The idea of CHANGE OVER TIME
I. The Beginning of Life
A. Origin of the Universe: Big Bang Theory
> 15 billion yrs. ago
B. Earth’s Origin
1. 4.6 billion yrs. ago out of gases
2. Gases formed our atmosphere
C. Life’s Origin
1. first cells probably resembled anaerobic
bacteria
2. Endosymbiotic Theory – Eukaryotic cells
arose from prokaryotic organisms
II. Theories of Evolution
A. Lamarck (French biologist)
1. Evolution results from the use and disuse of
physical features.
e.g. Birds
kept trying to use front limbs for flying
that they turned into wings
If didn’t use wings, they would shrink &
disappear
2. Traits are passed on to offspring
3. He was WRONG, but his ideas showed that
living things change over time
B. Malthus (English economist)
1. Stated that human population would increase
faster than food supply and living space
2. This idea would be applied to all species and
would influence Darwin’s theory
C. Charles Darwin (British naturalist)
1. The modern theory of evolution has taken
shape due to his work
2. Development of his theory
a. He sailed around world studying different
organisms (Ex: Galapagos Islands - finches)
Galapagos Islands
Darwin’s route
b. Combined what he saw with the ideas of Malthus
and made one key association:
Individuals with traits better suited to an env’t are
more likely to survive, reproduce, and pass on
traits (survival of the fittest) Natural Selection
3. His Theory: NATURAL SELECTION
“Survival of the Fittest” - Individuals w/ the best
traits are better suited for the env’t and will
reproduce more often.
this theory incorporates 3 principle aspects:
a. Genetic Variation - differences exists within a
species (e.g. some cows produce more milk,
some plants bear larger fruit). Caused by:
1. mutations (changes in base sequences)
2. sexual reproduction combines genes from
diff. parents
3. crossing-over during meiosis
b. Competition – An interaction b/n two or more
species that use the same scarce resources
(e.g. food, water, shelter).
Organisms produce more offspring than env’t
can support (ex. carrying capacity).
They compete for the same resources
c. Requires Adaptation
1. organisms respond to their env’t, undergo
changes, & increase their chances of survival
2. Thus, evolution can be thought of as:
Descent with Modification
“change over time”
Example: Galapagos Island Finches
Beaks adapted to diff. seasons (i.e. wet/dry)
Diff. plants produce diff. seeds
4. Publication of his work (1859)
After years of further research & improvements,
Darwin published his ideas in a book:
“The Origin of Species
by means of Natural Selection”
D. Darwin’s Ideas Updated
1. Natural selection causes change in a pop.
- the frequency of alleles increases/decreases
over time
- Genetic Drift – in small populations, a
particular allele may become more common
by chance (as compared to larger population)
2. Isolation of a population leads to species
formation (i.e. speciation)
geographic: physical barrier; island/mountain
reproductive: members of 2 pops. can’t interbreed
behavioral: two pops. have different habits
3. When one species becomes extinct, it is
replaced by another
III. Evidence of Evolution
Organisms have changed over time?
A. Fossil Record
1. Fossil evidence
a. Fossil – the preserved remains of an
organism. Forms imprints/molds in rock
and mud.
b. Radioactive dating - Use radioactive
isotopes to determine age
- decay rate of carbon-14 used to date
young fossils
2. Interpreting fossils
a. Paleontologist – studies fossils
b. Geologist – uses fossils to explain earth’s
history
a. Anthropologist – studies human evolution
3. History of Life on Earth
a. Hadean Eon – 4.5 billion yrs. ago
appearance of bacteria/cyanobacteria?
b. Paleozoic Era – 250 mil. yrs. ago
plants, aquatic life, 1st land animals
c. Mesozoic Era – 66 mil. yrs. Ago
age of reptiles (dinosaurs)
d. Cenozoic – present time
age of mammals, flowering plants
Important Note about the fossil record:
the fossil record is incomplete
1. Many species lived in unfavorable environments
that do not allow for fossil formation
Ex. Grasslands, mountains, deserts
2. Even though it is incomplete, the fossil record
still presents us w/ strong evidence of evolution
B. Other Evidence
1. Body structure
a. Homologous structures – Diff. organisms
have body parts w/ similar structure, but diff.
fxn (suggests a common ancestry)
b. Analogous structures – Diff. organisms have body
parts with a similar fxn, but not structure.
Insect wing Bat wing
Bird wing
c. Vestigial Structures – body parts are reduced in
size and appear to have no fxn
(e.g. appendix, human tail bone, snake legs)
2. Compare embriology and biochemistry
--similar embryos show a closer relationship
lamprey turtle chicken cat human
IV. Patterns of Evolution
1. Adaptive Radiation – diff. species evolve from
one ancestral species. Each has a diff. niche
Ex. Finches
2. Convergent Evolution – Natural selection produces
similar adaptations in diff. organisms in response
to similar envt’s. Ex:
Sharks (fish), penguin (bird), dolphin (mammal)
Wings/flippers perform the same fxn
3. Divergent Evolution – When two species gradually
become increasingly different. Can be linked to
one species having a new habitat.
ex. humans & apes
polar bear & brown bear
4. Coevolution – Species that interact closely often
adapt to one another.
Ex. Hawk moth and Orchids
5. Punctuated Equilibrium/Gradualism
a. Punctuated Equilibrium – organisms change
rapidly, over a short period of time. There
are also periods of no change
b. Gradualism – change occurs slowly, over a
long period of time
Example: Giraffe necks
Cladogram (a.k.a. phylogenic tree)
A diagram that depicts how organisms are related to one another by
showing how evolutionary lines evolved and branched off from
common ancestors over time
Vocab:
1. Clade – a group of species that includes a single common
ancestor and ALL descendents of that ancestor
1. A common ancestor of species E and C?
2. What two species are most closely
related?
a) A and B c) C and D
b) B and C d) E and A
3. What are the three clades in this
picture?
Refer to Cladogram Practice Packet
Cladogram #1
Cladogram #3
