Chapter 40: Population Ecology & Distribution

Question 1

What is ecology?

Answer 1

The scientific study of the interactions between animals and their physical and biotic environment. Modern ecology includes observation and experimentation.

Question 2

Interactions between an animal and its environment determine the 1) _________ of the organisms and their 2) ___________.

Answer 2

1) Distribution

2) Abundance

Question 3

1) ________ factors include non-living chemical/physical attributes of the environment.
2) ________ factors are the other organisms that make up the living component of the environment.

Answer 3

1) Abiotic

2) Biotic

Question 4

Levels of ecology

Answer 4

1) Global
2) Landscape
3) Ecosystem
4) Community
5) Population
6) Organismal

Question 5

Organismal ecology

Answer 5

Organismal ecology studies how an organism’s structure, physiology, and (for animals) behavior meet environmental challenges
• Organismal ecology includes physiological, evolutionary, and behavioral ecology

Question 6

Population ecology

Answer 6

Population ecology focuses on factors affecting population size over time
– Average abundance
– Pattern of changes in pop size over time

• A population is a group of individuals of the same species living in an area

Question 7

Community ecology

Answer 7

Community ecology deals with the whole array of interacting species in a community

• A community is a group of populations of different species in an area

Question 8

Ecosystem ecology

Answer 8

• Ecosystem ecology emphasizes energy flow and chemical cycling among the various biotic and abiotic components
• An ecosystem is the community of organisms (i.e., different species) in an area and the physical factors with which they interact

Question 9

Global ecology

Answer 9

Global ecology is concerned with the biosphere, or global ecosystem, which is the sum of all the planet’s ecosystems
- Global ecology examines the influence of energy and materials on organisms across the biosphere


Question 10

Landscape ecology

Answer 10

Landscape ecology focuses on the exchanges of energy, materials, and organisms across multiple ecosystems
 A landscape (or seascape) is a mosaic of connected ecosystems
 But not on a global scale
 Landscape ecology would examine the relationships among the terrestrial ecosystems in Northern Ohio, the river ecosystems that drain water from the land, and the ecosystem of Lake Erie.
 E.g., fertilizer & detergents from land end up in the lake where they contribute to toxic algal blooms

Question 11

Earth climate influences the 1) ________ and 2) ________ of terrestrial biomes.

Answer 11

1) Structure
2) Distribution

 The long-term prevailing weather conditions in an area constitute its climate
 Four major abiotic components of climate (& weather) are temperature, precipitation, sunlight, and wind
 Macroclimate consists of patterns on the global, regional, and landscape level

Question 12

Global climate patterns are determined largely by 1) ______ ______ and the planet’s 2) ________ in space. The warming effect of the sun causes temperature variations, which drive 3) _________ and the circulation of air and water. This causes 4) _________ variations in 5) __________.

Answer 12

1) Solar energy
2) Movement
3) Evaporation
4) Latitudinal
5) Climate

Question 13

Latitudinal variation in sunlight intensity is caused by the 1) _______ of Earth. Sunlight strikes the 2) ______, regions between 23.5 degrees north and 23.5 degrees south latitude, most directly. At higher latitudes, where sunlight strikes Earth at an 3) ______ angle, light is more 4) _________. Higher latitudes = 5) _______ to the poles

Answer 13

1) Curved shape
2) Tropics
3) Oblique
4) Diffuse
5) Closer

Question 14

Global air circulation and precipitation patterns are initiated by intense solar radiation near the equator
 Warm, wet air rising near the equator creates precipitation in the tropics
 Dry air descending at 30 north and south latitudes causes desert conditions
 This pattern of precipitation and drying is repeated at the 60 north and south latitudes and the poles

Answer 14

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Question 15

Variation in the speed of Earth’s rotation at different latitudes results in the major wind patterns
 Trade winds blow east to west in the tropics
 Westerlies blow west to east in temperate zones

Answer 15

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Question 16

Regional Effects on Climate

Answer 16

Major influences on climate are  Seasonality
 Large bodies of water
 Mountains

Question 17

Seasonality

Answer 17

 Seasonal variations of light and temperature increase steadily toward the poles
 Seasonality at high latitudes is caused by the tilt of Earth’s axis of rotation and its annual passage around the sun
 Belts of wet and dry air straddling the equator shift throughout the year with the changing angle of the sun
 Changing wind patterns affect ocean currents

Question 18

Bodies of Water

Answer 18

 Oceans, their currents, and large lakes moderate the climate of nearby terrestrial environments
 The California Current carries cold water southward along western North America
 The Gulf Stream carries warm water from the equator to the North Atlantic

Question 19

 During the day, air rises over warm land and draws a cool breeze from the water across the land
 As the land cools at night, air rises over the warmer water and draws cooler air from land back over the water, which is replaced by warmer air from offshore

Answer 19

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Question 20

Mountains

Answer 20

 Rising air releases moisture on the windward side of a peak and creates a “rain shadow” as it absorbs moisture on the leeward side
 Many deserts are found in the “rain shadow” of mountains

Question 21

 Slope & elevation affect the amount of sunlight reaching an area
 In the Northern Hemisphere, south-facing slopes receive more sunlight than north-facing slopes
 Every 1,000-m increase in elevation produces a temperature drop of approximately 6C
 Elevation mimics latitude

Answer 21

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Question 22

Climate and Terrestrial Biomes

Answer 22

 Biomes are major life zones characterized by vegetation type (terrestrial biomes) or physical environment (aquatic biomes)
 Note: typically NOT the same species in the same biomes in different parts of the world (remember “cactuses”
 Climate is very important in determining why terrestrial biomes are found in certain areas
 Climate affects the latitudinal patterns of terrestrial biomes

Question 23

 A climograph plots the temperature and precipitation in a region
 Biomes are affected not just by average temperature and precipitation, but also by the seasonal pattern of temperature and precipitation through the year

Answer 23

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Question 24

Natural and human-caused disturbances alter the distribution of biomes
 A disturbance is an event that changes a community by removing organisms and altering resource availability
 For example, frequent fires kill woody plants preventing woodlands from establishing

Answer 24

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Question 25

General Features of Terrestrial Biomes

Answer 25

 Terrestrial biomes are often named for major physical or climatic factors and for vegetation
 Terrestrial biomes usually grade into each other, without sharp boundaries
 The area of intergradation, called an ecotone, may be wide or narrow

Question 26

Vertical layering is an important feature of terrestrial biomes, and in a forest it might consist of an upper canopy, low-tree layer, shrub understory, ground layer of herbaceous plants, forest floor, and root layer
 Layering of vegetation provides diverse habitats for animals

Answer 26

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Question 27

 Terrestrial biomes can be characterized by distribution, precipitation, temperature, plants, and animals

Answer 27

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Question 28

Tropical forest occurs in equatorial and subequatorial regions
 Temperature is high year-round (25–29C) with little seasonal variation
 In tropical rain forests, rainfall is relatively constant, while in tropical dry forests precipitation is highly seasonal

Answer 28

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Question 29

 Tropical forests are vertically layered, and competition for light is intense
 Tropical forests are home to millions of animal species, including an estimated 5–30 million still undescribed species of insects, spiders, and other arthropods
 Rapid human population growth is now destroying many tropical forests

Answer 29

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Question 30

 Savanna occurs in equatorial and subequatorial regions
 Precipitation is seasonal
 Temperature averages 24–29C but is more seasonally variable than in the tropics

Answer 30

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Question 31

Grasses and forbs make up most of the ground cover
 The dominant plant species are fire-adapted and tolerant of seasonal drought
 Common inhabitants include insects and mammals such as wildebeests, zebras, lions, and hyenas
 Fires set by humans may help maintain this biome

Answer 31

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Question 32

Deserts occur in bands near 30 north and south of the equator and in the interior of continents
 Precipitation is low and highly variable, generally less than 30 cm per year
 Deserts may be hot (50C) or cold (–30C) with seasonal and daily temperature variation

Answer 32

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Question 33

Desert plants are adapted for heat and desiccation tolerance, water storage, and reduced leaf surface area
 Common desert animals include scorpions, ants, beetles, snakes, lizards, migratory and resident birds, and seed-eating rodents; many are nocturnal
 Urbanization and conversion to irrigated agriculture have reduced the natural biodiversity of some deserts

Answer 33

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Question 34

Chaparral occurs in midlatitude coastal regions on several continents
 Precipitation is highly seasonal with rainy winters and dry summers
 Summer is hot (30C); fall, winter, and spring are cool (10–12C)

Answer 34

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Question 35

 The chaparral is dominated by shrubs and small trees; many plants are adapted to fire and drought
 Animals include browsing mammals, insects, amphibians, small mammals, and birds
 Humans have reduced chaparral areas through agriculture and urbanization

Answer 35

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Question 36

 Temperate grasslands occur at midlatitudes, often in the interior of continents
 Precipitation is highly seasonal
 Winters are cold (often below −10C) and dry; summers are hot (often near 30C) and wet

Answer 36

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Question 37

 The dominant plants, grasses and forbs, are adapted to droughts and fire
 Native mammals include large grazers such as bison and wild horses and small burrowers such as prairie dogs
 Most grasslands have been converted to farmland

Answer 37

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Question 38

 Northern coniferous forest, or taiga, spans northern North America and Eurasia and is the largest terrestrial biome on Earth
 Precipitation ranges from 30–70 cm
 Winters are cold; summers may be hot (e.g., Siberia ranges from −50C to 20C)

Answer 38

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Question 39

 Conifers such as pine, spruce, fir, and hemlock dominate
 The conical shape of conifers prevents too much snow from accumulating and breaking their branches
 Animals include migratory and resident birds and large mammals such as moose, brown bears, and Siberian tigers
 Periodic insect outbreaks kill vast tracts of trees
 Some forests are being logged at an alarming rate

Answer 39

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Question 40

 Temperate broadleaf forest is found at midlatitudes in the Northern Hemisphere, with smaller areas in Chile, South Africa, Australia, and New Zealand
 Significant amounts of precipitation fall during all seasons as rain or snow
 Winters average 0C; summers are hot and humid (near 35C)

Answer 40

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Question 41

 Dominant plants include deciduous trees in the Northern Hemisphere and evergreen eucalyptus in Australia
 In the Northern Hemisphere, many mammals hibernate in the winter; birds migrate to warmer areas
 These forests have been heavily settled on all continents but are recovering in places

Answer 41

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Question 42

 Tundra covers expansive areas of the Arctic; alpine tundra exists on high mountaintops at all latitudes
 Precipitation is low in arctic tundra and higher in alpine tundra
 Winters are cold (below −30C); summers are relatively cool (less than 10C)

Answer 42

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Question 43

 Vegetation is herbaceous (mosses, grasses, forbs, dwarf shrubs, trees, and lichen)
 Permafrost, a permanently frozen layer of soil, restricts growth of plant roots
 Mammals include musk oxen, caribou, reindeer, bears, wolves, and foxes; many migratory bird species nest in the summer
 Settlement is sparse, but tundra has become the focus of oil and mineral extraction

Answer 43

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Question 44

Aquatic biomes are diverse and dynamic systems that cover most of Earth.  Aquatic biomes account for the largest part of the biosphere in terms of area
 They show less latitudinal variation than terrestrial biomes
 Marine biomes have salt concentrations of about 3%
 The largest marine biome is made of oceans, which cover about 75% of Earth’s surface and have an enormous impact on the biosphere


Answer 44

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Question 45

 Freshwater biomes have salt concentrations of less than 0.1%
 Freshwater biomes are closely linked to soils and the biotic components of the surrounding terrestrial biome

Answer 45

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Question 46

 Aquatic biomes can be characterized by their physical and chemical environment, geological features, photosynthetic organisms, and heterotrophs

Answer 46

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