Download Darwin and Evolution

Evolution
and
Darwin
What is evolution?
• A slow • A heritable change in the
characteristics within a
change
population from one
over
generation to the next
time
• The development of new
types of organisms from
preexisting types of
organisms over time
Evolution Primers
• Isn't Evolution Just a Theory???
History of Evolution
Charles Darwin – a brief history
• Born in England on February 12, 1809
• In 1831 began a 5-year journey on the HMS
Beagle as a naturalist
• Observations and specimen collections led him
to develop “the single best idea anyone has
ever had”
• “Developed a scientific theory of biological
evolution that explains how modern organisms
evolved over long periods of time through
descent from common ancestors”
• Darwin video clip
• Darwin set sail on the H.M.S. Beagle (18311836) to survey the south seas (mainly South
America and the Galapagos Islands) to
collect plants and animals.
• On the Galapagos Islands, Darwin observed
species that lived no where else in the world.
• These observations led Darwin to write a book.
Darwin’s Observations
1.Species vary globally – Darwin
noticed that different, yet
ecologically similar, animal species
inhabited separated, but ecologically
similar habitats around the globe
– Flightless birds (emu, ostrich, rhea)
– Convergent evolution
Darwin’s Observations
2. Species vary locally – Darwin noticed
that different, yet related, animal
species often occupied different
habitats within a local area
– Tortoise, mockingbirds
Darwin’s Observations
3. Species vary over time – Darwin
noticed that some fossils of extinct
animals were similar to living species
- fossils – preserved remains of
ancient, extinct organisms
Who is Charles Darwin?
Friends
• Friends Evolution Montage
Ideas that Shaped Darwin’s
Thinking
•
Lyell & Hutton –
–
–
–
•
Concluded that Earth is extremely old and that the
processes that changed Earth in the past are the same
processes that operate in the present (still changing)
Hutton (in 1785) – geological processes shape Earth
Lyell (in 1830) – uniformitarianism – geological processes
we see in action today must be the same ones that shaped
Earth millions of years ago
Lamarck – 1809
–
–
–
–
–
Inheritance of Acquired Characteristics 
Organism could change during their lifetimes by
selectively using or not using various parts of their
bodies; then pass these acquired traits on to their
offspring, enabling species to change over time 
One of the first naturalist to suggest that species are
not fixed 
One of the first to try and explain evolution scientifically
using natural processes 
Recognized that there is a link between an organism’s
environment and it’s body structures 
“The Inheritance of Acquired
Characteristics”
Lamarck vs Darwin
• Example:
-A giraffe acquired its long neck because
its ancestor stretched higher and higher
into the trees to reach leaves, and that the
animal’s increasingly lengthened neck was
passed on to its offspring.
-A muscle builder will pass the muscles on
to his offspring….
NOT TRUE
Ideas that Shaped Darwin’s
Thinking
• Malthus – 1798
– English economist
– Reasoned that if the human population
grew unchecked, there would not be
enough living space and food for
everyone
• Artificial Selection
– Nature provides variations, but humans
select those they find useful
Artificial Selection
• The selective breeding of domesticated
plants and animals by man.
• Question:
What’s the ancestor of the domesticated
dog?
• Answer: WOLF
• This is STELLA!!!!!
Darwin’s Contribution to
Science
Darwin developed a scientific theory
of biological evolution that explains
how modern organisms evolved over
long periods of time through descent
of common ancestors.
Darwin and Wallace
• Same conclusion about evolution as a result
of similar experiences
– Influenced by Lyell and Malthus
– Observed plant and animal life in several parts
of the world
– Wallace (1858) sent Darwin a manuscript
describing “natural selection”
– Wallace and Darwin arrived at the theory of
Natural Selection independently, and presented
their ideas in public together in 1858
Charles Darwin
Wallace kind of gets dissed
• Wrote in 1859: (11/24 – pub)
• “On the Origin of Species by Means of
Natural Selection”
• Main points:
1. Struggle for Existence (competition)
2. Variation and Adaptation
3. Survival of the Fittest
4. Natural Selection
Struggle for Existence
• Organisms produce more offspring
than can survive.
(OVERPRODUCTION)
– Grasshoppers can lay more than 200
eggs at a time. Only a small fraction of
these offspring survive to reproduce.
Variations and Adaptations
• There is variation in nature, and certain
variations – called adaptations – increase an
individual’s chance of surviving and
reproducing.
– Physical, physiological, and/or behavioral traits
that enhance an organisms chances for surviving
in its environment
• Green vs. yellow color in grasshoppers is a heritable
variation: green can blend into environment and avoid
predators
Survival of the Fittest
• Suggests that natural selection selects
mainly for survival… IT DOES NOT
• Selects for contribution of genes to future
generations
– Reproduction resulting in viable offspring
– Selects for individuals that are able to produce
the greatest number of offspring, that in turn,
can survive and reproduce
• Green grasshoppers have higher fitness and so
survive and reproduce more often than yellow
Natural Selection
• How Does Evolution Really Work?
Survival of the Sneakiest
• Survival of the Sneakiest
• Will the grey
mouse or white
mouse survive
more easily?
• Why?
• What
characteristic
is affecting
the fitness of
the mice?
• Peppered Moths:
Dark
Light
In the year Year
1848, 5% of the
population was
dark colored
moths while1848
95% was light 5%
colored.
95%
• In the year 1895, 98% was dark colored while 2% was light
1895
98%
2%
colored.
• In the year1995
1995, 19% was19%
dark colored while
81% 81% was light
colored.
•
What was the reason for the changes in the number of dark and light
colored moths?
•
In the early 1800s, England was not so industrialized yet and pollution was
still low. The trees had light colored bark so the light colored moths had a
better advantage and a better survival rate than dark colored ones.
•
In the late 1800s, England started to become more industrialized and
factories increases. These factories caused trees to become soot coated,
the bark was darker. The dark colored moths were then camouflaged and
survived more than light colored ones.
•
Then in the mid 1900s, the air started to become cleaner due to clean air
• http://www.sciencenetlinks.com/interactives/evolution.html
Another example of natural
selection…
Darwin’s Finches
– A Close Look at Darwin’s Finches
When Charles Darwin traveled to the Galápagos Islands, he found
a variety of species of finches. Although each species was
slightly different from the others, all the species were related.
None of the finch species he found were similar to finches on
the mainland.
When Darwin saw such extensive diversity of species in a single
group of birds, he hypothesized that they all could have
descended from a common ancestor. His observations of these
finches helped him formulate his concept of evolution.
The phylogenetic tree below shows the relationships Darwin
proposed among the species of finches. The tree is based on a
comparison of the anatomy, behavior, and location on the
island of each finch species. Look carefully at each species,
and notice the dramatic difference among the beaks. Each type
of finch has a beak adapted to its diet.
1. Which Darwin’s
of the ground
finches
above
wouldradiation.
be able to
eat the largest,
finches
are anillustrated
example of
adaptive
Adaptive
radiation
is the emergence
many species from a common
toughest nuts
and seeds?
Explain yourofanswer.
ancestor that was introduced to various new environments. For
radiation
to occur,
newdiagram.
environments
offer
2. Study theadaptive
insect-eating
finches
shownthe
in the
What must
can you
infer about
new opportunities and pose new problems of survival for the
the insects
of the Galápagos Islands?
species.
What does Darwin’s mechanism for
evolution suggest about living and
extinct species???
• All organism descended from a
common ancestor
• “Descent with modification”
• Homer Evolution
Evidence for Evolution
•
•
•
•
•
•
Biogeography
Fossil Record
Comparative Anatomy
Developmental Biology
Comparative Biochemistry
How Do We Know Evolution Happens?
•
Biogeography – study of where
organisms live now and where they and
their ancestors lived in the past
Patterns in the distribution
of living and fossil species
tell us how modern organisms
evolved from their ancestors
– Closely related species
differentiate in slightly
different climates
– Very distantly related
species develop
similarities in similar
environments
Adaptive Radiation
• Evolutionary process that gives
rise to new species adapted to
new habitats and ways of life
The Age of the Earth and
Fossils
– The Age of the Earth
• Earth had to be old enough for these proposed
changes to occur – plenty of time for Natural
Selection
• Earth is ~4.5 byo (determined by radioactive
dating) – plenty of time for natural selection to
take place
– Fossils discovered after Darwin fill in some of the
“gaps” in the fossil record
– One fossil shows the evolution of whales from a
land-based mammal (book figure 16-3)
Comparing Anatomy and Embryology
•
Homologous Structures
– Parts that are similar in
structure but different in
function
– Humans, penguins, alligators,
bats all have the same bones in
their arms but they are used
for different things
•
Similar Embryos
– Embryos of different
organisms are very similar and
have similar structures early
on
– Must have similar proteins at
work
•
Vestigial Structures
– Structures that are so
reduced in size or function
that they are merely traces of
similar organs in other species
(I.e. tailbone and appendix in
humans)
•
Analogous Structures
– Parts that are
similar in function
but not structure
– i.e. Wing of bee,
bird, bat
Genetics and Molecular
Biology
• All organisms have DNA
– Therefore similar RNA, similar genes,
and similar proteins
• All organisms have ATP
Evolution of Populations
Ch 17
• Process of change over time
• A change in the genes!!!!!!!!
Population Genetics
• The science of genetic change in
population.
• Population – all the members of a
species that occupy a particular area
at the same time
• Gene Pool – all the genes in all the
members of a population
Genes and Variation
• Genetics Joins Evolutionary Theory
– Variation is the raw material for natural selection
– Gene pool – consists of all the genes, including all the different alleles
for each gene, that are present in a population
– Relative frequency – the number of times that the allele occurs in a
gene pool, compared with the number of times other alleles for the
same gene occur
– Therefore – evolution is any change in the relative frequency of alleles
in the gene pool of a population over time
• 3 Sources of Genetic Variation
– Mutations
– Genetic Recombination in Sexual Reproduction (Ind assortment and
crossing over)
– Lateral Gene Transfer (conjugation)
• Single-Gene (2 pheno) vs. Polygenic Traits (many pheno/bell curve)
***Natural Selection acts directly on PHENOTYPES not actual
alleles*** some phenotypes are better suited to an environment
than others and they will survive, reproduce and pass on their
genes.
Evolution as Genetic Change in
Populations
How Natural Selection Works – 3 Types
Stabilizing Selection
Individuals with the average form of a trait have the highest
fitness
Represents the optimum for most traits
Results in a similar morphology between most members of the
species
Directional Selection
Individuals that display a more extreme form of a trait have
greater fitness than individuals with an average form of the trait
A shift in one direction
Peppered moth
Disruptive Selection
Individuals with either extreme variation of a trait have greater
fitness than individuals with the average form of the trait
A shift in both direction, away from the center
Shell color (dark rocks and light sand)
Genetic Drift
• Random changes in the frequency of a
gene in the absence of natural selection
 occurs because of CHANCE
• Occurs efficiently in small populations
because small changes affect more
members
• Two examples:
a. Bottleneck effect
b. Founder effect
Genetic Drift
a. Bottleneck Effect
• Genetic drift (reduction of alleles in a
population) resulting from a disaster that
drastically reduces population size.
– Examples:
1.
2.
Earthquakes
Volcano’s
b. Founder Effect
• Genetic drift resulting from the
colonization of a new location by a
small number of individuals.
• Results in random change of the gene
pool.
• Example:
1. Islands
(first Darwin finch)
Hardy-Weinberg Principle
• Genetic Equilibrium – situation in which
allele frequencies in the gene pool of a
population remain constant
• The concept that the shuffling of genes
that occurs during sexual reproduction, by
itself, cannot change the overall genetic
makeup of a population.
• Shows mathematically and theoretically
that there are situations where evolution
DOES NOT OCCUR
– Seldom achieved in nature
Hardy-Weinberg Principle
• This principle will be maintained in nature
only if ALL five of the following conditions
are met:
1. Very large population
2. Isolation from other populations (no
immigration, no emigration)
3. No net mutations
4. Random mating
5. No natural selection
Hardy-Weinberg Principle
Species
• A group of populations whose individuals
have the potential to interbreed and
produce viable offspring.
Speciation
• The evolution of new species. Species that
occupy an otherwise unoccupied niche face
no competition, they will therefore have a
100% success rate
Reproductive Isolation
• Any mechanism that impedes two species from
producing fertile and/or viable hybrid offspring
-factor necessary for the formation of a
new species.
• Barriers:
1. Geographic (rivers, mountains)
2. Behavorial - differences in courtship
behavior
3. Temporal - fertile periods (time)
Interpretations of Speciation
• Two theories:
1. Gradualist Model
(Neo-Darwinian):
Slow changes in
species overtime.
2. Punctuated
Equilibrium:
Evolution occurs in
spurts of relatively
rapid change.
Macroevolution
• The origin of taxonomic groups higher
than the species level.
Adaptive Radiation
aka Divergent Evolution
• Emergence of numerous species from a
common ancestor introduced to new and
diverse environments.
• Example:
Darwin’s Finches
Darwin’s Finches an example of
Adaptive Radiation
Convergent Evolution
• Species from different evolutionary branches
may come to resemble one another if they live
in very similar environments.
• Example:
1. Ostrich (Africa) and Emu (Australia).
2. Sidewinder (Mojave Desert) and
Horned Viper (Middle East Desert)
3. Shark and Dolphin
Coevolution
• Evolutionary change, in which one species
act as a selective force on a second
species, inducing adaptations that in turn
act as selective force on the first species.
• Example:
1. Acacia ants and acacia trees
2. Humming birds and plants with
flowers with long tubes
The Age of the
Earth and Fossils
– Fossils
• Trace the evolution of modern
species from ancient/extinct
ancestors
Radiometric Dating
• Relative dating vs.
– When unstable nuclei
release particles or
• Absolute dating
radiant energy until the
–
nuclei becomes stable
Half-life = The length
of time it takes for
one-half of a sample to
decay to stable form
The Earth is born…
Date
Event
4.6 bya
Earth was born
4 bya
Cooling of Earth, 1st solid rocks formed
on earth’s surface
4-3.8
bya
Volcanic activity & meteorites release
gases that produce earth’s atmosphere
Contained H2O vapor, CO, CO2, H2, N2, NH3, CH4
It did NOT contain oxygen
3.8 bya
Cooling continues, water appears,
beginning of oceans
Earth cool enough for liquid to stay on the ground
3.5 bya
Age of first prokaryotic microfossils
Heterotrophic – obtained nutrients from organic “soup”
Anaerobic – able to live in oxygen-free environment
3.4 bya
Appearance of 1st autotrophs
Organic soup begins to run out
Photosynthesis begins – using H2S instead of water
2.2 bya
Introduction of oxygen into the
atmosphere
More modern form of photosynthesis
appeared
Used H2O instead of H2S
Caused earth to cool as they converted CO2  O2
Led to aerobic respiration
Ozone layer protection
1.6-1.1
bya
1st eukaryotic cells evolved
Nucleus contains DNA, have membrane bound
organelles, etc.
Increased the speed of evolution
Increased genetic variation
1700s
Spontaneous Generation (abiogenesis) –
idea that life comes from non-life
Disproven through Redi, Spallanzani, & Pastuer
1953
Miller & Urey
mix methane, water, ammonia, and
hydrogen with energy (sun & lightning)
Primordial Soup
Amino acids & other organic compounds are produced
as by-products
Provide glimpse at how molecules (proteins) may 1st
have formed on the Earth
Sexual reproduction evolved
Multicellular organisms arose
Additional Info
The Age of the Earth and
Fossils
– The Age of the Earth
• Earth had to be old enough for these proposed
changes to occur
• Earth is ~4.5 byo (determined by radioactive
dating)
History of Earth (24hours)
12:00am – Earth is formed
5:00am – Prokaryotes appear
4:00pm – Eukaryotes appear
10:00pm – Invasion of land
11:59:30pm – Humans appear
Miller/Urey Experiment and
Primordial Soup
• Oparin and Haldane: hypothesized that the early
atmosphere was composed of: ammonia (NH3), hydrogen gas
(H2), water vapor (H20), and compounds made of carbon and
hydrogen, like methane (CH4). They thought that at high
temperatures, simple organic compounds (like amino acids)
could form. When earth cooled, and lakes and oceans
formed, theses simple compounds could be found in the
water and enter complex chemical reactions fueled by
lightning and ultraviolet violet radiation resulting in
macromolecules essential to life like proteins.
• Miller and Urey: 1953 set up an apparatus to test Oparin’s
hypotheses. Their experiment produced a variety of organic
compounds, including amino acids
EndosymbioticTheory
• What is the theory of
endosymbiosis? Theory that large
prokaryotic, unicellular organisms
engulfed (ate) smaller prokaryotic,
unicellular organisms. Engulfed
prokaryotes eventually gave rise to
modern mitochondria and
chloroplasts.
• What evidence supports the
hypothesis that mitochondria and
chloroplasts were once free living
prokaryotic cells? Replicate
independently and replicate like
prokaryotes (binary fission), have
their own DNA and their own
ribosomes (also similar to DNA and
ribosomes of prokaryotes)