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15.1 Notes – Darwin’s Evolution
Evolution
The process by which modern organisms have
descended from ancient organisms
Charles Darwin (1809-1882)
- Founder of modern evolutionary theory
- Sailed around the world on the HMS Beagle
- Study of plant/animal life in the Galapagos
islands
- Great diversity of life, many species similar but
different to previously known species
- Book named – On the Origin of Species
Patterns of Diversity
Noticed that plants/animals seemed really well
suited to survive in their environments, and that
similar ecosystems could contain very different
organisms. Different shaped beaks on birds.
Fossils
Preserved remains of ancient organisms, some
looked like current animals, and some looked
completely different than anything alive then
15.2 Notes – Ideas That Helped Darwin’s Thinking
Current Beliefs in 1800’s
Earth was a few thousand years old, planet nor
organisms ever changed and earth and
organisms have been in same form since
beginning of “time”
New evidence…
During this period of discovery, people found
fossils that didn’t support this, so thought
multiple periods of creation preceded by
catastrophic events
More new evidence…
Hutton & Lyell – recognized that earth is millions
of years old and processes are always changing
it.. (erosion, earthquakes, fires, etc.)
Lamarck’s Hypothesis
Selective use of traits led to acquiring or losing
these traits over a lifetime & these changes were
passed down from gen. to gen.
Thomas Malthus
English economist that studies population
growth
- Noted that if human population continued to
grow unchecked, we would run out of food and
living space
15.3 Notes – Darwin’s Case (Origin of Species)
Artificial Selection
A technique in which a breeder selects particular
traits (ex. dogs, horses, etc.) – similar to
selective breeding, humans selected traits they
found useful
Struggle for Existence
Members of each species compete to obtain
food, living space and other resources
Fitness
The ability of an individual to survive and
reproduce in its specific environment
Adaptations
Evolution of features that help an organism
better survive in an environment (lg. eyes of
nocturnal creatures)
Survival of the Fittest
Indiv. that are better suited to their environment
survive and reproduce most successfully
Natural Selection (N.S.)
A change in populations that occur when
organisms of favorable traits for an environment
survive, reproduce, and pass them on to the
next generation – survival of the fittest
N.S. over time…
Natural selection results in changes in the
inherited characteristics of a population. These
changes increase a species’ fitness in it’s
environ.
Descent w/ modification
Over time, N.S. produces organisms that have
different structures, occupy different habitats &
establish different niches… so species
descend, with changes, from other species over
time
Common Descent
All species, living and extinct, are derived from
common ancestors
Evidence of Evolution – “The Grand Unifying Theory of Life Sciences”
1) Fossil Record
Fossils show changes over time. Buried in
different rock strata from different periods helps
to date. Can compare older & newer strata to
see differences… MANY similarities
2) Geographic Distribution
Same species in different areas can be very
different while different species in similar areas
can be very similar 
● Homologous structures
Structures that have different mature
forms in different organisms but develop
from the same embryonic tissues (ex. Fig
15-15, forelimbs)
● Analogous structure
A body part that is similar in function, but
different in structure (insect v. bird wings)
● Vestigial structure
A body structure that is reduced in function
over generations (ostrich wings)
3) Embryological Similarities
The early stages of many animals are VERY
similar, especially backboned organisms (ex. Fig
15-17, fish, reptiles, birds & mammals ALL have
gill slits & tails as embryos)
4) Genetic similarities
Most reliable. All known organisms are based
on the same fundamental biochemical
organisation: A piece of DNA in a bacterium
codes for the same amino acid as in a human
cell. Also, ATP is used as energy currency by all
extant life.