Download Evolution_2016

Two different men…
Two different voyages…
One
extraordinary
idea…
Charles Darwin
Alfred Russell Wallace
and the
The Theory of Evolution
by
Natural Selection
“Evolution is just a theory…”
Before we continue, let’s clear something up…
A scientific theory is a
well-substantiated explanation of some
aspect of the natural world that is
acquired through the scientific method,
and repeatedly confirmed through
observations and experimentation.
A scientific theory doesn’t become
fact, a scientific theory explains facts.
It’s like an umbrella, under which are
facts, observations, and inferences
that are tied together by the theory.
Charles Darwin
Feb. 12, 1809 ~ Apr. 19, 1882
English naturalist/geologist
Journeyed around the world on board the
HMS Beagle from
Dec. 27, 1831 – Oct. 2, 1836
Noted similarities and differences between
species on South America and the
Galapagos Islands
Upon return to England, and after much thought and
consideration, put forth his theory of evolution by means of
natural selection. Based on observations from his Beagle journey,
as well as from selective breeding observations of dogs and
pigeons.
The Voyage
of the
HMS Beagle
Dec. 27, 1831 – Oct. 2, 1836
Darwin’s survey of South
America and the
Galapagos Archipelago
would lead him to
question how the
creatures of the
Galapagos came to be.
This journey, as captured
in his very detailed notes,
served as the basis for
later work, including his
his now famous book,
published in 1859, titled:
“On the Origin of
Species by Means of
Natural Selection, or
The Preservation of
Favoured Races in the
Struggle for Life”
His theory, as stated in
the introduction of the
book, set the stage….
“As many more individuals of each
species are born than can possibly
survive; and as, consequently, there is a
frequently recurring struggle for
existence, it follows that any being, if it
vary however slightly in any manner
profitable to itself, under the complex
and sometimes varying conditions of life,
will have a better chance of surviving, and
thus be naturally selected. From the
strong principle of inheritance, any
selected variety will tend to propagate its
new and modified form.”
Darwin, Charles (1859), On the Origin of Species by Means of Natural Selection, or the
Preservation of Favoured Races in the Struggle for Life , p. 5
Wallace arrived in Singapore in September of 1854,
and would spend nearly eight years collecting in the
Malay Archipelago. His journeys totaled more than
14,000 miles, and he collected over 125,000
specimens, including almost 110,000 insects, 7500
shells, 8050 bird skins, and 410 mammal and reptile
specimens, including probably more than 5000
species new to science.
In 1858, while suffering from what was most
likely malaria, Wallace realized that natural
selection must be the mechanism behind
evolutionary change. He wrote a detailed
account of that idea and sent it to Darwin.
Shocked that someone else had come to the
same conclusions he had, and afraid he would
lose the credit for his discovery, Darwin
consulted geologist Lyell and botanist Joseph
Hooker, who suggested that he write an
abstract and present it, together with Wallace’s
paper, at a meeting of the Linnean Society of
London. It was here, finally, that the theory of
evolution by means of natural selection was
unveiled to the world.
The Theory of Evolution
(Some refer to it as “change over time”)
“The process by which different kinds of living organisms are
thought to have developed and diversified from earlier forms
during the history of the earth.”
~Oxford English Dictionary
Or more simply put, it is a change in a populations genetic composition
over time. There are three key aspects to this:
1 – Populations evolve, individuals do not;
2 – Evolution has occurred when any genetic change happens to
any number of individuals in a population;
3 – Evolution can be measured in generational time.
Darwin and Wallace worked out the mechanism behind evolution,
natural selection, which is a central tenet of evolution, after reading Thomas
Malthus’ “An Essay on the Principle of Population” in which he stated that
sooner or later, human population would be checked by famine and disease.
Building the case for Natural Selection
Fact 1 – Populations can grow exponentially
Fact 2 – Populations tend to remain stable
Fact 3 – Resources are limited
Inference 1 – Struggle for existence (limited resources)
Fact 4 – Populations contain tremendous diversity
Fact 5 – Variability in populations is heritable
Inference 2 – Natural selection occurs within populations
Inference 3 – If natural selection occurs long enough,
evolutionary change results in that population
What you need to know….
~ Species – group of similar organisms that
can mate and produce fertile offspring
Examples of different
“species”
Walrus
“Not a species”
What we commonly call “Deer”
are actually part of the
Cervidae family made up of
34 species, including…
Red Deer
Elk
Lion
Mule
Deer
What you need to know….
~ Overproduction – more offspring are produced than can be supported
Loggerhead Sea Turtles
~ Each female produces an average of
70 to 150 offspring
~ Young turtles are on their own after they
hatch. Very few survive to maturity due to
predation and competition for resources.
Contrast this with animals such as:
Elephants
(one offspring, long
gestation period, remain
with herd for many years)
Bears
(1-3 offspring, stays with
mother for two seasons)
What you need to know….
~ Competition – limited resources lead to competition
within (intra) species and between (inter) species
Intraspecies competition
Limiting resource = competition within species
Limiting
resource
More deer using resource than
environment can support
Leads to die-off
Limiting
resource
Population reduced, enough
resource now available to
support new population size
What you need to know….
~ Competition – limited resources lead to competition
within (intra) species and between (inter) species
Interspecies competition
Limiting resource = competition between species
And the winner is?…
What you need to know….
~ Variations – differences between members of same species
May
lead
to
Adaptations
Genetic trait that
helps organism
survive and
reproduce
Darwin first noticed that differences in the beaks of
the various finches of the Galapagos Islands seemed
to correspond to their particular diets (small, soft
seeds vs. larger hard-shelled seeds vs. insects)
What you need to know….
~ Adaptations – genetic trait that helps an organism survive and
produce viable offspring
Daphne Major
This observation was confirmed
years later by researchers Peter
and Rosemary Grant studying
finches on Daphne Major, a small
island within the Galapagos
Archipelago.
Severe drought in 1977 caused plant life to wither. Small, soft seeds preferred by
finches were quickly eaten, leaving only large, tough seeds. Those finches that
were larger and had deep, strong beaks were able to open and eat these tougher
seeds. They survived to produce more offspring that were larger and had deep,
strong beaks.
But in 1984-85, there was an unusually heavy rainy season, resulting in more of
the smaller, soft seeds and less of the larger tough seeds. This time, the birds
with smaller beaks were better able to eat these seeds, and thus survived to
produce more offspring.
Darwin also observed differences between iguanas on the mainland of
South America and the iguanas on Galapagos.
Marine iguanas on Galapagos have
adapted to feed on algae that grows on
the rocks along the shore. The marine
iguanas are capable of swimming and
feeding underwater, but must come
ashore and warm themselves on the
black volcanic rocks.
Mainland iguanas have
adaptations that allow them to
climb trees for food.
Land iguanas on Galapagos feed
primarily on cactus.
Why are the Iguanas on Galapagos so much different
than those on the South American mainland?
Mainland Iguanas
Evolution, due to geographic isolation.
Galapagos
Iguanas
“Nothing in
biology
makes sense
except in
the light of
evolution.”
~ Theodosius
Dobzhansky
Overview
Life forms reproduce and therefore have a tendency to become more numerous.
The offspring differs from the parent in minor random ways.
If the differences are helpful, the offspring is more likely to survive and reproduce.
This means that more offspring in the next generation will have the helpful
difference.
These differences accumulate resulting in changes within the population.
Over time, populations branch off to become new species as they become
separated.
This process is responsible for the many diverse life forms in the world.
http://en.wikipedia.org/wiki/Introduction_to_evolution
What you need to know….
~ Species – group of similar organisms that can mate and produce
fertile offspring
~ Overproduction – more offspring produced than can be supported
~ Competition – between and within species for limiting resource
~ Variations – differences between members of same species
~ Adaptation – genetic trait that helps organisms survive and reproduce
~ Natural Selection – a process by which individuals better adapted to
environment are more likely to survive and reproduce
~ Evolution – gradual change in a species over time
When done writing these down,
read pages 140 to 150 in “Cells & Heredity”
What you need to know….
Vocabulary
Species
Overproduction
Competition
Adaptation
Variation
Natural Selection
Evolution
Traits
Scientific theory
Hypothesis
Concepts
Species change over time – factors and influences
How variations and adaptations lead to change
How geographic separation of a population can lead
to change
Causes of extinction
Fossils
Geologic Time