Campbell Biology Chapter 56 Review: Conservation Biology and Global Change

56.1 Biodiversity and what threatens it

pp. 1239–1244

On the AP exam? Yes

Topic 8.6 covers why more diverse ecosystems hold up better, Topic 8.7 covers invasive species and human-caused habitat change, and Topic 7.11 links low genetic diversity to extinction risk. You won't need the book's statistics or legal definitions.

In the course: Topic 8.6 Biodiversity, Topic 8.7 Disruptions in Ecosystems, Topic 7.11 Variations in Populations (notes, videos and more questions)

Key points

Biologists describe biodiversity at three levels: the genetic variety inside and between populations, the variety of species, and the variety of ecosystems across a region or the whole planet.
Species have always gone extinct. What's alarming now is the pace: human activity has pushed extinction rates far above the normal background rate. Scientists have named only a little over 2 million species, so nobody can measure the exact rate.
Losing one population can wipe out alleles found nowhere else, which leaves the species less able to adapt. Losing one species can ripple through its ecosystem, especially if it's a keystone species, pollinator or seed disperser.
Biodiversity pays off for people. Wild relatives of crops carry genes for disease resistance, many drugs started as natural compounds, and microbes supply enzymes used in biotechnology. Ecosystem services such as pollination, water filtering, flood control and soil building come free, so they're easy to undervalue.
The four big threats are habitat loss (the largest by far), overharvesting, introduced species, and global change such as climate change and polluted air and rain.
Introduced species often explode in numbers because they've escaped the natural enemies that kept them in check at home. Once established, they may eat native species or outcompete them.
Overharvesting hits hardest on large, slow-breeding species and on species with tiny ranges. Burning coal and other fuels releases sulfur and nitrogen oxides that form acid rain, which harms lakes and forests; pollution laws have cut sulfur emissions sharply in many countries.

Key terms (12)

biodiversity: The variety of life, counted at three levels: genes within species, the species themselves, and the ecosystems they form.
genetic diversity: The range of alleles within a population and the differences between populations of the same species. It's the raw material for adapting to change.
species diversity: How many different species live in an area and how evenly their numbers are spread.
ecosystem diversity: The variety of different ecosystems, such as wetlands, grasslands and reefs, across a region or the planet.
endangered species: A species in immediate danger of dying out, either everywhere it lives or across a large part of its range.
threatened species: A species not yet endangered but heading that way: without help, it will probably become endangered before long.
local extinction: When a species vanishes from one place, such as one lake or valley, but still survives somewhere else.
ecosystem services: The free benefits people get from working ecosystems, like clean water, pollinated crops, fertile soil and protection from floods.
introduced species: A species living outside its native range because people carried it there, deliberately or not. An invasive one spreads and causes harm.
overharvesting: Taking wild plants or animals faster than their populations can replace the losses.
habitat fragmentation: Breaking a large, continuous habitat into smaller, separated pieces, often by roads, farms or towns.
acid precipitation: Rain, snow or fog that is clearly more acidic than clean rain (about pH 5.6), mostly because of sulfur and nitrogen oxides from burning fuels.

Check yourself: 56.1 Biodiversity and what threatens it

4 questions on 56.1 Biodiversity and what threatens it. Pick an answer to see if you got it, and why.

Question 1 of 4

A wildflower grows in 30 mountain meadows. One meadow, cut off from the rest by a high ridge, holds the only plants known to carry an allele that lets them flower after a late frost. If that meadow is paved for a parking lot, which level of biodiversity suffers the clearest loss, even though the species survives in the other 29 meadows?

Question 2 of 4

A small gecko from the mainland arrives on an island in shipping crates. Within 15 years it is the most common lizard on the island, while its numbers back home have stayed steady for decades. Which explanation is most likely?

Question 3 of 4

Ecologists track a ground-nesting seabird on two similar islands. Introduced rats were removed from Island 1 in 2018; Island 2 still has rats. Year | Island 1: chicks fledged per 100 nests | Island 2: chicks fledged per 100 nests 2016 | 12 | 14 2017 | 10 | 13 2019 | 51 | 12 2021 | 63 | 15 Which conclusion do these data best support?

Question 4 of 4

Which of the following is an example of an ecosystem service?

0 of 4 answered

56.2 Saving small and shrinking populations

pp. 1244–1249

On the AP exam? Yes

Genetic drift, bottlenecks and the idea that low genetic diversity raises extinction risk are Topics 7.4 and 7.11. The effective population size formula, minimum viable population and population viability analysis aren't in the current course or on the formula sheet.

In the course: Topic 7.4 Population Genetics, Topic 7.11 Variations in Populations, Topic 8.3 Population Ecology (notes, videos and more questions)

Key points

Conservation biologists work in two broad ways. The small-population approach studies what being small does to a population. The declining-population approach asks what's causing a drop and how to stop it.
In a small population, genetic drift randomly loses alleles and relatives are more likely to mate. Inbreeding makes offspring more often homozygous for harmful recessive alleles, so fewer survive and reproduce, and the population shrinks further. This self-reinforcing spiral is called an extinction vortex.
Low genetic variation isn't always a death sentence. Some species recover in numbers after a bottleneck while staying genetically uniform, and some clonal plants spread widely with little variation. They may still struggle to adapt to a new disease or a changing climate.
A minimum viable population (MVP) is the smallest size that can keep a population going. It's estimated with computer models that include chance events like storms or disease. Population viability analysis uses such models to estimate the odds of survival over a set time.
Effective population size (Nₑ) reflects how many individuals actually pass on genes, not how many are alive. With Nf breeding females and Nm breeding males, $N_e = \frac{4N_fN_m}{N_f + N_m}$ . Uneven sex ratios and many non-breeders make Nₑ much smaller than the census count, and Nₑ is what governs how fast variation is lost.
Bringing in individuals from other populations adds gene flow, which can restore lost alleles and pull a population out of a vortex.
The declining-population approach works step by step: confirm the decline, learn the species' needs, list possible causes, test the most likely one with a controlled experiment, then manage the threat and keep monitoring. Real plans must also weigh human needs such as jobs and land use.

Key terms (10)

small-population approach: A conservation strategy that focuses on how being small, through drift and inbreeding, can drive a population to extinction.
declining-population approach: A conservation strategy that focuses on finding and fixing the environmental cause of a population's drop, whatever its size.
extinction vortex: A downward spiral in which a small population loses genetic variation and fitness, shrinks further, and loses even more variation.
inbreeding: Mating between close relatives. It raises the chance that offspring inherit two copies of the same harmful recessive allele.
genetic drift: Random changes in allele frequencies from one generation to the next. Its effects are strongest in small populations.
bottleneck effect: A sharp drop in population size that leaves the survivors with only a fraction of the original genetic variation.
minimum viable population (MVP): The lowest population size that models predict can last for the long term, despite chance events and genetic problems.
effective population size: The number of individuals that actually pass on genes, adjusted for things like sex ratio. Written Nₑ, it's usually much smaller than the total count.
population viability analysis: Using computer models to estimate a population's chance of surviving for a given number of years under different conditions or plans.
translocation: Moving individuals from one population to another, often to add genetic variation or start a new population.

Check yourself: 56.2 Saving small and shrinking populations

4 questions on 56.2 Saving small and shrinking populations. Pick an answer to see if you got it, and why.

Question 1 of 4

A census counts about 5,000 adults of a pond-breeding salamander. Yet genetic studies show the population is losing allele variety about as fast as an ideal population of only 300 would. Which explanation best fits?

Question 2 of 4

In a small, isolated wolf population, pups from matings between close relatives have more spinal defects than pups from unrelated parents. What best explains this?

Question 3 of 4

A ground-nesting songbird has dropped by 60% over 15 years in a coastal grassland that is otherwise intact. Managers suspect three causes: free-roaming cats, a new pesticide on nearby farms, and earlier mowing of the grass. Which study would most directly test the cat hypothesis?

Question 4 of 4

Two isolated populations of a small desert fish live in separate springs, and both had been shrinking for years. In 2016, biologists added 20 fish from a large, distant population to Spring 1 only. Year | Spring 1: adults | Spring 1: heterozygosity | Spring 2: adults | Spring 2: heterozygosity 2012 | 420 | 0.24 | 380 | 0.25 2016 | 150 | 0.19 | 140 | 0.20 2020 | 610 | 0.31 | 90 | 0.17 Which conclusion do these data best support?

0 of 4 answered

56.3 Conserving whole landscapes

pp. 1249–1254

On the AP exam? Background

Edges, corridors, hot spots and reserve design aren't in the current course. They connect to tested ideas: corridors allow gene flow (Topic 7.4), habitat change disrupts ecosystems (Topic 8.7), and more diverse ecosystems are more resilient (Topic 8.6).

In the course: Topic 8.6 Biodiversity, Topic 8.7 Disruptions in Ecosystems, Topic 7.4 Population Genetics (notes, videos and more questions)

Key points

Conservation now aims to protect whole communities, ecosystems and landscapes, not just one species at a time. That means planning alongside farms, towns and roads, and thinking about economics as well as ecology.
An edge, the boundary between two ecosystems, has conditions of its own: more light, wind and temperature swings than the interior. Some species thrive at edges, but species that need deep interior habitat lose out when land is chopped into small patches.
Small fragments have more edge for their area and hold smaller populations, so interior specialists tend to vanish first from the smallest patches.
A movement corridor links separated patches: a continuous band of habitat, a line of stepping-stone patches, or a wildlife bridge or tunnel at a road. Corridors let animals disperse and keep genes flowing, which reduces inbreeding, but they can also spread disease, parasites or fire.
A biodiversity hot spot covers little area but holds an outsized share of species found nowhere else, and much of its native habitat is already gone. Hot spots make sensible priorities, though the places richest in endemic birds aren't always richest in endemic insects, and climate change can move the conditions species need.
Reserves can't be frozen in time: many ecosystems need natural disturbance such as fire or flooding to keep their diversity. Big reserves suit wide-ranging animals and have less edge, while several separate reserves can slow the spread of disease. Most reserves are smaller than wide-ranging species need. About 17–18% of Earth's land and about 8% of the ocean were formally protected by 2024.
A zoned reserve has a protected core surrounded by buffer zones where people earn a living in ways that don't harm the core. No-take marine reserves let fish grow larger and more numerous, and some spill over into nearby fishing grounds.

Key terms (10)

edge: The border where two ecosystems meet, such as forest and field. Light, temperature and wind there differ from both sides.
interior species: A species that needs habitat far from any edge and declines when its habitat is broken into small pieces.
movement corridor: A link of usable habitat, such as a continuous band, a series of stepping-stone patches, or a wildlife crossing, that lets organisms move between separated patches.
biodiversity hot spot: A region that covers little area but holds an outsized share of species found nowhere else, and that has already lost much of its native habitat.
endemic species: A species found naturally in only one place in the world, such as a single island or mountain range.
nature reserve: Land or water set aside mainly to protect wildlife and natural ecosystems.
zoned reserve: A protected core area surrounded by zones where people live and work under rules that keep the core safe.
buffer zone: The land around a reserve's core where human use is allowed but limited, cushioning the core from heavier damage.
marine reserve: An area of ocean closed to fishing or other harvesting so that populations can recover.
landscape ecology: The study of how the arrangement of ecosystems across a region, including human land uses, affects the species living there.

Check yourself: 56.3 Conserving whole landscapes

4 questions on 56.3 Conserving whole landscapes. Pick an answer to see if you got it, and why.

Question 1 of 4Calculator allowed

A planner can protect either one square forest reserve 10 km on a side or four separate square reserves 5 km on a side, the same 100 km² in total. Edge effects such as extra light, wind and nest predators reach 0.5 km into the forest from every side. How much interior habitat, free of edge effects, does each option provide?

Question 2 of 4

Two populations of a woodland salamander live in forest patches separated by 2 km of cropland that the salamanders can't cross. A land trust plants a continuous strip of forest linking the patches. Over the next several generations, which genetic change is most likely?

Question 3 of 4

Managers plan a wildlife overpass to link two deer herds separated by a highway. They then learn that one herd carries a contagious, usually fatal brain disease that the other herd lacks. Which is the strongest argument for delaying the overpass?

Question 4 of 4Calculator allowed

Conservation planners compare four regions of similar size. Region | Plant species | Endemic plants (%) | Threatened species | Original vegetation remaining (%) W | 2,400 | 4 | 12 | 85 X | 900 | 60 | 15 | 90 Y | 3,100 | 8 | 140 | 30 Z | 2,800 | 55 | 160 | 25 Which region best fits the definition of a biodiversity hot spot?

0 of 4 answered

56.4 Global changes people are causing

pp. 1254–1260

On the AP exam? Yes

Topic 8.7 names eutrophication, biomagnification and climate change as human disruptions, and the nitrogen and carbon cycles are Topic 8.2. UV damage to DNA fits Topic 6.7. You don't need the chemistry of how chlorine destroys ozone. The book's 2009 figures are updated here.

In the course: Topic 8.7 Disruptions in Ecosystems, Topic 8.2 Energy Flow Through Ecosystems, Topic 6.7 Mutations (notes, videos and more questions)

Key points

Farming moves nutrients around. Harvested crops carry nitrogen and other nutrients away, so farmers add fertilizer. Factory-made fertilizer, fuel burning and planting legumes have together more than doubled the fixed nitrogen entering Earth's ecosystems.
When added nutrients go beyond what plants can absorb (the critical load), extra nitrate and phosphate wash into water. Algae bloom, then die, and decomposers use up the dissolved oxygen as they break them down. Fish suffocate, in lakes (eutrophication) and in coastal dead zones.
Some pollutants, such as PCBs, some older pesticides and methylmercury, are fat-soluble and hard to break down or excrete. They build up in tissues and grow more concentrated at each step up a food chain (biological magnification), so top predators carry the most.
Atmospheric CO₂ has risen from about 280 ppm before industrialization to more than 420 ppm today, mostly from burning fossil fuels and clearing forests. Greenhouse gases let sunlight through but absorb infrared radiation from the warmed surface, holding in heat. With no greenhouse effect at all, Earth's average surface temperature would be about −18°C.
Earth has warmed by roughly 1.3°C since the late 1800s, fastest in the Arctic. Effects include shrinking sea ice, more wildfires, shifting rainfall, and species moving toward the poles or uphill. Fragmented habitat makes those moves harder, which is why moving species on purpose (assisted migration) is being debated.
Extra CO₂ can speed plant growth, but in real ecosystems a shortage of nitrogen or other nutrients often limits the gain.
The ozone layer high in the atmosphere absorbs much of the sun's UV radiation. Chlorine released from CFCs breaks ozone down over and over, thinning the layer most over Antarctica each spring. More UV means more DNA damage. The Montreal Protocol (1987) phased out CFCs, and the ozone layer is slowly recovering; over Antarctica it's expected to return to 1980 levels around the 2060s.

Key terms (10)

critical load: The threshold for nutrient inputs: add more nitrogen or phosphorus than an ecosystem's plants can use, and the leftover begins to harm the ecosystem.
eutrophication: Nutrient overload in a body of water that sets off algal blooms. When the algae die, decomposers use up the oxygen.
dead zone: An area of a lake or sea where oxygen is so low that most animals die or leave, usually after nutrient runoff.
biological magnification: The build-up of a persistent toxin to higher and higher concentrations at each step up a food chain. Also called biomagnification.
greenhouse gas: A gas, such as CO₂, methane or water vapor, that absorbs infrared radiation and so traps heat near Earth's surface.
greenhouse effect: The warming of Earth's surface because greenhouse gases absorb outgoing infrared radiation and send some of it back down.
climate change: Long-term shifts in temperature, rainfall and other weather patterns. Today's rapid change is driven mainly by human greenhouse gas emissions.
ozone layer: A band of ozone (O₃) high in the atmosphere that absorbs much of the sun's harmful UV radiation.
chlorofluorocarbons (CFCs): Human-made chemicals once used in refrigerators and spray cans. They release chlorine that destroys ozone high in the atmosphere.
assisted migration: Planting or releasing a species beyond the edge of its historic range, in a place expected to suit it as the climate changes.

Check yourself: 56.4 Global changes people are causing

4 questions on 56.4 Global changes people are causing. Pick an answer to see if you got it, and why.

Question 1 of 4Calculator allowed

A persistent, fat-soluble insecticide washes into a marsh. Its concentrations in one food chain are shown below. Organism | Insecticide (ppm) Algae | 0.04 Insect larvae | 0.3 Small fish | 2.1 Heron | 18 About how many times more concentrated is the insecticide in herons than in algae?

Question 2 of 4

Four pollutants enter a lake at the same starting concentration. Which one is most likely to reach the highest concentrations in the lake's top predators?

Question 3 of 4

After heavy spring rains wash fertilizer from farms into a shallow coastal bay, researchers sample the water each week. Week | Algae (chlorophyll, µg/L) | Dissolved oxygen (mg/L) 1 | 4 | 8.1 3 | 38 | 9.4 5 | 52 | 7.0 7 | 11 | 1.8 9 | 6 | 4.5 What best explains the very low oxygen in week 7?

Question 4 of 4

Which statement best describes how rising CO₂ warms Earth's surface?

0 of 4 answered

56.5 Sustainability and the future

pp. 1260–1261

On the AP exam? Not tested

Sustainable development and biophilia aren't in AP Biology (they belong to AP Environmental Science). Useful links: human choices change how fast ecosystems are disrupted (Topic 8.7), and harvesting a population at its fastest growth rate uses the logistic model (Topic 8.4).

In the course: Topic 8.7 Disruptions in Ecosystems, Topic 8.4 Effect of Density on Populations (notes, videos and more questions)

Key points

No one can save every patch of habitat, so science helps decide which places matter most. The best plans protect nature and also improve life for the people who live nearby.
Sustainable development means meeting people's needs today without using up what future generations will need to meet theirs.
Research for sustainability looks at how climate and living things affect each other, how biodiversity keeps ecosystems working, and how to keep both wild and managed ecosystems productive.
Sustainability can't come from biology alone. It also needs economics, social science and personal choices, and people in wealthy countries have much larger ecological footprints than people in poorer ones.
Nature and people can do well together: countries have improved health, life expectancy and literacy while expanding conservation. That's a correlation, though, and on its own it doesn't prove one caused the other.
Biophilia is E. O. Wilson's idea that people have an inborn attraction to other living things, shaped by natural selection in our ancestors. People tend to protect what they understand and value.

Key terms (8)

sustainability: Using resources in a way that can keep going for the long term without wearing out the systems that supply them.
sustainable development: Economic growth that meets today's needs without taking away future generations' ability to meet theirs.
ecological footprint: The area of land and water needed to supply what a person or population uses and to absorb its wastes.
biophilia: The idea that humans have an inborn attraction to other living things and natural places.
renewable resource: A resource that can replace itself, like timber or fish, but only if it's used no faster than it regrows.
sustainable yield: The amount of a renewable resource that can be harvested each year without shrinking the stock over time.
life expectancy: The average number of years a newborn is expected to live, often used to track a population's well-being.
infant mortality rate: The number of babies per 1,000 live births who die before their first birthday.

Check yourself: 56.5 Sustainability and the future

4 questions on 56.5 Sustainability and the future. Pick an answer to see if you got it, and why.

Question 1 of 4

Villagers in a region depend on a nearby forest for timber, fruit and clean drinking water. Which plan best fits the idea of sustainable development?

Question 2 of 4Calculator allowed

A managed woodland holds 200,000 m³ of standing timber, and its trees add new wood equal to about 4% of that volume each year. What is the largest yearly harvest that keeps the standing volume roughly constant?

Question 3 of 4

A city compares four of its neighborhoods (invented data). Neighborhood | Parkland (% of area) | Median household income ($ thousands) | Children with asthma (%) N1 | 4 | 38 | 14 N2 | 9 | 52 | 11 N3 | 15 | 71 | 8 N4 | 22 | 95 | 6 A council member says these data prove that adding parks will cut asthma rates. Which response is best?

Question 4 of 4Calculator allowed

Country P has 10 million people, each with an ecological footprint of 7.0 global hectares. Country Q has 60 million people, each with a footprint of 1.5 global hectares. Which statement is correct?

0 of 4 answered