DARWIN’S THEORY
OF EVOLUTION
ENGAGE
What if I told you that birds, bananas, flowers, and fish are all related to
each other? This is one idea included in Darwin’s theory of evolution.
EXPLORE
Darwin’s theory of evolution contends that all life is related and has descended from a common
ancestor. Animals evolve over time in order to better adapt to their environment to survive and
have offspring. Darwin first published this theory in his 1859 work On the Origin of Species.
Key Figures
Charles Darwin – English biologist, naturalist, and geologist who lived from
1809 to 1882. He is best known for his theory of evolution, which became
widely accepted by the scientific community.
Thomas Malthus – An English scholar whose works influenced Darwin’s
theory of evolution.
Explanation
Evolution is simply a change over time. Darwin’s theory of evolution states
Charles Darwin
that all species of organisms come into existence through the natural
selection of inherited variations that help the organism to survive and reproduce. These changes
are coded in the molecules of organisms’ DNA and are transmitted from generation to generation
so that over time offspring are more suited to surviving in their environments. Over the history of
Earth, this has resulted in progressively more complex lifeforms.
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In August 1831, when Charles Darwin was 22, he
was invited to join a surveying voyage on the
HMS Beagle as a naturalist. The goal of the trip
was to chart the coastline of South America, but
Darwin had his own ideas. On December 27,
1831, the ship set sail, and it wouldn’t return for
nearly five years. Darwin spent most of this time
exploring the land in South America, making
geologic discoveries and making collections of
flora, fauna, and fossils. In the Galapagos Islands,
he saw a variety of unique species. Each island
had its own distinct types of wildlife. He
discovered 12 new finch species. This made him
start to question why organisms are similar and
different and why there are so many different
types of organisms. He studied the different
variations of finches to come to his conclusions,
Galapagos Islands
including overall size, beak shape, and claw
size. He concluded that animals are well suited for their specific environments. For example, birds
have different beak sizes that evolved due to different resources on different islands. He began to
develop a theory that all life descended from a common ancestor. Part of this theory was
that humans are related to animals.
Darwin’s thoughts began to turn to how different species had formed. In July 1837, when he
was 28, he began to keep another notebook that was focused on his thoughts and theories
about the variation of plants and animals. He had
accepted the idea that species could transmute or
evolve over time. In October 1838, he read the works
of Thomas
Malthus concerning
the
idea
that
populations increase until food sources run out and then
die out. From this idea, Darwin formed his theory
of natural selection, which stated that the lifeforms best
adapted to a particular environment survive and breed.
Darwin also took the work of certain geologists into
consideration because their evidence suggested that
the Earth was older than 6,000 years.
In 1845, he published a paper containing his thoughts
on the variety of finch species he had discovered on the
Galapagos Islands years earlier. He contended that all of
Large Ground Finch species
these species came from one original species that
evolved into the different types. Darwin finally published his most important work, On the Origin
of Species, on November 24, 1859, and all 1250 copies that were initially printed immediately sold
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out. He updated the book regularly, adding in the famous phrase ‘survival of the fittest’ in 1869
and using the word ‘evolution’ for the first time in 1872. Darwin’s ideas conflicted with some widely
held beliefs of the time, including the ideas that Earth was only 6,000 years old and that organisms
never change or go extinct. Darwin was not the first to put forth a theory of evolution. French
naturalist Jean-Baptiste Lamarck was one of the first scientists to recognize the existence of
evolution. He believed that traits acquired while living could be passed on to the next generation.
This theory can explain Earth’s biodiversity, which is the variety of life on Earth. According to the
theory, individual organisms in nature differ from one another because of adaptations that parents
produce in their offspring over many generations. Another tenet of the theory is that organisms
produce more offspring than can survive, which means that members of each species must
compete for resources. Those who win out in this competition survive. This is referred to as survival
of the fittest.
Darwin’s theory of evolution is seen as controversial by some, but his theories about natural
selection and evolution are generally accepted by the scientific community. Microevolution, which
is small changes within a species over generations, is virtually universally accepted. The skepticism
focuses on macroevolution, in which a species is believed to have evolved into a completely
different species.
Illustration of primate skeletons
EXTEND
Evidence of Darwin’s theory of evolution is found all around us in nature. Evolution is a
continual process that is going on in species even today. You can research some of the
more recent developments in evolution of species. For example, just within the last 50
years, the Algerian mouse and the common house mouse began mating. Their offspring
are immune to the poison warfarin, meaning they can’t be killed by pesticides. It might
be time to build a better mousetrap!
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Darwin’s Theory of Evolution
Complete the sections below with information from the article.
Vocabulary
Write the definition of each concept.
Definition
Definition
Darwin’s
Theory of
Evolution
Survival of the
Fittest
Ancestor
Microevolution
Natural
Selection
Macroevolution
Application
Evidence of Darwin’s theory of evolution is found all around us in nature. Evolution is a continual
process that is going on in species even today. What evolutionary changes do you notice?
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DARWIN’S THEORY
OF EVOLUTION
Evolution is simply a change over time. Darwin’s theory of evolution
states that all species of organisms come into existence through the
natural selection of inherited variations that help the
organism to survive and reproduce.
In the 1830s, English naturalist Charles Darwin
explored the Galapagos Islands in South America. He
discovered 12 new finch species. This made him start
to question why organisms are similar and different
and why there are so many different types of
Charles Darwin
organisms. He began to develop a theory that all life
descended from a common ancestor. He came to accept the idea that
species could transmute or evolve over time. From this idea, Darwin
formed his theory of natural selection, which stated that the lifeforms
best adapted to a particular environment survive and breed.
In 1845, he published a paper containing his thoughts on the variety
of finch species he had discovered on the Galapagos Islands years
earlier. He contended that all of these species came from one original
species that evolved into the different types. Darwin finally published
his most important work, On the Origin of Species, on November 24,
1859.
© Clark Creative Education