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ICSE Class 10 · Biology · Chapter 15

Human Evolution

8 topics · 15 questions

Smart summary

Everything you need, in order

Introduction to Evolution

  • Evolution: Gradual change in living organisms over generations. Results in formation of new species.
  • Evidence: (1) Fossil records, (2) Comparative anatomy, (3) Embryology, (4) Vestigial organs, (5) Biochemical similarities.
  • Theories: (1) Lamarckism (inheritance of acquired characters), (2) Darwinism (natural selection), (3) Modern synthetic theory.
  • Human Evolution: Study of how humans evolved from primate ancestors.
  • Hominids: Family of primates including humans and extinct ancestors.
  • Diagram Importance: Timeline of human evolution showing different species is essential.

Theories of Evolution

  • Lamarck's Theory: Organisms acquire characters during lifetime, pass to offspring. Example: Giraffe neck elongation.
  • Criticism: Not supported by experiments. Acquired characters not inherited.
  • Darwin's Theory: (1) Overproduction, (2) Struggle for existence, (3) Variations, (4) Survival of fittest, (5) Natural selection.
  • Natural Selection: Nature selects organisms best adapted to environment for survival and reproduction.
  • Modern Synthetic Theory: Combines Darwinism with genetics. Variations due to mutations, recombination, genetic drift.
  • Evidence for Darwinism: (1) Fossil records, (2) Geographical distribution, (3) Comparative embryology, (4) Vestigial organs.

Human Ancestors

  • Dryopithecus: Forest-dwelling ape. Lived 15-20 million years ago. Walked on all fours.
  • Ramapithecus: Lived 12-14 million years ago. Possible early human ancestor. Ate soft fruits and leaves.
  • Australopithecus: Lived 2-5 million years ago. Walked upright. Brain size: 400-500 cc.
  • Homo habilis: 'Handy man'. Lived 2 million years ago. Used tools. Brain size: 650-800 cc.
  • Homo erectus: 'Upright man'. Lived 1.5 million years ago. Used fire. Brain size: 900 cc.
  • Homo sapiens neanderthalensis: Neanderthals. Lived 100,000-40,000 years ago. Robust build, large brain.
  • Homo sapiens sapiens: Modern humans. Evolved 50,000 years ago in Africa.
  • Diagram Importance: Comparative skulls of different hominids showing evolution is crucial.

Evolution of Human Characteristics

  • Bipedal Locomotion: Walking on two legs. Freed hands for tool use.
  • Brain Development: Increased brain size from 400 cc to 1400 cc. Allowed complex thinking.
  • Jaw and Teeth: Reduced jaw size, smaller teeth. Diet changed from raw to cooked food.
  • Forehead and Chin: Prominent forehead, well-developed chin in modern humans.
  • Cultural Evolution: Development of language, art, technology.
  • Migration: Humans migrated from Africa to other continents.

Fossils and Dating Methods

  • Fossils: Remains or traces of ancient organisms preserved in rocks.
  • Types: (1) Petrified fossils, (2) Molds and casts, (3) Carbon films, (4) Trace fossils.
  • Fossil Sites: (1) Siwalik hills (India), (2) Olduvai Gorge (Africa), (3) Zhoukoudian (China).
  • Dating Methods: (1) Relative dating (stratigraphy), (2) Absolute dating (carbon dating, potassium-argon).
  • Carbon Dating: Measures radioactive carbon-14 decay. Used for fossils up to 50,000 years old.
  • Importance: Fossils provide evidence of evolutionary relationships.

Vestigial Organs

  • Vestigial Organs: Reduced, non-functional structures inherited from ancestors.
  • Examples: (1) Appendix - remnant of large cecum in herbivores, (2) Wisdom teeth - no space in modern jaw, (3) Tailbone (coccyx) - remnant of tail, (4) Body hair - reduced in humans, (5) Ear muscles - cannot move ears.
  • Significance: Evidence of evolution. Shows humans evolved from ancestors with different lifestyles.

Comparative Anatomy and Embryology

  • Homologous Organs: Similar structure, different function. Example: Human arm, dog forelimb, whale flipper.
  • Analogous Organs: Different structure, same function. Example: Bird wing, insect wing, bat wing.
  • Comparative Embryology: Embryos of different vertebrates show similarities. Example: Gill slits in human embryos.
  • Biochemical Evidence: Similar DNA, proteins, blood groups across species indicate common ancestry.

Human Evolution Timeline

  • Timeline: (1) 15-20 mya: Dryopithecus, (2) 12-14 mya: Ramapithecus, (3) 2-5 mya: Australopithecus, (4) 2 mya: Homo habilis, (5) 1.5 mya: Homo erectus, (6) 100,000 ya: Neanderthals, (7) 50,000 ya: Modern humans.
  • Out of Africa Theory: Modern humans originated in Africa and migrated to other continents.
  • Cro-Magnon Man: Early modern humans. Lived 40,000 years ago. Made cave paintings.
  • Neanderthal Extinction: Disappeared 30,000 years ago. Possibly due to competition with modern humans.

Quiz

Test your knowledge

Multiple choice

  1. Question 1 of 15Knowledge
    The theory of natural selection was proposed by:
  2. Question 2 of 15Knowledge
    The study of fossils is called:
  3. Question 3 of 15Knowledge
    Human beings belong to genus:
  4. Question 4 of 15Knowledge
    The brain size of Homo habilis was:
  5. Question 5 of 15Comprehension
    Vestigial organ in humans is:
  6. Question 6 of 15Knowledge
    The scientist who proposed inheritance of acquired characters is:
  7. Question 7 of 15Knowledge
    Neanderthals lived about:
  8. Question 8 of 15Knowledge
    The fossil site in India for human ancestors is:
  9. Question 9 of 15Assertion-Reasoning
    Assertion (A): Humans evolved from apes. Reason (R): Humans and apes share common ancestor.
  10. Question 10 of 15Knowledge
    The method used to date fossils up to 50,000 years old is:
  11. Question 11 of 15Knowledge
    The first hominid to use fire was:
  12. Question 12 of 15Comprehension
    Homologous organs show:
  13. Question 13 of 15Knowledge
    The Out of Africa theory suggests that:
  14. Question 14 of 15Comprehension
    Analogous organs are result of:
  15. Question 15 of 15Knowledge
    The earliest known hominid is:

0 of 15 answered