BIOL 189: Chapter 12 - Forces of Evolutionary Change

What is evolution?

Change in inherited characteristics of populations over successive generations.

What is the first key principle of evolution?

Common descent with modification.

What does common descent mean?

All organisms descended from a universal common ancestor.

How does descent occur?

Through genetic inheritance.

What does modification mean in evolution?

Organisms change in successive generations.

What is the second key principle of evolution?

Natural selection.

What is natural selection?

Individuals with advantageous inherited traits are more likely to survive and reproduce.

How can environmental changes affect natural selection?

Traits that provide a reproductive advantage become more common.

What did the 19th-century Britain pollution example demonstrate?

Environmental changes can favor different traits in a population.

What is the main idea of Section 12.2?

Historical observations and scientific discoveries helped develop evolutionary theory.

What does it mean that the living world is not fixed?

Species and populations can change over time, and extinction occurs.

What example of a potentially extinct organism appears in the slideshow?

The golden toad.

Who was Thomas Robert Malthus?

A scholar who wrote about population growth in 1798.

What book did Thomas Malthus write?

An Essay on the Principle of Population as it affects the Future Improvement of Society.

What did Malthus observe about reproduction?

Plants, animals, and humans produce far more offspring than can survive.

What is the struggle for existence?

Competition for limited resources because more offspring are produced than can survive.

Who was Georges Cuvier?

A scientist (1769-1832) who classified animals into four branches based on common functions.

What were Cuvier's four animal branches?

Vertebrata, Articulata, Mollusca, and Radiata.

What did Cuvier believe about extinction?

Extinction is a fact.

What did Cuvier believe caused extinction?

Periodic catastrophes.

What incorrect idea about evolutionary change was associated with Cuvier?

Change renders an organism unable to survive.

Who was Jean Baptiste Lamarck?

A French naturalist who proposed evolutionary ideas in 1801.

What did Lamarck believe about extinction?

He believed there was no extinction, only evolution. This idea was incorrect.

What is inheritance of acquired characters?

Lamarck's idea that characteristics acquired during an organism's life are passed to offspring.

What is the principle of use and disuse?

Using a structure or organ causes it to enlarge, while disuse causes it to shrink.

What did Lamarck believe about acquired changes?

He believed all changes were heritable. This was incorrect.

What is spontaneous generation?

The historical idea that living organisms can arise spontaneously from nonliving matter.

Who was Karl von Baer?

A scientist who developed ideas about embryonic development in 1828.

What did von Baer believe about embryos?

General characteristics appear earlier than specialized characteristics.

What does von Baer's work reject?

Recapitulation, or the idea that embryos pass through the adult forms of other species.

What did von Baer mean by embryos becoming separate from other forms?

Each embryo develops into its own specific animal form rather than passing through other animal forms.

Who was Charles Lyell?

A geologist (1797-1875) who argued that geological forces operating today also operated throughout history.

What book did Charles Lyell write?

Principles of Geology.

What does the statement "The present is the key to the past" mean?

Present-day processes help explain changes that occurred in Earth's history.

What did Hutton emphasize about geological change?

Most geological change happens slowly over long periods.

Where did Charles Darwin study before the Beagle voyage?

Edinburgh University, where he studied medicine, and Christ's College Cambridge, where he studied divinity.

What was Darwin passionate about?

Natural history and observing nature.

Who recommended Darwin for the Beagle voyage?

Professor Henslow.

What was Darwin's position on the HMS Beagle?

Naturalist.

How long did Darwin's Beagle voyage last?

Five years.

What did Darwin study during his voyage?

Organisms, fossils, geographical differences, and natural variation.

What did Darwin observe about Galápagos finches?

They were different types of finches related to an ancestral species from South America.

What did the finches help Darwin understand?

Related organisms can develop different characteristics in different environments.

What are the three observations supporting natural selection?

Heritable variation, limited resources, and overproduction of offspring.

What is heritable genetic variation?

Individuals within a species differ, and some differences can be inherited.

What are limited resources?

Habitats have limited supplies of the resources organisms need to survive.

What is overproduction of offspring?

More individuals are born than will survive to reproduce.

What is the struggle for existence?

Individuals compete for limited resources needed for survival.

What is unequal reproductive success?

Some individuals have inherited traits that make them more likely to obtain resources, survive, and reproduce.

What is descent with modification through natural selection?

Over generations, population characteristics change and can eventually produce new species.

Who was Alfred Russel Wallace?

A natural history collector and explorer (1823-1913) who independently developed the idea of natural selection.

What book did Wallace inspire?

A Voyage Up the River Amazon.

Where did Wallace explore?

First the Amazon, then Indonesia.

Which scientists' writings influenced Wallace?

Charles Lyell and Thomas Robert Malthus.

What idea did Wallace develop through his experiences?

Natural selection.

Who did Wallace ask Darwin to contact?

Charles Lyell.

Who was Gregor Mendel?

A scientist who explained the mechanism of heredity.

What is Mendel's particulate theory?

Hereditary information is passed through discrete units rather than blending together.

What is Mendel's Law of Segregation?

The two alleles for a gene separate during gamete formation.

What is Mendel's Law of Independent Assortment?

Different gene pairs can be inherited independently of one another.

What was the modern evolutionary synthesis?

The combination of evolutionary theory with genetics and other branches of biology.

When did the modern evolutionary synthesis develop?

1936-1947.

What branches of biology contributed to the modern synthesis?

Genetics, botany, paleontology, morphology, ecology, and cell biology.

Who wrote Evolution: The Modern Synthesis in 1942?

Julian Sorell Huxley.

Which answer supports natural selection: A, B, both, or neither?

Both A and B. Individuals with advantageous traits leave more offspring, making traits common.

What is natural selection?

Organisms better adapted to their environment tend to survive and produce more offspring.

What example of natural selection involving goats appears in the slideshow?

Myotonic goats, also called fainting goats.

How many kids can myotonic goats have per litter?

Up to three, while other goat species may have only one.

What is a selective pressure?

An environmental factor that influences which traits are favored.

What selective pressures generally do not affect embryos?

Movement, resources, and mating.

Does natural selection generally act more strongly on adults or embryos?

Adults. Natural selection drives adults rather than embryos.

What are genes?

Segments of DNA that code for one or more proteins.

What are alleles?

Different versions of the same gene.

What does polyallelic mean?

A gene has many possible alleles in a population.

What is allele frequency?

The percentage of a particular allele out of all alleles in a population.

How do you calculate allele frequency?

Number of copies of the allele divided by total copies of all alleles, multiplied by 100.

What is a species?

A group of organisms that can successfully interbreed and produce viable offspring.

What are viable offspring?

Offspring capable of reproduction.

What is a population?

A geographically isolated group of individuals belonging to the same species.

Why do populations evolve?

Environmental changes influence which individuals survive and reproduce.

What must an organism do to pass its genes to the next generation?

Survive and reproduce.

How can alleles provide an advantage?

Some alleles increase an individual's chances of survival or reproduction.

What is microevolution?

Changes in allele frequencies over a relatively short time frame.

What is an example of microevolution involving skin color?

Allele frequencies associated with skin color can change over a short period of time.

What is lactose persistence?

The ability to continue producing lactase into adulthood.

What does the LCT gene code for?

The enzyme lactase.

When is lactase normally expressed according to the slideshow?

During infancy.

What historical development helped create selection for lactose persistence?

The domestication of milk-producing animals.

How did lactose persistence develop?

A mutation in the LCT gene allowed lactase expression to continue in some adults.

Why was lactose persistence advantageous?

It provided an additional source of food through milk consumption.

What happened to individuals with the lactose-persistent allele?

Natural selection favored individuals carrying the allele.

What is Hardy-Weinberg equilibrium?

A condition in which allele and genotype frequencies do not change between generations.

What does Hardy-Weinberg equilibrium represent?

A non-evolving population used as a baseline for comparison.

What are the five conditions required for Hardy-Weinberg equilibrium?

No natural selection, no mutations, an infinitely large population, random mating, and no migration.

What does no natural selection mean in Hardy-Weinberg equilibrium?

No inherited trait gives an individual a reproductive advantage.

What does no mutation mean?

No new alleles are introduced through mutations.

Why must a Hardy-Weinberg population be infinitely large?

To prevent random changes in allele frequencies due to population size.

What does random mating mean?

Individuals mate without choosing partners based on particular genotypes.

What does no migration mean?

Individuals do not enter or leave the population.

What is the Hardy-Weinberg allele frequency equation?

p + q = 1