Charles Darwins' influential books on the theory of evolution by natural selection include:

- The Descent of Man (1871)
- The Expression of Emotions in Man and Animals (1872)

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According to the theory of evolution by natural selection, organisms that are better suited for their environments tend to survive and reproduce in contrast to those that are ill-suited to their environments. This theory was co-developed by Charles Darwin.

Theory of Evolution By Natural Selection

Spielman, R. M., Jenkins, W. J., & Lovett, M. D. (2020, April 22). Psychology (2nd ed.). OpenStax. https://openstax.org/books/psychology-2e/pages/1-introduction

OpenStax Psychology (2nd ed.) Textbook

Evolutionary Biology studies the processes that produced the diversity of life on earth or study of the phylogenetic history of organisms on earth.

Evolutionary Biology

Championed by figures like William James, functionalism is a psychological perspective that investigates how mental activities help an organism adapt to its environment. This school of thought was heavily influenced by Darwin's theory of evolution, proposing that behaviors, like physical traits, are naturally selected because they serve a function for survival and reproduction. Functionalism focuses on the operation of the mind as a whole, rather than breaking it down into its individual components, which was the aim of structuralism.

Functionalism in Psychology

The concept of an evolutionary tree, visually representing life's diversification from a common ancestor, was first sketched by Charles Darwin. This diagram, described as lines that split into branched structures, illustrates his principle of 'descent with modification,' showing how species diverge over time, with some lineages thriving and others leading to extinction.

Darwin's First Evolutionary Tree Diagram

Based on the principles of evolution by natural selection, predict the most likely long-term outcome for the finch population described in the case study and explain the reasoning behind your prediction.

Finch Beak Adaptation

Based on the principles of how organisms change over time due to environmental pressures, predict and explain the most likely outcome for the insect population described in the case study below after many generations.

Predicting Population Changes

The adaptive advantage of the sickle-cell mutation is contingent upon the geographic environment. In areas where malaria is widespread, like parts of Africa, possessing a single copy of the sickle-cell mutation is beneficial because it protects the carrier from malaria. Conversely, in regions where malaria is scarce, such as the United States, the sickle-cell gene provides no health benefits. In these environments, the mutation is a liability: carriers with one gene copy may suffer minor health issues, and those with two copies face a severe disease with no offsetting benefits.

Environmental Context of the Sickle-Cell Trait's Adaptiveness

Genetic variation within a population is essential for natural selection to occur. This diversity in genes and traits allows some individuals to be better adapted to environmental changes than others. Consequently, these better-suited individuals are more likely to survive and reproduce, passing their advantageous genes to the next generation. In a genetically identical population, environmental shifts would affect all individuals equally, leaving no basis for selection and adaptation.

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