Ch. 25 - Phylogenies and the History of Life

Freeman - Biological Science 8th Edition

Freeman8th EditionBiological ScienceISBN: 9780138276263Not the one you use?Change textbook

Freeman 8th Edition

Ch. 25 - Phylogenies and the History of Life

Problem 3

Chapter 25, Problem 3

Which of the following best characterizes an adaptive radiation?
a. Descendant species occupy a large geographic area.
b. A single lineage diversifies rapidly, and descendant species occupy many habitats and ecological roles.
c. Natural selection is particularly intense, because disruptive selection occurs.
d. Species recover after a mass extinction.

Verified step by step guidance

Understand the concept of adaptive radiation: Adaptive radiation is an evolutionary process where a single ancestral species rapidly diversifies into a variety of new forms. This typically occurs when the species encounters a new environment with diverse ecological niches.

Identify the key characteristics of adaptive radiation: It involves rapid diversification, and the resulting species occupy different habitats and ecological roles. This is often seen in environments with little competition, such as islands or after a mass extinction event.

Analyze each option: a) Descendant species occupy a large geographic area - This does not necessarily imply rapid diversification or occupation of different ecological roles. b) A single lineage diversifies rapidly, and descendant species occupy many habitats and ecological roles - This directly describes the process of adaptive radiation. c) Natural selection is particularly intense, because disruptive selection occurs - While natural selection can be a factor, it does not specifically define adaptive radiation. d) Species recover after a mass extinction - This can lead to adaptive radiation, but it is not a defining characteristic.

Compare the options to the definition: Option b aligns most closely with the definition of adaptive radiation, as it emphasizes rapid diversification and occupation of various ecological niches.

Conclude by selecting the best characterization: Based on the analysis, option b best characterizes an adaptive radiation.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Adaptive Radiation

Adaptive radiation refers to the rapid evolution of diversely adapted species from a common ancestor when introduced to new environments. This process often occurs when a species encounters varied ecological niches, leading to the development of distinct traits that allow them to exploit different habitats and roles within an ecosystem.

Ecological Niches

An ecological niche is the role and position a species has in its environment, including how it obtains resources, interacts with other organisms, and contributes to the ecosystem. Understanding niches is crucial in adaptive radiation, as species diversify to fill different niches, reducing competition and increasing survival chances.

Disruptive Selection

Disruptive selection is a type of natural selection that favors extreme values of a trait over intermediate values, leading to increased genetic diversity within a population. While it can drive speciation, it is not the primary mechanism in adaptive radiation, which is more about diversification into new ecological roles rather than just trait variation.

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Natural Selection

Related Practice

Textbook Question

Choose the best definition of a fossil.

a. A rock that contains information about an organism

b. A bone, tooth, shell, or other hard part of an organism that has been preserved

c. Any trace of an organism that lived in the past

d. Any part of a dead organism

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Textbook Question

Critique the following statement: The absence of a trait cannot be used as a synapomorphy in phylogenetic analysis; only shared derived traits that are present in the clade can be used.

Textbook Question

Which of the following is an example of homoplasy?

a. Hair in humans and fur in mice

b. Astragalus ankle bones in hippos and deer

c. Hox genes in humans and flies

d. Streamlined bodies in dolphins and ichthyosaurs

Textbook Question

What important assumption does parsimony make when assessing which phylogenetic tree is most accurate? Why was parsimony misleading in the case of the astragalus during the evolution of artiodactyls?

Textbook Question

You can use a 'one-snip test' to identify monophyletic groups—meaning that if you 'cut' any branch on a tree, everything that 'falls off' is a monophyletic group. Why is this valid?