Download Natural Selection

Natural
Selection
Slide # 2
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
Source:
http://evolution.berkeley.edu/evolibrary/misconceptions_faq.php#a1
Slide # 3
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.
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: structural = stingers, thorns, camouflage
physiological = being heterozygous for
sickle cell anemia (protection against
malaria), endotherms maintain constant
body temp & can live in colder climates
than amphibians and reptiles
Charles Darwin : His
Journey and
Observations
Slide # 5
Charles Darwin explained how
Natural Selection could cause a
population to adapt and change
over time. (note he states- a
“population” will change -not an
“individual”)
Slide # 6
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.
Slide # 7
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
Slide # 8
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
Slide # 9
Darwin’s Observations on the Galapagos Islands
1.Fewer types of
organisms on the islands
2.Island species differ from
mainland species & from
island to island
3.Finches on Galapagos
resemble mainland finch,
but there were more
types on the islands
Ideas that Shaped
Darwin’s Thinking
Slide # 11
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
Charles Lyell
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
Slide # 13
Old Theories of Evolution:
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 organisms cannot
change or adapt to their environment)
a.Said that changes in organisms occur
to help an organism reach perfection.
• Problem: No organism is perfect
Lamarck
Zoologist;
came up with
the word
invertebrate.
Most
scientists
thought these
creatures
were too
lowly to study
Slide # 14
Example of Lamarck’s Hypothesis
Example of Lamarck’s hypothesis:
1. Male crab uses small front claw
to ward off other males
2. Because it has been used a lot,
front claw becomes larger.
3. Larger claw trait is passed on to
offspring.
Even though his hypothesis is flawed, he was
the first to address the fact that organisms adapt
to their environment
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!
The Evidence that
Darwin used to Develop
the Theory
Slide # 17
Evidence that Supports Evolution: Fossil Record
1. Fossil: preserved remains (bones,
teeth, shells) or evidence (imprint or
footprint) of ancient organisms.
a. Fossils found in sedimentary rock
b. Younger sediments deposited on
top of older sediments
c. Older sediments contain older,
simpler fossils
d. Younger sediments contain younger,
more complex fossils
2. Fossils found in sediments of
organisms that are extinct.
Trilobites
are extinct!
Evidence that Supports Evolution:
Geographic Distribution of Living Species
1. Biogeography: the geographical
distribution of species in relation to
geography and other species
2. Influenced by continental drift
Flying squirrels and sugar
gliders look similar, but are
only found on their
respective continents.
Similarities in appearance
are due to development
under similar selection
pressures.
Slide # 19
Evidence that Supports Evolution: Homologous Structures
1. Homologous structures: similar
structures but different functions
a. Structures develop from same
clump of embryonic cells
b. Provides evidence that four-limbed
vertebrates descended from a
common ancestor.
2. Vestigial structures: structures or
organs that are reduced in size; do not
seem to serve a useful function
3. Homologous & vestigial structures
imply that common genes are
involved.
Homologous structures:
forelimbs of vertebrates
Pelvis & femur bones
are vestigial in whales
Slide # 20
Evidence that Supports Evolution:
Similarities in Embryology
1. The embryos of vertebrates are very similar during early
development.
** All vertebrate embryos have: 1.) Notochord, 2.) dorsal hollow nerve
cord, 3.) pharyngeal slits, and 4.) post-anal tail
2. The same groups of embryonic cells develop in the same
order and in similar patterns to produce tissues & organs.
3. Common cells & tissues growing in similar ways produce
homologous structures.
4. Implies that common genes are involved.
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? It had not yet been discovered!