Download Darwin*s Theory of Evolution

Darwin’s Theory of Evolution
16.3 and 16.4
Natural Selection
• The process by which organisms with
variations most suited to their local
environment survive and leave more offspring.
• Operates like artificial selection, but occurs IN
NATURE.
When Does Natural Selection Occur?
1. When more organisms are born than can
survive (the carrying capacity has been
reached).
When Does Natural Selection Occur?
2. When there is natural heritable variation and
adaptation.
An adaptation is a heritable characteristic that
increases an organism’s ability to survive.
When Does Natural Selection Occur?
3. There is variable fitness among individuals.
High fitness- adaptations suitable to the
environment, can survive and reproduce.
Survival of the fittest
Common Descent: Evolutionary Trees
Evidence That Supports
Evolution Theory
F- fossils
A- anatomical structures
M- molecular evidence
E- embryological evidence
Support for Evolution 1: Fossils/
Age of Earth
• Earth is 4.5 billion years old according to
radioactive dating.
• Paleontologists have recently discovered
fossils that form a series that traces the
evolution of modern species from extinct
ancestors.
– Examples: whales from land mammals, birds from
dinosaurs, fish from four-legged land animals.
Types of Whales
Whale Evolution Theory
Support for Evolution 2: Anatomical
Structures
• Homologous structures are shared by related
species and have been inherited from a
common ancestor.
– Results from descent with modification from a
common ancestor.
Analogous Structures
• Analogous structures are body parts that
share a common function, but not structure.
Vestigial Structures
• Vestigial structures are inherited from
ancestors but have lost much or all of their
original function due to different selective
pressures.
– Example: hip bones in dolphins
Support for Evolution 3:
Molecular Biology
• Universal genetic code and homologous
molecules.
• Examples: cytochrome c, Hox genes
Support for Evolution 4: Embryology
• Similar patterns of embryological
development.
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Testing Natural Selection
• This is difficult because evolution takes
millions of years.
• Peter and Rosemary Grant have spent 35 years
studying the Galapagos finches.
– Natural selection takes place in wild finch
populations frequently and sometimes rapidly.
– Variation within a species increases the likelihood
that the species can adapt to and survive
environmental change.
Modern Example of Evolution:
Antibiotic Resistance and Superbugs
Bacterial Conjugation