Book cover for Campbell Biology Concepts & Connections

Campbell Biology Concepts & Connections

Martha R. Taylor, Jean L. Dickey, Eric J. Simon, Kelly Hogan, Jane B. Reece

ISBN #9780134296012

9th Edition

631 Questions

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82,520 Students Helped

Homework Questions

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Summary
Learning Objectives
Key Concepts
Example Problems
Explanations
Common Mistakes

Summary

This chapter outlines the evolutionary journey of vertebrates from primitive invertebrate chordates to the diverse array of modern species, including amphibians, reptiles, birds, mammals, and hominins. It emphasizes the importance of shared derived characters in defining major clades, the evolutionary innovations such as jaws, fins, limbs, and amniotic eggs that facilitated the transition to new environments, and the role of fossil records in illuminating these evolutionary pathways. The chapter also highlights how adaptations in primates have culminated in the emergence of modern humans, underscoring the dynamic and continuous nature of evolutionary change.

Learning Objectives

1

Describe the shared derived characteristics of chordates and explain how these features define major vertebrate clades.

2

Trace the evolutionary progression from simple invertebrate chordates to jawed vertebrates and further to tetrapods adapted for terrestrial life.

3

Analyze the morphological and physiological adaptations that distinguish amphibians, reptiles, birds, mammals, and primates/hominins.

4

Interpret how fossil discoveries have filled gaps in our understanding of vertebrate evolution.

5

Evaluate the evolutionary innovations that have allowed vertebrates to exploit diverse ecological niches.

Key Concepts

CONCEPT

DEFINITION

Shared Derived Characters (Synapomorphies)

Unique evolutionary traits that are present in an ancestral species and shared exclusively by its evolutionary descendants, used to define major clades.

Chordates

Animals that possess a notochord, a dorsal nerve cord, pharyngeal slits, and a post-anal tail at some stage in their development.

Jawed Vertebrates (Gnathostomes)

A subgroup of vertebrates characterized by the presence of hinged jaws, which allowed for more efficient feeding mechanisms.

Tetrapods

Vertebrates with four limbs, evolved from lobe-finned fishes, capable of terrestrial locomotion.

Amniotes

Tetrapods that lay eggs on land or retain the fertilized egg within the mother, featuring adaptations such as a terrestrially adapted egg.

Feathered Reptiles

Birds, which evolved from theropod dinosaurs, characterized by the presence of feathers and specialized structures for flight.

Hominins

The branch of primates that includes modern humans, their immediate ancestors, and other extinct relatives, characterized by bipedal locomotion and other adaptations.

Example Problems

Example 1

In the primate phylogenetic tree below, fill in groups (a)-(e). Of the groups, which are anthropoids and which are apes? (GRAPH CAN'T COPY)

Example 2

In the chordate phylogenetic tree below, fill in the shared derived character that defines each clade. (GRAPH CAN'T COPY)

Example 3

A lamprey, a shark, a lizard, and a rabbit share all the following characteristics except a. pharyngeal slits in the embryo or adult. b. vertebrae. c. hinged jaws. d. a dorsal, hollow nerve cord.

Example 4

Why were the Tiktaalik fossils an exciting discovery for scientists studying tetrapod evolution? a. They are the earliest frog-like animal discovered to date. b. They show that tetrapods successfully colonized land much earlier than previously thought. c. They have a roughly equal combination of fishlike and tetrapod-like characteristics. d. They demonstrate conclusively that limbs evolved as lobe-fins dragged themselves from pond to pond during droughts.

Example 5

Fossils suggest that the first major trait distinguishing hominins from other primates was a. a larger brain. b. erect posture. c. forward-facing eyes with depth perception. d. tool making.
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Step-by-Step Explanations

QUESTION

How do shared derived characters define the major clades of chordates?

STEP-BY-STEP ANSWER:

Step 1: Identify the ancestral traits (e.g., notochord, dorsal nerve cord) that are present in all chordates.
Step 2: Examine which derived characteristics (such as jaw formation in vertebrates) appear in later branches of the tree.
Step 3: Analyze how these unique traits are used to group species into distinct clades, differentiating vertebrates from invertebrate chordates.
Final Answer: Shared derived characters serve as evolutionary markers that define the branching points in the chordate lineage, allowing scientists to classify organisms into major groups such as jawless and jawed vertebrates.

Shared Derived Characters

QUESTION

What steps illustrate the transition from aquatic vertebrates to tetrapods capable of terrestrial life?

STEP-BY-STEP ANSWER:

Step 1: Recognize that early vertebrates were aquatic and possessed fins for movement.
Step 2: Identify the fossil evidence showing gradual modifications from fins to limb-like structures (e.g., Tiktaalik).
Step 3: Understand the selective pressures that favored the development of weight-bearing limbs for movement on land.
Final Answer: The transition to tetrapods was driven by adaptations in fin structure and function, enabling aquatic vertebrates to gradually exploit terrestrial environments.

Evolution of Tetrapods

QUESTION

What distinguishes reptiles and mammals as amniotes from other tetrapods, and how did the terrestrial egg evolve?

STEP-BY-STEP ANSWER:

Step 1: Define amniotes as tetrapods with adaptations for terrestrial reproduction.
Step 2: Compare the characteristics of amphibians, which require water for reproduction, with those of reptiles and mammals.
Step 3: Discuss the evolution of the amniotic egg, which provides a protective environment for the developing embryo on land.
Final Answer: Reptiles and mammals are distinguished as amniotes by the development of fertilized eggs adapted to life on land, a key innovation that allowed vertebrates to colonize diverse terrestrial habitats.

Evolution of Amniotes

QUESTION

How have evolutionary changes in primates led to the emergence of hominins?

STEP-BY-STEP ANSWER:

Step 1: Identify the morphological traits of primates that are adaptations to arboreal life, such as grasping hands and stereoscopic vision.
Step 2: Analyze fossil evidence that shows gradual changes, including bipedalism and brain size increases, in the hominin lineage.
Step 3: Correlate these anatomical changes with environmental and behavioral factors that promoted survival and adaptation.
Final Answer: The evolution of hominins from primates involved modifications in skeletal structure and brain development, paving the way for bipedalism and complex behaviors that characterize modern humans.

Primate and Hominin Evolution

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Common Mistakes

  • Confusing shared derived characters (synapomorphies) with traits that have evolved independently (convergent evolution).
  • Assuming that all vertebrate adaptations developed simultaneously rather than through gradual evolutionary changes.
  • Overlooking the complexity of transitional fossils and the incomplete nature of the fossil record when interpreting evolutionary history.
  • Misunderstanding the distinct reproductive adaptations (e.g., the amniotic egg) that differentiate amniotes from other tetrapods.