୨୧ aya dy ୨୧
• Darwin’s Theory of Evolution by Natural Selection
• Evidence of evolution
• Mechanisms of evolution
• Species extinction
What is evolution?
• Change in a population over time
• All changes that have transformed life on Earth, from its
earliest beginnings to the diversity that characterizer it
today
• The process by which new species originated from pre-
existing species.
✿ Occurrence of evolution ✿
In the mid – nineteenth century, biologist were already familiar
with the idea of evolution both from written works and
observations
They had read Thomas Malthus’ essay “The Essay of the
Principles of Population”
Population —————- Availability of resources
,⋆౨ৎ˚ Carolus Linnaeus
“Systema Natvrae” (book)
• Plants and animals are grouped based on their
characteristics
• It pinpoints evolution from a common ancestor.
Creationism
Religious belief that life originated
From specific acts of divine creation
However creationist have trouble explaining many known facts
such as fossilized remains
But theory of evolution does not deny God in his role of
creation; rather it does recognize that species have the ability
to change over time
Jean Baptiste Lamarck and Charles Darwin both have similar
and different ideas on how life on Earth came to be.
They both agreed that life evolved from fewer simpler
organisms to many, more complex organisms
, ⋆౨ৎ˚ Jean Baptiste Lamarck
• A french naturalist
• Known for the Theory of Inheritance of Acquired
Characteristics or Theory of Use and Disuse also known
as Lamarckism
• Concludes that new organs arise from new needs and
develop in proportion to the degree that they are used.
• In the beginning, giraffes were believed to have short
necks and fed on leaves from short trees.
• As trees grew taller, giraffes had to stretch their necks to
reach the leaves.
• According to Lamarck, giraffes acquired longer necks
during their lifetime, and these acquired characteristics
were passed on to their offspring.
⋆౨ৎ˚ Examples:
A deer that runs swiftly to escape wolves will develop strong
running muscles in its legs
Snakes are believe to have legs in the past and has lost them to
access narrow places.