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Transcript
Descent with
modification
One of the key words of our
modern time is Evolution
Outline
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1. Key concepts
2. Darwin developed the theory of evolution
based on his observations and other
evidence
a. Darwin’s observations
b. Factors that influenced Darwin’s
thinking
3. Natural selection: A mechanism of evolution
4. More evidences
5. Key terms
6. Conclusions
Key Concepts:
Evolutionary theories gave early scholars new
ways to interpret the occurrences in the world
Today, biological evolution is interpreted as
heritable changes
Darwin and Wallace explained evolution on the
basis of Natural Selection
The traits that characterize a population can
change over time
Lamarck’
Lamarck’s Theory of Evolution
Lamarck
Theory of
Inheritance of
Acquired
Characteristic
Early Beliefs, and New Discoveries
Aristotle – believed that each kind of organism was
distinct from all the rest
Linnaeus (classification)
Hutton (gradual geologic change)
Lamarck (species can change)
Malthus (population limits)
Cuvier (fossils, extinction)
Lyell (modern geology)
Darwin (evolution, natural selection)
Mendel (inheritance)
American Revolution
1750
Wallace (evolution, natural selection)
French Revolution
U.S. Civil War
1800
1850
1900
1795 Hutton proposes his theory of gradualism.
1798 Malthus publishes “Essay on the Principle of Population.”
1809 Lamarck publishes his theory of evolution.
1830 Lyell publishes Principles of Geology.
1831–1836 Darwin travels around the world on HMS Beagle.
1837 Darwin begins his notebooks on the origin of species.
1844 Darwin writes his essay on the origin of species.
1858 Wallace sends his theory to Darwin.
1859 The Origin of Species is published.
1865 Mendel publishes inheritance papers.
Charles Darwin
[1809-1882] called
evolution
“Descent with
modification”
Darwin - Voyage of the Beagle - 1831
At age 22, Charles Darwin began a five-year,
round-the-world voyage aboard the Beagle
He collected and examined the species that
inhabited the regions the ship visited
EQUATOR
Galapagos
Islands
Darwin’
Darwin’s observations
Prevailing ideas about species: they
did not change or interbreed
Darwin’s evidence for change came
from:
1. his observations of living organisms
2. geologic evidence and fossil record
3. theories of population growth
Darwin’
Darwin’s Mechanism of
Evolution by Natural Selection
Darwin’s Mechanism of Evolution by Natural
Selection consists of observations on four aspects
of the natural world:
1. Variation: Variation among individuals means they
individually have different ability to obtain resources.
2. Overproduction: The reproductive ability of each species
has the potential to cause its population increase.
3. Limits on population growth: Limited resources in the
environment produces a struggle for existence
4. Differential Reproductive Success: Selection pressures act
upon individuals that compete for resources, producing
differential reproductive success
Individuals that have difficulty producing members of the next
generation have their genes reduced and possibly lost from
subsequent populations
Darwin’
Darwin’s Theory Takes Form
Armadillo – 10 pounds
Glyptodont – fossil from S. A. (2 tons!)
Galapagos Islands today
An example of natural
selection: Darwin’
Darwin’s finches
Factors that influenced
Darwin’
Darwin’s thinking
•
•
Geology: as Earth changed, so did types
of fossil organisms in rock strata
Population studies: many organisms are
produced; only a few survive to
reproduce [Thomas Malthus (1766-1834)
Essay on Disease, Famine, and Population
Size]
•
Artificial breeding experiments: humans
“select” desirable traits in plants and
animals; so does “nature”
Artificial Selection
In the process of artificial selection
Humans have modified other species over many
generations by selecting and breeding
individuals that possess desired traits
Terminal
bud
Lateral
buds
Brussels sprouts
Cabbage
Flower
cluster
Leaves
Cauliflower
Kale
Flower
and
stems
Broccoli
Stem
Kohlrabi
Wild mustard
Artificial Selection in Pigeons
WILD ROCK DOVE
Darwin used pigeons to explain connections
between evolution and variation in traits
Natural selection: A
mechanism of evolution
Darwin’s explanation for species diversity:
Nature “selects” organisms which have
inheritable traits (adaptations) suited to
their environment which allow them to
survive to reproductive age
Survivors then breed and pass on these
characteristics to their offspring
Natural Selection
Selection can increase the frequency of a trait in a
population
Environment may favor a trait over another
Alfred Wallace
Developed same theory as Darwin
The Origin of Species
1859 - Darwin
Evidence for the Theory of Evolution
The Origin of Species
Darwin made two major points in his book
He presented evidence that the many
species of organisms presently
inhabiting the Earth are descendants of
ancestral species
He proposed a mechanism for the
evolutionary process, natural selection
Descendents of these ancestors accumulated diverse
modifications or adaptations that fit them to specific ways of
life and habitats.
Fossils
The study of fossils
Helped to lay the
groundwork for
Darwin’s ideas
Fossils are remains
or traces of
organisms from
the past
Usually found in
sedimentary rock,
which appears in
layers or strata
A sycamore leaf
dropped 50 mya
Tree fern dated 250 mya
Barosaurus
• This evolutionary tree of the elephant family is
based on evidence from fossils.
Homology
Homology
Is similarity resulting from common ancestry
Anatomical Homologies
Homologous structures between organisms
Are anatomical resemblances that represent variations on a
structural theme that was present in a common ancestor
Human
Cat
Whale
Bat
Figure 22.14
Comparative embryology
Reveals additional anatomical homologies not
visible in adult organisms
Pharyngeal
pouches
Post-anal
tail
Chick embryo
Figure 22.15
Human embryo
Evidence From
Comparative Embryology
Vestigial organs
Are some of the most intriguing homologous
structures
Are remnants of structures that served
important functions in the organism’s
ancestors
Molecular Homologies
Biologists also observe homologies
among organisms at the molecular level
Such as genes that are shared among
organisms inherited from a common
ancestor
Anatomical resemblances among
species
Are generally reflected in their molecules,
their genes, and their gene products
Species
Percent of Amino Acids That Are
Identical to the Amino Acids in a
Human Hemoglobin Polypeptide
100%
Human
Rhesus monkey
95%
Mouse
87%
Chicken
69%
Frog
Figure 22.16
Lamprey
54%
14%
The Evolution of DrugDrug-Resistant HIV
Scientists designed the drug 3TC to interfere with
reverse transcriptase, the enzyme that HIV uses to
copy its RNA genome into the DNA of the host cell.
Because 3TC is similar in shape to the cytosine
nucleotide of DNA, HIV’s reverse transcriptase
incorporates 3TC into its growing DNA chain instead
of cytosine. This error terminates elongation of DNA
and thus prevents HIV reproduction.
3TC-resistant varieties of HIV have a form of reverse
transcriptase that can discriminate between cytosine
and 3TC.
These viruses have no advantage in the absence of 3TC. In
fact, they replicate more slowly than viruses with normal
reverse transcriptase.
Once 3TC is added to their environment, it becomes a
powerful selective agent, favoring reproduction of
resistant individuals.
Darwin’s main ideas can be summarized in
three points.
1. Natural selection is differential success in
reproduction (unequal ability of individuals to
survive and reproduce).
2. Natural selection occurs through an
interaction between the environment and the
variability inherent among the individual
organisms making up a population.
3. The product of natural selection is the
adaptation of populations of organisms to
their environment.
Evolution
Natural selection
Fossils
Descent with modification
Artificial selection
Homology
Vestigial organs
In Conclusion
The Theory of Evolution by Natural Selection
states
More offspring are produces than the environment can
support
Variant forms of a trait may be more or less adaptive
under environmental conditions
An adaptive trait allowed organisms to survive and
reproduce more frequently. The frequency of that
adaptive trait increases in a population
In Conclusion
Comparative anatomy, biogeography,
embryology, fossils, and a lot of other
evidence showed changes in lines of
descent
Natural Selection results in modification of
traits and can bring about the evolution of
a new species