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Evolution
What is the connection between these
terms ????
• Evolution• Reproduction• Genetics-
Evolution
The term evolution means- a slow and gradual change
over time.
More specific:
Evolution is the change in the inherited traits of a
population from one generation to the next.
These traits are the expression of genes that are copied
and passed on to offspring during reproduction.
• A change in the genes!!!!!!!!
Old Theories of Evolution
• Jean Baptiste Lamarck (early 1800’s) proposed:
“The inheritance of acquired characteristics”
• He proposed that by using or not using its body parts,
an individual tends to develop certain characteristics,
which it passes on to its offspring.
• Need v.s. no need
“The Inheritance of Acquired Characteristics”
• Example:
A giraffe acquired its long neck because its ancestor
stretched higher and higher into the trees to reach
leaves, and that the animal’s increasingly lengthened
neck was passed on to its offspring.
True or false?
Not quite…..
If you cut the tails off of mice for 22 generations, then
the next generation will be tail less. False!!!!!
(Weismann 1870s)
Charles Darwin
• Darwin set sail on the H.M.S. Beagle (1831-1836) to
survey South American shores and the Galapagos
Islands.
• On the Galapagos Islands, Darwin observed species
that lived no where else in the world.
• These observations led Darwin to write a book.
Charles Darwin
• Wrote in 1859: “On the Origin of Species by Means
of Natural Selection”
• Two main points:
1. Species were not created in their present form,
but evolved from ancestral species.
2. Mechanism for evolution:
NATURAL SELECTION
Charles Darwin
Video clip about Darwin :
• Evolution: Who Was Charles Darwin?
• http://www.pbs.org/wgbh/evolution/library/11/2/q
uicktime/e_s_4.html
Geologic Time Scale
4 main eras
Precambrian:
– little is known about the Precambrian, despite it making up
roughly seven-eighths of the Earth's history
• At the start of the era, life = bacteria, algae, sponges
The PALEOZOIC Era
• Lasted from about 540 to 250 million years
including the development of most
invertebrate groups
• The evolution of fish, reptiles, insects, and
vascular plants
• The formation of the supercontinent of
Pangea, and two distinct ice ages.
The MESOZOIC ERA
•Mesozoic means 'middle animals’
• It is often called the “Age of the
Dinosaurs”
new dawn
The CENOZOIC ERA
“age of new life”.
•mammals diverged from a few small, simple forms into
a diverse collection of terrestrial, marine, and flying
animals.
• flowering plants,insects and birds also evolved
substantially in the Cenozoic.
Natural Selection
• Individuals with favorable traits are more likely to
leave more offspring better suited for their
environment.
NATURAL SELECTION
•Overproduction- make many more offspring
than can actually
•Competition- space and food
•Adaptations- any kind of inherted trait that
improves an organisms chances of survival
•Variation-characteristics of individuals; escape
, get food, find a mate.
•Speciation- formation of a new species as a
result of subtle adaptations.