SBI3U
Evolution
Evolution is the biological history of life on Earth, from the earliest microorganisms to the diversity of modern-day organisms.
Key Definitions
Species: a group of organisms whose members can breed with one another and
produce fertile young.
Evolution: the idea that all species are descendants of ancient species that were
different from modern-day species.
Adaptation: an inherited characteristic that improves an organism’s ability to
survive and reproduce in a particular environment.
Steps Leading to Charles Darwin’s Theory
The work of many scientists changed the scientific thinking in the 19th century. In
developing his theory, Charles Darwin built on these scientists’ ideas and added his
own ideas. Before Darwin’s time, two main ideas about the natural world prevailed:
1) Species were fixed and did not change over time
2) Earth was less than 10 000 years old and also relatively unchanging
The work of many scientists challenged these ideas.
1. James Hutton, a Scottish geologist, was one of the first to challenge the
idea that the Earth was young. He observed rock formations and studied the
rates of erosion and sedimentation. He concluded that it must have taken
millions of years, not thousands, to form the current landscape.
2. In 1830 Charles Lyell found more evidence to support Hutton’s theory.
3. The idea that a species was fixed was also being challenged. A French
naturalist named Georges Cuvier compared the bones of modern-day
elephants with fossilized mammoths. He concluded that the mammoth’s
skeleton was different enough from an elephant’s that the mammoth had
become extinct. The discovery of dinosaur fossils was also evidence that
some organisms became extinct long ago.
4. In the early 1800’s another French naturalist, Jean-Baptiste Lemarck,
recognized that species are not permanent. He proposed that species evolve
or change over time. He explained evolution as a process of adaptation.
Lemarck’s Three Guiding Ideas:
1) Using or not using certain body parts causes an organism to
develop certain characteristics
2) Enhanced characteristics would be passed on to offspring
(inheritance of acquired characteristics)
3) All organisms have a tendency towards perfection
5. In 1831 the HMS Beagle set sail on a voyage around the world. The main
mission was to chart poorly known stretches of the South American
coastline. Charles Darwin was the ship’s naturalist. Darwin collected
thousands of specimens of plants and animals from the Brazilian jungle to
the grasslands of Argentina to the Antarctic. He maintained extensive
journals of his observations, studies and thoughts. He observed three main
patterns:
1) Species Vary Globally: distantly related species living in
similar habitats in different parts of the world looked
similar and acted in similar ways (e.g. South America has
rheas, Australia has emus and Africa has ostriches)
2) Species Vary Locally: related animal species occupied
different habitats within a local environment and had
different features (this was most obvious on the islands like
the Galapagos Islands)
3) Species Vary Over Time: he observed fossils and noted that
the fossil remains look unlike any living creature
6. In 1838 Darwin continued to think about the question of how species change.
He read an essay by Thomas Malthus who said that much of human suffering
was due to the human population’s potential to grow. Darwin recognized that
Malthus’ ideas could be applied to all species: the production of more
individuals than the environment can support leads to a struggle for
existence.
Questions – to be answered in complete sentences on a separate piece of paper
1. a) Write down two examples of physical and behavioural traits that you have.
b) Identify which traits you have inherited and which ones you have
acquired.
c) Can any of your inherited traits be altered during your life? Explain.
d) Can any of your acquired traits be passed on to your offspring? How?
2. A cave salamander is blind. (Its eyes are non-functional) Explain how this
inability could have evolved from sighted ancestors.
3. Which of Darwin’s observations from his voyage interests you the most?
Explain why.
Evolution
Evolution is the biological history of life on Earth, from
the earliest micro-organisms to the diversity of modernday organisms.
Key Definitions
Species: a group of organisms whose members can breed
with one another and produce fertile young.
Evolution: the idea that all species are descendants of
ancient species that were different from modern-day
species.
Adaptation: an inherited characteristic that improves an
organism’s ability to survive and reproduce in a particular
environment.
Steps Leading to Charles Darwin’s Theory
The work of many scientists changed the scientific
thinking in the 19th century. In developing his theory,
Charles Darwin built on these scientists’ ideas and added
his own ideas. Before Darwin’s time, two main ideas about
the natural world prevailed:
1) Species were fixed and did not change over time
2) Earth was less than 10 000 years old and also
relatively unchanging
The work of many scientists challenged these ideas.
1) James Hutton, a Scottish geologist, was one of the
first to challenge the idea that the Earth was young.
He observed rock formations and studied the rates
of erosion and sedimentation. He concluded that it
must have taken millions of years, not thousands, to
form the current landscape.
2) In 1830 Charles Lyell found more evidence to
support Hutton’s theory.
3) The idea that a species was fixed was also being
challenged. A French naturalist named Georges
Cuvier compared the bones of modern-day elephants
with fossilized mammoths. He concluded that the
mammoth’s skeleton was different enough from an
elephant’s that the mammoth had become extinct.
The discovery of dinosaur fossils was also evidence
that some organisms became extinct long ago.
4) In the early 1800’s another French naturalist, JeanBaptiste Lemarck, recognized that species are not
permanent. He proposed that species evolve or
change over time. He explained evolution as a
process of adaptation.
Lemarck’s Three Guiding Ideas:
1) Using or not using certain body parts causes an
organism to develop certain characteristics
2) Enhanced characteristics would be passed on to
offspring (inheritance of acquired
characteristics)
3) All organisms have a tendency towards
perfection
5) In 1831 the HMS Beagle set sail on a voyage around
the world. The main mission was to chart poorly
known stretches of the South American coastline.
Charles Darwin was the ship’s naturalist. Darwin
collected thousands of specimens of plants and
animals from the Brazilian jungle to the grasslands
of Argentina to the Antarctic. He maintained
extensive journals of his observations, studies and
thoughts. He observed three main patterns:
1) Species Vary Globally: distantly related species
living in similar habitats in different parts of
the world looked similar and acted in similar
ways (e.g. South America has rheas, Australia
has emus and Africa has ostriches)
2) Species Vary Locally: related animal species
occupied different habitats within a local
environment and had different features (this
was most obvious on the islands like the
Galapagos Islands)
3) Species Vary Over Time: he observed fossils
and noted that the fossil remains look unlike
any living creature
6) In 1838 Darwin continued to think about the
question of how species change. He read an essay by
Thomas Malthus who said that much of human
suffering was due to the human population’s
potential to grow. Darwin recognized that Malthus’
ideas could be applied to all species: the production
of more individuals than the environment can support
leads to a struggle for existence.
Questions – to be answered in complete sentences on a separate
piece of paper
1. a) Write down two examples of physical and behavioural
traits that you have.
b) Identify which traits you have inherited and which ones
you have acquired.
c) Can any of your inherited traits be altered during your
life? Explain.
d) Can any of your acquired traits be passed on to your
offspring? How?
2. A cave salamander is blind. (Its eyes are non-functional)
Explain how this inability could have evolved from sighted
ancestors.
3. Which of Darwin’s observations from his voyage interests
you the most? Explain why.