Ch. 49: The Anthropocene: Humans as a Planetary Force

Ecosystem Services

Benefits to humans provided by biodiversity, such as cleaner air and water, greater primary productivity, improved resilience to environmental disruption, and untapped sources of food and molecular compounds for use in medicine and agriculture.

Biodiversity

Biological diversity; the aggregate number of species, or, more broadly, also the diversity of genetic sequences, cell types, metabolism, life history, phylogenetic groups, communities, and ecosystems.

Explain why amphibians are sometimes called "canaries in a coal mine."

Both amphibians and canaries are remarkably responsive to certain changes in their environment. Much like canaries once warned miners of excess carbon monoxide levels underground, so too can amphibians warn us about dangerous levels of pesticides in the environment. The overexposure of frogs to atrazine severely affects their ability to reproduce and/or results in deformed offspring. Such observations in frogs warned scientists that atrazine may also negatively affect human reproduction

Which of the following is the direct cause of the dead zone in the Gulf of Mexico? 1) decomposition of algal blooms by aerobic bacteria 2) ocean acidification 3) increased growth of algal populations

1) decomposition of algal blooms by aerobic bacteria

Which of the following does not contribute to the formation of dead zones? 1) ocean acidification 2) eutrophication 3) fertilizers from agricultural runoff

1) ocean acidification

Which of the following nutrients is responsible for eutrophication in the Gulf of Mexico? 1) Carbon 2) Phosphorous 3) Nitrogen

2) Phosphorous

Which of the following statements about invasive species is false? 1) Invasive species often thrive in new areas because they have few natural predators. 2) Invasive species reduce community diversity through displacement, competition, and predation. 3) The effect of invasive species on natural communities is always a reduction in diversity.

3) The effect of invasive species on natural communities is always a reduction in diversity.

In addition to carbon dioxide, which of the following are also considered to be greenhouse gases? 1) Water vapor 2) Oxygen 3) Methane 4) Water vapor and methane

4) Water vapor and methane

Greenhouse Gases: 1) Keep average surface temps from going below freezing. 2) Absorb heat energy and emit it in all directions. 3) Include carbon dioxide and methane. 4) Make life on Earth's surface possible. 5) All the above.

5) All the above

Greenhouse gas

A gas in the atmosphere that allows incoming solar radiation to reach the Earth's surface, but absorbs radiation re-emitted as heat, trapping it in the atmosphere and causing the temperature to rise.

R-Strategist

A species that produces large numbers of offspring but provides few resources for their support.

K-Strategist

A species that produces relatively few young but invests considerable resources into their support

Ocean Acidification

An increase in the abundance of carbon dioxide in the oceans that causes the pH of seawater to go down.

Describe what is meant by the term "ecological footprint."

An individual's "ecological footprint" is represented as the amount of land (generally given in hectares) needed to supply all the resources and energy that person uses.

Corridors

Areas that provide species with routes for migration from one reserve to another.

Name three sources of atmospheric CO2.

Carbon dioxide can be introduced into the atmosphere by both natural and man-made processes. The burning of fossil fuels and forests (to make way for crops) is a major source of human-produced CO2. On the other hand, volcanic eruptions are natural processes that introduce CO2 into the atmosphere.

Explain the relationship between atmospheric CO2 levels and mean temperature.

Carbon dioxide is a greenhouse gas that is normally present in Earth's atmosphere. This gas absorbs solar radiation reflected off Earth's surface and re-emits it, ultimately warming the planet. The problem arises when excess CO2 is introduced into the atmosphere by human activities (e.g., burning fossil fuels). Excess CO2 in the atmosphere causes more of this reflected radiation to be absorbed and re-emitted, resulting in an increase in temperature. Thus, higher levels of CO2 in the atmosphere can translate into an increase in mean global temperature.

True or False: Humans have not altered the selective landscape for many pathogens.

False Humans have altered the selective landscape for many pathogens.

What is the difference between global warming and the greenhouse effect?

Global warming is the measured increase in Earth's surface temperatures over the past 50 years. The greenhouse effect describes a process by which global warming can occur. The greenhouse effect is the result of the capacity of some molecules—especially carbon dioxide, methane, and water vapor—to absorb heat energy and then emit it in all directions. Without the greenhouse effect, Earth would not be habitable. However, in recent decades, increasing amounts of greenhouse gases in the atmosphere have resulted in global warming.

How long did it take our numbers to double, from 1 billion to 2 billion? How about from 2 billion to 4 billion? What does this pattern say about the rate of population growth?

In the 130 years from 1800 to 1930, our numbers doubled from 1 to 2 billion, and they doubled again in just the 45 years from 1930 to 1975. This pattern indicates that the rate of human population growth increased in this time.

Describe several possible solutions to the problem of feeding a growing human population.

Increasing crop yields is one way to assure that a growing global population can be fed. This can be accomplished through devoting more land to agriculture and utilizing fertilizer. Other solutions include genetically engineering plants that are resource-efficient or resistant to predators or diseases. However, all of these methods carry with them certain dangers: increasing atmospheric CO2 levels, jeopardizing aquatic environments due to eutrophication, or selecting for hardier pests. Providing for a growing human population will likely require the integration of these methods.

How do invasive species affect species diversity of communities and ecosystems?

Invasive species may outcompete native species for available resources, diminishing the population size and, in time, the diversity of native species. Introduced animals may prey on native species, reducing their numbers. Or introduced species may simply increase local species diversity.

Invasive Species

Non-native species; since they are removed from natural constraints on population growth, invasive species can expand dramatically when introduced into new areas, sometimes with devastating consequences for native species and ecosystems.

Describe several possible solutions to the problem of increased atmospheric CO2.

Planting more trees via reforestation efforts helps to remove excess CO2 already in the atmosphere. The use of alternative energy sources such as wind power also means that less fossil fuels (one of the main sources of human-generated CO2) are burned.

Biodiversity Hotspots

Relatively small areas that have unusually high numbers of endemic species and that are under threat from human activities.

How do reserves and corridors help to conserve biodiversity?

Reserves provide protected (and managed) areas in which habitat loss, overexploitation, and species invasions can be minimized or even reversed. All reserves are limited in size and so corridors that connect reserves effectively increase the size and capacity for conservation of protected areas.

Describe the two ways organisms can respond to changes in CO2 levels and temperatures.

Some organisms can respond to temperature changes while remaining in the same environment; often, these organisms have to modify their behavior (i.e., like plants changing their flowering times). However, other organisms are forced to migrate to more suitable climates

The interplay of pathogens and antibiotics again brings up the problem of the Red Queen. How does the Red Queen hypothesis apply to these kinds of interaction?

The Red Queen hypothesis suggests that organisms need to keep evolving (running) just to stay in the same ecological niche (place). As new antibiotics are developed, pathogens like malaria frequently evolve resistance, so researchers must continually strive to develop new medicines as natural selection erodes the effectiveness of the old.

Conservation Biology

The efforts by biologists and policymakers to address the challenge of sustaining biodiversity in a changing world crowded with people.

Sustainable Development

Use of natural resources at rates no higher than the rate at which they can be replenished.

Anthropocene Period

The modern era, so named to reflect the dominant impact of humans on Earth.

Logistic Growth Rate

The pattern of population growth that results as growth potential slows down as the population size approaches K, its maximum sustainable size.

Exponential Growth Rate

The pattern of population increase that results when r (the per capita growth rate) is constant through time.

Intrinsic Growth Rate

The per capita growth rate; the maximum rate of growth when no environmental factors limit population increase.

Eutrophication

The process in which added nutrients lead to a great increase in the populations of algae and cyanobacteria.

Ecological footprint

The quantification of individual human claims on global resources by adding up all the energy, food, materials, and services used and estimating how much land is required to provide those resources.

In what ways do habitat loss, overexploitation, and invasive species threaten biodiversity?

Theory and observation show that the number of species a habitat can support reflects the areal extent of the habitat—smaller areas support fewer species. Overexploitation of specific species can reduce population sizes below the level required to sustain the species. At the same time, removal of key species can shift the ecological balance in regional ecosystems, threatening additional species. As invasive species expand in habitats into which they have been introduced, they may outcompete indigenous species, reducing their populations to unsustainable levels.

Describe the causes and consequences of eutrophication.

To increase crop yields, farmers often treat their land with nitrogen or phosphate-based fertilizers. However, a large percentage of this fertilizer (and the nutrients it contains) is carried off by rainfall to rivers and lakes. This nitrogen and phosphate-rich run-off unintentionally "fertilizes" bodies of water. As a result, the native cyanobacteria and algae living in rivers or lakes experience population explosions. This overgrowth of cyanobacteria and algae in response to excess (human-introduced) nutrients is known as eutrophication, and can be remarkably detrimental to the environment. Excess cyanobacteria and algae provide a robust food source for aquatic bacteria, and as bacteria feed, they rapidly deplete the oxygen (via aerobic respiration) in their environment. This process can result in the appearance of "dead zones"—areas literally devoid of life—in rivers or lakes. Without the proper amount of oxygen in the water, fish, crustaceans, and other aquatic life can't survive.

True or False: Human activities have reduced the quality and size of many habitats, decreasing the number of species they can support.

True

True or False: Nitrogen fertilizer transported to lakes and the sea causes eutrophication.

True

True or False: Overexploitation threatens species and disrupts ecological relationships within communities.

True