4. Darwin’s Theory of Evolution is one
of the most solid theories in
science. It was first formulated
by Charles Darwin in his
groundbreaking book “On the
Origin of Species,” published
in 1859.
5. Charles Darwin was a British naturalist who
proposed the theory of biological evolution
by natural selection.
Darwin defined evolution as "descent with
modification," the idea that species change
over time, give rise to new species, and
share a common ancestor.
6. The basic idea of biological evolution is
that populations and species of
organisms change over time.
7. In the 1850s, Darwin wrote an
influential and controversial book
called On the Origin of Species. In it, he
proposed that species evolve (or, as he
put it, undergo "descent with
modification"), and that all living
things can trace their descent to a
common ancestor.
8. Darwin also suggested a mechanism
for evolution: natural selection, in
which heritable traits that help
organisms survive and reproduce
become more common in a population
over time.
9. Darwin proposed that species can change
over time, that new species come from pre-
existing species, and that all species share a
common ancestor. In this model, each
species has its own unique set of heritable
(genetic) differences from the common
ancestor, which have accumulated gradually
over very long time periods.
10. Repeated branching events, in which
new species split off from a common
ancestor, produce a multi-level "tree"
that links all living organisms.
11. Darwin referred to this process, in
which groups of organisms change
in their heritable traits over
generations, as “descent with
modification." Today, we call
it evolution.
12. Ideas aimed at explaining
how organisms change, or evolve,
over time date back to Anaximander
of Miletus, a Greek philosopher who
lived in the 500s B.C.E.
13. Noting that human babies are born
helpless, Anaximander speculated
that humans must have descended
from some other type of creature
whose young could survive without
any help.
14. He concluded that those ancestors
must be fish, since fish hatch from
eggs and immediately begin living
with no help from their parents. From
this reasoning, he proposed that all
life began in the sea.
15. In the theory of natural selection,
organisms produce more offspring
than are able to survive in their
environment.Those that are better
physically equipped to survive, grow
to maturity, and reproduce.
16. Those that are lacking in such fitness,
on the other hand, either do not reach
an age when they can reproduce or
produce fewer offspring than their
counterparts.
17. Natural selection is sometimes summed up
as “survival of the fittest” because the
“fittest” organisms—those most suited to
their environment—are the ones that
reproduce most successfully, and are most
likely to pass on their traits to the next
generation.
18. This means that if an environment
changes, the traits that enhance survival in
that environment will also gradually
change, or evolve. Natural selection was
such a powerful idea in explaining
the evolution of life that it became
established as a scientific theory.
19. Darwin’s theory starts with the
premise that within a population,
there is variation in traits. For
example, consider the different beak
shapes among the Galapagos finches
that Darwin studied.
20. According to the theory, individuals
with traits that enable them to adapt
to their environments have a better
chance of survival and producing more
offspring.These offspring inherit those
advantageous traits.
21. Over time, the traits that enhance
survival and reproduction become
more common in the population,
leading to evolution.
22. Natural selection doesn’t necessarily
favor the strongest or fastest; it favors
traits that enhance an organism’s
ability to survive and reproduce.
23. Darwin’s theory explains how species
change over time through natural
selection, leading to the diversity of
life we observe today. It’s a
fundamental concept in biology and
has withstood scientific scrutiny for
over a century and a half.
24. According to the theory, individuals
with traits that enable them to adapt
to their environments will help them
survive and have more offspring,
which will inherit those traits.
Individuals with less adaptive traits
will less frequently survive to pass
them on.
25. Over time, the traits that enable species to
survive and reproduce will become more
frequent in the population and the
population will change, or evolve,
according to medical sciences Through
natural selection, Darwin
suggested, genetically diverse
species could arise from a common
ancestor.
26. For example, the modern-day horse once
looked more like a fox. Humans organlles
looked like monkeys.
Birds(finches) had migrated to the islands
from the mainland, and species gradually
evolved to fit their new environments.
27. Humans continue to evolve as a species. Blue
eyes came about just 10,000 years ago when
a gene mutation turned off the switch to
produce brown eyes. Other relatively recent
mutations include an ability to digest milk.
The process of natural selection and survival
of the fittest may have a more limited effect
on modern human evolution,
28. Darwin simply ploughs ahead and argues that
we humans are like other animals and hence
are the product of evolution through
selection. “It is known that man is
constructed on the same general type or
model with other mammals
29. All the bones in his skeleton can be
compared with corresponding bones in a
monkey, bat, or seal. So it is with his
muscles, nerves, blood-vessels and internal
organalles .
30. He acknowledged that humans share a
common ancestor and that all living humans
belong to a single species with a single origin,
approximately 200,000 years ago.
