Transcript 10.4 Evidence of Evolution

10.1 Early Ideas About Evolution
KEY CONCEPT
There were theories of biological and geologic
change before Darwin.
10.1 Early Ideas About Evolution
Early scientists proposed ideas about evolution.
• Evolution is the biological change process by which
descendants come to differ from their ancestors.
• A species is a group of organisms that can
reproduce and have fertile offspring.
10.1 Early Ideas About Evolution
Theories of geologic change set the stage for Darwin’s
theory.
• There were three theories of geologic change.
– catastrophism
– gradualism
– uniformitarianism
10.1 Early Ideas About Evolution
• Uniformitarianism is the prevailing theory of
geologic change.
10.2 Darwin’s Observations
KEY CONCEPT
Darwin’s voyage provided insight on evolution.
10.2 Darwin’s Observations
Darwin observed differences among island species.
• Variation is a difference in a physical trait.
– Galápagos tortoises that live in areas with tall plants
have long necks and legs.
– Galápagos finches that live in areas with hard-shelled
nuts have strong beaks.
10.2 Darwin’s Observations
What he saw:

Tortoises on Galapagos had:
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Birds on Galapagos had:
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Examples in the current world:
10.2 Darwin’s Observations
• MOVIE- ROCK POCKET MICE
10.2 Darwin’s Observations
• An adaptation is a feature that allow an organism to better
survive in its environment.
– Species are able to adapt to their
environment.
– Adaptations can lead to genetic
change in a population.
What are some human adaptations?
10.2 Darwin’s Observations
Darwin observed fossil and geologic evidence supporting
an ancient Earth.
• Darwin found fossils of extinct animals that resemble
modern animals.
10.2 Darwin’s Observations
• He saw land move
from underwater to
above sea level
due to an
earthquake.
• Darwin extended
his observations to
the evolution of
organisms.
10.3 Theory of Natural Selection
KEY CONCEPT
Darwin proposed natural selection as a mechanism for
evolution.
10.3 Theory of Natural Selection
Several key insights led to Darwin’s idea for natural
selection.
• Darwin noticed a lot of variation in domesticated plants
and animals.
• Artificial selection is the process by which humans
select traits through breeding.
neck feathers
crop
tail feathers
10.3 Theory of Natural Selection
 Artificial selection is controlled breeding by humans
to produce more individuals with specific traits.
 How can we see that in our world today?

Dog breeding
 How do companies benefit from artificial
selection?


Food supply
Medicine
10.3 Theory of Natural Selection
• Natural selection is a mechanism by which individuals
that have inherited beneficial adaptations produce more
offspring on average than do other individuals.
• Heritability is the ability of a trait to be passed down.
• There is a struggle for survival due to overpopulation
and limited resources.
• Darwin proposed that adaptations arose over many
generations.
10.3 Theory of Natural Selection
Natural selection explains how evolution can occur.
• There are four main principles to the theory of natural
selection.
– Variation– overproduction– adaptation– descent with modification• Fitness is the measure of survival ability and ability to
produce more offspring.
10.3 Theory of Natural Selection
Natural selection acts on existing variation.
• Natural selection can act only on traits that already exist.
• Structures take on new functions in addition to their
original function.
five digits
wrist bone
10.3 Theory of Natural Selection
Why are adaptations
important?
You must be born with a trait to pass it
to your offspring.
Some traits you acquire throughout
your life. Those are not adaptations
that will be passed down.
Adaptations are traits that you have the
are good for an environment.
If a wolf has a really thick coat and the
weather becomes really cold- he
survives, he reproduces, and his
offspring would live to pass on the thick
coat.
What happens if you don’t have a
specific characteristic?
The animal doesn’t reproduce or doesn’t
survive
 Adaptations: are
characteristics that an
organisms HAS not grows: If
the environment changes,
which animals survive?
 Fitness is the measure of an
animals ability to reproduce and
survive.
10.4 Evidence of Evolution
KEY CONCEPT
Evidence of common ancestry among species comes
from many sources.
10.4 Evidence of Evolution
Evidence for evolution in Darwin’s time came from
several sources.
• Fossils provide evidence of evolution.
• Fossils in older layers are more primitive than
those in the upper layers.
10.4 Evidence of Evolution
Fossils
Fossils: fossils can be looked at
over time.
(Sect 12.1) Law of superposition: rock
layer at the top is younger than rock
layer at the bottom.
(Sect 12.1) Fossils can be dated.
Radiometric dating helps to use
molecules to decide how old a fossil
is. Half-life**
Fossils can be compared
between different layers of
rock to decide there relative
age
Which is younger? Older?
10.4 Evidence of Evolution
• The study of geography provides evidence of evolution.
– Geographical locations have different characteristics, but
sometimes very similar animals (biogeography)
10.4 Evidence of Evolution
• Embryology provides evidence of evolution.
– identical larvae, different adult body forms
– similar embryos, diverse organisms
Larva
Adult crab
Adult barnacle
10.4 Evidence of Evolution
Embryology
Embryology: Embryos of many
organisms are VERY similar. If
they are not related, why are they
so similar?
What do the embryos share?
Who are you looking at?
10.4 Evidence of Evolution
• The study of anatomy provides evidence of evolution.
– Homologous structures are similar in structure but
different in function.
– Homologous structures are evidence of a common
ancestor.
Human hand
Mole foot
Bat wing
10.4 Evidence of Evolution
• The study of anatomy provides evidence of evolution.
– Analogous structures have a similar function, but
Human hand different structure.
Mole foot
– Analogous structures are not evidence of a common
ancestor.
Fly wing
Bat wing
10.4 Evidence of Evolution
Anatomy
physical structures of organisms can
support evolution
Homologous structures: bat wing,
whale fin, and human arm
Show common ancestry
Similar in structure, but different
function
Analogous structures: bird wing &
butterfly wing
NOT common in ancestry
Similar in function, but different
structure
10.4 Evidence of Evolution
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.
• Ostrich wings are examples of vestigial structures.
10.5 Evolutionary Biology Today
KEY CONCEPT
New technology is furthering our understanding of
evolution.
10.5 Evolutionary Biology Today
Fossils provide a record of evolution.
• Paleontology is the study of fossils or extinct organisms.
10.5 Evolutionary Biology Today
• Paleontology provides evidence to support evolution.
10.5 Evolutionary Biology Today
Molecular and genetic evidence support fossil and
anatomical evidence.
• Two closely-related organisms will have similar DNA
sequences.
10.5 Evolutionary Biology Today
• Pseudogenes are sequences providing evidence of
evolution.
– no longer function
– carried along with functional DNA
– can be clues to a common ancestor
10.5 Evolutionary Biology Today
Evolution unites all fields of biology.
• Scientist from any fields contribute to the understanding
of evolution.
• The basic principles of evolution are used in many
scientific fields.