Homework Questions

• PG. 287Q3: Explain why harmful mutations do not accumulate

over time and cause harm to populations.

ANSWER:Harmful mutations cause harm to the individual and

evolution will select against individuals with harmful mutations. These individuals will not breed with others, causing the harmful mutation to disappear from the population.

Homework Questions

• PG. 287Q9: How do the genetic diversity of a population and mutation

rates limit the ability of breeders to create organisms with desired traits?

ANSWER:Hint: Think of the blue rose.Breeders can only work with the genetic diversity that is already

present in the organisms population. If a trait does not exist in an organisms genome, a breeder cannot just create that mutation. Mutations are random and rare. This means that beneficial mutations are unlikely to happen.

Homework Questions

• PG. 319Q28: What is artifical selection, and why is it called

artificial?

ANSWER:Artificial selection is directed breeding in which

individuals that exhibit a particular trait are chosen as parents of the next generation. It’s called artificial because it is controlled by human choice, not by nature.

The Modern Synthesis:Evolution and Genetics

Charles Darwin- Born in Shrewsbury, England on February 12, 1809

- Born into a wealthy family as the 5th of 6 children

- Grandfather, Erasmus Darwin, had proposed that all life came from a single organism, “the Great First Cause”

- Darwin was encouraged to become a doctor, but was fascinated with the natural world

The Voyage of the Beagle• December 27, 1831, he joins the HMS Beagle as a naturalist

on a five year voyage• The ship’s mission was to map the coast of South America for

Britain• As a naturalist, Darwin was to observe and collect specimens

How did he begin to craft his theory of evolution?

Observations in South America• In Argentina, Darwin

uncovered fossils of the Megatherium and Glyptodon

• These fossils looked like giant sloths and armadillos

• The fossils were found in the same geological range as these modern animals

• Fossils of marine organisms also found in the Andes Mountains

• Island chain 1000 km west of Ecuador

• Discovered many new species with many similarities to species found on South America

• No native amphibians or large land mammals – why?

Observations in the Galapagos Islands

• Marine Iguana:– Closely resembles

iguanas from the South American Mainland

– Is the only known lizard able to dive and forage in water

Observations in the Galapagos Islands

• Giant land tortoises– At least five unique

species were found on different islands

Observations in the Galapagos Islands

• Darwin at first thought they were one species with variation

• 13 species with distinct characteristics

• Their beaks show variation in shape and size– Why?

Darwin’s Finches

• After leaving the Beagle in 1836, Darwin spent more than 20 years gathering evidence on evolution

• He knew that his theories would be controversial

• By the time he presented his theory, Darwin was able to not only explain that evolution had happened, but also how it occurred…mostly

Forming the Theory

• By 1844 Darwin had prepared an essay on his theory of Evolution, but did not publish it

• 1858 - received a letter from Alfred Russell Wallace, who had also concluded that evolution must be true

• This pressure led Darwin to publish his theory as On the Origin of Species in 1859

On the Origin of Species

Backlash

• Please read 294-295 and complete #1-4