Transcript Evolution

Lecture 4`
Evolution, Biodiversity, and
Population Ecology
What will I learn today?
1.
2.
3.
4.
What is evolution
Discuss your feeling about evolution
Learn examples of biodiversity
Learn basics of ecology necessary to
understand environmental biology
Costa Rican Cloud Forest
Case study
There one year and gone the next!
Monteverde cloud forest
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Golden toads of Costa Rica
What happened?
Science wants to know the truth based on sound
principles
•Were the frogs hunted to death?
•Were the frogs eaten by predators?
•Were the frogs killed by a disease?
•Did they leave the region?
•Did they become something else?
•Were they caught and sold to the pet trade?
•???? What else ????
Scientific Analysis
By looking over the data… conclusions could be drawn.
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Environment kills!
• In late 1960’s lots of these frogs
• The forests were moist and had lots of cloud
cover
• In late 1990’s all the frogs were extinct!
• The forests were drier and there was little
cloud cover
• Something has caused a change in the
climate…
1960’s
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1990’s
Global Warning
The death of the frogs has been linked to the
warming of the oceans and the resulting
deflection of the clouds, reducing the amount of
moisture. Frogs needs moisture to live.
• Actually, the real answer now is that the
increased temperatures at night and lower
temperatures in the day promote a fungus to
grow and kill the frogs!
This is our first example of GLOBAL
WARMING killing species - remember!
Evolution
Introduction to evolution…
Evolution by natural selection is one of the bestsupported and most illuminating concepts in all of
science, yet it has remained socially controversial
among some nonscientists who fear it threatens
their religious beliefs.
What is evolution?
• In the strict sense it is:
“Change over time”
Rivers change direction over time
Mountains form and erode over time
• Biological evolution is:
“Change in the genetic information over
generations”
We will understand this over the course of the
course…
Evolution is our best
supported scientific theory
• LAYMAN - a theory is a hunch, a
guess, a shot in the dark!
• SCIENTIST - a theory is something
well supported by evidence.
• Watch this great definition of a scientific
theory
How are there so many life
forms on Earth?
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About 1.5 million plus species known
Expect to find up to 100 million
All arose due to Evolution
How?
By process of speciation…
Many possible ways
One method is by physical isolation:
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DNA damage
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What causes the DNA to change?
Many factors alter DNA…
1.
2.
3.
4.

Cosmic radiation
Copying errors during DNA replication
Cellular heat
Chemicals in the environment
Any changes have to pass to offspring
to be classified as evolution…
Natural Selection
• More babies are born than can be
supported by the environment
• Each baby is slightly different from the
others in the population
• Some are better suited to that
environment over others
• These survive and the others do not…
• This video provides a great explanation
Examples of
Evolution
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• Selective breeding
by humans
• Dogs from wolf
• Crops from weeds
Microbes & real-time
evolution
• The time it takes for large creatures to
evolve is very long.
• However, since the discovery of
microbes we can see evolution in
action…
• The video, about TB, provides and
excellent example
Massive death
• The Earth has seen 5 mass extinction in
the past
• Each killed off between 50% to 95% of
species alive at the time
– Permian period 250 million years ago
• Global warming
– K-T event 5 million years ago
• Killed the dinosaurs and was caused by a
meteor impact
Round 6 has started
• Today we are seeing another round
• Caused by humans
– Population growth issues
– Development
– Resource depletion
– Relocations
• Species loss is forever!
God and Evolution
• Naturally, science is now trying to
understand where we came from, who
we are, and why?
• These questions and the answers
impinge on other human values…
• This video presents an opinion on this
topic
Biodiversity
Biodiversity
• Biodiversity - refers to the sum total of
all organisms in an area.
• Species - is a particular type of
organism that can freely breed and
produce fertile offspring.
• Population - is a group of individuals of
a particular species that live in the same
area.
Ecology
• Habitat - specific environment in which
an organism lives
– Both living and non-living parts
• Niche - a habitat supplying the factors
necessary for the existence of an
organism or species
– No two species can share the same exact
niche - one will go extinct!
Populations follow rules
• Understanding these is important in
predicting the future.
• Age structure diagrams (age pyramids)
can tell us how that population will
develop in the future…
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The shape of the graph is very important
Population demographics
• Another key measure is growth rate
• The rate of growth of a population is
measured using this formula
•
(Crude birth rate + immigration rate) - (Crude death rate + emigration
rate) = Growth rate
• Thus, a growth rate of 6/1,000 would be
expressed as: 6/1,000 × 100% = 0.6%
Exponential Growth
• A population that increases by a fixed
percentage each year is said to exhibit
exponential growth
This form of growth
cannot be sustained
for long. Something
(food, shelter, space,
waste) will change it.
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Carrying capacity
• Every population eventually is constrained by
limiting factors, physical, chemical, and
biological characteristics of the environment
that restrain population growth.
• The interaction of these factors determines
the carrying capacity
– the maximum population size of a species that a
given environment can sustain.
Carrying Capacity
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As we have seen, the global human population has
risen from fewer than 1 billion 200 years ago to
6.7 billion today, and we have far exceeded our
historic carrying capacity.
1. What accounts for the increase in Earth’s carrying
capacity for us?
2. Do you think there are limiting factors for the
human population?
3. What might they be?
4. Do you think we can keep raising our carrying
capacity in the future?
5. Might Earth’s carrying capacity for us decrease?
Conclusions
1. You may appreciate evolution theory a
bit more.
2. The evolutionary processes of natural
selection, speciation, and extinction help
determine Earth’s biodiversity.
3. Understanding how ecological
processes work at the population level
is crucial to protecting biodiversity
threatened by the mass extinction event
that many biologists maintain is already
underway.