Download Natural Selection - Helena High School

Evolution
To see where we might be going, we must
understand where we have been
Robert Tamarkin, 1993
Definition?
•Theory supported by evidence
•Biological evolution concerns changes in
living organisms during the history of life on
earth.
•Sharing of common ancestors
•Darwin term: descent with modification
Branched Tree of Life
with a common
ancestor
Formation of the Earth
• 4.6 billion years old
• Universe 13.7 billion years old
• Complex: but woven out of 30ish main molecules
– oxygen, hydrogen, carbon, nitrogen, Sulphur
and phosphorus. (evidence #1)- present in early
Earth- amino acids, RNA, DNA, Phosphorus,
ATP
• Collision Theory and gravity.
Evidence of Evolution
Earth is Old: Fossils
•Fossils: the remains or impression of a prehistoric
organism preserved in petrified form or as a mold
or cast in rock.
–record shows changes in organism over the past
3.6 billion years.
–Transitional species – show the link between an
ancestral form and that of the descendants (many
examples)
Changes begin
from simple to
more complex
Generally
older
fossils
are lower
in the
strata
First Life Form –
simple cells – fossil
evidence 3.4 billion
years ago
Fossil Record Supports Evolution
• Millions of fossils have been discovered
• Fossil record shows changes of organisms through time from simple to
more complex.
• Documents the order of appearance of groups and types of organisms
• Transitional Species show transitions from fish to tetrapods (fish to
salamanders, salamanders to reptiles), dinosaurs to birds, proto-horses to
horses , apes to human, synapsid to mammals.
• Document major crises in Earth’s history and the recovery from events.
Example of transitional species- Whales
Meet the transitional
species
From Land to Water
Tiktaalik – 375 million
years ago – Out of the
soup- Whales represent a
return to water (50 million
years ago) Tiktaalik – out
of the water.
Features- flexible neck,
limb-like fins suitable for
shallow waters and land
Oxygen Environment
•What type of organisms increased in
numbers to pump oxygen into the air?
Photosynthetic
Red beds
Luckily- happened slowly 2.7 to 2.0
Radiometric Dating
Radiometric Dating
*Fossils
strata
show relative dating by comparing data in the rock
*Radiometric Dating ability to use absolute dating - done by
comparing proportions of radioactive isotopes in the sample.
* Radiometric Elements are unstable (called parents) and they
decay into different elements (daughter elements). Uranium to
lead.
http://science.howstuffworks.com/29145-100-greatest-discoveries-radiometric-datingvideo.htm
•Earth’s oldest crustal
rocks – 4.03 billion years
old.
•Oldest metamophised
sediment – zircon crystals
found in Canada- 4.4
billion years old.
Radiometric Dating Supports Evolution
• many naturally-occurring elements are radioactive and they break down, or
decay, at known predictable rates.
• isotope pairs are useful in dating the Earth such as rubidium/strontium,
thorium/lead, potassium/argon, argon/argon, or uranium/lead, all of which
have very long half-lives, ranging from 0.7 to 48.6 billion years.
• Subtle differences in the relative proportions of the two isotopes can give
good dates for rocks of any age.
• Dates are often cross-tested using different isotope pairs.
• Results from different techniques, often measured in rival labs, continually
confirm each other.
• Repeatable results
Natural Selection
Charles Darwin
• Not exactly a star student, but he revolutionized the scientific view of the natural
world with his Theory of Natural Selection
• Traveled on the Beagle where his journey began in 1831 for a 5 year voyage
• The Beagle traveled from Europe to the Galapagos Islands then to Australia
around the Cape of Good Hope and back to Europe
Observations aboard the Beagle
1. Species vary globally
a. Two similar species live in different areas of the
world
2. Species vary locally
a. Differences among tortoises in the Galapagos islands
3. Species vary overtime
a. Fossils of extinct animals looked similar to living
animals
Putting the pieces together !
• Some of the species Darwin noted
had never been identified before
• There were similarities between the
finches on the Islands when
compared to the ones in South
America.
• What could it be????
Natural Selection
• Natural Selection:
Organisms best suited to
their environment survive
and are able to produce
offspring
• Fitness-How well an
organism can survive
• Adaptation- Any heritable
characteristic that
increases an organisms
ability to survive
Conditions Necessary for Natural
Selection
• Overpopulation- individuals in a population have
a capacity to produce more offspring than the
environment can support
• Variations – size, form, speed, camouflage
• Struggle for existence – competition
• Those best suited to the environment will survive
and pass along their characteristics to their
offspring.
Directional Selection
• Most common
• Peppered Moths in England and the Industrial
Revolution
• Antibiotic resistance in bacteria and the use of
antibiotics
• Pesticide resistance in insects
Directional
Selection –
depends on the
Rainfall
Seed Size increases
during droughtFavors larger beaks
Allele Frequency Changes
Peppered Moths During the
Industrial Revolution in
England
Dark Color is Dominant
Show a change over time in
three generations following
darkening of the trees
Antibiotic Resistance
•Antibiotic-Resistant Mycobacterium
tuberculosis (TB)
•Methicillin-Resistant Staphylococcus
aureus (MRSA)
•Vancomycin-Resistant Enterococci
•(VRE)
•Neisseria gonorrhoeae (Gonorrhea)
•Clostridium difficile.
•Gram-negative Bacteria.
Stabilizing and Disruptive Selection
Stabilizing –
intermediate
phenotypes selected
*Examples –
• Disruptive Selection – two
extreme phenotypes selected
• Darwin’s Finches – Example short beak birds and long beak
birds were able to eat different
types of foods.
Human birth weight
Plant height
• Disruptive may result in
speciation
Disruptive Selection
•Extreme phenotypes are selected for
by the environment
•Example: African Finches – Large
and small beaked birds have a
higher survival rate than
intermediate (environmental force –
food availability)
Artificial Selection
• Artificial selection is when nature provides the variation amongst a species and
human select the traits that they find most useful.
Table Buddy Collaboration
• Describe a situation and follow the steps of natural
selection
• Overpopulation
• Variation of one adaptation – size, strength, speed,
color, etc.
• Describe the struggle for existence and the
outcome of the adaptation with the best fitness
after three generations- include genotypes and
phenotypes in your depiction.
Comparing anatomy
• Homologous Structure: structures that are
shared by related species and that have been
inherited from a common ancestor
Table Buddy Colaboration
•Research for 5 minutes examples of
homologous structures – list in your
notes
•Come up with a reason why
homologous structures support the
theory of evolution.- explain in your
notes.
Analogous Structures
• When the function is common but the
structure is different and example of this is
the wing of a bird and the wing of a
butterfly.
Vestigial Structures
• inherited from ancestors but have lost much
or all of their original function due to
different selection pressures acting on the
descendent
The Process of Speciation
•Species – population-members can
interbreed and produce fertile
offspring
•speciation-formation of new species
Table Buddy Collaboration
Green algae evolution to land
plant draw a
picture and explain process
Molecular Evidence
of Evolution
Other Supports
• All organism are cellular – membranes filled with
water – genetic material, proteins, lipids, carbs,
salts, etc.
• Most organisms use sugar for fuel in s similar
process
• -proteins as building blocks and messengers- same
amino acids to make them
Only three differences in plants and animal cells
Amino Acid Differences in Cytochrome c (CR)
Organism
Number of amino acid
differences
Human
Chimpanzee
0
0
Rhesus monkey
1
Rabbit
9
Pig
Dog
Horse
Moth
Yeast
10
10
12
24
38
DNA Similarities
Collaboration – One Minute Summary 
• Discuss with your table buddy what you
would like to summarize as evidence of
evolution covered in this unit – must include
examples, all evidence presented. I will have
you summarize in a 30 second to one minute
summary -
Descent with Modification
• A shared character is one that two lineages have
in common, and a derived character:
character the sets the group
Examples of derived characters
Amniotic egg, lungs, vertebral
Columns, etc.