: DNA / cytochrome c / hemoglobin

Q1. Which of the following is an example of evolution observed in a short time frame?

A) Formation of homologous organs
B) Divergence of Darwin’s finches
C) Industrial melanism in moths
D) Evolution of whales from land mammals

✅ Answer: C
📘 Explanation: The peppered moths in England showed natural selection over decades due to changing environmental conditions.

Q2. Which of the following evidences supports biochemical basis of evolution?

A) Homologous organs
B) Similarity in protein structures among diverse organisms
C) Fossil records
D) Embryological features

✅ Answer: B
📘 Explanation: Similar proteins or genes across species suggest common ancestry on a biochemical level.

Q3. What caused the increase in melanic moths after industrialisation?

A) They were genetically superior
B) They were protected by humans
C) They could camouflage better on soot-covered trees
D) They reproduced faster than white-winged moths

✅ Answer: C
📘 Explanation: Camouflage on dark bark reduced predation, leading to natural selection of melanic moths.

In unpolluted rural areas, the population of melanic moths was:

A) Very high
B) Equal to white moths
C) Very low
D) Absent

---

✅ Answer: C
📘 Explanation: Without soot, tree trunks were light-colored and white moths camouflaged better, so melanic moths were picked off more often.

Assertion (A): White-winged moths were more common before industrialisation.
Reason (R): Their colour helped them camouflage on lichen-covered tree trunks.

A) Both A and R are true, and R is the correct explanation
B) Both A and R are true, but R is not the correct explanation
C) A is true, but R is false
D) A is false, but R is true

✅ Answer: A

Assertion (A): Industrial melanism in moths is a proof of natural selection.
Reason (R): Environmental conditions favoured the survival of the dark-winged moths.

✅ Answer: A
📘 Explanation: Melanic moths survived better in darkened environments, proving natural selection in action.

Q7. Similarities in gene sequences across species suggest common ancestry.

✅ Correct

✅ Correct

All white-winged moths were eliminated post-industrialisation.

❌ Incorrect
📘 Explanation: No variant was completely wiped out, only the proportion of melanic moths increased.