Figure 4.1 The American alligator plays an important ecological role in its marsh and swamp habitats in the southeastern United States. Since being classified as an endangered species in 1967, it has recovered enough to have its status changed from endangered to threatened—an outstanding success story in wildlife conservation. Fig. 4-1, p. 77

Figure 4.2 Natural capital: the major components of the earth’s biodiversity—one of the earth’s most important renewable resources. See an animation based on this figure at CengageNOW™. Question: What are three examples of how people, in their daily living, intentionally or unintentionally degrade each of these types of biodiversity? Fig. 4-2, p. 79

Figure 4.3 Overview of the evolution of life on the earth into six major kingdoms of species as a result of natural selection. For more details, see p. S46 in Supplement 7. Fig. 4-3, p. 81

Prokaryotes Eukaryotes Eubacteria Archaebacteria Protists Plants Fungi Animals Cenozoic First humans Mesozoic Extinction of dinosaurs Paleozoic Plants colonize land 500 Origin of multicellular organisms 1,000 1,500 Oldest eukaryotic fossils 2,000 Millions of years ago Accumulation of O2 in atmosphere from photosynthetic cyanobacterium 2,500 Precambrian Figure 4.3 Overview of the evolution of life on the earth into six major kingdoms of species as a result of natural selection. For more details, see p. S46 in Supplement 7. 3,000 3,500 Oldest prokaryotic fossils 4,000 Earth cool enough for crust to solidify Origin of Earth 4,500 Fig. 4-3, p. 81

Figure 4.4 Fossilized skeleton of an herbivore that lived during the Cenozoic era from 26–66 million years ago. Fig. 4-4, p. 82

Figure 4.5 Evolution by natural selection. (a) A population of bacteria is exposed to an antibiotic, which (b) kills all but those possessing a trait that makes them resistant to the drug. (c) The resistant bacteria multiply and eventually (d) replace the nonresistant bacteria. Fig. 4-5, p. 83

A group of bacteria, including genetically resistant ones, are exposed to an antibiotic Eventually the resistant strain replaces the strain affected by the antibiotic The genetically resistant bacteria start multiplying Most of the normal bacteria die Figure 4.5 Evolution by natural selection. (a) A population of bacteria is exposed to an antibiotic, which (b) kills all but those possessing a trait that makes them resistant to the drug. (c) The resistant bacteria multiply and eventually (d) replace the nonresistant bacteria. Normal bacterium Resistant bacterium Fig. 4-5, p. 83

A group of bacteria, including genetically resistant ones, are exposed to an antibiotic Normal bacterium Resistant bacterium Eventually the resistant strain replaces the strain affected by the antibiotic The genetically resistant bacteria start multiplying Most of the normal bacteria die Figure 4.5 Evolution by natural selection. (a) A population of bacteria is exposed to an antibiotic, which (b) kills all but those possessing a trait that makes them resistant to the drug. (c) The resistant bacteria multiply and eventually (d) replace the nonresistant bacteria. Stepped Art Fig. 4-5, p. 83

Figure 4.6 Over millions of years, the earth’s continents have moved very slowly on several gigantic tectonic plates. This process plays a role in the extinction of species, as land areas split apart, and also in the rise of new species when isolated land areas combine. Rock and fossil evidence indicates that 200–250 million years ago, all of the earth’s present-day continents were locked together in a supercontinent called Pangaea (top left). About 180 million years ago, Pangaea began splitting apart as the earth’s tectonic plates separated, eventually resulting in today’s locations of the continents (bottom right). Question: How might an area of land splitting apart cause the extinction of a species? Fig. 4-6, p. 85

225 million years ago 135 million years ago 65 million years ago Present Figure 4.6 Over millions of years, the earth’s continents have moved very slowly on several gigantic tectonic plates. This process plays a role in the extinction of species, as land areas split apart, and also in the rise of new species when isolated land areas combine. Rock and fossil evidence indicates that 200–250 million years ago, all of the earth’s present-day continents were locked together in a supercontinent called Pangaea (top left). About 180 million years ago, Pangaea began splitting apart as the earth’s tectonic plates separated, eventually resulting in today’s locations of the continents (bottom right). Question: How might an area of land splitting apart cause the extinction of a species? Fig. 4-6, p. 85

225 million years ago 135 million years ago 65 million years ago Present Figure 4.6 Over millions of years, the earth’s continents have moved very slowly on several gigantic tectonic plates. This process plays a role in the extinction of species, as land areas split apart, and also in the rise of new species when isolated land areas combine. Rock and fossil evidence indicates that 200–250 million years ago, all of the earth’s present-day continents were locked together in a supercontinent called Pangaea (top left). About 180 million years ago, Pangaea began splitting apart as the earth’s tectonic plates separated, eventually resulting in today’s locations of the continents (bottom right). Question: How might an area of land splitting apart cause the extinction of a species? Stepped Art Fig. 4-6, p. 85

Figure 4.7 Changes in ice coverage in the northern hemisphere during the past 18,000 years. Question: What are two characteristics of an animal and two characteristics of a plant that natural selection would have favored as these ice sheets (left) advanced? (Data from the National Oceanic and Atmospheric Administration) Fig. 4-7, p. 85

Northern Hemisphere Ice coverage 18,000 years before present Northern Hemisphere Ice coverage Modern day (August) Legend Continental ice Sea ice Land above sea level Figure 4.7 Changes in ice coverage in the northern hemisphere during the past 18,000 years. Question: What are two characteristics of an animal and two characteristics of a plant that natural selection would have favored as these ice sheets (left) advanced? (Data from the National Oceanic and Atmospheric Administration) Fig. 4-7, p. 85

Figure 4.8 Geographic isolation can lead to reproductive isolation, divergence of gene pools, and speciation. Fig. 4-8, p. 87

Arctic Fox Northern population Gray Fox Southern population Adapted to cold through heavier fur, short ears, short legs, and short nose. White fur matches snow for camouflage. Northern population Spreads north and south and separates Different environmental conditions lead to different selective pressures and evolution into two different species. Early fox population Gray Fox Adapted to heat through lightweight fur and long ears, legs, and nose, which give off more heat. Southern population Figure 4.8 Geographic isolation can lead to reproductive isolation, divergence of gene pools, and speciation. Fig. 4-8, p. 87

Figure 4.9 Male golden toad in Costa Rica’s high-altitude Monteverde Cloud Forest Reserve. This species has recently become extinct, primarily because changes in climate dried up its habitat. Fig. 4-9, p. 87

Figure 4.A An example of genetic engineering. The 6-month-old mouse on the left is normal; the same-age mouse on the right has a human growth hormone gene inserted in its cells. Mice with the human growth hormone gene grow two to three times faster and twice as large as mice without the gene. Question: How do you think the creation of such species might change the process of evolution by natural selection? Fig. 4-A, p. 88

Figure 4.10 Variations in species richness and species evenness. A coral reef (left), with a large number of different species (high species richness), generally has only a few members of each species (low species evenness). In contrast, a grove of aspen trees in Alberta, Canada, in the fall (right) has a small number of different species (low species richness), but large numbers of individuals of each species (high species evenness). Fig. 4-10a, p. 89

Figure 4.10 Variations in species richness and species evenness. A coral reef (left), with a large number of different species (high species richness), generally has only a few members of each species (low species evenness). In contrast, a grove of aspen trees in Alberta, Canada, in the fall (right) has a small number of different species (low species richness), but large numbers of individuals of each species (high species evenness). Fig. 4-10b, p. 89

Figure 4.11 Specialist species such as the giant panda have a narrow niche (left) and generalist species such as a raccoon have a broad niche (right). Fig. 4-11, p. 91

Niche separation Niche breadth Specialist species with a narrow niche Generalist species with a broad niche Niche separation Number of individuals Figure 4.11 Specialist species such as the giant panda have a narrow niche (left) and generalist species such as a raccoon have a broad niche (right). Niche breadth Region of niche overlap Resource use Fig. 4-11, p. 91

Figure 4.12 As generalists, cockroaches are among the earth’s most adaptable and prolific species. This is a photo of an American cockroach. Fig. 4-12, p. 92

Figure 4.13 Specialized feeding niches of various bird species in a coastal wetland. This specialization reduces competition and allows sharing of limited resources. Fig. 4-13, p. 93

surface water in search of small crustaceans, insects, and seeds Ruddy turnstone searches under shells and pebbles for small invertebrates Dowitcher probes deeply into mud in search of snails, marine worms, and small crustaceans Black skimmer seizes small fish at water surface Brown pelican dives for fish, which it locates from the air Herring gull is a tireless scavenger Avocet sweeps bill through mud and surface water in search of small crustaceans, insects, and seeds Flamingo feeds on minute organisms in mud Figure 4.13 Specialized feeding niches of various bird species in a coastal wetland. This specialization reduces competition and allows sharing of limited resources. Scaup and other diving ducks feed on mollusks, crustaceans, and aquatic vegetation Louisiana heron wades into water to seize small fish Oystercatcher feeds on clams, mussels, and other shellfish into which it pries its narrow beak Knot (sandpiper) picks up worms and small crustaceans left by receding tide Piping plover feeds on insects and tiny crustaceans on sandy beaches Fig. 4-13, p. 93

Figure 4.14 Life cycle of a frog. Populations of various frog species can decline because of the effects of harmful factors at different points in their life cycle. Such factors include habitat loss, drought, pollution, increased ultraviolet radiation, parasitism, disease, overhunting by humans, and nonnative predators and competitors. Fig. 4-14, p. 94

Adult frog (3 years) Tadpole develops into frog Young frog Sperm Tadpole develops into frog Sexual reproduction Tadpole Figure 4.14 Life cycle of a frog. Populations of various frog species can decline because of the effects of harmful factors at different points in their life cycle. Such factors include habitat loss, drought, pollution, increased ultraviolet radiation, parasitism, disease, overhunting by humans, and nonnative predators and competitors. Eggs Fertilized egg development Egg hatches Organ formation Fig. 4-14, p. 94