Transcript Evolution - Alvin ISD

Evolution
Understanding the
Diversity of Life – Part 1
1
Evolution
“Nothing in
biology makes
sense EXCEPT in
the light of
evolution.”
Theodosius
Dobzhansky
2
Charles Darwin in later years
History of Evolutionary
Theory
3
Early Ideas about Earth’s Organisms
• Aristotle believed
species were fixed
creations arranged
by their complexity
4
Early Ideas about Earth’s Organisms
Carolus Linnaeus
• 1st to group similar
organisms and
assign them Latin
names
• Two word name
(Genus species)
• Known as Binomial
nomenclature
5
Early Ideas about Earth’s Organisms
Georges Cuvier
• Some species’ fossil records
disappeared in more recent
layers
• Stated that species disappear
due to a catastrophic event of
the earth’s crust
6
Early Ideas about Earth’s Organisms
James Hutton & Charles Lyell
• Stated that various
geological forces constantly
changed the planet very
slowly
• Idea Known as Gradualism
or Uniformitarianism
7
Early Ideas about Earth’s Organisms
Hutton & Lyell,
cont.
• Proposed that the
Earth was millions
of years instead of
a few thousand
years old
8
Early Ideas about Earth’s Organisms
Reverend Thomas Malthus
• Stated that populations
could not grow indefinitely
• This growth would be
stopped by:
1. Disease
2. Famine
3. War
9
Lamarck’s Theory of Evolution
Jean-Baptiste Lamarck
• One of first scientists to
understand that organisms
change over time
• Put forth an idea called
Inheritance of Acquired
Characteristics through
Law of Use and Disuse
10
Lamarck’s Theory of Evolution
• Proposed that by selective use or disuse
of organs, organisms acquired or lost
certain traits during their lifetime
Examples:
blacksmiths & their sons (muscular arms)
giraffe’s necks longer (from stretching)
• These traits could then be passed on to
their offspring
• Over time this would lead to new species
11
12
Lamarck’s Mistakes
Inheritance Of Acquired Traits
• Traits Acquired During Ones Lifetime
Would Be Passed To Offspring
• If true, clipped ears would pass to
offspring!
13
Charles Darwin the
Naturalist
14
Charles Darwin
• Born Feb. 12, 1809
• A naturalist
• Collector/identifier of
plant and animal
specimens
• Formed his ideas about
evolution sailing on the
HMS Beagle for the
Galapagos Island in
1831
15
The Galapagos Islands
• Small group of
islands 1000 km
west of Ecuador
• Very different
climates and
geography on each
island
• Animals on each of
the islands similar
but unique
16
The Galapagos Islands
• Finches on the islands resembled a
mainland finch
• Different types of finches appeared on
the islands where the available food was
different (seeds, nuts, berries, insects…)
• Finches had beaks adapted to their type
of food gathering
17
18
The Struggle for
Existence
Darwin’s Observations and
Conclusions
19
Darwin’s Observations
• Patterns of Diversity
• Unique adaptations in
organisms
• Species not evenly
distributed
20
Giant
Ground
Sloth
21
Glyptodon – Ancestor of Modern Armadillo
22
Darwin’s Observations
• Unlimited resources will allow
organisms increase
exponentially, generation to
generation
• In nature, populations tend to
remain stable in size
• Environmental resources are
what limits population size
23
Darwin’s Observations
•Individuals of a
population vary in
their characteristics
with no two individuals
being exactly alike.
•Much of this variation
between individuals is
inheritable.
24
Darwin’s Conclusions
•Production of more
individuals than can be
supported by the
environment leads to a
struggle for existence
•Only a fraction of offspring
survive each generation
•He called this “Survival of
the Fittest”
25
Darwin’s Conclusions
•Individuals who
inherit characteristics
most fit for their
environment are
likely to leave more
offspring than less fit
individuals
•He called this
“Natural Selection”
26
Darwin’s Theory of
Evolution
Organisms Change Over Time
27
Evolution:
Defined
•Evolution is the
slow , gradual
change in the
alleles of a
population over
time
28
Darwin’s Theory of Evolution
•The unequal ability of individuals to
survive and reproduce leads to a gradual
change in a population, with favorable
characteristics accumulating over
generations (Natural Selection)
•This creates new species
29
Darwin’s Theory of Evolution
Descent with
Modification:
• Organisms descended
from common
ancestors
• Organisms change
with time, diverging
from a common form
30
Darwin’s Theory of Evolution
Natural Selection:
• Driving force for
evolution
• During the struggle for
resources, strongest
survive & reproduce
• Idea that at least some
of the beneficial
differences between
individuals are
inheritable
.
31
32