Chapter 25

The Mesozoic era began approximately _____ million years ago.

251

The Precambrian time began at least _____ million years ago.

4,600

Which of the following best characterizes an adaptive radiation?

A single lineage diversifies rapidly, and descendant populations occupy many habitats and ecological roles.

What is the relationship between speciation and adaptive radiation?

Adaptive radiation is a form of speciation.

_____ were the dominant vertebrate life form during the Paleozoic era.

Amphibians

Which is the best definition of adaptive radiation? See Section 25.3 ( page 507) .

An adaptive radiation occurs when a single lineage produces many ecologically diverse descendant species in a relatively short period of time.

Which of the following pieces of evidence supports the hypothesis that the adaptive radiation of many groups observed during the Cambrian explosion was due to new ecological opportunities? See Section 25.3 ( page 507) .

Animals were present at all levels of the ocean, not just on the ocean floor.

According to this study, which of the following appears to be true?

As food scarcity increases, chimpanzee tool use for hunting increases.

The scientific community was slow to accept the asteroid impact hypothesis. Why?

At the time, most geologists thought that the Earth changed slowly and gradually, and not by major catastrophes.

We are living during the _____era.

Cenozoic

How could an asteroid impact kill off such a large number of different species all over the planet?

Debris from the impact orbiting around the Earth shielded sunlight, halting photosynthesis. The impact was so extreme that life at ground zero was vaporized. Tsunamis, landslides, earthquakes, and heat caused by the impact killed organisms near the site of impact.

How do lizard species on mainland California compare in diversity to those found on islands? See Section 25.3 ( page 507) .

Due to more open ecological opportunities on a given island, greater differences occur between island species.

Which of the following pieces of evidence supports the hypothesis that the adaptive radiation of many groups observed during the Cambrian explosion was due to morphological innovation? See Section 25.3 ( page 507) .

Duplication and then diversification of Hox genes occurs just prior to and during this time.

How did Ediacaran animals differ from Cambrian animals? See Section 25.3 ( page 507) .

Ediacaran animals lacked shells, limbs, heads, and feeding appendages.

Human impacts such as habitat loss and pollution are causing the extinction of many species. Based on your understanding of background extinctions and mass extinctions, which statement is most accurate?

Extinction is normal, but the extinction rate and cause of extinction suggests that a mass extinction is underway.

True or false? 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.

False; the loss of a trait, such as the loss of legs in snakes, can be a valuable synapomorphy for a clade.

How do foraminifera found in rock layers above the K-T boundary compare to those in rock layers below?

Foraminifera above the boundary are smaller and less diverse than those below.

Which sequence of eons, from oldest to youngest, is correct? See Section 25.2 ( page 504) .

Hadean, Archaean, Proterozoic, Phanerozoic

Iridium is a component of cosmic dust that rains down upon the earth at a constant rate. Why did Luis Alvarez suggest measuring iridium levels in the K-T boundary?

He was looking for a way to determine how quickly the layer had been deposited.

Why is bipedalism considered a synapomorphy for hominins (the group that includes humans)? See Section 25.1 ( page 497) .

Hominins are the only mammal group to walk on two legs.

When it comes to chimpanzees, which of the following is true?

Males catch most of the prey.

Dinosaurs went extinct during the _____.

Mesozoic

Flowering plants first appeared during the _____.

Mesozoic

Which statement is the best summary of the map?

New branches are still forming on the tree of life, and many branches are being lost.

Can the presence of feathers and wings be considered a synapomorphy that triggered the adaptive radiation of birds? Why or why not?

No, because if feathers and wings existed before the origin of true birds, then these traits cannot be considered a synapomorphy for true birds because they are not unique to this group.

Theropod dinosaurs are the bipedal ("two-footed") carnivores of Tyrannosaurus rex fame that many people imagine when they think of dinosaurs

No, theropods are a monophyletic group that includes birds.

Which structures are homologous? See Section 25.1 ( page 497) .

Oak leaf and maple leaf

A "one-snip test" is recommended 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?

One snip gets an ancestor and all of its descendants.

Reptiles first appeared during the _____ era.

Paleozoic

Seed plants first appeared during the _____.

Paleozoic

Fossilization continues even today. If you wanted to increase the probability that your deceased favorite pet would become fossilized, what actions would you take?

Place the corpse in an environment where decomposition is slow (such as a swamp or bog).

Animals first appeared during the _____.

Precambrian

Life arose during the _____.

Precambrian

The first prokaryotic cells appeared during the _____.

Precambrian

What evidence supports the impact hypothesis for the end-Cretaceous extinction? See Section 25.4 ( page 512) .

Sedimentary rocks from the K-Pg boundary layer contain large amounts of iridium.

What is exceptional about the early animal faunas from the Ediacaran and Cambrian Periods? See Section 25.3 ( page 507) .

Soft-bodied animals are well represented in these faunas.

Which statement is correct? See Section 25.1 ( page 497) .

Synapomorphies identify monophyletic clades.

Select the statements about the K-T boundary that are true.

The K-T boundary dates to 65 million years ago (when the dinosaurs disappeared). The K-T boundary in Zumaia, Spain is sharp--representing an abrupt change in the marine ecosystem. The K-T boundary separates rock layers of the Cretaceous period from those of the Tertiary period.

Which is strong evidence that similar traits in different evolutionary lineages are the result of homology and not homoplasy? See Section 25.1 ( page 497) .

The traits are also found in many intervening lineages on the tree of life.

Which addition to the map would be best?

The tree of life contains three major branches called bacteria, archaea, and eukarya.

Which of the following best describes chimpanzees?

They are omnivores.

Is extensive loss of hair observed in humans and whales an example of homoplasy or homology? See Section 25.1 ( page 497) .

This is homoplasy since whales and humans, who are not closely related, evolved this feature separately by convergent evolution.

Which of the following is a chimpanzee most likely to use a tool to help catch?

a bush baby

You are a primatologist studying chimpanzee behavior. According to this recent study, which of the following are you most likely to see using a tool?

a female chimpanzee

New ecological opportunities and key innovations often trigger which process?

adaptive radiations

Choose the best definition of a fossil.

any trace of an organism that lived in the past

Which characteristic was NOT advantageous for organisms in the million years after the catastrophic asteroid impact?

large body size

Which evidence is consistent with the asteroid impact hypothesis?

shocked quartz in the K-T boundary layer tektites, a type of melted rock spherules, glass-like beads in the K-T boundary layer iridium

Which of the following is an example of homoplasy?

streamlined bodies in dolphins and ichthyosaurs

What was the critical piece of evidence that supported the hypothesis that an asteroid struck Earth 65 million years ago?

the Chicxulub crater in Mexico