Evolution Essential ?s
•How & why have species changed with time?
•What is the benefit & value of evolution?
•How can the theory of evolution be applied totoday?
•What evidence & thought have contributed tothe theory of evolution?
Evolution
Change in genetic make-up overtime
Process by which modernorganisms have descended fromancient organisms
The History of theDevelopment of EvolutionaryThought
1st HypothesisUse & Disuse
Jean – BaptisteLamark
1809
French naturalist
•Tendency Towards Perfection & Complexity
•organisms continually change to become betteradapted to their environment & improve survival
•Use & Disuse of Organs
•structure that are used frequently will becomelarger and be more developed during a lifetime
•structures not used will become weaker or disappear(vestigial organs) during a lifetime
•Inheritance of Acquired Traits
•newly acquired traits can be passed on to offspring
Evaluation of Lamark’s Theory
•Incorrect because…..
•acquired traits (those gained during an organismslifetime) are NOT inherited
•acquired behaviors CANNOT develop heritablecharacteristics
•Correct because….
•organisms adapt to their environment overtime toincrease survival
2nd HypothesisNaturalSelection
CharlesDarwin
1831
Voyage on the H.M.S. BeagleThe Trip around the World
•Observed many various organisms
•Researched their patterns of diversity
•Studied living organisms & fossils
•Concluded that the earth is constantlychanging
The Galapagos Islands
•Most influential location to Darwin’sdevelopment of the theory of evolution
•13 small islands off the
West coast of South
America by Ecuador
•Close proximity
•Extremely diverseclimates & environments
•Isolated from each other
•Organisms on each island vary greatly incharacteristics to be specialized & betteradapted to their diverse environments
Darwin’s Theory of EvolutionPublished in 1931“The Origin of Species”
Natural Selection
•Organisms varying in inheritable characteristics
(mechanics of genetics was unknown at this time!)
•Large population size causes competition forresources & restricts survival rate
NaturalSelection
•Organisms with traitsthat are better “fitted”or adapted to theirenvironment surviveand reproduce moresuccessfully passing ontheir superior genes tothe next generation
•Fitness
•resulting adaptations thatincrease the survival of anorganism
•Adaptations
•any inheritedcharacteristic thatincreases an organism’ssurvival
“Survival of the Fittest”
Descents with Modification
•Over many successive generations:
•pressures of natural selection
•change traits of a population
•increase overall fitness of the population
•Species evolve:
•differences in structures & niches
•resulting in the formation of a new species
•remaining related to each other by acommon ancestor
3 Types of NaturalSelection
Stabilizing Natural Selection
•Nature eliminates both extreme traits
•Nature favors average traits
•Graph narrows
increasing the
number of
species with
the average trait
Directional Natural Selection
•Nature eliminates only 1 extreme trait
•The other extreme trait is favored
•Graph & population diversity shifts towardfavored trait
Distributive Natural Selection
•Nature eliminates the average trait & favorsthe extreme traits
•Graph & population diversity shifts towardsthe 2 extreme traits
•Possibly
leading to
creating
2 new
species
Finches of the Galapagos Islands
Darwin’s most famous discoveries came from hisobservations on the variations of finch species onthe Galapagos Islands
which had extremely diverse and extensive genepools, supporting his theory of evolution
•All of the Finches from the Galapagos Islandevolved from the same founder species
•The Finches
were separated
to different islands
over several years
•On each island they
experience different
natural pressures
•Finches on each island developed variations tomake them better adapted to their differentenvironments of each island
•Eventually the
Finches became
specialized and
different from each
other becoming
separate & new
species on
each island
Finch’s of the Galapagos Islands
