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Evolution
• Evolution- change in allele frequency in a population over time (decent with
modification)
• Population- Group of individuals of a single species that occupy the same
general area
• Allele- an alternative version of a gene
• Gene- a discrete unit of hereditary information consisting of a specific
nucleotide sequence in DNA, codes for a protein that leads to a physical
characteristic
Types of Evolution
• Microevolution- evolution within a species
• Macroevolution- evolution that produces a
new species
• Origins of life according to evolution
Lamarckian Evolution
Lamarck’s theory
is incorrect
3 concepts
•Theory of need
•Theory of use and disuse
•Theory of inheritance of
acquired characteristics
Charles Darwin
•
•
•
•
Naturalist on the HMS Beagle
Surveying ship
5 year voyage beginning in 1831
Made observations and collected specimens
along the way, many from the Galapagos Islands
• Returned to England and began to develop his
theory of Evolution
•Galapagos finches that Darwin observed have different beaks
based on the food that they eat
•Darwin believed the differences in their beaks were due to
evolution
•He believed the different species of finches adapted to
different environments at different times, so they could get
the food that was available there
•Darwin believed they evolved from a common ancestor
Artificial Selection
Species definitely have the ability to change over time
to become very different than what they once were.
In artificial selection we select what alleles we want to
be passed to the next generation over others.
Charles Darwin
• Published “On the Origin of Species by Means of Natural
Selection” in 1859
• Published “The Descent of Man” in 1871
Evolution by Natural Selection
• Mechanism of evolution- evolution is what
happens, natural selection is how it happens
• Individuals whose inherited traits give them a
higher probability of surviving and reproducing in a
given environment tend to have more offspring
than other individuals which leads to the
accumulation of favorable traits in a population
over generations
Evolution by Natural Selection
• Traits must be genetically based
• Genes must lead to a reproductive advantage
• Causes the allele frequency in the population
to change
• Takes many generations
• Remember: favorable traits are based on the
environment
Survival of the fittest
• Somewhat misleading
• Does not necessarily mean physical strength
• It means better adapted to the current
environment
What leads to Evolution?
• There must be genetic variation within the population
– Mutation- altering of the nucleotide sequence can make a gene
more advantageous.
• Environmental change- an allele that was once not an
advantage becomes an advantage because the environment is
different.
• Immigration (gene flow)- individuals with more advantageous
genes join a population.
• Genetic drift- random selection of a gene because of an event
that significantly decreases population size and eliminates all
or most individuals with a particular gene.
Microevolution
• Pests and pesticides
• Bacterial resistance to
antibiotics
• Selection to avoid
predation
Microevolution- evolution within
a species
Macroevolution
• Macroevolution- evolution that produces a
new species
• What is a species?
Species
• A species according to the biological species
concept is a group of populations whose members
have the potential to interbreed in nature and
produce fertile offspring
Reproductive Barriers
Prezygotic Barriers
• Habitat isolation- species live in different habitats
within the same area and rarely meet
• Temporal isolation- breeding occurs at different times
of the day or different seasons
• Behavioral isolation- different courtship rituals or other
behaviors prevent mate recognition between species
• Mechanical isolation- differences in physical structures
prevent successful mating
• Gametic isolation- male and female gametes of
different species fail to unite
Reproductive Barriers
Postzygotic Barriers
• Reduced hybrid viability- the development or
survival of hybrids is impaired
• Reduced hybrid fertility- hybrids fail to produce
functional gametes
• Hybrid breakdown- offspring of hybrids are feeble
or infertile
Figure 14.3G
Horse
Donkey
Mule
Macroevolution
Allopatric Speciation
1. Geographic barrier splits a population
2. Microevolution occurs separately in the populations
3. Some kind of reproductive barrier evolves so that even
if the populations were brought back together,
individuals from the 2 populations could not produce
fertile offspring and they would be considered two
different species
Figure 15.7B
Zones of violent tectonic activity
Direction of movement
North
American
Plate
Juan de Fuca
Plate
Eurasian Plate
Caribbean
Plate
Arabian
Plate
Cocos Plate
Pacific
Plate
Nazca
Plate
Philippine
Plate
South
American
Plate
Scotia Plate
Indian
Plate
African
Plate
Antarctic
Plate
Australian
Plate
Figure 15.8
Pacific
Plate
North
American
Plate
San Francisco
San Andreas Fault
Los Angeles
California
Origins of Life
Creation/Evolution
• We are going to look at the theory for how all
life could have evolved from a common
ancestor through natural processes.
• We want to look at the evidence for this part
of evolution.
• Some use these theories as a way to justify
their atheism.
• I believe God was involved in some way.
• Even if you don’t agree with any of the origins
of life theory, it is important to understand it
so you can explain why your theory is better.
Creation/Evolution
• There are different theories for how creation and
evolution can coexist.
• We will look at these in more detail later.
•
•
•
•
Creation Research Society
Biologos
Reasons to Believe
Institute for Creation
Research
Origin of Life According to Evolution
• Abiotic synthesis of monomers
– Miller/Urey experiment 1953- mixed
gases that simulated the early
atmosphere, according to the theory
at that time. Used an electric spark to
simulate a lighting strike that could
have provided the energy to
rearrange the atoms. Some amino
acids and hydrocarbons formed.
– Whether or not Miller/Urey’s mixture
of gases accurately simulated the
early atmosphere is debated
• Monomers spontaneously join to
form polymers
• Protocells form- membrane enclosed
droplets that can maintain an internal
chemistry different than the
surrounding environment
Origin of Life According to Evolution
• Self-replicating molecules form
– Complimentary pairing of RNA nucleotides
– Later DNA replaced RNA as the primary genetic material
Figure 15.3B_s1
1
Collection of
monomers
Figure 15.3B_s2
G C
U A
U G C A U
G G C
1
Collection of
monomers
2
U U U
Formation of
short RNA
polymers:
simple “genes”
Figure 15.3B_s3
G C
U A
G U
U G C A U
U G C A U
G G C
1
Collection of
monomers
2
U U U
Formation of
short RNA
polymers:
simple “genes”
3
Assembly of a
complementary
RNA chain, the first
step in the
replication of the
original “gene”
Origin of Life According to Evolution
• Prokaryotes
– Stromatolites are believed to
be some of the earliest fossils.
They are layered rock columns
formed by photosynthetic
prokaryotes. Still built today
Origin of Life According to Evolution
• Single celled eukaryotes
– Endosymbiont theory- mitochondria and
chloroplasts were formerly small prokaryotes that
began living within larger cells
– These organelles have their own DNA
• Multicellular eukaryotes
Evidence
• Fossils- any direct or indirect evidence of a once-living organism
• Definitely there were things that were different than the things
that are alive today, and some appear to be intermediates, like
Archaeopteryx, which is somewhat bird-like and reptile-like
Evidence
• Biogeography- many fossils and organisms are more
alike when they are closer geographically. Also, it
looks like marsupials evolved once Australia was
separated from other land masses
• The earth is changing
– Tectonic activity- Earth’s crust is divided into plates that
move
– Earthquakes, volcanoes
Evidence
• Comparative Anatomy- mainly deals with similarities in bone
structure and stages of embryological development.
• Homologous structures- parts in different species that are
structurally similar, but serve different functions
Evidence
• Molecular Biology- common genetic “language”,
which is DNA and RNA.
Table 15.6