Most fishery collapses do not cause the biological extinction of the harvested species, because fishing becomes unprofitable before the last individuals are caught.
Correct Answer
True
True. When a fish stock collapses, catching the few remaining fish no longer pays, so fishing pressure drops long before the species disappears. The harm is a collapsed fishery and a restructured ecosystem, though slow-growing species such as whales and some sharks can still be pushed toward extinction.
Category: Major Threats
Question 2
The collapse of the western Atlantic cod fishery was caused mainly by an introduced predator.
Correct Answer
False
False. The western Atlantic cod fishery collapsed from overharvesting after modern factory trawlers greatly increased fishing pressure in the 1980s. It is a classic example of overharvesting, not of an exotic species.
Category: Major Threats
Question 3
Amphibians that use both water and land during their life cycle face a lower risk from habitat loss than species that use a single habitat.
Correct Answer
False
False. Species that need two habitats face a higher risk, because losing either habitat, or the connection between them, can eliminate a population. This is one reason amphibians are especially vulnerable.
Category: Major Threats
Question 4
Current levels of carbon dioxide in the atmosphere are lower than the highest levels recorded over the past 400,000 years.
Correct Answer
False
False. Over hundreds of thousands of years, carbon dioxide cycled between roughly 180 and 280 parts per million. Since the industrial era it has risen far above that range, to levels higher than any in that long record.
Category: Major Threats
Question 5
Climate change has already shifted the ranges of many European bird species northward.
Correct Answer
True
True. Studies show European bird ranges moving north as the climate warms, although many are not moving as fast as the warming would require. Similar shifts have been seen in plants, butterflies, fishes and mammals.
Category: Major Threats
Question 6
Seawater contracts as it warms, which slows the rate of sea-level rise.
Correct Answer
False
False. Seawater expands as it warms, and this thermal expansion adds to sea-level rise along with water from melting glaciers and ice sheets. Rising seas threaten shorelines and low islands.
Category: Major Threats
Question 7
White-nose syndrome is a fungal disease that kills bats hibernating in caves in North America.
Correct Answer
True
True. White-nose syndrome is caused by a fungus thought to have been introduced from Europe. It has killed large numbers of cave-hibernating bats in eastern North America and threatens endangered species such as the Indiana bat.
Category: Exotic Species
Question 8
Islands are less vulnerable than continents to invasive species because their isolation protects them.
Correct Answer
False
False. Islands are especially vulnerable to invasive species. Their isolation produces many endemic species that evolved without certain predators and competitors, so introduced species can devastate them, as the brown tree snake did on Guam.
Category: Exotic Species
Question 9
Most species that humans introduce into a new ecosystem fail to establish a lasting population.
Correct Answer
True
True. Most introductions fail because the founding population is too small or poorly adapted to the new environment. The few that thrive and spread can become invasive and harm native species.
Category: Exotic Species
Question 10
The fossil record shows that rates of speciation and extinction have stayed constant throughout Earth's history.
Correct Answer
False
False. The fossil record shows that speciation and extinction rates have fluctuated greatly, including five mass extinctions. The number of species at any time reflects the balance between these two changing rates.
Category: Extinction Through Time
Question 11
Each of the five major mass extinctions in the fossil record eliminated more than half of the species living at the time.
Correct Answer
True
True. A mass extinction is marked by the loss of a large share of species in a short span of geologic time, and each of the five major events removed more than half of existing species.
Category: Extinction Through Time
Question 12
The current wave of species extinctions is driven mainly by human activity.
Correct Answer
True
True. The ongoing extinction, often called the sixth mass extinction, is linked mainly to human causes such as habitat destruction, overhunting and introduced species, with many recorded losses since the 1500s.
Category: Extinction Through Time
Question 13
Steller's sea cow survived for more than two centuries after Europeans first encountered it.
Correct Answer
False
False. Steller's sea cow was discovered by Europeans in 1741 and hunted for meat and oil until the last one was killed in 1768, only 27 years later.
Category: Extinction Through Time
Question 14
The passenger pigeon, once one of the most abundant birds in North America, went extinct when the last individual died in a zoo in 1914.
Correct Answer
True
True. Overhunting and the clearing of forests drove the passenger pigeon from enormous migrating flocks to extinction. The last known bird died at the Cincinnati Zoo in 1914.
Category: Extinction Through Time
Question 15
After wolves were reintroduced to Yellowstone, elk populations grew larger.
Correct Answer
False
False. Wolves preyed on elk and reduced their numbers, which allowed streamside vegetation to recover and increased the diversity of other species. This cascade is why wolves are considered a keystone species.
Category: Conservation Strategies
Question 16
Removing aging dams can restore natural water-level changes and allow migratory fish to return to spawn upstream.
Correct Answer
True
True. Dam removal restores natural flow patterns, improves water quality and lets fish such as salmon and other anadromous species reach their spawning grounds again.
Category: Conservation Strategies
Question 17
Many widely used antibiotics, such as penicillin, were originally derived from compounds made by fungi or bacteria.
Correct Answer
True
True. Penicillin comes from a mold, and many other antibiotics come from chemicals that fungi and bacteria produce to compete with other microbes. This is one way biodiversity directly supports human health.
Category: Value to Humans
Question 18
Ecosystem diversity refers to the number of different alleles found within a single population.
Correct Answer
False
False. The variety of alleles within a population is genetic diversity. Ecosystem diversity is the number of different ecosystems in an area or on Earth.
Category: Types and Patterns
Question 19
Most of the eukaryotic species on Earth have not yet been formally described and named by scientists.
Correct Answer
True
True. About 1.5 million eukaryotic species have been described, while estimates of the total run to several million or more. At the current pace of description, many species may go extinct before they are ever named.
Category: Types and Patterns
Question 20
The North American prairie ecosystem remains largely intact today.
Correct Answer
False
False. The prairie that once stretched across central North America has largely been replaced by crop fields, pasture and suburbs. Many prairie species survive, but the ecosystem's interactions and productivity have been lost.
Category: Types and Patterns