Chapter 15 Darwin

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Chapter 15Darwins Theory of Evolution
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15-1 The Puzzle of Lifes Diversity

• The variety of organisms is called biological
  diversity. How did all these different organisms
  arise? How are they related?
• - Evolution change over time
• - Theory of evolution a collection of
  scientific facts, observations and hypotheses

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Voyage of the Beagle

• - Charles Darwin made numerous observations and
  collected evidence that led him to propose a
  revolutionary hypothesis about the way life
  changes over time.
• - 1831 He sailed on the HMS Beagle around the
  world
• - Observed collected plant and animal specimens

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Darwins Voyage
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Darwins Observations

• - He saw variety in traits, method of
  reproducing, where they live
• - He saw fossils and compared to current living
  organisms in area
• - Galápagos Islands 1000 km west of S. America
• - islands had different climates and slightly
  different organisms

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The Journey Home
Giant Tortoises of the Galápagos Islands
Pinta
Tower
Marchena
Pinta IslandIntermediate shell
James
Fernandina
Santa Cruz
Isabela
Santa Fe
Hood Island Saddle-backed shell
Hood
Floreana
Isabela Island Dome-shaped shell
Darwin observed that the characteristics of many
animals and plants varied noticeably among the
different Galápagos islands
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Galapagos organisms
Galapagos tortoise
Marine Iguana
Frigate bird
Albatross
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15-2 Ideas That Shaped Darwins Thinking

• An Ancient, Changing Earth
• Hutton and Lyell (geologists) helped scientists
  recognize that Earth is many millions of years
  old, and the processes that changed Earth in the
  past are the same processes that operate in the
  present.

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15-2 Ideas That Shaped Darwins Thinking

• Lamarcks Evolution Hypothesis
• - Jean-Baptiste Lamarck ( French naturalist)
  proposed that by selective use or disuse of
  organs, organisms acquired or lost certain traits
  during their lifetime. These traits could then be
  passed on to their offspring. Over time, this
  process led to change in a species.

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• - Organisms have tendency towards perfection.
• - Organisms can alter traits.
• - New traits can be passed to offspring.
• - Ex If you lift weights to build muscle, your
  children will be born with big muscles.
• - This theory has been disproved by many
  experiments and observations.

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Figure 157 Lamarcks Theory of Evolution

1. Male uses small claw to attracts mates and wards
   off predators.
2. Front claw becomes larger through use.
3. The acquired characteristic, a large claw, is
   passed to offspring.

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• Population Growth
• Thomas Malthus (economist) reasoned that if the
  human population continued to grow unchecked,
  sooner or later there would be insufficient
  living space and food for everyone.

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15-3 Darwin Presents His Case

• Darwin discovered that the Galápagos Islands were
  home to species that are found nowhere else, but
  similar to organisms from S. America.
• Publication of On the Origin of Species
• - Darwin proposed a mechanism for evolution
  called natural selection in the book On the
  Origin of Species 1859

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Evolution by Natural Selection

• - Struggle for existence Darwin observed high
  birth rates and a shortage of basic needs cause
  competition
• - Fitness the ability of an individual to
  survival and reproduce in its environment

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• - Adaptation an inherited characteristic that
  increases an organisms chance of survival
• 1. structural porcupines sharp quills
• 2. physiological the way a plant does
  photosynthesis
• 3. behavioral how animals live and hunt in
  groups

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• - Process of survival of the fittest
• 1. Individuals in a population compete for
  resources
• 2. Those with characteristics best suited to the
  environment survive and reproduce pass on the
  beneficial characteristics
• 3. Over many generations, the beneficial
  characteristics appear in more members
• - Ex Peppered moths of Manchester

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• - Common descent principle that all species,
  living and extinct, were derived from common
  ancestors

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Evidence of Evolution

• - Fossil record fossils from deeper rock layers
  are older than fossils from shallower layers
• - Geographic distribution of living species
  Darwin saw many different species of finches in
  Galápagos Islands descended with modification
  from a common mainland ancestor

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Figure 1514 Geographic Distribution of Living
Species
Beaver
Beaver Muskrat Beaver andMuskrat Coypu
Capybara Coypu andCapybara
NORTH AMERICA
Muskrat
Capybara
SOUTH AMERICA
Coypu
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• - Homologous Body Structures structures that
  have different mature forms but develop from the
  same embryonic tissues
• - Ex limbs of reptiles, birds and mammals are
  constructed from same basic bones
• - Scientists can compare how similar the bones
  are to find degree of relations

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Figure 1515 Homologous Body Structures
Turtle
Alligator
Bird
Mammal
Ancient lobe-finned fish
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• - Vestigial organs organs that are reduced in
  size and resemble homologous organs of other
  species
• - Ex legs of skinks (lizards), appendix and
  tailbone of humans, snakes and whales have femur
  and pelvis bones

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VestigialOrgans
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• - Embryology The early stages, or embryos, of
  many animals with backbones are very similar

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Concept Map
Evidence of Evolution
includes
which is composed of
which indicates
which implies
which implies
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Summary of Darwins Theory

• - Individuals differ variation is heritable
• - More offspring are born than can survive
• - Organisms compete for limited resources
• - Organisms best suited for the environment live,
  reproduce, and pass on traits natural selection
• - Species have descended with modification from
  common ancestors

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Strengths and Weaknesses of Evolutionary Theory

• - Questions as to precisely how new species arise
• - Uncertainty in how life began