RECOGNIZING EVIDENCE FROM WHICH
DARWIN EXPLAINED THE EVOLUTION OF
LIFE
Theory of Evolution
Charles Darwin was an English scientist who studied
nature. He is known for his theory of evolution by
natural selection. According to this theory, all living
things are struggling to survive. The living things that
have the most helpful traits for their environment tend
to survive.
Darwin first presented his theory in 1858. The idea of
evolution was not new then, but Darwin’s theory
explained how evolution occurred. When Darwin
published On the Origin of Species in 1859, the book
was an immediate success.
Voyage of the Beagle
He make and expedition on a ship
called the Beagle, the trip lasted for
almost five years and circled the
globe.
Darwin’s job was to observe and collect
specimens, including plants, animals,
rocks, and fossils, his most important
observations were made on the
Galápagos Islands.
The 16 Galápagos Islands lie 966
kilometers (about 600 miles) off the west
coast of South America. Some of the
animals Darwin observed on the islands
were giant tortoises and birds called
finches.
Darwin’s Theory of Evolution
Darwin’s theory of evolution by natural
selection contains two major ideas:
1) Evolution is a change in the inherited traits
of organisms over time. Living things have
changed as descendants diverged from
common ancestors in the past.
2) Natural selection is the process in which
living things with beneficial traits produce
more offspring. As a result, their traits
increase in the population over time.
Giant Tortoises
These gentle giants are found almost nowhere else in the
world. Darwin was amazed by their huge size. He was also
struck by the variety of shapes of their shells. Each island
had tortoises with a different shell shape. The local people
even could tell which island a tortoise came from based on
the shape of its shell.
Darwin’s Finches
The finches on different islands had beaks that differed in size and
shape.
He found that the different beaks
seemed to suit the birds for the
food available on their island. In
figure above used its large, strong
beak to crack open and eat big, tough
seeds. Finch number 4 had a long,
pointed beak that was ideal for
eating insects.
ADAPTATION AND SURVIVAL OF LIVING THINGS
The adaptations of living things
allow them to survive in a
particular environment.
An individual grows, develops
and changes, but evolution is a
process that occurs in all apecies
over time.
The differences in the
characteristics of the individuals
in a population are called:
Population variability
Darwin stated that some
organisms would disappear, NATURAL SELECTION
others would reproduce and
pass on their features to their
descendants.
Through time some of these
features will extend to the
population; that is, more
individuals will have the
adaptation, which will make
them more suitable to survive
and reproduce
https://www.boredpanda.com/animal-camouflage-39/
Evidence
Evidence of
common
ancestry
among species
comes from
many sources.
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Five Evidences for Evolution
1.Fossils
2.Geographical Distribution
3.Embryology
4.Comparative Anatomy
5.Molecular and Genetic (DNA)
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#1 Fossil Evidence
❑ Fossils
oEarth is Millions of years
old!
oFossils in older layers are
more primitive than those in
the upper layers.
oExtinct Fossils resemble
modern animals.
oThis shows a common
ancestry.
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Types of Fossils
❑ Permineralization occurs
when minerals carried by
water are deposited around a
hard structure
❑A natural cast forms when
flowing water removes all of
the original tissue, leaving an
impression.
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Types of Fossils
❑Amber-preserved
fossils are organisms
that become trapped in
tree resin that hardens
after the tree is
buried.
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Types of Fossils
❑ Impressions are imprints left in
rock
❑ Preserved remains form when an
entire organism becomes encased
in material such as ice, ash, tar …
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Relative Dating of Fossils
❑ Estimates the time during
which an organism lived
❑ It compares the
placement
of fossils in layers of rock
❑ Scientists infer the order
in which species existed
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#2 Geographical Distribution
the natural arrangement and apportionment of the various
forms of animals and plants in the different regions and
localities of the earth.
❑ Populations can show variation
from one island to another
❑Island species most closely
resemble nearest mainland
species
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#3 Embryology
❑ Embryo (early developmental stage)
❑Identical larvae, different adult body
forms
❑ Similar embryos, related but diverse
organisms
❑ Shows
common
ancestry Larva
Adult crab Adult barnacle
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#3 Embryology
Vertebrates
all share gill
slits and a
tail in their
early
embryo
stage
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#4 Comparative Anatomy
ARM LEG Flipper Wing
❑ Homologous
structures
are similar in
structure but
different in
function.
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#4 Comparative Anatomy
❑ Analogous structures are similar in
function but differ in structure
❑ Analogous structures DO NOT
show common ancestry
Fly wing
Bat wing
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Structural patterns are clues to
the history of a species.
❑Vestigial structures are remnants of organs or
structures that had a function in an early ancestor.
❑Examples include ostrich wings, human appendix,
and wisdom teeth, whale and snake pelvis/hind legs
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Pythons have tiny
femurs (leg bone)
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#5 Molecular and Genetic
Evidence
❑ Two closely-related
organisms will have similar
DNA, RNA, and protein
(amino acid) sequences.
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