Download Evidences of Common Ancestry

How did the Earth come to be?
The three most widely accepted ideas:
1. Spontaneous generation
2. Divine creation
3. Extra-terrestrial (meteor or
asteroid)
What
was the
early
earth
like?
Cyanobacteria– believed to be
responsible for oxygenating the earth
Biogenesis vs. Spontaneous
generation
Biogenesis
•Living things come only
from other living things
•Pasteur
•Redi
•Spallanzani
Spontaneous
Generation
•Living things can arise from
non-living things
•Attempts to explain origin of
life on earth
•Miller & Urey
Pasteur’s experiment (Redi & Spallanzani had similar experiments) was meant to
prove that living things cannot spontaneously generate from non-living.
Miller-Urey
Experiment
(produced molecules of life
from a non-living environment)
The Bubble Model– primordial soup
1. Chemical environment (earth
is cooling, volcanoes, storms)
2. Primitive proteins
are formed.
4. Primitive bacteria
are formed.
3. Molecules form
into cell structures.
Endosymbiosis– the process that could have
resulted in the evolution of prokaryotes to
eukaryotes
1) infolding of the plasma membrane became ER & Golgi
2) Engulfing smaller bacteria became organelles like mitochondria & chloroplasts
The Fossil Record
•How they determine the age of the earth
•How they track the progression of living things
on earth
•Carbon-14 dating tells the approximate age of
fossils (based on half-life)
radioisotopes have a known rate of
decay, measuring the amount of a
radioisotope tells its approximate age
•Examples: sediments, molds, bones, casts,
prints, shells
2 Theories of Evolution
Lamarck
• Proposed that species
descended from a
common ancestor
• Believed in acquired
traits– not from heredity
but from experience and
behavior
Jean Baptiste
Lamarck (17441829)
Darwin
• Proposed the idea of
natural selection
• Believed that genetic
traits are passed to
offspring
• Survival of the fittest
Charles Darwin
(1809-1882)
Darwin’s voyage on the H.M.S. Beagle,
1831-1836
Darwin was the ship’s naturalist, meant to collect specimens & make
observations. At some points, the ship left him at ports for months
at a time. He trekked hundreds of miles through unmapped territory,
and collected fossils and specimens.
After extensive study in the Galapagos, Darwin determined that over
millions of years, large differences can occur among species
Evolution by Natural Selection
(Darwin’s theory)
1. All species have genetic variation
2. Living things face many challenges in the
struggle for existence.
3. Individuals of the same species compete with
one another for survival.
4. Individuals that are better able to cope with the
challenges of their environment tend to leave
more offspring than those less adapted.
5. The population changes to reflect the
characteristics of the individuals more suited
for survival.
The process of natural selection
changes a population over time.
1. All species have variety.
2. Organisms struggle for
survival.
3. Individuals compete with
each other.
4. Individuals who are more
fit for survival live longer
and reproduce more
successfully.
5. The traits of the more fit
will be passed down to
new generations.
Long necks= adaptive advantage
Patterns of Evolution
• Coevolution– change of two or more
species in close association with each
other
Predator-prey relationships
Pollination relationships are very
common examples of coevolution.
Patterns of Evolution
• Convergent evolution– two species appear
similar though they have no connection.
Phenotypes were selected to suit the
environment.
Patterns of Evolution
• Divergent evolution- two or more related species
become more and more dissimilar (due to
change in habitat, environmental causes)
– Adaptive radiation– many species evolve from a
single ancestor (Darwin’s galapagos finches)
– Artificial selection– species are bred to emphasize
certain traits. (ex. Dogs & race horses)
Evidences of Common Ancestry
Anatomy– structures that are similar
Embryology– development of embryos
is similar
Biochemistry– DNA and proteins are
the same
Evidence of common ancestry
• Homologous structures– similar structures
across diverse species
NOT evidence of common ancestry
• Analogous structures– similar functions, look
somewhat alike, but have different development
& anatomy – implies common adaptive
advantages
Evidence of common ancestry
• Vestigial structures– apparently useless
features that may be leftovers from an ancestor
tailbone
appendix
Evidence of common ancestry
• Embryological similarity
Evidence of common ancestry
• Embryological similarity
Evidence of common ancestry
• Embryological similarity
Evidence of common ancestry
• Embryological similarity
Evidence of common ancestry
• Macromolecular similarity– many species
share almost the same DNA, and they’re all
made of adenine, guanine, cytosine, and
thymine.