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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: - PowerPoint PPT Presentation
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CHAPTER 16: DARWIN’S THEORY OF EVOLUTIONSection 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: 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
RECENT FOSSIL FINDS History of life incomplete Always more to learn Evidence shows change
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