Biology 109 Chapter 15: History of Life

The earliest discovered fossils are of ________ dating back to ________ years ago.
prokaryotes . . . 3.5 billion
The findings of Pasteur and others have established that
life does not arise from nonliving matter today, but in the conditions of early Earth, such an event
could have occurred.
What was the probable role of oxygen gas in the early stages of life’s appearance on Earth?
Oxygen gas tends to disrupt organic molecules, so its absence promoted the formation and stability of complex organic molecules on the early Earth.
Miller-Urey-type experiments have shown that
complex organic molecules can be produced by physical processes from inorganic components.
Which of the following environments is thought to have promoted the dehydration synthesis of polypeptides and other macromolecules from smaller organic monomers on a prebiotic Earth?
hot sand, clay, or rock along the seashore
________ are membranes containing concentrated organic molecules and have some lifelike properties, but are not alive.
Plants and fungi first became established on land during the
If all of Earth’s history were compressed into an hour, humans would first appear less than
1 second ago
The 14C:12C ratio can be used to date fossils that are up to approximately how old?
75,000 years
You find the frozen remains of a woolly mammoth in an Alaskan glacier. You analyze a bit of the tusk and find that its 14C:12C ratio is about one-fourth (25%) of the baseline level typically found in living
organisms. Given that the half-life of 14C is 5,730 years, when did the mammoth die?
almost 12,000 years ago
Potassium-40 can be used to date ________ that are ________ old.
volcanic rocks and associated fossils . . . hundreds of millions of years
The Mesozoic era is often called the age of reptiles. Which of the following also occurred during this era?
the first mammals and flowering plants appeared on land
The earliest known land plants date to the
Ordovician (early Paleozoic era).
Which of the following options correctly lists the varieties of life in the order that they appear in the geologic record, from earliest to most recent?
plants and fungi on land; land arthropods; amphibians; reptiles; flowering plants
The earliest known flowering plants date to the
Cretaceous (late Mesozoic era).
Geologists have evidence that over the past 1.5 billion years,
Earth’s land masses have joined into a single continent and split back apart again on three occasions.
It is estimated that the modern continents began to take shape
65 million years ago.
When the continent of Pangaea first split apart, it formed
a northern landmass called Laurasia and a southern landmass called Gondwana.
Geological evidence indicates that two land masses became separated by a deep ocean channel 45 million years ago and have been moving apart ever since. You are studying a group of organisms that is widespread
as a native part of the biota on both of the land masses. What can you conclude about the group’s
evolutionary history?
It depends on the dispersal abilities of the organism. If the organism cannot move across the open ocean, it is very likely that the group’s ancestors were present on the original land mass before it broke up.
During the ________, over 96% of marine species and many terrestrial species became extinct, possibly because intense volcanic activity warmed Earth’s climate.
How can the success of one group of organisms promote the adaptive radiation of a second group?
by providing new food resources, habitats, etc. for the second group
In the axolotl, development is altered. Adult axolotls retain features (external gills and aquatic life) that were juvenile in its ancestors, a phenomenon known as
Studies of skull structure suggest that the main genetic differences between humans and chimpanzees are
due not so much to the genes themselves, but rather in how genes are expressed during development.
The example of the stickleback indicates that morphology can be altered
by altering the expression of a developmental gene in some parts of the body but not others.
Anti-evolutionary thinkers sometimes argue that natural selection could not produce a complex structure like the vertebrate eye. They claim that all of the parts of the eye must have arisen at once, asking why natural
selection would favor the development of part of an eye that is not yet capable of forming a focused image.
Which of the following statements is consistent with a survey of eye structure in the molluscs?
There are many intermediate stages of eye complexity that fulfill different adaptive functions.
The concept of ________ suggests that feathers originally evolved ________.
exaptation . . . for some other function and only later became adapted for flight
The model of species selection is analogous to natural selection. In this analogy, ________ are like individuals within a population, and ________ is analogous to reproduction.
species . . . speciation
Cave-dwelling catfish and cave-dwelling salamanders share striking similarities: both organisms lack pigmentation and their eyes are reduced or absent. The most recent common ancestor to these organisms had normal pigmentation and fully developed eyes. The similarities between cave catfish and cave salamanders
are an example of
analogy (convergent evolution).
The similarities in function of hummingbird wings and the wings of a butterfly reflect
analogy but not homology.
You notice that a structure is similar between two organisms. The outward appearance of the structure is not very similar, but the feature is quite complex and there are many striking similarities in the fine details of
how it is put together. Which of the following is most probable?
The organisms both inherited the structure from a common ancestor that had a similarly arranged structure.
The situation in which a structure that evolved in one context is later adapted for another function is called
an exaptation.
In mammals, the presence of four limbs is ________ and hair is ________.
a shared ancestral character . . . a shared derived character unique to mammals
A systematist includes a lizard in a phylogenetic analysis of relationships among bird families. In this analysis, the lizard would be treated as
the outgroup
The existence of nest-building in crocodiles and birds led to a prediction that this behavior was also present in ________.
fossil dinosaurs
________ makes it possible to trace phylogenies among microbial groups for which there is no fossil record.
Molecular systematics
A(n) ________ has been used to estimate that HIV-1 M first spread to humans in the 1930s.
molecular clock
You compare homologous nucleotide sequences between several pairs of species with known divergence times. A pair of species that diverged 1 million years ago has two nucleotide differences, a pair that diverged
2 million years ago has four nucleotide differences, and a pair that diverged 3 million years ago has six
nucleotide differences. You have sequence data for another pair of species where the divergence time is
unknown. There are five nucleotide differences between them. Based on your clock, when did their line of ancestry diverge?
2.5 million years ago
The branching “tree of life” analogy
fails to account for horizontal gene transfer, in which species on different branches exchange genes.

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