This video segment from Evolution: "Evolutionary Arms Race" tells the story of the leafcutter ant and the fungus it farms -- an example of mutually beneficial symbiosis. [4:59]

Biology 2e is designed to cover the scope and sequence requirements of a typical two-semester biology course for science majors. The text provides comprehensive coverage of foundational research and core biology concepts through an evolutionary lens. Biology includes rich features that engage students in scientific inquiry, highlight careers in the biological sciences, and offer everyday applications. The book also includes various types of practice and homework questions that help students understand—and apply—key concepts. The 2nd edition has been revised to incorporate clearer, more current, and more dynamic explanations, while maintaining the same organization as the first edition. Art and illustrations have been substantially improved, and the textbook features additional assessments and related resources.

By the end of this section, you will be able to do the following:

Define ecology and the four basic levels of ecological research
Describe examples of the ways in which ecology requires the integration of different scientific disciplines
Distinguish between abiotic and biotic components of the environment
Recognize the relationship between abiotic and biotic components of the environment

By the end of this section, you will be able to do the following:

Discuss the predator-prey cycle
Give examples of defenses against predation and herbivory
Describe the competitive exclusion principle
Give examples of symbiotic relationships between species
Describe community structure and succession

College-level online course highlighting the fundamentals of ecology. Course topics include coevolution of the biosphere, geosphere, atmosphere, and hydrosphere; photosynthesis and respiration; and the carbon, nitrogen, and water cycles. Other topics include energy flow through the biosphere and changes in ecosystems. This course features selected lecture notes, assignments with solutions, projects and examples, and exams with solutions.

Let's explore Earth with a microscope! Dive deep down into the diverse world of microbes with our scientists from the Joint Genome Institute. We'll also hear from students about their experiences taking part in environmental research and internships.

Introduction to Sociology 2e adheres to the scope and sequence of a typical, one-semester introductory sociology course. It offers comprehensive coverage of core concepts, foundational scholars, and emerging theories, which are supported by a wealth of engaging learning materials. The textbook presents detailed section reviews with rich questions, discussions that help students apply their knowledge, and features that draw learners into the discipline in meaningful ways. The second edition retains the book’s conceptual organization, aligning to most courses, and has been significantly updated to reflect the latest research and provide examples most relevant to today’s students. In order to help instructors transition to the revised version, the 2e changes are described within the preface.

Understand types of economic systems and their historical development
Describe capitalism and socialism both in theory and in practice
Discussion how functionalists, conflict theorists, and symbolic interactionists view the economy and work

Question and answer site that contains a discussion of commensalism as it pertains to sea slugs. Nice photographs of aquatic commensalistic relationships.

This lesson will introduce the three types of symbiotic relationships and give examples of each. It is 4 of 4 in the series titled "Symbiotic Relationships."