Natural Selection

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Natural Selection
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True or False
Slide 2

1. Evolution is a theory about the origin of life.

False
2. Organisms are always getting better through
evolution
False no perfect organism
3. Natural selection involves organisms trying
to adapt
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.phpa1
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Important Vocabulary
Slide 3

• 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

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Charles Darwin His Journey and Observations
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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)

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Route of Darwins 5 Year Trip
Slide 6
Galapagos Islands
Darwin spent a lot of time and collected a lot of
specimens from the Galapagos Islands.
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Charles Darwin An Unlikely Evolutionist
Slide 7

• Who was Charles Darwin?
• 1809 English naturalist
• Went on a 5 year voyage on the HMS Beagle as an
  unpaid scholar
• Collected plants animals during journey
• Darwin did not set out to develop a theory of
  evolution
• Observations and specimens collected helped
  Darwin formulate his theory of evolution

Charles Darwin
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Darwins Observations
Slide 8

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

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Darwins Observations on the Galapagos Islands
Slide 9

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

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Ideas that Shaped Darwins Thinking
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The Work of Lyell Influenced Darwins Ideas
Slide 11

• Charles Lyell English geologist
• 1830 On the Principles of Geology
• 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.
• Earths geologic features formed as a result of
  gradual processes.
• Must take millions of years to change geography
• 2. Darwin read Lyells work while on his voyage
  agreed with Lyells conclusions

Charles Lyell
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The Work of Malthus Influenced Darwins Ideas
Slide 12

• 1798 Thomas Malthus --Economist
• Essay on the Principle of Population
• Said that plants and animals tend to have more
  offspring than nature can support
• Food production increase at a slower rate than
  population
• Darwin read Malthuss essay after he returned
  from his voyage
• Darwin concluded that all organisms produce more
  offspring than the population can support

Thomas Malthus
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Old Theories of EvolutionLamarcks Theory of
Use and Disuse
Slide 13

• 1801 Theory of Inheritance of Acquired
  Characteristics
• Theory of inheritance of acquired
  characteristics Use and disuse
• 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)
• 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
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Example of Lamarcks Hypothesis
Slide 14

• Example of Lamarcks hypothesis
• Male crab uses small front claw to ward off other
  males
• Because it has been used a lot, front claw
  becomes larger.
• 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
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Darwin explained Evolution by Natural Selection
Slide 15

• 1859 Darwin published On the Origin of Species
• 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.
• 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!
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The Evidence that Darwin used to Develop the
Theory
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Evidence that Supports Evolution Fossil Record
Slide 17

• 1. Fossil preserved remains (bones, teeth,
  shells) or evidence (imprint or footprint) of
  ancient organisms.
• Fossils found in sedimentary rock
• Younger sediments deposited on top of older
  sediments
• Older sediments contain older, simpler fossils
• Younger sediments contain younger, more complex
  fossils
• Fossils found in sediments of organisms that are
  extinct.

Trilobites are extinct!
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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.
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Evidence that Supports Evolution Homologous
Structures
Slide 19

• 1. Homologous structures similar structures but
  different functions
• Structures develop from same clump of embryonic
  cells
• 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
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Evidence that Supports Evolution Similarities
in Embryology
Slide 20

• 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.

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Post Darwin DNA Evidence Supports Evolution
We can compare DNA sequences to which are most
closely related
We can compare amino acid sequences to which are
most closely related
Why didnt Darwin use DNA evidence in developing
his theory?
It had not yet been discovered!