Transcript Evidence for Evolution - Ms. Chambers' Biology

Charles
Darwin
and
His Big
Idea:
Influences
and
Evidence
Tuesday February 1, 2011
Warmup:
Natural selection is sometimes described
as “survival of the fittest”.
Lilly says that “fit” means “bigger,
faster, stronger” like an Olympic
athlete.
• Do you agree or disagree? Why? Give
an example.
Today we will explore:
•
What influenced Darwin?
•
What evidence did Darwin use to support his
idea of evolution by natural selection?
• Born 1809 in England
• Studied medicine and
theology
• Joined HMS Beagle crew in
1831
• Ship naturalist
– Collected specimens
– Made observations
– Recorded thoughts
Darwin Movie- PBS “Evolution”
• Patterns of Diversity
– Plants & animals well suited to
environments
– Similar ecosystems had
different animals present
• Fossils – preserved
remains of ancient
organisms
• Some resembled living
organisms
• Some had no living
counterpart
•
•
•
Small group of islands west of South America
Observed many different organisms on the
islands
– Tortoises
– Finches
Islands had different climates and different
species
Darwin observed that the
characteristics of many
animals and plants
varied noticeably among
the different islands of
the Galapagos
What would cause such variation to occur?
Common ideas at Darwin’s time:
1. Earth was only a few thousand years
old
2. Neither the Earth nor its species had
changed (Earth and living things are
fixed)
3. Geological features had been produced by
SUDDEN catastrophic events that humans
rarely witnessed
Ideas that shaped Darwin’s Thinking
• James Hutton (1795)
– Geologic forces shape Earth
– Layers of rock form very slowly
– Estimates Earth is
millions of years old
Ideas That Shaped Darwin’s Thinking
• Thomas Malthus (1798):
– Growing human population will overwhelm
resources
– Darwin realized this applies even more to
plants and animals that have tons of
offspring!
Ideas That Shaped Darwin’s Thinking
• Charles Lyell (1833):
– Geological processes occurring now have
shaped earth’s features throughout history
– Scientists must explain past events using
processes they can observe
Ideas That Shaped Darwin’s Thinking
• Jean-Baptiste Lamarck (1809)
– Recognized living things have changed over time
– These traits can be passed on
– “inheritance of acquired characteristics”
• Organisms can alter the size/shape of their organs by
using bodies in new ways
• (slight problem with this idea)
Concept Map: Evidence for Natural
Selection
Evidence of
Evolution
includes
The fossil record
Geographic
distribution of
living species
Homologous
body structures
Similarities
in early
development
which is composed of
which indicates
which implies
which implies
Physical
remains of
organisms
Common
ancestral
species
Similar genes
Similar genes
What is Evolution?
• Process by which
today’s organisms
have descended
from ancient
organisms (ancestry)
+
• Change over time
=Descent with
Modification
Evidence for Evolution
How do we know evolution
happens?
Fossil Record
• Provides a peek at the past shows
how living things have changed
over the past 3.5 billion years.
• May have bits missing, but fossil
evidence clearly shows that life is
old and has changed over time.
Transitional Fossils
Early whale ancestor.
Land mammal, but clearly related to whales
and dolphins based on specializations of
ear.
Gray Whale:
lives today.
The position of nostrils has changed over time.
We would expect to see fossils that show intermediate forms.
Geographic Distribution
• Some species are only found in certain
parts of the world, likely because they
evolved there
•Alligators in United States
•Marsupials on the islands of Australia and
New Zealand
Geographic
Distribution
• Organisms show more similarity to
species nearby than in similar climates
but far apart.
• Implies ancestry
– Example: species on Galapagos Islands
share more similarities with species on
mainland South America than they do with
species that live on other islands with
similar climates across the world
Homologous Structures
• Similar characteristics due to
relatedness
Homologous Structures
• The leaves look and function differently from
each other, but are all derived from a common
ancestral form.
QuickTime™ and a
decompressor
are needed to see this picture.
Homologous Structures
• Frogs, birds, rabbits, and lizards have different
forelimbs, but they all share the same set of bones.
Extinct, but
shows
common
ancestry
Homologous Structures
http://www.pbs.org/wgbh/evolution/library/04/2/l_042_01.html
Each species has a different function for their limb. Does it seem
possible that they all developed the same bone structure
independent of each other?
“What could be more curious…?”
Vestigial Organs
• Traits that are not useful to an
organism, but remain from a useful
ancestral trait
•Ear-wiggling muscles
•Tail in human and all vertebrate embryos.
•Appendix
•Wisdom teeth
•Hip bone of a whale
Embryology/Development
• Which of
these is a
pig
embryo?
Different
vertebrates
show striking
similarities in
early stages of
development.
http://lhs2.lps.org/staff/sputnam/Biology/U6Evolution/embryology.jpe
Embryology/Development
• Snakes have legged ancestors
– Hind limb buds as embryos, but lose them before
adulthood
– Fossil evidence also shows snakes with hind limbs
Cellular/ Molecular Evidence
• All organisms are made of cells
–Membranes filled
with water,
proteins, lipids,
carbohydrates,
genetic material
–Most use
sugar for fuel
–Produce
proteins as
building
blocks and
messengers
Molecular Evidence
• DNA: simple four-base code that
provides instructions for all living
things
• All life is linked to a common
ancestor
• Different species share some of
the same genes
– Worms share 25% of their genes with
humans!
Molecular Evidence
• The more similar the DNA of two
living organisms, the more closely
they may be to one another
– Note: many other factors play a role as
well
• Activity:
– study the amino acid sequence in the
hemoglobin of humans, gorillas, and
horses
– use the data to show the similarities in
DNA of these organisms