Zoology – EVOLUTION: History and Evidence
I.
Origins of Darwinian Evolutionary Theory
A. Pre-Darwinian
Evolutionary Ideas
1.
Before the 18th
century,
speculation on origin of species was not scientific.
2.
_________________________________ portrayed a constant world after a creation
event.
3.
Early Greek philosophers considered some ideas of evolutionary change.
a.
_____________________ were recognized as former life destroyed by
_________________________________.
c. Lacking a
full evolutionary concept, the idea faded before the rise of
_____________________.
4.
Biblical account of creation became a tenet of faith.
a.
Evolutionary views were heretical.
b.
__________________________________________ calculated
_____________________
as date of life’s creation.
5. French
biologist Jean Baptiste de _____________________ offered first complete
explanation in _____________________.
a. He convincingly argued that fossils
were remains of _____________________
animals.
b. Lamarck’s mechanism was inheritance
of ___________________________.
c. He explained long necks of giraffes
to stretching efforts of ancestral giraffes.
d. Lamarck’s
concept is ____________________________;
individuals transform
their own traits to evolve.
e. In
contrast,
6.
Geologist Sir Charles _____________________ established the principle of
_____________________.
a.
Uniformitarianism consists of two important principles:
1)
Laws of physics and chemistry remain the same throughout earth’s
history.
2)
Past geological events occurred by natural processes similar to those
observed today.
b. Natural
forces acting over long periods could explain formation of fossil-bearing
rocks.
c.
Earth’s age must be measured in _____________________ of years.
1) It is now accepted that earth is
________________ years old.
2) Life has existed on earth for more than 3.5
billion years.
d.
Geological changes are natural and without direction; both concepts underpinned
II. Major revolutions in evolutionary thought
occurred in last 150 years.
A.
First
revolution - Charles Darwin, Origin of Species, 1859
1.
Evolution
by natural selection
B.
Second
revolution - 1930’s – an intersection of concepts provides better understanding of the mechanisms
of evolution.
1.
Darwinian natural selection
2.
Mendelian genetics
3.
Population genetics
C.
Third
revolution – Now – The Evolution of Development = “evo-devo”
1.
Organisms
with nearly identical genomes can look very different because different
developmental programs created them.
2.
Regulatory
genes can act as developmental switches.
3.
Homeobox
genes (hox genes for short) - Regulatory genes that act as
developmental switches. These genes
determine the body plan.
a.
The
genes of a Chihuahua and a Great Dane are almost identical.
b.
The
incredible difference in their body size is actually due to how long the
operators (master switch) of the genes controlling bone growth remained active.
4.
Impact
of mutations can alter master switches.
5.
There
is a similarity of master switches in plants and animals
III. Darwin’s Great Voyage of Discovery (_____________________)
A. In 1831,
Charles Darwin (almost 23) sailed aboard the small survey ship _____________.
B. Darwin
made extensive observations in the five-year voyage.
1.
Darwin collected the fauna and flora of ___________________________________
and adjacent regions.
2.
He unearthed long extinct fossils and associated fossils of South and
3.
He saw fossil seashells embedded in the
4.
Observing earthquakes and severe erosion confirmed his views of geological
ages.
C. The __________________________________________
provided unique observations.
1.
These volcanic islands are on the equator 600 miles west of __________________.
2.
Each island varied in tortoises, iguanas, mockingbirds and ground finches.
3.
The islands had similar climate but varied vegetation.
4.
Island species therefore originated from
varying conditions of different islands.
D. Darwin
conducted the remainder of his work at home in _____________________.
1. In 1838, Darwin read an essay on
population by Thomas R. ______________.
2.
Having studied artificial selection, a “struggle for existence” because
of
overpopulation gave him a mechanism for evolution of
wild species by natural selection.
3.
In 1858, he received a manuscript from a young naturalist, ____________________,
summarizing the main points of natural selection.
4.
Geologist Lyell and botanist Hooker persuaded
Wallace’s paper.
5.
Darwin then rushed to publish a shorter “abstract” version in 1859:
______________________________________________________________.
6.
1250 copies sold of first printing in one day.
IV. Darwin’s Theory –
Evolution Occurs by _____________________________
A. Natural
selection gives a natural explanation for origins of adaptation.
B. Darwin’s
theory of natural selection consists of four observations and
three
conclusions.
1.
Observation 1: ____________________________________________________
____________________________________________________________________.
a)
If all individuals produced survived, populations would explode exponentially.
b)
1) Elephant females breed at the earliest at 9
years, and bear one calf every four years until age fifty optimally. It would take a female 40 years to bear 10
calves.
2.
Observation 2: ______________________________________________________
______________________________________________________________________
_____________________________________________________________________.
a) Conclusion
1: The struggle for food, shelter,
and space becomes
increasingly severe with overpopulation. There is competition for
_______________________________________________________________.
1)
In each generation, many individuals must die young, fail to reproduce,
produce few offspring, or produce less-fit
offspring that fail to survive &
reproduce
in their turn.
2)
Survivors represent only a small part of those produced each
generation.
3.
Observation 3: _____________________________________________________
__________________________________________. Individual members of a
population differ from one another in their
ability to obtain resources, withstand
environmental extremes, escape predators, etc.
a)
Conclusion 2: The most well-adapted (the “fittest”) individuals
in one
generation will usually leave the most
offspring. This is ____________________
_________________________________: the process by which the environment
selects for those individuals whose traits
best adapt them to that particular
environment.
4. Observation
4: ______________________________________________________
_____________________________________________________________________.
a)
Darwin only noted the resemblance of parents and offspring.
b) Gregor Mendel’s mechanisms of heredity were applied to
evolution many years later.
c) Conclusion
3: Over many generations,
differential, or unequal, reproduction among individuals with different genetic
makeup changes the overall genetic composition of the population. This generates new adaptations and new
species.
C. Natural
selection can be viewed as a two-part process: random and non-random.
1. Production of variation among organisms is
random; mutation does not generate
traits preferentially.
2. The nonrandom component is the survival of
different traits.
D.
Microevolution - the changes in allele frequencies from
generation to generation that may accumulate over long time periods to produce
new types of organisms.
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1. We can literally see that evolution through
natural selection is occurring around us today 2. Peppered moths of England & the Industrial
Revolution 3. 1990’s Florida’s cockroaches –Combat used
corn syrup (glucose) as the bait for its poison. A rare mutation, in which cockroaches won’t
eat glucose, became widespread after Combat was used. 4. Any pesticide, herbicide, or antibiotic & resistance is an example. |
5.
Artificial
selection demonstrates
that organisms may be modified by controlled breeding.
a.
In
a few hundred to at most a few thousand years, man has bred radically different
dog breeds, from Chihuahua to Great Dane, from the wolf by selecting qualities
that were found desirable & selectively breeding for them.
b.
What
man can do, cannot nature do by selecting for those individuals best adapted to
that environment
E. Macroevolution
- the larger scale
changes that result in extinction and formation of new
species.
V. Evidence for Macroevolution
A. Biogeography
–
the study of the distribution of organisms in space and time, can yield important information about evolutionary
processes.
1. 
The patterns of species distribution
across geographical areas can usually be explained through a combination of
historical factors such as speciation, extinction, and continental drift.
2. Islands are typically geographically isolated from mainlands. This isolation
can result in speciation. (e.g. The
birds of the Galapagos Islands)
a.
Species on a given island may more
closely resemble species on a nearby mainland, rather than species on a
distantly located island with similar environmental conditions.
3. Continental drift - connections between continents dictate what
species are geographically isolated or united (e.g. members of the camel
family)
B. Paleontology - the fossil
record provides evidence of evolutionary change over time. We can see how fossil forms differ from
modern forms, evidence of successive change across the strata of different
ages, and what organisms have become extinct.
1. The living
world is constantly changing in form and diversity. Change in animal life is directly seen in the
600-700 million-year animal fossil history.
Watch this fun video about the geologic time scale of earth: http://youtu.be/7PQURsc2SYs
2. A fossil is
a remnant of past life.
a.
Insects in amber and frozen mammoths are
actual remains.
b.
Teeth and bones can petrify or become
infiltrated with silica and other minerals.
c.
Molds, casts, impressions and fossil excrement
are also fossils.
3. Most
organisms leave no fossils; the record is always incomplete and requires
interpretation.
a.
The fossil record is biased because
preservation is selective.
b.
Vertebrate skeletons and invertebrates with
shells provide more records.
c.
Soft-bodied animals leave fossils only in
exceptional conditions such as the Burgess Shale.
4. Fossils
occur in stratified layers; new deposits are on top of older material.
a.
The law of stratigraphy dates oldest
layers at the bottom and youngest at the top.
Watch this video on stratigraphy: http://youtu.be/VLBzMvsiYq8
b.
“Index” or
“guide” fossils are “indicators” of specific geological periods.
5. Another way
to determine the age of a fossil is radiometric
dating.
a.
In the late 1940s, this dating method was
developed that determines age of fossils.
b.
Radiocarbon dating (sometimes
simply known as carbon dating) is a method that estimates the age of
carbon-bearing materials up to about
58,000 to 62,000 years. Carbon
dating works because most C (carbon) in the atmosphere is stable C-12. However, a small (but measurable) proportion
of atmospheric C is unstable, C-14. The half-life of carbon-14 is
5,730 ± 40 years. That means that 5,730 years after death, half of the C-14
in your fossil will have decayed into stable N-14
1)
Carbon is incorporated into plants when they
use CO2 to make sugar. During
its lifetime, an animal will incorporate this C (carbon) in its body from
eating plants. Once the animal dies, it
no longer adds C to its body.
2) The unstable
C-14 begins to steadily break down into stable N-14. The amount of C-14 remaining in the fossil
tells us how long the animal has been dead with an extreme degree of accuracy.
Watch this video demonstrating carbon dating: http://youtu.be/udkQwW6aLik
c.
Radioactive decay of naturally occurring
elements is independent of heat and pressure.
d.
Potassium-Argon Dating – to date even older
fossils
1) Potassium-40
(40K) decays to
argon-40 (40Ar) and
Calcium-40 (40Ca).
2) Half-life of
potassium-40 is 1.3 billion years; half of remainder will be gone at end of
next 1.3 billion years, etc.
3) Calculating
the ratio of remaining potassium-40 to amount originally there provides
mathematically close estimate of age of deposit.
6. 
Evolutionary Trends - Fossil record
allows observation of evolutionary change over broad periods of time.
a.
Animals species
arise and go extinct repeatedly.
b.
Animal species typically survive 1-10 million
years; there is much variability.
c.
Horse Evolution
Shows Clear Trends
1) From Eocene
to Recent periods, genera and species of horses were replaced.
2) Earlier
horses had smaller sized and fewer grinding teeth, and more toes.
3) Reduction in
toes and increase in size and numbers of grinding teeth correlate with
environmental changes.
C. Comparative Anatomy –
1. All plants
and animals descending from a common ancestor is divergent evolution.
a.
Homologous
structures – structures that may differ in function but that have similar anatomy due to
descent from a common ancestor.
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1) For example,
vertebrate limbs show the same basic structures (one upper arm bone, two
forelimb bones, wrist bones, and finger bones) modified for different functions
(swimming in penguins & whales, flight in bats & birds, running in
dogs & sheep, grasping in humans & shrews) 2) Darwin saw
homology as major evidence for common descent. 3) It is
inconceivable that nearly the same bone arrangements could be ideal for such
different functions, as would be expected if each animal were created separately. This
is exactly what we would expect if the forelimbs of these animals evolved
from a common ancestor. |
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b.
Vestigial
structures –
structures that serve no apparent purpose in modern animals. “Evolutionary baggage” inherited from an
ancestor.
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1) For example,
vampire bats have molar teeth even though they live on a diet of blood &
therefore don’t chew their food. 2) Pelvic bones
exist in whales and certain snakes. 3) The appendix
is a vestigial structure in humans |
2. Through convergent evolution, natural selection has shaped unrelated organisms into
similar forms in similar environments.
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1) Natural
selection predicts that, given similar environmental demands, unrelated
organisms might independently evolve superficially similar structures. 2) Such
outwardly similar body parts in unrelated organism, called analogous structures, often have completely different
internal anatomy because they are not derived from a common ancestor. 3) For
example: wings of flies & birds;
also fat-insulated, streamlined shapes of seals (mammals) & penguins
(birds) |
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D. Molecular Biology – We can look in modern
animals for common sequences of DNA that have been inherited from a shared
ancestor. This helps us determine
patterns of relatedness.
1. The amino acid sequences of proteins
are remarkably similar across a huge spectrum of species.
2. The chromosomes of chimpanzees &
humans are extremely similar, showing that these species are closely related.
E. Developmental
Patterns – shared
embryological stages are indicative of a shared evolutionary ancestry.
