Download Evolution is the biological history of life on Earth, from the earliest

SBI3U
The History of Evolutionary Theory
Key Definitions
Species: a group of organisms whose members can breed with one another and produce fertile
young.
Ex. Horses and donkeys are different species. They can mate, but their offspring are mules that
are sterile. Therefore mules are not considered a species, but a “hybrid”.
Evolution: the process in which changes in the inheritable traits (ie. the genes) of species occur
over time. (It follows that all modern-day species are descendants of ancient species, which were
very genetically different.)
Adaptation: any inheritable trait that increases an individual’s ability to survive or reproduce (in
a particular environment) compared to organisms that do not have that trait.
The History of Evolutionary Theory: Steps Leading to Charles Darwin’s Theory
The work of many scientists led to the development of evolutionary theory 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, in 1795, that it must have taken millions of years, not
thousands, to form the current rock formations.
2. In 1830 Charles Lyell found more evidence to support Hutton’s theory: geological change
is slow and gradual, not sudden and catastrophic.
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 Lamarck, recognized that
species are not permanent. He proposed that species evolve or change over time. He
explained evolution as a process of adaptation.
Lamarck’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
**Although disproved, Lamarck was one of the first scientists to propose that
environment played a role in an organism’s development of new traits (adaptation)
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). This suggests
organisms will develop similar adaptations to similar environmental conditions.
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—ie. Darwin’s finches). This suggests organisms struggle
to obtain enough resources to survive, therefore adapt to different ecological
niches to fulfill their needs.
3. Species Vary Over Time: he observed fossils and noted that the fossil remains
look unlike any living creature. This suggests organisms’ traits change over time.
When certain traits are no longer beneficial for survival in a changed environment,
an organism must adapt or become extinct.
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 eye tissue is 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.
SBI3U
The History of Evolutionary Theory
Key Definitions
Species: a group of organisms whose members can breed with one
another and produce fertile young.
Ex. Horses and donkeys are different species. They can mate, but
their offspring are mules that are sterile. Therefore mules are
not considered a species, but a “hybrid”.
Evolution: the process in which changes in the inheritable traits (ie.
the genes) of species occur over time. (It follows that all modernday species are descendants of ancient species, which were very
genetically different.)
Adaptation: any inheritable trait that increases an individual’s
ability to survive or reproduce (in a particular environment)
compared to organisms that do not have that trait.
The History of Evolutionary Theory: Steps Leading to Charles
Darwin’s Theory
The work of many scientists led to the development of evolutionary
theory 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, in 1795, that it must have
taken millions of years, not thousands, to form the current
rock formations.
2. In 1830 Charles Lyell found more evidence to support
Hutton’s theory: geological change is slow and gradual, not
sudden and catastrophic.
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
Lamarck, recognized that species are not permanent. He
proposed that species evolve or change over time. He
explained evolution as a process of adaptation.
Lamarck’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
**Although disproved, Lamarck was one of the first scientists
to propose that environment played a role in an organism’s
development of new traits (adaptation)
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). This
suggests organisms will develop similar adaptations to
similar environmental conditions.
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—ie. Darwin’s finches). This
suggests organisms struggle to obtain enough resources
to survive, therefore adapt to different ecological niches
to fulfill their needs.
3. Species Vary Over Time: he observed fossils and noted
that the fossil remains look unlike any living creature.
This suggests organisms’ traits change over time. When
certain traits are no longer beneficial for survival in a
changed environment, an organism must adapt or become
extinct.
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 eye tissue is 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.