Human Evolution Class 10 ICSE Notes
ICSE Class 10 Biology Chapter 14 Human Evolution Notes, Summary, Definition, Diagram. Human Evolution Notes.
Introduction –
Evolution – slow and continuous process whereby complex forms of life have emerged from simpler forms through millions of years.
Charles Darwin – Theory of natural selection/ Darwanism
Natural selection – Individuals reproduce and pass on their good qualities to their offsprings.
Lamarck’s theory
i.) Use and disuse –
– Before food was available /grown on ground. So Giraffe (herbivores) ate from there. But as competition increased giraffe evolved to eat the fruits trees by stretching their neck and fore-limbs.
ii.) Inheritance of acquired characters-
– Organisms could pass its modifications to its offspring.
– Lamarck postulated that the long neck and fore-limbs of giraffe were passed on to them by their ancestors and same character will continue to appear generation after generations.
Vestigial organs –
→ Organs that is of no use for now or this generation or was being used in past but persist now and generation after generation in a reduced form.
→ Example-
a.) Wisdom teeth
b.) Vermiform appendix
c.) Pinna
Darwin’s theory of natural selection
Facts-
1.) Overproduction –
→ More individuals produced to increase that chance of survival.
→ Example- Oysters lay 60-80 millions eggs in a single spawn. Paramecium divides at a rate of 3 times in 48hrs.
2.) Struggle for existing –
→ Intense competition between organisms for food, shelter, breeding places. Competition may be intraspecific (same species) and interspecific (different species).
3.) Variation –
→ The progeny of same parents are not exactly alike in all respects.
→ Without variation, there will be no change and no possibility of evolution to occur.
4.) Survival of fittest –
→ Individual which complete and adapt the environment than other and more likely to survive. This is called “ survival of the fittest”.
→ Example- Dark and light moth.
Before Industrialisation, there was lichen present on bark of trees due to which light moth get concealed and dark moth became prey.
But after Industrialisation, due to dust the bark of tree become dark, which conceals dark moth and light moth becomes prey known as Industrial melanism.
Human evolution –
Carl Linnaeus – gave scientific name “Homo sapiens”.
Major changes from ape to human form-
→ Bipedal locomotion and the freezing of forelimbs from grounds.
→ Increase in the cranial capacity.
→ Reduction in the size of canines due to omnivorous feeding habits.
→ Loss of jaw power
→ Development of chin
→ Development of forehead and brow ridges.
→ Increase in height
→ Erect posture by the development of lumbar curve
→ Reduction in body hair
Human ancestors
i.) Australopithecus – 120cm tall (3.5-4 feet) , cranial capacity – 450-600cm3
ii.) Homo habilis – 150cm tall (4.5-5 feet), cranial capacity – 680-735cm3
– First man-like ancestor.
iii.) Homo erectus – 120-150cm tall (5-5.5 feet), cranial capacity – 800-1125cm3
– First to hunt animals.
iv.) Neanderthals – 160cm tall (5.5 feet) , cranial capacity – 1450cm3
v.) Cro-magnon – 180cm tall (5.5-6 feet), cranial capacity – 1450-1600cm3
vi.) Homo-sapiens sapiens (modern man)- upto 190cm,fully erect, cranial capacity – 1450-1600cm3
Glossary –
i.) The origin of species – published by Charles Darwin, 1859, in which idea of natural selection is explained.
ii.) Father of evolution- Charles Robert Darwin
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