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”