Transcript Notes for evolution unit

Biological Evolution
What is a theory in the scientific sense?
In science, a theory is a
hypothesis that has enough
evidence to support it to be
safely considered a fact.
Examples of scientific
theories:
• Heliocentrism
• Gravity
• Existence of atoms
• Cell theory
• Germ theory of disease
• Evolution
What Westerners Believed Before 1850:
• Most people in the West (except
for a few geologists) believed that
the Earth was very young (less
than 10,000 years old) and that
the creation story in the Bible
was mostly literally true.
• Some Scientists in the 1740’s
began to believe that organisms
could, in fact, change over time,
but not enough to evolve into
completely new species.
• One scientist, Jean Baptiste
Lamarke, suggested that species
could change, and that they
passed on acquired
characteristics to their offspring.
(Lamarkeism)
Who was Charles Darwin?
In 1831, Darwin agreed to
serve as a Naturalist aboard
the HMS Beagle on a
research and survey voyage.
From 1831-1836, he made
many observations in South
America, the Galapagos
Islands and Australia that
gradually led him to his
theory of evolution by
means of natural selection.
In 1859, after many years
of collecting evidence, he
published On the Origin of
Species.
It was a very controversial
book and became an
instant best seller.
Darwin’s Main Ideas:
1. All life forms on Earth
are descended
(evolved from) from a
single common
ancestor; that is, all
living things are
related to one another.
2. Living things mainly
evolve due to natural
selection.
How natural selection works:
1.
2.
3.
4.
5.
Random genetic mutations
(variation) occur in some
offspring.
Overproduction of offspring
Struggle for survival
(competition for limited
resources)
Natural selection: only those
organisms that are best adapted
to their environment will
survive long enough to pass
their genes on to the next
generation. (i.e., survival of the
fittest)
Genetic adaptations are passed
on to offspring.
Evidence for evolution:
Evidence from Morphology:
1. Many organisms have
body structures very
similar to other
organisms, suggesting a
common ancestor.
2. Some organisms have
Vestigal structures in
their bodies, suggesting
that they evolved from
other creatures that
actually needed those
things.
Evidence from biogeography:
1. Organisms from the same
region seem to have
similar body structures.
2. Fossils of organisms seem
to have a lot in common
with organisms that live
there now.
3. The same types of
environments seem to
produce the same types of
organisms, even in very
different regions of the
world.
Evidence from Paleontology:
1. The fossil record shows a
gradual change in
organisms over a very
long period of time
(over 500 million years).
2. Fossils that are more
recent have more in
common with living
organisms than older
fossils do.
Evidence From Embryology:
1. In all mammals, the development of embryos
is very similar among all species.
2. The early development of embryos in recent
species seems to display the evolution of that
embryo from earlier species.
Evidence From Genetics:
1. All living things are the
result of the replication
of the same selfreplicating compound,
DNA.
2. Species that most
resemble one another
have similar DNA
sequences, which
suggests recent common
ancestry.
Does everyone accept the theory of evolution?
• Among scientists, the
acceptance of the
theory of evolution is
over 98%.
• Among the general
population in the US,
the acceptance rate is
much lower: 61% in
2015. (31% actively
reject evolution, 8%
aren’t sure.)
Reasons people don’t
accept evolution:
1. It disagrees with
deeply held
fundamentalist
religious beliefs.
2. It was never properly
taught to them. (see
#1)
What is the Catholic position on evolution?
We’re OK with this idea.
LO: Describe theory of evolution
SLE: Meet or exceed NGSS
Checkpoint Quiz on evolution basics:
1. What is the title of the book which introduced
the idea of evolution to the world?
2. What are the two main ideas of evolution?
3. Describe the stages of natural selection.
4. How do genes support the idea of evolution?
5. How does biogeography support the idea of
evolution?
LO: Model effects of environment on natural
selection.
SLE: Work collaboratively.
After you’ve recorded your “Battle of the Beaks” data, respond to these
prompts in complete sentences:
1. Which beak types seemed to be most successful with:
a. Paper clips?
b. Macaroni?
c. Rubber bands?
d. Toothpicks?
2. After you switched foods, did you have results similar to the results
obtained by another student using a different type of beak? What are some
reasons for this?
3. Do you think that an area with a greater variety of foods (paper clips, etc.)
would have a greater diversity of beaks? Why or why not?
4. In general, what type of beak seems to be able to survive in the greatest
variety of different environments? Give at least one reason for your response.
LO: Identify and describe evidence for evolution.
SLE: Meet or exceed NGSS
Evolution slide show:
Create a short slide show that
describes evidence for the
theory of evolution. Include
evidence from:
• Morphology
• Biogeography
• Embryology
• Paleontology
• Genetics
More requirements:
• Include a title page
• One picture per slide
• Each slide should include a
definition of that branch of
science (morphology, etc.)
• Each slide should describe
how that branch of science
provides evidence for
evolution.
• Each slide should provide an
example of evidence from
that branch of science
History of Life on Earth:
3.5 Billion Years ago-544 Million
Years ago:
Pre-Cambrian Time:
• The first life, almost certainly
bacteria, evolved 3.8-3.5 billion
years ago, either in tidal pools
near the shore or near volcanic
vents in the deep ocean. (Almost
nothing about the origin of life is
known for certain.)
• Algae and fungi first evolved
around 1 billion years ago.
• The earliest multi-celled animals
and plants evolved in the ocean
around 600 million years ago.
544-246 Million Years Ago:
Paleozoic Era:
• 544 million years ago, a huge variety
of invertebrate multi-celled life
suddenly emerge (Cambrian
Explosion).
• The earliest fish evolved around 505
million years ago.
• First plants and animals migrated to
land around 400 million years ago.
• Tropical forests become widespread
around 360 million years ago.
• A mysterious mass extinction event
(Permian Extinction) kills 90% of all
life on Earth 246 million years ago.
245-66 Million years ago:
Mesozoic Era:
• Reptiles, then dinosaurs become
the dominant life form on Earth.
• Mammals and the first birds
evolved around 200 million years
ago.
• Flowering plants (including grass)
evolved around 145 million years
ago
• A 10km-wide asteroid strikes the
earth 66 million years ago,
causing a mass extinction and
bringing the Mesozoic era to a
sudden end.
65 million years ago-present:
Cenozoic Era:
• Flowering plants become the
most common kind of plant
• Mammals become the
dominant life form on land
• First hominids evolved 4
million years ago
• Modern humans appeared in
Africa 200 thousand years ago.
• Ice Ages begin
• First modern humans migrated
out of Africa 60,000 years ago.
Modern Views of Evolution:
Types of Evolution:
Anagenesis (rare): The entire
species evolves together.
Speciation (more common): One
population of a species moves
into a new area, becomes
isolated from the original
population, and evolves into a
different species because of
different conditions in the new
environment.
Gradualism vs. Punctuated
Equilibrium:
Gradualism: Species evolve in tiny
steps over many millions of years.
Punctuated Equilibrium: Species
stay the same for many millions
of years, then evolve in fast
spurts because of sudden
changes in the environment
which place a lot of natural
selection pressure on
populations.
LO: Identify and describe evidence for evolution.
SLE: Meet or exceed NGSS
Checkpoint Quiz on Evidence for Evolution:
Discuss at least three observations of nature or
ideas about those observations that have led
scientists to the conclusion that Darwin’s theory
of evolution is true: (Write a 3-5 sentence
paragraph in response to this prompt, including
a topic sentence; 5 points are possible.)