Chapter 3: Evolution by Natural Selection

What is the theory that explains how species evolve over time?

Evolution by Natural Selection

What are Darwin's four postulates?

1. Individual species are variable; 2. Some variation is passed on to offspring; 3. More young are born than can survive; 4. Survival and reproduction are not random.

What does 'fitness' refer to in the context of natural selection?

Fitness refers to the ability to survive and reproduce.

What is the phrase often associated with natural selection?

Survival of the fittest

What is an adaptation?

A trait that increases an individual's fitness in its environment.

Who independently developed the concept of natural selection alongside Darwin?

Alfred Russel Wallace

What is an example of artificial selection mentioned by Darwin?

Animal and plant breeding.

What was the heritability of beak depth in Darwin's finches?

0.65

What happened to the finch population during the 1977 drought?

84% of the finch population died.

What type of beak was favored during the drought in the Galápagos Islands?

Deep beaks were favored because they could crack hard fruits.

What is the significance of the Grants' study on finches?

It provided evidence for Darwin's theory of natural selection in real-time.

What does the term 'virion' refer to in the context of HIV?

A virus particle that can infect host cells.

What is the role of AZT in HIV research?

AZT is a drug used to treat HIV, and variations in virions' resistance to it are studied.

What is the main focus of the study of Darwin's finches?

Variation in beak morphology and its relation to feeding habits.

What environmental factors influence natural selection?

Food availability, climate conditions, and competition.

What is the outcome of nonrandom survival and reproduction?

Certain traits become more common in the population over time.

What does 'natural selection is testable' imply?

The four postulates can be independently verified through observation and experimentation.

How did the Grants measure the surviving finches after the drought?

They measured beak depth and other physical traits.

What is a common ancestral population in the context of Darwin's finches?

A single flock from which all finch species in the Galápagos are derived.

What was the effect of El Niño on finch selection?

It favored small birds with shallow beaks due to the abundance of small, soft seeds.

What is the significance of measuring heritability in a population?

It helps determine how much of the variation in a trait is due to genetic factors.

What is the relationship between population size and natural selection?

Larger populations may exhibit more variation, affecting the dynamics of natural selection.

What is the role of environmental changes in natural selection?

They can shift which traits are favorable for survival and reproduction.

What is meant by 'survival of the survivors'?

It emphasizes that those who survive are not necessarily the 'best' but those who are fit for their environment.

What is the impact of domestication on natural selection?

It provides insights into how artificial selection can mimic natural processes.

What is the main takeaway from Darwin's studies on finches?

Natural selection leads to adaptations that enhance survival and reproduction in specific environments.

What is the primary mechanism of evolution?

Natural selection

What does natural selection act upon?

Individuals

What changes occur in populations as a result of natural selection?

Changes in allele frequencies

Why is natural selection considered backward looking?

It acts on traits that were advantageous in past environmental conditions.

What is necessary for natural selection to cause evolution?

Traits must have a genetic basis.

What was the outcome of the artificial selection experiment with corn?

Selected ears of corn increased oil content from 4-6% to 20% over 60 years.

What is an example of a trait that was repurposed through natural selection?

The giant panda's thumb, which is a modified wrist bone used to strip bamboo.

What does the term 'preadaptation' or 'exaptation' refer to?

Traits that evolve for one function but are later used for another.

Can natural selection create perfect organisms?

No, it can only work with existing variation.

What is the misconception about natural selection's directionality?

Natural selection is nonrandom but not progressive; it does not always lead to increased complexity.

What is the role of group selection in natural selection?

Group selection does not exist; natural selection acts on individuals.

What were the three problems with Darwin's ideas that needed resolution?

How variability is created, how traits are inherited, and the age of the Earth.

What discovery resolved the issue of Earth's age for evolutionary theory?

The discovery of radioactive isotopes demonstrated that the Earth is sufficiently old for evolution.

What are the two main propositions of the Modern Synthesis?

Gradual evolution results from small genetic changes acted upon by natural selection, and macroevolution can be explained by microevolution.

What is the significance of mutation in evolution?

Mutation creates new alleles, leading to variation within populations.

What was the outcome of the Scopes Monkey Trial?

John Scopes was fined $100 for teaching evolution, but the prosecution's arguments had significant flaws.

What did the U.S. Supreme Court rule regarding the teaching of evolution in 1967?

It struck down state laws prohibiting the teaching of evolution.

What is 'Creation Science'?

A reformed argument by fundamentalists seeking equal time for creationism in schools.

What is Intelligent Design Theory?

The belief that complex organs must have been designed by an intelligent creator.

What is the scientific evidence for evolution based on?

Empirical data and hypothesis testing, without invoking supernatural explanations.

What is the importance of discussing scientific evidence in debates about evolution?

It ensures that discussions are based on testable and verifiable information.

What does natural selection increase in populations?

Adaptation to the environment.

What is the misconception regarding the randomness of natural selection?

Natural selection is nonrandom; it selects for traits that confer survival advantages.

What is the relationship between natural selection and existing traits?

Natural selection acts on existing traits and cannot create new ones instantly.

What is the role of variation in natural selection?

Variation is essential for natural selection to act upon and drive evolution.

What can happen if environmental conditions change?

Organisms may not be well adapted to new conditions if they were selected for past conditions.

What did Darwin mistakenly believe about variation in organisms?

He thought variation would eventually be used up.

How do alleles get passed on to offspring?

Through segregation and independent assortment during reproduction.

What is the significance of the Modern Synthesis in evolutionary biology?

It integrated new data to resolve issues in Darwin's original theory and established a comprehensive framework for understanding evolution.