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Evolution
Objectives:
12.0 Describe protective adaptations of animals,
including mimicry, camouflage, beak type, migration,
and hibernation.
12.1 Identifying ways in which the theory of evolution
explains the nature and diversity of organisms
12.2 Describing natural selection, survival of the
fittest, geographic isolation, and fossil record
Lamarck’s Theory of Evolution




Proposed that selective use or disuse
of organs caused organisms to acquire
or lose certain traits during their
lifetime.This would lead to those traits
being passed on (or not) to their
offspring.
EX:You work out and have huge biceps,
so your offspring will have huge biceps.
WRONG!!!! (Why?)
Adam and Eve – ribs?
Thomas Malthus
Reasoned that if human population
continued to grow unchecked, sooner
or later there would be insufficient
living space and food for everyone.
 What are some “forces” that influence
(decrease) human population?
Answer: war, famine, disease
 Darwin realized this applied even more
strongly with plants and animals!
(Why?)

Natural Selection (Darwin)
We have already agreed that artificial
selection happens, so why couldn’t
natural selection occur on a slower
scale?
1. Struggle for existence 
a. competition among members of a
population for resources
b. “hiding” from predators
Natural Selection
2.
Survival of the fittest
a. Those who survive long enough to
produce offspring and pass on their traits
b. Adaptation – any inherited characteristic
that increases an organism’s chance of
survival
3.
Descent with modification
a. Over long periods of time, natural
selection produces organisms that look
different from their ancestors
b. Carried to its fullest extreme: common
descent says we all have one common
ancestor.
Evidence (Support) of Evolution
1.
2.
Geographic distribution- species that
are better adapted to their
environment survive in higher
numbers.
Homologous body structures –
similarities among body parts of
animals with backbones (vertebrates):
a.
b.
c.
d.
e.
Arms
Wings
Flippers
Forelegs
Vestigial organs – have no apparent use
now, but still show up in some form (i.e.,
human appendix)
Evidence (Support) of Evolution
3.
4.
Similarities in early development
Fossil record
a. Intermediate stages of organisms
found as scientists work their way
through sediment layers
b. GAPS exist!
Galapagos Tortoises
Summarizing Darwin (p.386)



Individual organism differ, and some of
this variation is heritable.
Organisms produce more offspring than
can survive, and not all that survive
reproduce. (Do you have an aunt, uncle,
or family friend with no children?)
Because more organisms are produced
than can survive, they compete for limited
resources.
Summarizing Darwin (p.386)


Each unique organism has different
advantages and disadvantages in the
struggle for existence. Individuals best
suited to their environment survive and
reproduce most successfully. (What is this
called?) These individuals pass on their
heritable traits to their offspring.
_______ selection causes species to
change over time.
Species alive today are descended with
modification from ancestral species.
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