Campbell Biology Chapter 52 Review: An Introduction to Ecology and the Biosphere

52.1 Climate, latitude and a warming planet

pp. 1144–1150

On the AP exam? Background

Global wind belts and rain shadows aren't in the current course. What is tested: water's high specific heat keeps coastal temperatures steady (Topic 1.1), abiotic factors shape ecosystems (Topic 8.6), and climate change is moving where species can live (Topic 8.7).

In the course: Topic 8.7 Disruptions in Ecosystems, Topic 1.1 Structure of Water and Hydrogen Bonding, Topic 8.6 Biodiversity, Topic 8.3 Population Ecology (notes, videos and more questions)

Key points

Ecology studies how living things interact with each other and with their surroundings. Ecologists work at many scales: one organism, a population of one species, a community of many species, an ecosystem with its nonliving parts, a landscape of linked ecosystems, and the whole biosphere.
Climate is the long-run pattern of weather in a place, set mostly by temperature, rainfall, sunlight and wind. It's the biggest single control on which organisms can live where.
Near the equator, sunlight hits the ground almost head-on, so each square meter gets more energy than at high latitudes, where the same light is spread at a slant. Earth's tilted axis makes this change through the year, which is why seasons get stronger toward the poles.
Warm, moist air rises near the equator, cools and drops heavy rain. That air, now dry, sinks again around 30° north and south, which is why many big deserts sit at those latitudes. Earth's spin bends surface winds into steady east–west belts.
Big bodies of water heat up and cool down slowly because water has a high specific heat, so coasts have milder summers and winters than inland areas. Mountains force moist air upward to drop rain on the windward side, leaving a dry rain shadow behind them; air also gets colder as you climb, by roughly 6–7°C per 1,000 m.
Small-scale conditions, called microclimate, can differ a lot from the regional climate: the shade under a tree, a burrow or the moist soil under a rock each offer their own temperature and humidity. Physical, nonliving conditions are abiotic factors; the other organisms around are biotic factors.
Burning fossil fuels and clearing forests have raised CO₂ and other greenhouse gases, and Earth's average surface temperature is now roughly 1.3°C above late-1800s levels. Many species' ranges are shifting toward the poles and uphill, and species that disperse slowly may not keep pace.

Key terms (14)

ecology: The study of how organisms interact with one another and with the nonliving world around them.
population: All the individuals of one species living in the same area at the same time.
community: All the populations of different species that live together and interact in one place.
ecosystem: A community plus the nonliving parts of its surroundings, like soil, water and air, which energy and matter move through.
landscape: A patchwork of neighboring ecosystems, linked by the energy, materials and organisms that move between them.
biosphere: Every ecosystem on Earth taken together: all the places where life exists.
climate: The typical weather a place has over many years, mainly its temperature, rainfall, sunlight and wind.
macroclimate: Climate patterns at a large scale, such as for a whole region or latitude band.
microclimate: Conditions in a very small spot, like under a log or inside a burrow, that can differ sharply from the area around it.
abiotic factor: A nonliving part of the environment, such as temperature, water, light, salt or soil, that affects living things.
biotic factor: A living part of an organism's environment: the predators, prey, competitors, parasites and partners it deals with.
rain shadow: A dry area on the downwind side of a mountain range. The air dropped its moisture while climbing the other side.
greenhouse gas: A gas such as CO₂ or methane that traps heat in the atmosphere. Adding more of it warms the planet.
range shift: A change in where a species lives, such as moving toward the poles or uphill as the climate warms.

Check yourself: 52.1 Climate, latitude and a warming planet

4 questions on 52.1 Climate, latitude and a warming planet. Pick an answer to see if you got it, and why.

Question 1 of 4

An ecologist wants to know why the number of a lizard species on a hillside dropped by half over 10 years. She tracks birth rates and death rates of the lizards each year. At which level of ecology is she mainly working?

Question 2 of 4

Over a year, a square meter of ground near the equator receives more solar energy than a square meter near the Arctic Circle. Which statement best explains why?

Question 3 of 4

On an island, winds nearly always blow from the east. A ridge 2,000 m high runs north to south down the middle of the island. A weather station on the east coast records 310 cm of rain per year, and one on the west coast records 45 cm. Which explanation best fits these data?

Question 4 of 4

A valley at 400 m elevation has a mean annual temperature of 22°C. Assuming air temperature falls by about 6.5°C for every 1,000 m of elevation, what mean temperature would you expect at a ridge top 2,400 m above sea level?

0 of 4 answered

52.2 Land biomes: shaped by climate and disturbance

pp. 1150–1156

On the AP exam? Background

You won't be asked to name biomes or recall their rainfall. What carries over: abiotic factors shape which species live in an ecosystem (Topic 8.6), similar environments select for similar traits (Topic 7.2), and disturbances such as fire and land clearing reshape ecosystems (Topic 8.7).

In the course: Topic 8.7 Disruptions in Ecosystems, Topic 8.6 Biodiversity, Topic 7.2 Natural Selection (notes, videos and more questions)

Key points

A biome is one of Earth's major life zones. On land, biomes are named for their main type of vegetation, and that vegetation mostly follows climate, so biomes line up in rough bands by latitude.
A climograph plots a place's average yearly temperature against its average yearly rainfall. Forests sit at the wet end, grasslands are drier, and deserts are driest. Biomes still overlap on such a plot, because averages hide the timing of rain and cold, and soils differ too.
Biomes blend into each other across a transition zone called an ecotone, which can be narrow or very wide. Within a biome, plants form vertical layers, from the tallest canopy down to roots, and each layer gives animals different places to feed and shelter.
The same biome on different continents often holds unrelated species that look and act alike, because similar conditions select for similar traits. This is convergent evolution.
Disturbance is normal, not rare. Fires, storms, insect outbreaks and human activity clear patches and free up resources, so biomes are patchy mosaics. Grasslands, savannas, chaparral and many conifer forests depend on regular fire; without it, woody plants move in.
A quick tour: tropical forests are warm all year, wet and the richest in species; deserts get under about 30 cm of rain a year; savannas are warm grasslands with scattered trees and long dry seasons; chaparral has wet winters, dry summers and fire-adapted shrubs; temperate grasslands have cold winters and deep, fertile soil.
Farther toward the poles, temperate broadleaf forests drop their leaves before winter, northern coniferous forest (taiga) is the largest land biome, and tundra has permanently frozen subsoil (permafrost) and no trees. Humans have turned huge areas of nearly every biome into farms and cities.

Key terms (15)

biome: A major type of ecosystem found over large areas, such as desert or tundra. Land biomes are named for their main vegetation.
climograph: A graph that plots a place's average yearly temperature against its average yearly rainfall, used to compare biomes.
ecotone: The zone where two biomes or communities meet and blend, with a mix of species from both.
canopy: The top layer of a forest, made of the crowns of the tallest trees, which captures most of the sunlight.
disturbance: An event like a fire, flood, storm or logging that removes organisms and changes which resources are available.
convergent evolution: When unrelated species evolve similar traits because they face similar environments, not because they share an ancestor with that trait.
tropical forest: A biome near the equator that is warm all year. Rain forests are wet year-round; tropical dry forests have a long dry season.
desert: A biome with very little rain, under about 30 cm a year. It can be hot or cold, with sparse plants built to save water.
savanna: A warm grassland with scattered trees, a long dry season and frequent fires, often home to large grazing animals.
chaparral: A biome of tough-leaved shrubs and small trees with mild, rainy winters and hot, dry summers. Its plants recover quickly after fire.
temperate grassland: A biome dominated by grasses, with cold winters, hot summers, periodic drought and fire, and very fertile soil.
northern coniferous forest: Also called taiga, the largest land biome: a band of cone-bearing trees like spruce and pine across the far north, with long, cold winters.
temperate broadleaf forest: A biome with rain in every season, cold winters and hot summers, dominated in the north by trees that shed their leaves each fall.
tundra: A treeless biome of the far north and high mountains with very cold winters, short cool summers and low-growing plants.
permafrost: Soil that stays frozen all year. It blocks deep roots and drainage, which helps keep trees out of the tundra.

Check yourself: 52.2 Land biomes: shaped by climate and disturbance

4 questions on 52.2 Land biomes: shaped by climate and disturbance. Pick an answer to see if you got it, and why.

Question 1 of 4

A site has a mean temperature of 27°C in every month. It gets about 45 cm of rain a year, almost all of it during a four-month wet season. The ground is covered with grasses, with acacia trees scattered far apart, and grass fires often sweep through between rains. Which biome is this most likely to be?

Question 2 of 4

A grassland preserve was burned every 3 years for decades. Then managers stopped all burning. Which change is most likely over the next 30 years?

Question 3 of 4

Kangaroo rats in North American deserts and jerboas in Asian deserts both hop on long hind legs, are active at night and get most of their water from the seeds they eat. The two groups are only distantly related. What is the best explanation for their similarities?

Question 4 of 4

A student walks a 3 km straight line from open prairie into a forest, listing plant species every 100 m. Grasses and prairie wildflowers fade out gradually over about 1.5 km while tree seedlings and shade plants slowly increase, with many spots holding both. What does this middle stretch represent?

0 of 4 answered

52.3 Water biomes: zones, layers and turnover

pp. 1157–1163

On the AP exam? Background

Zone names like littoral or neritic aren't tested. What carries over: producers capture the energy that feeds ecosystems (Topic 8.2), water is densest near 4°C (Topic 1.1), mutualisms like coral and algae (Topic 8.5), and eutrophication and warming damage water ecosystems (Topic 8.7).

In the course: Topic 8.7 Disruptions in Ecosystems, Topic 8.2 Energy Flow Through Ecosystems, Topic 1.1 Structure of Water and Hydrogen Bonding, Topic 8.5 Community Ecology (notes, videos and more questions)

Key points

Aquatic biomes are sorted mainly by their physical and chemical conditions, like salt, depth, light and flow, rather than by climate, and each type turns up at many latitudes. Seawater is about 3% salt; fresh water is under 0.1%.
Oceans cover about 71% of Earth's surface. Their evaporation supplies most rainfall, their heat drives weather, and their tiny drifting producers (phytoplankton) do roughly half of all photosynthesis on Earth.
Light fades quickly with depth. The sunlit photic zone supports photosynthesis; the dark aphotic zone below doesn't. Open water is the pelagic zone, and the bottom is the benthic zone, where many animals live on detritus (dead organic matter) sinking from above.
Sun-warmed water floats on cold, deep water, separated by a thin layer of sudden temperature change called a thermocline. In temperate lakes, water is densest at about 4°C, so in spring and fall the whole lake mixes (turnover), carrying oxygen down and nutrients up.
Nutrient-poor (oligotrophic) lakes are clear and well oxygenated. Nutrient-rich (eutrophic) lakes grow lots of algae, and decomposers breaking down the dead algae can strip oxygen from deep water. Fertilizer and sewage runoff push lakes toward eutrophic and can cause fish kills.
Wetlands and estuaries, where rivers meet the sea, are among the most productive places on Earth and filter pollutants. Streams run cold, clear and oxygen-rich near their sources and become warmer and murkier downstream. Intertidal zones are flooded and exposed by tides every day.
Coral reefs grow in warm, clear, shallow tropical water and depend on algae living inside coral tissue; heat stress makes corals expel them (bleaching). In the deep sea, hydrothermal vent communities run on chemoautotrophic prokaryotes that get energy from chemicals like hydrogen sulfide (H₂S), not sunlight.

Key terms (15)

aquatic biome: A major type of water ecosystem, like a lake, estuary or coral reef, defined mostly by its physical conditions such as salt and depth.
photic zone: The upper layer of a body of water that gets enough light for photosynthesis.
aphotic zone: The deeper, dark layer of water where too little light reaches for photosynthesis.
pelagic zone: The open water of a lake or ocean, from the surface down, away from the bottom.
benthic zone: The bottom of a lake, river or ocean, along with the organisms (the benthos) that live in or on it.
detritus: Dead organic matter, like fallen leaves, dead plankton and waste, that decomposers and many bottom-dwellers feed on.
phytoplankton: Tiny photosynthetic organisms, such as algae and cyanobacteria, that drift in water and are major producers.
thermocline: A thin layer in a lake or ocean where temperature drops sharply, separating warm surface water from cold deep water.
turnover: The seasonal mixing of a temperate lake in spring and fall that brings oxygen down to deep water and nutrients up to the surface.
oligotrophic lake: A lake low in nutrients, with little algae, clear water and plenty of oxygen even near the bottom.
eutrophic lake: A lake rich in nutrients, with lots of algae. Decomposition can use up the oxygen in its deep water.
estuary: The place where a river meets the sea, with salt levels that change across the area and with the tides.
wetland: An area flooded or soaked with water at least part of the time, with plants adapted to waterlogged soil.
intertidal zone: The strip of shore that is underwater at high tide and exposed to air at low tide.
coral reef: A tropical ecosystem built from the limestone skeletons of corals, which rely on algae living in their tissues.

Check yourself: 52.3 Water biomes: zones, layers and turnover

4 questions on 52.3 Water biomes: zones, layers and turnover. Pick an answer to see if you got it, and why.

Question 1 of 4

Dissolved oxygen was measured at several depths in a temperate lake in late July and again in mid-November. Depth (m) | July O₂ (mg/L) | November O₂ (mg/L) 0 | 9.1 | 8.4 5 | 8.8 | 8.3 10 | 4.0 | 8.3 15 | 1.2 | 8.2 20 | 0.6 | 8.2 Which explanation best accounts for the difference between the two dates?

Question 2 of 4

In a lab, a tall tank of fresh water is cooled slowly from the top. Long after a thin skin of ice forms at the surface, thermometers show the water at the bottom has stopped cooling at about 4°C. Which property of water explains this?

Question 3 of 4

Heavy rains wash fertilizer from farm fields into a small lake. Which sequence of events is most likely to follow?

Question 4 of 4

Around a deep-sea hydrothermal vent 2,500 m below the surface, there are dense populations of tube worms, clams and crabs. No light reaches this depth. What forms the base of this food web?

0 of 4 answered

52.4 What limits where a species lives

pp. 1163–1167

On the AP exam? Yes

You don't need to memorize the order of questions ecologists ask, but the ideas are tested: behavior (Topic 8.1), species interactions (Topic 8.5), abiotic factors (Topic 8.6), invasive species (Topic 8.7), osmoregulation (Topic 2.7) and heat denaturing proteins (Topic 3.2).

In the course: Topic 8.5 Community Ecology, Topic 8.6 Biodiversity, Topic 8.7 Disruptions in Ecosystems, Topic 8.1 Responses to the Environment, Topic 2.7 Tonicity and Osmoregulation, Topic 3.2 Environmental Impacts on Enzyme Function (notes, videos and more questions)

Key points

Ecology goes beyond mapping a species: the goal is to explain why it turns up in some places and is missing from others. The answer plays out on two time scales: interactions in ecological time (days to years) and natural selection over many generations in evolutionary time.
A useful checklist when a species is missing from an area: Can it get there (dispersal)? Does it choose not to live there (behavior)? Do other species keep it out (biotic factors)? Are the physical conditions wrong (abiotic factors)?
Dispersal means organisms, or their seeds, spores or gametes, spreading out from where they began. Barriers like oceans and mountains can keep a species out of places where it could thrive, and rare long-distance colonists can found new populations and even spark adaptive radiations.
When a species gets carried somewhere new and sets up a lasting, breeding population, that shows there were livable places it simply hadn't reached: its possible range is wider than the one it actually fills. Accidental moves like this can produce invasive species that harm native ones.
Behavior can limit range too: some animals only lay eggs or settle in very specific habitats, even when others would work. Biotic limits include predators, herbivores, competitors, parasites, disease, and missing food or pollinators. Removal or exclusion experiments test these.
Abiotic limits include temperature (ice crystals rupture cells, and most proteins denature above about 45°C), water (drying out), oxygen (scarce in deep or stagnant water and flooded soil), salinity (which strains osmoregulation), light (too little for producers, or too much UV), and soil pH and minerals.
Physical conditions shift with the season, the time of day and even across a few meters, and many organisms ride out the harshest stretches by going dormant, hibernating or migrating.

Key terms (15)

distribution: The geographic area where a species is actually found.
dispersal: The spread of organisms, or of their seeds, spores or gametes, to new places away from their parents or birthplace.
potential range: Everywhere a species could survive and reproduce, which can be bigger than where it lives now.
transplant: Moving organisms to a place where they don't currently live, on purpose or by accident, to see if they can survive and breed there.
invasive species: A species introduced to a new area that spreads quickly and harms native species, often because its usual predators and diseases are missing.
habitat selection: When animals choose where to live or lay eggs, which can keep them out of places they could otherwise survive.
herbivore: An animal whose diet is mainly plants or algae.
predator: An organism that kills and eats other organisms, its prey.
desiccation: Drying out. Losing too much water is a constant danger for land organisms and for shore animals at low tide.
osmoregulation: How an organism controls the balance of water and dissolved salts in its body.
thermophile: An organism, usually a prokaryote, that thrives at high temperatures that would kill most life.
ecological time: The short time scale, from minutes to years, over which organisms interact with each other and their surroundings.
evolutionary time: The long time scale, over many generations, during which natural selection changes populations.
adaptive radiation: The rapid evolution of many new species from one ancestor as they spread into different ways of life.
tree line: The elevation (or latitude) beyond which trees can't grow, because of cold, wind, drought and strong sunlight.

Check yourself: 52.4 What limits where a species lives

4 questions on 52.4 What limits where a species lives. Pick an answer to see if you got it, and why.

Question 1 of 4

A wildflower grows only on a mainland coast. Botanists plant seedlings on an island 50 km offshore with similar soil and climate. The transplanted plants grow and flower well for years, but they never set seed, and no new plants appear. The bee species that pollinates the flower on the mainland is absent from the island. What most likely limits the wildflower's distribution on the island?

Question 2 of 4

To test whether predatory fish limit a frog species, researchers set up three kinds of plots in stream pools and measured tadpole survival. Treatment | Tadpole survival (%) Full mesh cage that keeps fish out | 78 No cage | 12 Cage with large openings that let fish in | 15 What is the main purpose of the cage with large openings?

Question 3 of 4

A warbler breeds only in mature pine stands. In oak woods right next to the pines, insect food is just as plentiful and nest predators are no more common, and pairs that researchers kept in large aviaries in the oak woods raised as many chicks as pairs in pine. Yet wild warblers arriving each spring settle only in pine, even when every pine stand is crowded. What mainly limits the warbler's distribution?

Question 4 of 4

A freshwater mussel is moved into seawater, which has a much higher salt concentration than the mussel's body fluids. If the mussel can't adjust, what will happen to it first?

0 of 4 answered