Lecture 4` Evolution, Biodiversity, and Population Ecology

Lecture 4`Evolution, Biodiversity, and

Population Ecology

What will I learn today?

1. What is evolution

2. Discuss your feeling about evolution

3. Learn examples of biodiversity

4. 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

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.



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.

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

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!

EvolutionIntroduction to evolution…

Evolution by natural selection is one of the best-supported 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 timeMountains 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

http://www.pbs.org/wgbh/evolution/library/11/2/quicktime/e_s_1.html

How are there so many life forms on Earth?

• 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:

DNA damage• What causes the DNA to change?• Many factors alter DNA…

1. Cosmic radiation2. Copying errors during DNA replication3. Cellular heat4. 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

• 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…



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.

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

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?

Conclusions1. 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.

Documents

Lecture 4` Evolution, Biodiversity, and Population Ecology