Evolution
Mrs. Rago
Bio
Charles Darwin
 English scientist who developed theory of evolution
 Studied species on the Galapagos Islands
 Observed the species to compare features from each
Natural Selection
 Mechanism for change in populations
 Occurs when an organism with certain variations
(characteristics) survive, reproduce, & pass on their
variations to the next generation
 These variations make the organism more likely to survive and
reproduce
Reproduction in Natural Selection
 Favorable traits make individual more likely to survive &
reproduce
 Individuals with the best traits pass them on to their offspring
Convergent Evolution
 Process by which different species evolve similar traits
 Different ancestors but species with similar traits that have
evolved to deal with the problem
Divergent evolution
 Descendants of a single ancestor diversify into species that
each fit different parts of the environment
Coevolution
 When 2 or more species have evolved adaptations to each
other’s influence
Artificial Selection
 Breeding organisms to produce offspring with identical traits
 Example: breeding pure bred dogs
On the Origins of Species
 Book by Charles Darwin
 First book on evolution
Structural Adaptations
 Changes that have developed in an organism’s form over time
 Example: thorns on some plants
 Take a long time to occur
 Millions of years
Mimicry
 Structural adaptation that allows one species to resemble
another species
 Useful for a harmless species to resemble a harmful species,
so that predators avoid the harmless species
King snake-non venomous
Coral snake- venomous & deadly
Camouflage
 An adaptation that allows a species to blend into their
surroundings and avoid predators
Physiological adaptations
 Occur much faster
 Changes in an organisms metabolic processes
 Example: resistance to penicillin, insects & weeds resistant to
specific pesticides
Evidence for Evolution
 Fossil record
 Shows evidence of evolution but it is incomplete
 Anatomy
 Homologous structures
 Similar structures that come from a common ancestor
 Analogous Structures
 Similar structures that are similar because they are used for the same
purpose
 Vestigial Structures
 A body structure that has no function in a present-day organism but was
probably useful to an ancestor
 Example: wings of an ostrich
 Embryology
 Embryo is the earliest stage of growth & development of both
plants & animals
 Biochemistry
 Evidence for evolution, shows similarities in DNA or RNA
Atmosphere of Early Earth
 Large meteor impacted earth
 More comets hit earth and brought ice with them which
along with gases from volcanoes produces the water we now
find on earth
Atmosphere of Early Earth
 Very little free oxygen
 Water vapor
 Carbon
 Nitrogen
Evolution of photosynthesis
 Archaebacteria
 Do not require oxygen
 First group to develop
 Cyanobacteria
 Produce oxygen from their chemical reactions
 This changed earth’s atmosphere
Early Earth
 Very hot
 Lots of volcanoes meteorites
 Lots of gases
 Humans would never have survived early earth