News: Evolution & Extinction.

Evolution & Extinction

09:14 AM CDT on Tuesday, July 15, 2008
http://www.dallasnews.com/sharedcontent/dws/spe/nie/weeklylessons/stories/20080707-dnnielesson.59af00de.html

"An 1898 photograph of a passenger pigeon in captivity."
Research published recently in the journal Nature concludes that the
current methods for assessing species extinction underestimate the
risks.

Most often, a species risk for extinction takes into account how many
individuals are born, how many die, and how environmental
conditions?like habitat loss?affect species populations. Experts have
estimated that more than 16,000 species are at risk of
extinction.?that includes about one in three amphibians, one in four
mammals, one in eight birds, and 70% of the world's plant species.

A team of scientists, however, found that additional factors such as
the ratio of males to females can have a huge impact on the survival.
This is especially true if the population is already small and
vulnerable to other risks. This makes the current estimates even more
worrisome.

Numerous animals and plants have gone extinct due to natural forces
and also due to human activity, including over-harvesting and habitat
destruction. What the forces of evolution produced over millions of
years can be destroyed relatively quickly. North America's passenger
pigeon is one example. As many as five billion birds lived in the
United States east of the Rocky Mountains. People reported that
migrating flocks often darkened the sky for days. Humans wiped them
out by the early 1900s, however. The last one, "Martha", was held in
captivity until her death in 1914. She is now stored at the
Smithsonian Museum, preserved as part of American history.

Unfortunately, how fast the forces of evolution can have an effect
largely depends on how quickly new generations are born. Strains of
short-lived microbes, for example, can evolve and adapt pretty quickly
to changing conditions. This is why antibiotics can become ineffective
as disease treatments. A passenger pigeon, on the other hand, could
live up to a decade or more. Therefore, this species could not adapt
to such a swift change in its environment.

Evolution has provided the Earth with an awe-inspiring inventory of
species to research and conserve for future generations. In fact, as
you will discover in this lesson, species are often surprisingly
related. You will also investigate the theories of Charles Darwin and
the variety of factors and forces that have shaped the nature of life.

How Life Is Related

Start your investigation at the University of California's Museum of
Paleontology, (http://www.ucmp.berkeley.edu/exhibits/index.php) where
you will explore What did T. Rex Taste Like?: An introduction to how
is life related.
http://www.ucmp.berkeley.edu/education/explorations/tours/Trex/index.html
Hit the Student Start button, and Go to the beginning of the module
where you will learn how to navigate the site.

Then, begin your tour of phylogenetics by opening Folder 1.
http://www.ucmp.berkeley.edu/education/explorations/tours/Trex/phyframe1.html
Click through the pages to see how species are classified by
scientists into three main groups: Archaea, Bacteria, and Eukaryota.
When you have read about all three, you can click more to move on.

Continue through the module, learning about common ancestors and how
traits get passed along through lineages. Then, stop for a review of
these first concepts.

When you have completed the review, open Folder 2 to discover how
caimans, a type of reptile, and parrots are related. As you learn more
about tracing lineages, click the points that illustrate common
ancestors among species shown on the diagram. Again, stop for a
review.

In Folder 3, delve deeper into cladograms and what they mean. How is
identifying key features helpful to determining common ancestors? What
key feature do caimans and parrots share? Stop for the complete
review.

In Folder 4, find out how scientists use cladograms to answer
questions about life's history. In this folder, re-organize the
cladogram information into a table. Then, move on to compare T. Rex
with the other key features. When you have narrowed down the
cladogram, examine more key features. Did you conclude that T. Rex
was more closely related to caimans or to parrots?

Make sure to stop and review what you have learned so far, and then
move on to Folder 5, where you can help solve T.Rex's identity crisis.
What types of scientific evidence did you use to determine
relationships between different species?
Darwin's Big Ideas

Now that you have seen how life forms can be related, your next
objective is to investigate what caused new species to branch off from
their ancestors. To do that, visit Evolution: A journey into where
we're from and where we're going
http://www.pbs.org/wgbh/evolution/index.html at PBS.

Begin your journey in the Students section with the Evolving Ideas
video set. Here, watch all seven videos (QuickTime or RealPlayer):

* Isn't Evolution Just a Theory?
* Who Was Charles Darwin?
* How Do We Know Evolution Happens?
* How Does Evolution Really Work?
* Did Humans Evolve?
* Why Does Evolution Matter Now?
* Why Is Evolution Controversial Anyway?

When you have completed watching the videos, return to the site's
home page to learn more about Darwin. Watch the video, Show 1:
Darwin's Dangerous Ideas. Then, read excerpts from Darwin's Diary,
which capture what it was like for him to sail on the Beagle and also
what he observed. Also, explore An Origin of Species example,
illustrating what Darwin noticed about the pollencreepers.

In the site's Change section, watch Show 2: Great Transformations.
Afterward, journey through Deep Time, check your relationship skills
with All in the Family, and watch the video in the Genetic Tool Kit.
How do embryos reveal not only the role of genetics in an organism's
growth, but also in the ancestral relationships that humans share with
other species?

Similarly, explore the site's Extinction, Survival, Sex, Humans, and
Religion sections.

Now, do some independent research to identify one species of animal
that has become extinct since 1900. Investigate the habitat it
primarily occupied, and list its reported traits. For each
characteristic, write a brief paragraph of how you think that trait
helped the species survive in its preferred habitat. Write down one or
more other species that share that identical or similar
characteristic. Speculate on the possible ancestral relationships.

If you have time, check out some of the other Student Resources at the
University of California's Museum of Paleontology. Learn more about
Similarities and Differences, examine The Evolution of Flight, and
take the excellent in-depth course, Evolution 101
http://evolution.berkeley.edu/evolibrary/article/evo_01.

[There are a lot more links in the original artice, I've only included
the main ones.]

--
Bob.

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