Transcript LIFE OVER TIME

LIFE OVER TIME
What processes have created
diverse species & adaptations
throughout history?
Theories of Evolution began when
scientists began asking these questions…
What is a Scientific Theory?
 Fact: An observation that has been repeatedly confirmed with not dispute.
For example, there are 23 pairs of chromosomes in human cells.
 Law: A descriptive generalization about how some aspect of the natural
world behaves under stated circumstances. For example, one of
Newton's laws of motion that states that for every action, there is an equal
and opposite reaction.
 Hypothesis: A testable statement about the natural world that explains
why something occurs.
 Theory: A well-supported explanation of some aspect of the natural world
that can incorporate facts, laws, and tested hypotheses. For example, the
cell theory states that cells are the basic unit of all living organisms and
that all new cells arise from the division of pre-existing cells.
What is Evolution?
Evolution = a series of gradual or rapid changes
in living & nonliving things through time
Evolution of Stars
Evolution of the Earth System
(water, landforms, atmosphere)
Evolution of Living Things
Evolution of Scientific ideas
Theories of Evolution
Theories of Evolution are…
• attempts to explain changes & diversity in
living things through time
• supported by a great deal of research & study
Theories of Evolution are Not…
• attempts to explain the origins & purpose of life!
• a religion or belief system
Early Theories of Evolution
 Jean-Baptiste de Lamarck (1744-1829)
• Law of Use & Disuse - organisms respond to
changes in their environment by developing new
organs or changing the structure/function of old
organs. . . .
• Theory of Inheritance of Acquired Characteristics
these acquired characteristics were then passed on
to the organism's offspring. . . .
 Giraffes Long Necks
The Basis for Modern
Theories of Evolution
 Charles Darwin (1809-1882)
• Artificial Selection - selective breeding in pigeons
• Natural Selection - organisms with certain
variations survive, reproduce & pass on these traits
to their offspring
 Galapagos Island Animal Species
An Intro to Modern Theory
 http://evolution.berkeley.edu/evosite/evo
101/IIntro.shtml
How Does Evolution Happen?
Fundamental to the process of evolution
is genetic variation within populations
upon which selective forces can act in
order for long term change to occur.
Genetic Drift
(Random)
Genet ic Variation
Natural Selec tion
(Non-random)
Change in Populations
(Evo lution)
What Causes Genetic
Variation?
 Mutations
 Gene Flow (Migration)
 Sex
Genetic Drift
 Change in the genetic makeup of
a population by chance events
(random!)
 It does NOT work to produce
adaptations!
Examples:
1. Ellis-van Creveld syndrome in Amish
2. Stepping on a bug!
3. A bird left on an island - Galapagos
Natural Selection
1. There is Genetic Variation
2. There is Selective Pressure environmental conditions
3. There is Survival of Some
4. There is Reproduction by
the Survivors
5. Adaptations Show
How Do New Species Form?
 Species = Group of similar organisms that can
interbreed & produce fertile offspring
 Speciation =
Evolution of a new species
Causes of Speciation
1. Geographic Isolation = when a physical barrier
divides a population
 Each population adapts to its environment thru natural
selection & develops its own gene pool. Over time the
separate groups become so different they can no
longer interbreed! (Galapagos Animals)
2. Reproductive Isolation = when organisms no longer
mate & produce fertile offspring
 Mating times change to different parts of the year for
groups in different areas (Tree frogs)
 Mutations in chromosomes occur to make breeding
difficult (Plants - crops)
How Fast is Speciation?
1. Gradualism = species originate through a
gradual change in adaptations (10,000+ yrs)
 Fossils show camels evolved slowly & steadily over
time (pg 408)
2. Punctuated Equilibrium = species originate in
rapid bursts (10,000 yrs or less) with long
periods of equilibrium in between
 Fossils show that higher temps & competitive species
caused rapid changes in isolated populations elephants!
EVIDENCE OF EVOLUTION
1. Adaptations - a structure or behavior that helps
an organism better survive in its environment
(arose from Natural Selection)
A. Mimicry
B. Camo
 C. Physiological - antibiotic resistance in bacteria = superbugs
EVIDENCE OF EVOLUTION
2. Fossil Record
A. Give clues to what ancient organisms
looked like
B. Compare to organisms today to see
relationships
C. A link to show change over time
EVIDENCE OF EVOLUTION
3. Comparative Anatomy
A. Homologous Structures = body structures on diff.
organisms that are similar in structure/function evidence of common ancestor
B. Vestigial Structures = body structures in an organism
that no longer serve a purpose but may have in
an ancestor - show what used to be
EVIDENCE OF EVOLUTION
4. Embryos = all vertebrates look similar
as embryos - suggests all related
EVIDENCE OF EVOLUTION
5. DNA Similarities
EVIDENCE OF EVOLUTION
Examples of Recent Evolution (Change):
1. Natural Selection in Action - Peppered Moths
2. Artificial Selection - Crops, Dogs - People?
The End
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