Evidence of
Evolution
Unit 4: Chapters 10 & 12
Important Vocabulary
1. Species: A group of organisms that can
breed together to produce fertile offspring.
2. Population: A localized group of individuals
belonging to the same species.
3. Evolution: A slow change in a population
over time.
Charles Darwin explained
how Natural Selection could
cause a population to adapt
and change over time. (note
he states- a “population” will
change -not an “individual”)
What is a theory vs. a hypothesis?
Hypothesis
Theory
An educated guess that
has to be testable by
scientific methods
Has to be wellsupported and has been
tested over and over
Is an explanation of a
phenomenon that has
occurred in the natural
world.
Who influenced Charles Darwin?
The Work of Lyell Influenced Darwin’s Ideas
1. Charles Lyell – English geologist
a. Earth’s geologic features formed as a
result of gradual processes.
b. Floods, earthquakes, and glaciers of the
present do not cause great destruction
(ex: Grand Canyon) of Earth’s surfaces
c. Must take millions of years to change
geography, thus the earth must be
millions of years old.
2. Darwin read Lyell’s work while on his voyage
& agreed with Lyell’s conclusions
Charles Lyell
The Work of Malthus Influenced Darwin’s Ideas
1. 1798: Thomas Malthus -- Englishman
a. Essay on the Principle of
Population
b. Said that humans tend to have
more offspring than nature can
support
c. Food production increases at a
slower rate than population
2. Darwin read Malthus’s essay after he
returned from his voyage
3. Darwin concluded that all organisms
produce more offspring than the
environment can support
Thomas Malthus
Darwin explained Evolution by Natural Selection
1. 1859: Darwin published On the Origin of
Species
a. Proposed that natural selection was the
mechanism for evolution.
• Individuals vary in one or more traits &
there can be slight differences in their
ability to survive & reproduce.
b. Nature selects those individuals w/
favorable traits to leave more offspring
that are better suited (FIT) for their
environment.
c. Descent with modification occurs over
time
• Each living species has descended,
with changes, from other species over
time
Published 25
years after
Darwin wrote it!
Evidence that Supports Evolution: Fossil Record
1. Fossil: preserved remains (bones,
teeth, shells) or evidence (imprint or
footprint) of ancient organisms.
a. Fossils found in sedimentary rock
b. Younger sediments deposited on
top of older sediments
c. Older sediments contain older,
simpler fossils
d. Younger sediments contain
younger, more complex fossils
2. Fossils found in sediments of
organisms that are extinct.
Trilobites
are extinct!
Age of Fossils
Paleontologists determine the age of fossils using two techniques:
1. Relative dating: age of a fossil is determined by comparing its
placement with that of fossils in other layers of rock.
Paleontologists estimate the age based on the age of other fossils
found near it.
1.
Radioactive (absolute) dating: Scientists use radioactive decay
to assign absolute ages to rocks.
Evidence that Supports Evolution:
Geographic Distribution of Living Species
1. Similar animals on each
continent live in similar
ecological conditions
a. They were exposed to
similar pressures of
natural selection.
b. Because of similar
selection pressures,
different animals ended
up evolving similar
characteristics
Beaver
Beaver
NORTH
AMERICA
Muskrat
Beaver and
Muskrat
Muskrat
Coypu
Capybara
SOUTH
AMERICA
Coypu and
Capybara
Capybara
Coypu
Evidence that Supports Evolution: Homologous Structures
1. Homologous structures: similar
structures but different functions
a. Structures develop from same clump
of embryonic cells
b. Provides evidence that four-limbed
vertebrates descended from a
common ancestor.
2. Vestigial structures: structures or
organs that are reduced in size; do not
seem to serve a useful function
3. Homologous & vestigial structures imply
that common genes are involved.
Homologous structures:
forelimbs of vertebrates
Pelvis & femur bones
are vestigial in whales
Evidence that Supports Evolution:
Similarities in Embryology
1. The embryos of vertebrates are
very similar during early
development.
2. The same groups of embryonic
cells develop in the same order
and in similar patterns to produce
tissues & organs.
3. Common cells & tissues growing in
similar ways produce homologous
structures.
4. Implies that common genes are
involved.
Embryos of vertebrates
develop gill slits and tails.