a tropical murder mystery chapter 10 evolution and extinction finding the missing birds of guam
TRANSCRIPT
A TROPICAL MURDER MYSTERY
CHAPTER 10 EVOLUTION AND EXTINCTION
Finding the missing birds of Guam
Do Now
• What is the Brown Treesnake?• How is it harmful to humans?• How is it harmful on the island of
Guam?• How are scientists trying to eradicate
the Brown Treesnake from Guam? Is it working?
Invasive species are hard-to-eradicate, non-native species that cause ecological, economic, or human health problems.
Extinctions are the complete loss of a species from an area. They may be local (gone from an area) or global (gone for good).
Evolutionary biology helps us understand the diversity of life and how populations change over time. It does not study creation or the
origin of life.
The island of Guam used to be home to 18 native species of
birds.
In the 1960s, Guam began losing its bird population. By the 1980s, four species had gone extinct and 10 more species were in danger of extinction.
Guam’s scientists thought disease was the problem. Locals thought non-native snakes were the problem.
Before they started disappearing, the birds of Guam were a diverse
bunch. Populations usually contain individuals that are
genetically different from each other.
Populations need genetic diversity to evolve. If a new challenge—such as a new predator—the population’s survival depends on having
individuals that can deal with the new species.
According to evolutionary theory, selective pressure
on a population favors certain inherited traits over
others.
These traits include better camouflage, tolerance for
drought, or enhanced sense of smell.
The traits that an environment favors are called adaptations. The process by which these traits are passed on is called natural selection.
Do Now• Considering what you already know about
evolution and extinction, if a mass extinction occurred in 2014…
• Which Ecosystems would be most vulnerable? Be specific.
• What type of species would be vulnerable? • What type of species would thrive?• What factors of evolutionary biology are in
effect here?
Individuals with adaptations are best suited for their
environment and leave more offspring than those who are
less suited.
Over time, the population will contain
more and more of these better-adapted
individuals and their offspring.
Ultimately, this changes how common certain
genes are in the population.
When this occurs, the population has experienced evolution—or changes in the
gene frequencies in a population.
It is important to note that individuals are
selected for, but populations evolve.
Individuals do not change their own genetic makeup to produce
new adaptations – they pass their traits on to the next generation.
Individuals may adjust their behavior to accommodate
environmental changes, but if that trait is not genetically
controlled, it cannot be inherited.
Founder EffectBottleneck
Under certain conditions, populations can diverge into subpopulations or even new
species (speciation).
Genetic Drift
Do Now
• Describe the differences between the following methods of populations diverging from their original genetic make-up.
• Genetic Drift• Bottleneck• Founder Effect• Can a species believed to be extinct actually
be surviving in an unknown area? Examples?
________________ is a change in gene frequency within a population.
A. AdaptationB. EvolutionC. Natural SelectionD. Genetic Diversity
Clicker Question
Do Now
• Please read the article.• Do all species experience an increase in
mortality with age? Why or why not?• Does evolution lead to senescence?• What are the evolutionary trade-offs between
reproduction and mortality?• How does this relate to evolution as we have
studied in CH 10? Be Specific.
Lobsters will not die of old age…
Lobsters will not die of old age… why?Is this an evolutionary favorable
characteristic?
In coevolution, two species provide the selective pressure that determines which of the other’s traits is favored by natural
selection.
Extinction can occur quickly if the rate of change exceeds the
ability of a population to adapt.
Studies proved the snakes were the culprit—the
eradication of the birds happened so fast it prevented
the birds from coevolving survival strategies.
Extinction is nothing new: more than 99 percent of all species that have ever lived on
the planet have gone extinct.
Today, most scientists agree we are witnessing a sixth mass extinction, largely driven by human actions.
Most scientists also agree that extinction rates are
accelerating worldwide—although they disagree about
the exact rate.
Humans also affect the evolution of populations through artificial selection: deciding which individuals to breed to
produce a population with desired traits.
By changing an environment rapidly, humans apply new selective pressures to an environment – such as
introducing tree snakes to Guam.
Our changes can be so great that natural selection can’t keep up and a population
collapses.
In Guam, things are looking up for the birds—snakes are being controlled through trapping to allow the bird populations to
recover.
If extinction is a natural process, should humans step in to protect animals that are becoming extinct?
A. YesB. No
Why or why not?
Clicker Question
Selfish Genes
• How can genes be selfish? Is it advantageous from an evolutionary perspective?
• How are genes cooperative? Be specific.• Agree or disagree with the following
statement providing evidence from what we have learned in class.
• “Nature dooms all that damages what it depends on”