Download Natural Selection and Early Evolutionists

Natural
Selection
True or False
1. Evolution is a theory about the origin of life.
False
2. Organisms are always getting better through evolution
3. Natural selection involves organisms trying to adapt
False – no perfect
organism
False ~ results from
genetic variation
4. Evolutionary theory is invalid because it is incomplete and cannot
give a total explanation for the biodiversity we see around us.
False ~ All scientific theories are works in progress . As
new evidence is discovered, theories are revised or even
disproven
Important Vocabulary
1. Species: A group of organisms whose individuals
can breed together to produce fertile offspring.
2. Population: A localized group of individuals
belonging to the same species.
 Examples: a herd of bison
3. Evolution: A slow change in a population over time.
4. Adaptation: any structural or physiological change
that gives an organism an advantage in the
environment.
 Examples: stingers, wings, camouflage,
maintaining a constant body temperature,
containing a poisonous chemical
Charles Darwin explained how
Natural Selection could cause a
population to adapt & change over
time. (“population” will change -not
an “individual”)
Route of Darwin’s 5 Year Trip
Galapagos
Islands
Darwin spent a lot of time and collected a lot
of specimens from the Galapagos Islands.
Charles Darwin: An Unlikely Evolutionist
1.Who was Charles Darwin?
a.1809: English naturalist
b.Went on a 5 year voyage on the
HMS Beagle as an unpaid
scholar
 Collected plants & animals
during journey
c. Darwin did not set out to develop
a theory of evolution
d.Observations and specimens
collected helped Darwin
formulate his theory of evolution
Charles Darwin
Darwin’s Observations
1. In Argentina, Darwin saw
earthquakes raising the earth
several feet
2. Shells of marine animals found
far inland & at great heights in
Andes Mts
3. Fossils of huge sloths &
armadillo-like animals (both
extinct) – similar to modern
forms
4. Animals on Galapagos were
similar but not same as those
on mainland S. America &
Antarctica
Galapagos penguin
•14 inches tall
•5 lbs
•Eat small fish &
sardines
•Nests in burrows
Chinstrap penguin
•28 inches tall
•9-14 pounds
•Eat small fish & krill
•Build nests out of
small stones
Darwin’s Observations on the Galapagos Islands
Finches on Galapagos
resemble mainland
finch, but there were
more types on the
islands
The Work of Lyell Influenced Darwin’s Ideas
1. Charles Lyell – English geologist
a. 1830: On the Principles of Geology
b. Natural forces & processes that shaped ancient Earth
are the same forces acting on Earth today.
EX: Rain erodes mountains & molten rock pushes up
to create new ones.
a. Earth’s geologic features formed as a result of gradual
processes
b. Must take millions of years to change geography.
2. Darwin read Lyell’s work while on his voyage & agreed
with Lyell’s conclusions
Malthus: Organisms have more offspring than
nature can support
Slide # 12
The Work of Malthus Influenced Darwin’s Ideas
1. 1798: Thomas Malthus --Economist
a. Essay on the Principle of
Population
b. Said that plants and animals tend
to have more offspring than nature
can support
c. Food production increase at a
slower rate than population
2. Darwin read Malthus’s essay after he
returned from his voyage
3. Darwin concluded that all organisms
produce more offspring than the
population can support
Thomas Malthus
Lamarck’s Theory of Use and Disuse
1.1801: Theory of Inheritance of Acquired Characteristics
a.“Theory of inheritance of acquired characteristics” &
“Use and disuse”
b.If an organism changes in order to adapt to its
environment, those changes are passed on to
offspring.
(We now know that individual organism cannot
change or adapt to their environment)
Said that changes in organisms occur to help an
organism reach perfection.
Problem?: there are NO perfect organisms
Example of Lamarck’s Hypothesis
Slide # 15
Darwin explained Evolution by Natural Selection
1.1859: Darwin published On the Origin
of Species
a.Proposed that natural selection was
the mechanism for evolution.
• Individuals vary in one or more
traits & there can be slight
differences in their ability to
survive & reproduce.
b.Nature selects those individuals w/
favorable traits to leave more
offspring that are better suited (FIT)
for their environment.
Published 25
years after
Darwin wrote it!
Evidence that Supports Evolution: Fossil Record
Youngest, most complex fossils
Oldest, simplest fossils
1. Fossil: preserved remains (bones, teeth, shells) or evidence
(imprint or footprint) of ancient organisms.
Geographic
Distribution of Living
Species
1. Biogeography: the
geographical distribution of
species in relation to geography
and other species
2. Influenced by continental drift
3. Leads to convergent evolution:
the appearance of apparently
similar structures in organisms
in different lines of descent
Convergent:
Con-: together, with, jointly
Verge-: to move or incline in a certain
direction
Homologous Structures
Homologous
Homo- : same, common
-logos: relation,
reasoning, computation
-ous: possessing, full of
Homologous structures: similar structures; different functions
a. Structures develop from same clump of embryonic cells
b. Provides evidence that four-limbed vertebrates descended
from a common ancestor.
Vestigial Structures
Vestigial
Vestige: a mark, trace, or
sign
-al: having the form or
character
Pelvis & femur bones are vestigial in whales
Vestigial structures: structures or organs that are reduced in size; do not
seem to serve a useful function
Similarities in
Embryology
Pharyngeal
pouches
Hollow dorsal
nerve cord
1. The embryos of vertebrates are
very similar during early
development.
2. The same groups of embryonic
cells develop in the same order
and in similar patterns to produce
tissues & organs.
3. Implies common genes are
involved
Postanal tail
Notochord
Post Darwin: DNA Evidence Supports Evolution
We can compare amino acid sequences
to which are most closely related
We can compare DNA
sequences to which
are most closely
related
Why didn’t Darwin use DNA evidence in developing his
theory?