Transcript Ch 10 Principles of Evolution

Chapter 16 and 17
Microevolution
Evolution
• The change in a species over time.
• The processes that have transformed life on earth
from it’s earliest forms to the vast diversity that
characterizes it today.
Early Ideas About Evolution
• Many of the early ideas regarding the
existence of living organisms were strongly
influenced by religion and philosophy.
• However, in the 1600s, scholars began a
revolution that created the basis of empirical
and scientific thought.
Early Ideas About Evolution
1. Hippocrates
– Proposed that all things can be traced to preceding
causes.
2.
Aristotle
– Believed that each kind of organism was distinct
from all the rest.
– Classified organisms into two groups: plants and
animals
3.
Georges de Buffon (1700s)
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proposed that species shared ancestors instead of arising
separately.
Suggested that Earth was much older than 6000 years
4.
Jean Baptiste Lamarck
(early 1800’s)
– Proposed that all organisms evolved
toward perfection and complexity.
– theory of inheritance of acquired
characteristics- changes in an environment
caused an organism’s behavior to change,
leading to greater use or disuse of a
structure or organ.
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For example the giraffe: short neck giraffes needed to reach leaves higher in
trees, so they stretched their neck to reach them.
This stretched neck was passed on to offspring, who in turn, stretched their own
necks and passed on that neck to their offspring.
5. James Hutton (late 1700s)
– Proposed that the changes in landforms resulted from
slow changes over a long period of time (Theory of
Gradualism).
6. Georges Cuvier (early
1800s)
proposed the Theory of Catastrophism - natural disasters have
shaped landforms and caused species to become extinct.
7. Charles Lyell (1830s)
Proposed the Theory of Uniformitarianism -geologic
processes that shape Earth are uniform over time.
Struggle for Survival
Thomas Malthus
-proposed that resources such as food, water,
and shelter were natural limits to population
growth.
-Human population would grow uncontrollably
without limits.
As a result, Darwin suggested that
-A similar struggle takes place in nature.
-Resources are limited, and organisms had more offspring than could survive.
Charles Darwin
• “Father of Evolution”
• Influenced by Charles Lyell who published
“Principles of Geology”.
• In 1831, Darwin, on the ship HMS Beagle, set sail
from England to map the coast of South America.
• While on the Galapagos Island, he observed
the following:
1. Species found on one island differed from those
on nearby islands. (Variation)
2. Some differences seemed well suited to the
animals’ environments and diets.
3. Fossils provided evidence of species changing
over time.
4. Fossils suggested that modern animals might be
related to fossil forms.
5. Fossil shells of marine organisms were found
high up in the Andes mountains.
After his voyage
• When he returned in 1836, Darwin began
discussing his ideas with other scientists.
According to Darwin’s ideas, evolution occurs from generation to
generation due to two interacting factors:
1) Genetic Variation
 Differences occur among individuals of a given
species.
2)Natural Selection
 In each generation, many more offspring are
produced than will survive. Individuals with more
favorable traits will be better suited for the
environment. Over time, favorable traits will become
more prevalent in a population.
Artificial Selection
Darwin noticed a lot of variation among domesticated
plants and animals as a result of artificial selection.
– process in which humans/breeders choose as
parents those individuals with traits that are
desirable from a human perspective.
– the underlying cause of the phenotypic variation is
usually related to differences in alleles that
determine the trait.
– through the selection of certain traits, breeders
can produce a great amount of diversity.
Main Principles of Natural Selection
1. Variation
– Differences exist in every population.
2. Overproduction
– many offspring raises the chance of survival but
results in competition between offspring for
resources.
3. Adaptation
– better adapted = better chances of survival.
4. Descent with Modification
– Over time, natural selection will result in more
individuals being well suited for the environment if
conditions remain favorable.
Natural Selection can occur in several ways:
1)Directional Selection
-new allele introduced into a population
by mutation
2) Stabilizing Selection
-reduces genetic diversity
3) Diversifying Selection
-Likely occur in populations that
occupy heterogeneous
environments-so some members are
more likely to survive than others.
4) Balancing Selection
-maintains genetic diversity
Evidence of evolution
Evidence of Evolutionary Change
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Fossil record
Comparative Anatomy
Embryonic development
Studies of natural selection
Selective breeding
Molecular structure (DNA, Amino Acid
sequence)
Fossil Records provide
evidence that living
things have evolved
Fossils show the history of
life on earth and how
different groups of
organisms have changed
over time
Comparative Anatomy
scientific study of comparable
body parts in order to identify
similarities and differences.
Homologous Body
Structures
Structures that have
different mature
forms but develop
from the same
embryonic tissues
Turtle
Alligator
Bird
e.g. Wing of bat,
human arm, leg of
turtle
Homologous Body Structures
Analogous Structures
• Similar features of organisms that evolve
independently.
Examples:
• Wings structure in various flying animals
– same function but differ in bone structure,
wing coverings, shape, and sizes
• fins
– Animals such as penguins and fish both have
fin-like structures
Vestigial Structures
• Bones or other structures present in
organisms but are reduced in size and
function.
Example:
– Hind leg and hip bones in whales
Similarities in Embryology
• the study of the development
of an embryo from
fertilization to the fetus stage.
• In their early stages of
development, chickens, turtles
and rats look similar, providing
evidence that they shared a
common ancestry.
Embryological development
Chapter 17
Speciation –Development of
new species
Species
• refers to a particular kind of
organism.
Ernst Mayr
• is used to define characteristics particular
to one kind of animal.
• “Species are groups of interbreeding
natural populations that are
reproductively isolated from other such
groups.”
• Differences in phenotype do not
disqualify some members
• Mayr’s definition does not apply to
asexual creatures (as they do not have an
extensive gene pool – each offspring being
a clone of the parent), but it does help
classify sexually reproducing organisms.
Extinction
• The irrevocable
loss of one
species.
• Example – the
loss of the dodo
bird
Mass Extinction
• Loss of several species at
once due to a catastrophic
event.
• The loss of dinosaurs could
be considered mass
extinction.