• ADD GENETIC BASIS ACT ON
ALLELES, etc revise review also
Evolution - Populations
Chapter 16, part of 17
Normal (Standard) Distribution
• The normal distribution is often used to
describe, at least approximately, any
variable that tends to cluster around the
mean.
Bell Curve
• 68.268949% of the area under the curve is
within one standard deviation of the mean.
• 95.449974% of the area is within two
standard deviations.
Standard Deviation
• In a set of data, measures how much
variation or dispersion from the average
exists.
• Low standard deviation indicates that the
data points tend to be very close to the
mean.
• High standard deviation indicates that the
data points are spread out over a large
range of values.
Bell Curve – Normal Distribution
Standard Deviation of 1
Directional Selection
• Higher fitness is associated with one end
(extreme) of the population. Change
occurs, and over time, that end survives,
passes on genes to more offspring, so
entire population shifts or adapts.
Directional Selection
Stabilizing Selection
• Higher fitness is associated with the
middle of the trait, the majority, so no
adaptation occurs.
Stabilizing Selection
2
1
Disruptive Selection
• Higher fitness associated with both ends
of the population/trait, so over time the
middle/majority is less fit/dies out and you
have two separate adaptations.
Disruptive Selection
Speciation
• Changes in an organism that lead to a
new species
• Species: A group of organisms that can
breed and produce fertile offspring in the
wild.
– Controversy/point for further study as more
knowledge is gained
• DNA, Genetic engineering, sub-species
Darwin – Species Problem
– No one definition has satisfied all naturalists;
yet every naturalist knows vaguely what he
means when he speaks of a species.
Generally the term includes the unknown
element of a distinct act of creation.
–
http://evolution.berkeley.edu/evosite/evo101/V
Speciation.shtml
Isolating Mechanisms
• Reproductive Isolation
– Two populations can not interbreed and
produce fertile offspring.
– At that time there are two separate gene
pools, and respond as two separate groups
– This reproductive isolation can happen in a
variety of ways
Behavioral Isolation
• Different courtship rituals
• Different mating songs
Geographic Isolation
• Physical barriers – rivers, mountain
ranges, bodies of water
Temporal Isolation
• Different times for reproduction
break
• End of ch. 16 notes – rest are ch. 17
Part of CH. 17
Organic Chemistry Formation of
Life
• Early Earth – 3.8 billion years ago
– Brown water, lots of iron
– very little or no oxygen in atmosphere
– Thunderstorms, lightning
– Not good for life as we know it
1950’s – Miller & Urey
• Methane, ammonia, hydrogen, water in a
clean, pure sealed flask
• Zapped with electric sparks to simulate
lightning
• Amino acids formed in the mixture
• Repeated experiments have had similar
results
• 1995 Cytosine and uracil produced this
way
Theory
• Amino acids could have formed in these
early “oceans”
• http://www.ucsd.tv/miller-urey/
Microspheres
• Protein based “bubble” that is selectively
permeable (water can pass in & out)
• Ability to store/release energy
• May contain amino acids, other chemical
compounds
• Not living, but has a few traits of cells
Evolution of RNA & DNA
• Somehow RNA then DNA formed,
survived in microspheres, got complex
enough to regulate the microsphere,
replicate, divide and became living
organism
Coacervate
• A coacervate is a tiny spherical droplet of
organic molecules (specifically, lipid
molecules) which is held together by
hydrophobic forces from a surrounding
liquid.
• Theory - metabolism predated information
replication.
Endosymbiotic Theory
• Eukaryotic cells evolved from prokaryotic
• One cell inside another
• Eventually inner cell adapted/evolved to
become nucleus
The Panspermia Theory
• Hypothesis
• Life on Earth originated somewhere else
and was transported here
Timing of Life
•
•
•
•
•
•
•
•
•
Earth –
Rocks –
Life – prokaryotic –
Eukaryotic
Diverse megascopic life Vertebrates –
Mammals
Genus Homo –
Homo Sapiens –
• “modern” humans –
4.6 billion
3.8 billion
3.4 – 3.5 billion
1.2 billion
0.54 billion
0. 45 billion
0.07 billion
0.0025 billion
0.0001 billion
0.00005 billion
Cambrian “Explosion” – 0.55 billion
Ordovician – 0.5 billion
Triassic
Cretaceous
Tertiary
Evolution Patterns
• Extinction
– More than 99% of all species that have ever
lived on Earth have died out and are now
extinct
• Mass Extinction
– Multiple times in Earth’s history entire
ecosystems and large numbers of living
organisms have been wiped out in relatively
short time periods
Mass Extinctions
• Many geologic time boundaries begin/end
at these mass extinctions
• Major changes in the climate and types of
dominant species arise from these events
Adaptive Radiation
• One species evolves into multiple different
species that live in different ways
Convergent Evolution
• Different species start as completely
different and evolve in the same type of
environment to become more similar
– Similar body types
– Similar body parts
Coevolution
• Organisms with close connections evolve
together
– Flowering plant and primary pollinator
– Predator and its primary prey
Gradualism
• Slow and steady evolution
• Small changes over long time periods
Punctuated Equilibrium
• Long stable period of little/no evolution,
with a brief period of rapid change (all is
relative)