Chapter 25

Single-celled prokaryotes had the Earth to themselves for approximately __________.

1.5 billion years

The early atmosphere may not have been as reducing as originally postulated by Haldane, Oparin, Miller, and Urey. In light of current thinking about the composition of the early atmosphere, what is regarded as a likely place for the abiotic synthesis of organic molecules to have occurred?

Near volcanoes

What evidence most strongly suggests that an impact by an asteroid or meteorite may have caused the extinction of the dinosaurs?

Sedimentary rocks contain a layer of iridium, a mineral uncommon on Earth.

Although they originated around 180 million years ago, mammals underwent an adaptive radiation starting approximately 65 million years ago. Why?

etween 180 and 65 million years ago, mammals were outcompeted by the well-established dinosaurs.

In the species selection model, __________ is to macroevolution as __________ is to microevolution.

differential speciation success; differential reproductive success

What is the correct ordering of divisions of the geologic record from largest to smallest?

eon, era, period, epoch

The earliest organisms were most likely _____.

prokaryotic (Prokaryotes originated a few hundred million years after Earth's crust cooled and solidified.)

The Miller and Urey abiotic synthesis experiment (and subsequent, similar experiments) showed that __________.

simple organic molecules can form spontaneously under conditions like those thought to prevail early in Earth's history

Evolution works by _____.

"tinkering" with existing structures (Evolution, and in particular natural selection, can only select for the best available traits. Modifications to those traits are usually made in small, incremental steps and new inventions are rare.)

How does continental drift affect living organisms?

-It causes climate change, which puts selective pressure on organisms. -It causes changes in habitats, such as when large amounts of shallow marine habitat were lost in the formation of Pangaea. -It may cause an increase or decrease in competition among different species. -It happens so slowly that it does not affect living organisms.

Earth probably formed _____ years ago, and the first life evolved as early as _____ years ago.

3.9 million years ago ... 2.0 billion years ago (Because fossils of bacterial communities have been discovered that are 3.5 billion years old, it is reasonable to assume life originated around 3.9 billion years ago.)

Which of the following is a true statement concerning the history of Earth's biological diversity? A. Most animal phyla did not originate until after the last mass extinction event. B. The majority of species that ever lived are now extinct. C. There has been a steady increase in biological diversity at the level of families since the beginning of the Paleozoic era. D. Prior to the origin of humans, no extinction event had ever affected more than 20% of species. E. Typically, extinctions occur only during periods of disruptive change to the global environment.

B. The majority of species that ever lived are now extinct.

What was one ecological change that occurred following the Permian mass extinction? A. The number of marine genera has decreased steadily to the present day. B. The percentage of marine predators increased. C. Marine community diversity increased at the expense of terrestrial adaptive radiations. D. Mammal species became a smaller component of terrestrial food webs. E. Each species lost in the extinction was replaced by a species from the same lineage and filling the same ecological role.

B. The percentage of marine predators increased.

Fossilized stromatolites __________. A. provide evidence that plants moved onto land in the company of fungi around 500 million years ago B. formed around deep-sea vents C. resemble structures formed by bacterial communities that are found today in some warm, shallow, salty bays D. all date from 2.7 billion years ago E. contain the first undisputed fossils of eukaryotes and date from 2.1 billion years ago

C. resemble structures formed by bacterial communities that are found today in some warm, shallow, salty bays (Stromatolites are older than 2.7 billion years. Stromatolites did not form around thermal vents. Stromatolites are layered rocks of prokaryotes, not plants.)

The original atmosphere of Earth had little oxygen. What was the likely first source of oxygen that led to an oxygen atmosphere?

Cyanobacteria (Most atmospheric oxygen gas (O2) is of biological origin, produced during the water-splitting step of photosynthesis, and the first photosynthetic organisms were bacteria similar to today's cyanobacteria. The amount of atmospheric O2 increased gradually from about 2.7 to 2.4 billion years ago during the Archaean eon.)

Which of the following would not have been a consequence of tectonic plate movements bringing previously separated landmasses together in the formation of the supercontinent of Pangaea about 250 million years ago? A. Ocean basins became deeper. B. Habitat destruction led to extinctions. c. Interior regions of the supercontinent became extremely cold and dry. D. Allopatric speciation increased. E. Shallow coastal seas were drained.

D. Allopatric speciation increased. (Allopatric speciation would be expected when supercontinents break apart )

Adaptive radiations can be a direct consequence of four of the following five factors. Select the exception. A. Evolutionary innovation B. An adaptive radiation in a group of organisms (such as plants) that another group uses as food C. Vacant ecological niches D. Colonization of an isolated region that contains suitable habitat and few competitor species E. Genetic drift

E. Genetic drift

If the wings of extant flying birds originally arose as thermoregulatory devices in ancestral reptiles, then the bird wings could be accurately described as __________.

Exaptations (Exaptations are structures that had one function originally, and later evolved other, or different, functions.)

Why is the four-stage hypothesis for the abiotic origin of life useful?

It leads to predictions that can be tested. Science is concerned with testable hypotheses and reproducible experiments.

What were the two major "problems" that had to be solved before plants, animals, and fungi could move into terrestrial habitats?

Reproduction and prevention of dehydration

Why is RNA, rather than DNA, thought to have been the first genetic material?

RNA can also function as a catalyst.

Why do some scientists believe that RNA, rather than DNA, was the first genetic material?

RNA has both information storage and catalytic properties. (RNA has been shown to catalyze certain reactions (as part of ribosomes, rRNA participates in the catalysis of the peptide bonds that form proteins). It can also store information and perform some self-replication.)

What evidence supports the hypothesis that mitochondria and plastids evolved from prokaryotic endosymbionts?

They have a single circular chromosome similar to bacterial chromosomes; their ribosomes are more like prokaryotic ribosomes than eukaryotic ribosomes. (endosymbiont refers to a cell that lives within another cell, called the host cell)

Which of the following is an internal structure that appears in eukaryotic cells and is also present in more ancient prokaryotic cells?

Vesicles are an internal structure that appears in eukaryotic cells and is also present in more ancient prokaryotic cells.

Radiometric dating _____.

allows us to indirectly date fossils up to billions of years old based on minerals in surrounding volcanic strata (By dating minerals in volcanic strata above and below the fossils, we can determine a reasonable age range for the fossils.)

The oldest fossils usually _____.

are found in the deepest strata. (Younger sediments are deposited over older sediments; thus, relatively older fossils are found in deeper strata than relatively younger fossils.

The fossil record is __________.

biased in favor of species that existed for a long time

The ratio of carbon-14 to carbon-12 in a fossil can be used to determine the age of the fossil because __________.

carbon-14, unlike carbon-12, decays at a continuous rate after the death of an organism

Macroevolution differs from microevolution in that macroevolution __________.

includes broad evolutionary changes above the species level

Retention of juvenile body features into sexual maturity is referred to as the presence of __________.

paedomorphosis

The amphibians, reptiles, and mammals comprise which group?

tetrapods

Miller and Urey's experiments that attempted to recreate conditions on early Earth were significant because _____.

they showed that organic molecules such as amino acids could be produced from inorganic molecules (Miller and Urey showed that under conditions postulated to have existed on early Earth, it was possible to spontaneously form essential organic molecules.)

Prior to the Cambrian explosion, all large animals had what characteristic in common?

they were all soft bodied

The atmosphere of early Earth probably contained no O2 until the emergence of organisms that _____.

used water as an electron source for photosynthesis (Oxygen began to accumulate in the atmosphere due to the action of photosynthetic cyanobacteria.)