What is Evolution
• It means that all living things on Earth are descended from a
• The great diversity of organisms is the result of more than 3.5
billion years of evolution that has filled every available niche
with life forms.
• The millions of different species of plants, animals, and
micro-organisms that live on Earth today are related by
descent from common ancestors.
Organisms constantly strive to improve themselves
Changes are adaptations to environment acquired
in an organism's lifetime.
A structure is modified or changed by use or
The modification is inherited to the offspring.
Inheritance of acquired characteristics.
The Development of long
necks in giraffes is an example of
Lamarck’s Theory of Evolution.
“Giraffes got their long necks by
striving to reach the leaves on the
tops of trees, so their babies were
born with long necks”
Charles Darwin (1809-1882)
He was an English Naturalist.
He travelled around the world
on his ship, the Beagle.
Studied species and fossils in
the Galapagos Islands and
around the world.
Why did some species survive
while others became extinct?
Natural selection Published
The Origin of Species in1859
Darwin's theory of evolution has four main parts:
Organisms have changed over time, and the ones
living today are different from those that lived in the
Change is gradual and slow, taking place over a
long time. This was supported by the fossil record.
All organisms come from common ancestors by a
process of branching.
The mechanism of evolutionary change is natural
On The Galapagos Islands
He studied different species of finches and the
slight variations in their beaks-
He noticed that the shapes of tortoise shells also
varied slightly from island to island.
He found fossils of animals that had recently
He kept a journal and collected fossils and
specimens for further study.
These are some of the finches that
Darwin studied on his voyage.
Though they are all finches, their
beaks distinguish them from one
Some finches developed short,
strong beaks that made it possible
for them to crack nuts.
Some developed long, fine beaks to
reach insect larvae in tiny holes
This is an example of how these
finches adapted to their environment
to survive (natural selection)