Transcript Chapter 16: Darwin’s Theory of Evolution

CHAPTER 16: DARWIN’S THEORY
OF EVOLUTION
Section 16-4: Evidence of Evolution
BIOGEOGRAPHY
The study of where organisms live now and
where they and their ancestors lived in the
past
 Patterns of distribution tell how modern
organisms evolved from ancestors
 Two patterns important to Darwin:
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Closely related but different – Galapagos species
similar to mainland species, suggests natural
selection caused variations
 Distantly related but similar – similar habitats
can lead to similar adaptations in distantly related
species

THE AGE OF THE EARTH AND FOSSILS
Hutton/Lyell argued Earth was old – but how
old?
 Modern geologists use radioactive dating to
determine age of rocks/fossils
 Earth is about 4.5 billion years old
 Darwin’s study of fossils convinced him, but
paleontologists had not yet found enough fossils
of intermediate species
 Since then, many have been found
 Whales from ancient land mammals
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RECENT FOSSIL FINDS
History of life incomplete
 Always more to learn
 Evidence shows change
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COMPARING ANATOMY AND EMBRYOLOGY
All vertebrate limbs have same basic bone
structure
 Animals with similar structures evolved from
common ancestor
 Homologous structures – same basic
structure, shows common ancestry – different
function
 Study anatomical details, development in
embryos, pattern of appearance
 Similarities/differences show how recently
organisms shared a common ancestor

COMPARING ANATOMY AND EMBRYOLOGY
Common structure = common descent, not
common function
 Body parts that share common function but not
structure are analogous structures
 Bee wing and bird wing

COMPARING ANATOMY AND EMBRYOLOGY
Vestigial structures – inherited from ancestors
but have lost much of their original function
 Ex: hipbones of dolphins, wings of flightless birds
 Maybe presence of structure has no affect on
fitness

COMPARING ANATOMY AND EMBRYOLOGY
Early developmental stages of many vertebrates
look similar
 Cells develop in the same order
 Shows common ancestry

GENETICS AND MOLECULAR BIOLOGY
Central dogma
 Genetic code is universal – most organisms share
the same genes
 Shows common ancestry

HOMOLOGOUS MOLECULES
Homologous proteins share structural/chemical
similarities
 Ex: Similar versions of cytochrome c (cellular
respiration) found in all living cells
 Can also have homologous genes – Hox genes
direct limb development
 Minor changes in genes leads to major changes in
structures

TESTING NATURAL SELECTION

Gather evidence by observing it in action

Grants and the Galapagos finches (read in text!)
Showed competition and environmental change drive
natural selection
 Heritable variation the key – increased variation
increases likelihood of adapting/surviving changes

EVALUATING EVOLUTIONARY THEORY
Theory of evolution considered the grand
unifying theory of the life sciences
 Constantly being reviewed as new data is
gathered
 Questions that remain are about how evolution
works, not whether it occurs
