CHAPTER 22: DESCENT WITH MODIFICATION, A

DARWINIAN VIEW OF LIFETuesday, September 2, 2014

DARWIN & THEORY OF EVOLUTION BY NATURAL SELECTION

-The Origin of Species in 1859

-The Origin of Species focused biologists’ attention on the great diversity of organisms

-Darwin noted that current species are descendants of ancestral species

-Evolution is the change of genetic composition in a population from generation to generation

-Evolution can be viewed as both a pattern and a process

CONCEPT 22.1: THE DARWINIAN REVOLUTION CHALLENGED TRADITIONAL VIEWS OF A YOUNG EARTH INHABITED BY UNCHANGING SPECIES

-Aristotle, viewed species as fixed and that life-forms could be arranged on a scale/ladder of increasing complexity Scala Naturae

-Carolus Linnaeus interpreted organismal adaptations as evidence that the Creator had designed each species for a specific purpose

Linnaeus was the founder of taxonomy, the branch of biology concerned with classifying organisms

He developed the binomial format for naming species (for example, Homo sapiens)

Aristotle

Linnaeus

IDEAS ABOUT CHANGE OVER TIME

• The study of fossils helped to lay the groundwork for Darwin’s ideas

• Fossils are remains or traces of organisms from the past, usually found in sedimentary rock, which appears in layers or strata

FIGURE 22.3

Paleontology, the study of fossils, was largely developed by French scientist Georges Cuvier

Cuvier advocated catastrophism, speculating that each boundary between strata represents a catastrophe

Geologists James Hutton and Charles Lyell perceived that changes in Earth’s surface can result from slow continuous actions still operating today Lyell’s principle of uniformitarianism states that the mechanisms of change are constant over time This view strongly influenced Darwin’s thinking

During the 18th century, several naturalists proposed that life evolves as the environment changes

But no one had a mechanism for how this would occur

Erasmus Darwin, Charles’ grandfather

LAMARCK’S HYPOTHESIS OF EVOLUTION

Lamarck hypothesized that species evolve through: 1) use and disuse of body parts, and 2) the inheritance of acquired characteristics

The mechanisms he proposed are unsupported by evidence

DARWIN’S OBSERVATIONS 1. There is unity in lifeHe noticed that some features of extinct fossils matched extant organisms

Animals in temperate South America resembled those in tropic S. America, but were different than those in temperate North America

2. there is diversityNoticed diversity of finches and mockingbirds; his famous observations are probably the diversity in finch beaks

3. organisms match, or are adapted to, their environmentFinch beak shape matched the types of food they ate

a) Lamarck thought evolution had occurred. b) Lamarck’s proposal that individuals evolve by the

principle of use and disuse is well supported by evidence.

c) Lamarck was wholly wrong. d) Lamarck published his ideas only after Darwin

published his.

Which of the following statements about Lamarck is/are accurate?

a) Lamarck thought evolution had occurred. b) Lamarck’s proposal that individuals evolve by the

principle of use and disuse is well supported by evidence.

c) Lamarck was wholly wrong. d) Lamarck published his ideas only after Darwin

published his.

Which of the following statements about Lamarck is/are accurate?

EVOLUTION BY NATURAL SELECTION

-Natural selectionProcess in which individuals with certain inherited traits tend to survive and reproduce at higher rates than other individuals without those traitsAdapations are inherited traits that enhance organismal survival and reproduction in specific environments

FIGURE 22.8Hyracoidea(Hyraxes)

Sirenia(Manateesand relatives)

†Deinotherium

†Mammut

†Platybelodon

†Stegodon

†Mammuthus

Elephas maximus(Asia)

Loxodonta africana(Africa)

Loxodonta cyclotis(Africa)

†Moeritherium

†Barytherium

60

Millions of years ago

34 24 5.5 2104 0

Years ago

LIFE AS DARWIN SAW IT…

FIGURE 22.8Hyracoidea(Hyraxes)

Sirenia(Manateesand relatives)

†Deinotherium

†Mammut

†Platybelodon

†Stegodon

†Mammuthus

Elephas maximus(Asia)

Loxodonta africana(Africa)

Loxodonta cyclotis(Africa)

†Moeritherium

†Barytherium

60

Millions of years ago

34 24 5.5 2104 0

Years ago

Evolutionary treeof elephants

KEY COMPONENT OF NATURAL SELECTION!! YOU MUST KNOW THIS!! 1. Individuals in a population vary in traits 2. These traits must be heritable 3. Species can produce more offspring than their environment can support

*Individuals do not evolve!! Only populations do!

EXIT TICKET To the right is a picture of a population of Asian ladybird beetles. They vary in spot number and color.

Question: Under what conditions would natural selection act on the color and spot number of beetles in this population? Your job is to convince me in your defense.

HOMEWORK 1) Read chapter 22, pp 452-460

2) Draw the beaks of the finches on page 457, figure 22.6 and explain why the beaks are different shapes

3) Print out the clover study document posted on the class wiki page

http://drcaobiology.cmswiki.wikispaces.net/

4) Make sure your mastering biology account works b/c our first online assignment is due this ThursdayMake sure you can access the etextMake sure you have access to our course page, called DrCaoBiologyMake sure your student id is entered!!! This is important for grades