Download Ch. 15 Darwin`s Theory of Evolution

Ch. 15 Darwin’s Theory of
Evolution
You can acquire new pants,
but you can’t change your
GENES!
Ch. 15 Outline
• 15-1: The Puzzle of Life’s Diversity
– The Voyage of the Beagle
– Darwin’s Observations
– The Journey Home
Ch. 15 Outline
• 15-2: Ideas that Shaped Darwin’s Thinking
– An Ancient, Changing Earth
– Lamarck’s Evolution Hypotheses
– Population Growth
• 15-3: Darwin Presents His Case
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Publication of On the Origin of Species
Inherited Variation and Artificial Selection
Evolution by Natural Selection
Evidence of Evolution
Summary of Darwin’s Theory
Strengths and Weaknesses of Evolutionary Theory
The Puzzle of Life’s Diversity
• The variety of living things is called
biological diversity
• Evolution: The process by which
species change over time
• Scientific Theory: Well-supported
testable explanation. It explains a
phenomena.
Voyage of the Beagle
• Darwin’s Hypothesis, supported by
a large body of evidence has
become the theory of evolution.
• Charles Darwin
– From England
– Joined the crew of the H.M.S. Beagle
as the ship’s naturalist
– 5 year trip around the world
– Darwin collected specimens at each
stop
Voyage of the Beagle
• Argentina and Australia have similar
grassland ecosystems.
• Grassland ecosystems were inhabited
by very different animals.
• Darwin made numerous observations
and collected evidence that led him to
propose a hypothesis about the way life
changes over time.
– This hypothesis is now called the theory of
evolution.
Darwin’s Observation
• Patterns of diversity
–Many plants and animals seemed
well suited to their environment
–Organisms survived and
reproduced in many different ways
–Not all organisms lived
everywhere
Darwin’s Observation
• Living Organisms and Fossils
• Darwin collected fossils
– Fossil: Preserved Remains of ancient
organisms
• Some fossils didn’t resemble any
living organisms
Darwin’s Observation
• Some fossils didn’t resemble any
living organisms
• Why had so many species
disappeared?
• How were they related to living
species?
Darwin’s Observations
• The Galapagos Islands
– Off the west coast of South America
– The Location that most influenced
Darwin
– Each Island had a different climate
and different organisms
– Noticed the birds had different
shaped beaks on each island and
tortoises had different shaped
shells
Darwin’s Finches
The Journey Home
• After returning back to England,
Darwin wondered if the birds he
collected all belonged to the same
species at some time
• Darwin’s wrens, warblers, and
blackbirds were ALL really finches!
The Journey Home
Darwin’s Question
• Were the animals on different
islands he visited once been
members of the same species?
An Ancient, Changing Earth
• James Hutton and Charles Lyell
– Developed the theory that the earth is
very old. This idea was contrary to
what people thought at the time.
• Hutton and Geological Change:
– Hutton was a geologist. He proposed
that layers of rock form very slowly
and others are pushed up from the
sea floor to form mountains. (This
takes a long time)
Lyell’s Principles of Geology
• Lyell believed that the same
processes that changed the Earth in
the past still operate in the present.
• Darwin was influenced by
Hutton and Lyell’s work. He
reasoned, if the Earth can change
over time (earthquakes, volcanoes)
maybe life can change too!
Lamarck’s Evolution Hypotheses
• Before Darwin’s work, JeanBaptiste Lamarck observed that
life changes and the species
descend from other species.
Lamarck’s Evolution Hypotheses
• Lamarck had two ideas:
1. Organisms can alter their bodies
by “use and disuse”
• Use: Use a structure and it will change
• Disuse: Structures not used will disappear
2. Acquired characteristics can be
inherited.
• If you increase your muscle mass your
children will inherit your big muscles
Lamarck’s Evolution Hypotheses
• Although Lamarck’s ideas were
incorrect, he was one of the first
ones to realize that organisms
are adapted to their
environments and propose a
theory of evolution.
Use and Disuse
Population Growth
• Another influence of Darwin was
Thomas Malthus. This scientist
published a book in which he stated
that babies were being born
faster than people were dying.
– Sooner or later food and living
space will run out.
Population Growth
Thomas Malthus’ Reasoning
• if the human population continued
to grow unchecked, sooner or later
their would be insufficient living
space and food for everyone
Population Growth
• Darwin thought this applied to
plants and other animals even
more because humans usually only
have one offspring at a time.
– So why wasn’t the Earth completely
covered in maple trees (for example)?
Why were some surviving and others
not?
Darwin Presents His Case
• After Darwin returned to England
in 1836, he continued to study his
specimens.
• He discovered that the birds
from the Galapagos were all
finches, not wrens, warblers or
blackbirds like he thought
(these finches were found nowhere
else in the world).
Darwin Presents His Case
• The same was true for the
tortoises
– All the species resembled ones on the
South America mainland, but they
were a different species.
Darwin Presents his Case
• Over 20 years later, Darwin
published all his findings in a book
called, On the Origin of Species.
• He didn’t publish it earlier because
it went against the common beliefs
about organisms.
Darwin Presents his Case
• Not only did Darwin propose the
theory of evolution, he also
proposed a mechanism by which
it happens:
–Natural Selection
Evolution by Natural Selection
• Darwin realized members of each
species competed for resources
(struggle for existence).
• He noted that organisms better
suited to their environment (ex.
Run faster, hide from predators)
survived to reproduce and pass
on their genes.
Evolution by Natural Selection
• Natural Selection
– Genetic variation is found in wild
species as well as in
domesticated plants and animals
Evolution by Natural Selection
• Artificial Selection
– In artificial selection, nature
provided the variation, and
humans selected those variations
that they found useful.
Evolution by Natural Selection
• Struggle for Existence
– Members of each species compete
regularly to obtain food, living space,
and other necessities of life.
Evolution by Natural Selection
• Fitness: The ability of an animal
to survive and reproduce
• Adaptation: an inherited
characteristic that increases an
organism’s chance of survival
Evolution by Natural Selection
• Successful adaptations, Darwin
concluded, enable organisms to
survive and reproduce.
– Types of adaptations
• Anatomical (Structural)
• Physiological processes
• Behavior
Evolution by Natural Selection
– Types of adaptations
•Anatomical
–Porcupine’s quills
•Physiological processes
–Photosynthesis in plants
•Behavior
–Animals living and hunting in
small groups
Evolution by Natural Selection
• Survival of the fittest:
individuals that are better suited
for their environment survive and
reproduce most successfully.
(Natural Selection)
• How is artificial selection compared
to (or like) natural selection? How
is it different?
Evolution by Natural Selection
• How is artificial selection compared
to (or like) natural selection? How is
it different?
– Like: Only certain individuals of a
population produce new individuals
– Different: Natural Selection—
• Traits being selected contribute to an
organism’s fitness to the environment
• Takes place without human control or
direction
Evolution by Natural Selection
• Over time, natural selection results
in changes in the inherited
characteristics of a population.
• These changes increases a
species’ fitness in its environment.
Evolution by Natural Selection
• Darwin proposed that over long periods
of time:
• natural selection produces organisms
that have different structures.
• These species establish different niches,
or occupy different habitats
• Species today look different than their
ancestors
Evolution by Natural Selection
• Descent with Modification: Each
living species has descended, with
changes from other species over time.
– Implies that all living organisms are related
to each other
– All species – living and dead were derived
from common ancestors
Evidence of Evolution
• Fossil Record
• Geographic Distribution of
Living Species
• Homologous Body Structures
• Embryology
Evidence of Evolution
Fossil Record
• Darwin saw fossils as a record of
the history of life on earth
• Earth is very old
• Species lived then died out over
course of time
• Transitional fossils document
various intermediate stages in the
evolution of modern species from
organisms that are now extinct
Evidence of Evolution
• Geographic Distribution of
Living Species
– All of Darwin little brown birds that he
collected from the Galapagos were
finches.
– They all were slightly different
– Darwin decided that they all could
have descended with modification
from a common ancestor, but
changed over time, adapting to their
environment
Evidence of Evolution
• Geographic Distribution of Living
Species
– Different species lived in South America or
Australia even though the environments were
similar.
– These species descended from different
ancestors.
– They were exposed to similar pressures of
natural selection, so different animals
ended up evolving certain features in
common.
Evidence of Evolution
• Homologous Body Structures
– Even though arms, wings, legs and flippers
vary greatly in form and function, they are all
constructed from the same basic bones
– All limb bones develop from the same clump of
cells in embryos
– Structures which have different forms but
mature forms but develop from the same
embryonic tissue are called homologous
structures
Evidence of Evolution
• Homologous Body Structures
– Bat wings are more similar to the front
wings of humans, whales and other
mammals
Evidence of Evolution
• Homologous Body Structures
– Organs that are reduced in size and
traces of homologous organs in other
species are called vestigial organs
– In humans, the appendix is a
vestigial organ
Evidence of Evolution
• Embryology
– Embryos of many animals with backbones
are very similar
– Look especially similar during early stages
of development
– Same groups of embryonic cells develop
in the same order and in similar
patterns to produce the tissues of all
and organs of all vertebrates.
Homologous Structures
Turtle
Alligator
Ancient lobe-finned fish
Bird
Mammal