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Evolution by Natural Selection

Finches

Different types of finches include:

  • Large tree finch (Vegetarian)

  • Small tree finch

  • Warbler finch

  • Woodpecker finch

  • Cactus eater

  • Ground finches

  • Cactus finch

  • Small ground finch

  • Medium ground finch

  • Large ground finch

Finches have different beak types, including probing, grasping, and parrot beaks. They also have different eating habits, such as insect, seed, and fruit eaters.

Chapter 22 Overview

This chapter covers:

  • Evolution by natural selection as a crucial theory in modern biology.

  • Evidence for evolution.

  • Evolution in action through case studies.

  • The rise of evolutionary thought.

  • The pattern of evolution: species change and are related.

  • The process of evolution by natural selection.

  • Common myths about natural selection and evolution.

What is a Theory?

A theory:

  • Explains a broad class of observations.

  • Is widely supported by evidence.

  • Consists of two components: pattern (observations) and process (mechanism).

Sample Question

A phenomenon becomes a scientific theory when it is consistently observed to possess both pattern and process.

Theory of Evolution

Evolution is the change in the heritable characteristics of biological populations over successive generations.

Survival of the Fittest

The theory of natural selection, associated with Charles Darwin, is often described as "survival of the fittest."

Models of Biodiversity

Models of biodiversity have changed through time:

  • Plato

  • Aristotle

  • Lamarck

  • Darwin and Wallace

Plato and Typological Thinking

  • Greek philosopher.

  • Claimed every organism was a perfect, unchanging essence created by God.

  • Species were static.

  • Typological thinking: Each organism is an example of a perfect essence.

Aristotle and the Scale of Nature

  • Greek philosopher.

  • Organized typological thinking into a linear scheme: Great Chain of Being.

  • Species were static and organized by increasing size and complexity.

  • Humans were at the top of the chain, surpassed only by angels and God.

Lamarckian Evolution

  • French naturalist, biologist, and academic.

  • First to propose a theory of evolution.

  • Species are not static; they change through time.

  • Inheritance of acquired characteristics: Individuals acquire traits during their lifetime and pass them to future generations.

  • Simple organisms originate at the base of the chain by spontaneous generation.

  • Lamarckian evolution is progressive, producing larger, more complex species over time.

Darwin and Wallace

  • Proposed change in species through time.

  • Does not follow a linear or progressive pattern.

  • Based on variation among individuals in populations.

  • Evolutionary change does NOT occur at the individual level.

Darwinian Evolution: Theory of Natural Selection

Organisms in a population with genotypes that code for favorable traits live to reproduce and pass their genes to future generations.

Theory of Evolution by Natural Selection

  • Overturned the idea that species are static and unchanging.

  • Replaced typological thinking with population thinking.

  • Scientific: proposed a testable mechanism for change.

Pattern of Evolution

Darwin described evolution as descent with modification:

  • Change over time produces modern, modified species from ancestral species.

  • Species change through time.

  • Species are related by common ancestry.

Evidence of Evolution

  • Species can be observed changing today.

  • Vestigial traits are evidence of change through time.

  • Transitional features link older and younger species.

  • Extinction changes the species present over time.

  • Vastness of Geological Time

  • Descent from common ancestor

  • Change Through Time

  • Formation of new species from pre-existing species

  • Related species share morphologies.

  • Similar species are found in the same geographic area

Vestigial Traits and Homology

  • Vestigial Trait: A reduced or incompletely developed structure with no or reduced function, similar to functioning organs in ancestral or related species.

  • Homology: Similarity among organisms of different species due to shared ancestry. Features exhibiting such similarity are homologous.

Process of Evolution by Natural Selection

  1. Variation: Organisms carry different genetic information.

  2. Competition: Overproduction of offspring leads to competition for survival.

  3. Adaptations: Individuals with beneficial adaptations are more likely to survive and pass on their genes.

  4. Selection: Over many generations, there is a change in allele frequency (evolution).

Components

  • Organisms produce more offspring than can survive, leading to a struggle for survival.

  • Individuals with favorable characteristics have a higher rate of survival and produce more offspring.

  • Favorable characteristics become more common.

Biological Fitness, Adaptation, and Selection

  • Biological fitness: Ability of an individual to produce surviving, fertile offspring relative to others in the population.

  • Adaptation: Heritable trait that increases an individual’s fitness in a particular environment.

  • Selection: Differential reproduction as a result of heritable variation.

Sample Questions

  • Typological thinking refers to the idea that a divine entity creates each type of organism in a perfect state of being (T/F)

  • Evolution occurs rapidly, resulting in immediate and significant changes (T/F)

  • Evolution occurs slowly but only takes 1-2 generations to result in significant changes (T/F)

  • Biological fitness refers to the ability of the organism to outcompete other organisms for resources (T/F)

  • Lamarckian evolution is built on the premise that species are not static, changing over time via the inheritance of acquired characteristics (T/F)

  • Darwinian evolution has a pattern of evolution that clearly illustrates that change over time has occurred and that species are related by common ancestry. What is process or mechanism of Darwinian evolution?

  • A version of a gene is called an…

  • Evolution is defined generally as…

  • Compare and contrast Lamarckian Evolution and Darwinian Evolution.

Terms To Know

  • Theory

  • Evolution

  • Typological

  • Population

  • Vestigial trait

  • Phylogenetic tree

  • Homology

  • Morphology

  • Fossils

  • Fossil record

  • Natural selection

  • Fitness

  • Adaptation

  • Selection

Summary

The 4 postulates that outline the process of evolution by natural selection can be summarized by this statement: Heritable variation leads to differential reproductive success.

Evidence of evolution is shown by various examples of

  • Species changing through time

  • Species being related by common ancestry

Darwin and Wallace proposed a revolutionary theory of evolution: theory of natural selection works at the population level (not individual level).