Page 698 - Environment: The Science Behind the Stories

idEntify lEarning goals

and rEcognizE misconcEptions

3

NEW! FAQs highlight and correct
areas would sometimes fly into death zones. Today, thousands
common misconceptions about Great Collie
of honeycreepers from mountain forests die each year when
they fly downslope and are bitten by malarial mosquitoes. As
environmental isssues. Dane
environmental conditions vary in time and space, adaptation
becomes a moving target.
One-quarter of Hakalau is Almost no area remains
above the 13°C isotherm above the 13°C isotherm,
and malaria-free, and Chihuahua Saint Bernard
so malaria will encompass
nearly all of it is above the the whole refuge.
FaQ Isn’t evolution based on just one man’s
17°C isotherm.
beliefs?
Because Charles Darwin contributed so much to our early
understanding of evolution, many people assume the con-
cept itself hinges on his ideas. But scientists and laypeople
Native Hawaiian forest at Hakalau Forest NWR, and the endangered ‘akiapo¯la¯‘au 17°C
isotherm had been observing nature and puzzling over fossils for a long
Evolution, Biodiversity, 13°C before Darwin. Once he and Alfred Russel Wallace indepen- (a) Ancestral wolf (Canis lupus) and derived dog breeds
time, and the notion of evolution was being discussed long
and Population Ecology isotherm Hakalau
dently proposed the concept of natural selection, scientists
Forest NWR
finally gained a precise and feasible mechanism to explain
(b) With 2°C of climate warming
(a) Today how and why organisms change across generations. Later,
geneticists discovered Gregor Mendel’s research and worked Cabbage Broccoli
Figure 3.21 Researchers have modeled how a warming climate will affect the native birds of
out how traits are inherited—and modern evolutionary biol-
Upon completing this chapter, you will be able to: Hakalau Forest NWR. Avian malaria cannot survive where temperatures dip below 13°C, and it peaks where
ogy was born. Twentieth-century scientists Fisher, Wright,
Explain natural selection and cite evidence for this Outline the characteristics of populations that help predict summer temperatures average 17°C. Today (a), 24% of Hakalau lies above (cooler than) the 13°C isotherm
Dobzhansky, Simpson, Mayr, and others ran experiments and
process population growth and is free of malaria. If climate warms by 2°C, however (b), then the isotherms move upslope, and only 1% of
Brussels
developed sophisticated mathematical models, documenting
Describe how evolution influences biodiversity Assess logistic growth, carrying capacity, limiting factors, Hakalau will remain cooler than 13°C and malaria-free. Data from: Benning, T.L., et al. 2002. Interactions of climate change Cauliflower
and other fundamental concepts in population ecology sprouts
phenomena with extensive evidence and making evolution-
Discuss reasons for species extinction and mass extinction with biological invasions and land use in the Hawaiian Islands: Modeling the fate of endemic birds using a geographic information
events Identify efforts and challenges involved in the conservation of systems. Proc Natl. Acad. Sci. 99: 14246–14249.
biodiversity ary biology into one of science’s strongest fields. Since then,
List the levels of ecological organization
evolutionary research by thousands of scientists has driven
Conclusion
our understanding of biology and has facilitated spectacular
The challenges of climate change mean that scientists
advances in agriculture, medicine, and biotechnology.
and managers need to come up with new ways to help save
declining populations. We will learn about the many efforts The honeycreepers of Hakalau Forest National Wildlife
Learning Objectives at the beginning of each being made across the world in our exploration of biodiversity Refuge, along with many other Hawaiian species, have
and conservation biology in Chapter 11. In Hawai‘i, it remains helped to illuminate the fundamentals of evolution and pop-
chapter define what you should be able to do after to be seen how effectively management and ecotourism can ulation ecology that are integral to environmental science.
(b) Ancestral Brassica oleracea and derived crops
Evidence of selection is all around us
completing the chapter. MasteringEnvironmentalScience stem the tide of challenges and help preserve natural systems The evolutionary processes of natural selection, speciation,
Figure 3.4 Selective breeding, or artificial selection, has
M03_WITH7428_05_SE_C03.indd 47 04/07/13 2:01 PM in the long term. Resources and efforts to preserve habitat and extinction help determine Earth’s biodiversity. Under-
resulted in our many breeds of dogs and varieties of crops.
The results of natural selection are all around us, visible in
also links assessments to learning objectives so and protect endangered species will likely need to be stepped standing how ecological processes function at the popula-
With dogs (a), we began with the gray wolf (Canis lupus) as the
every adaptation of every organism. In addition, scientists
professors can track students’ progress. up. Programs to restore altered communities to their former tion level is crucial to protecting biodiversity threatened by
ancestral wild species, and by breeding like with like and select-
the mass extinction event that many biologists maintain is
have demonstrated the rapid evolution of traits by selection
condition—as is being done at Hakalau Forest—will also be
ing for the traits we prefer, we have produced breeds as different
necessary. The restoration of ecological communities is one now underway. Population ecology also informs the study
in countless lab experiments, mostly with fast-reproducing
as Great Danes and Chihuahuas. By this same process we have
phenomenon we will examine in our next chapter, as we shift of human populations (Chapter 8), another key endeavor in
organisms such as bacteria, yeast, and fruit flies.
created our immense variety of crop plants (b). Cabbage, brussels
from populations to communities. environmental science.
The evidence for selection that may be most familiar
sprouts, broccoli, and cauliflower were all generated from a single
to us is that which Darwin himself cited prominently in his ancestral species, Brassica oleracea.
work 150 years ago: our breeding of domesticated animals.
Reviewing objectives CHAPTER 3 • Ev ol u T i on, Bi odivER si T y, A nd Po P ul AT i on E C ology
In domesticated dogs, cats, and livestock, we have conducted
selection under our own direction. We have chosen animals millennia (Figure 3.4b). Through selective breeding, we have
Reviewing Objectives at the with traits we like and bred them together, while not breed- created corn with bigger, sweeter kernels; wheat and rice
with larger and more numerous grains; and apples, pears, and
ing those with variants we do not like. Through such selective
oranges with better taste. We have diversified single types into
end of each chapter use a learning you should now be able to: • We have produced our pets, farm animals, and crop plants
breeding, we have been able to augment particular traits we
by artificial selection. (p. 52)
objective framework to help you review Explain natural selection and cite evidence for this many—for instance, breeding variants of the plant Brassica
prefer.
oleracea to create broccoli, cauliflower, cabbage, and brussels
Describe how evolution influences biodiversity
concepts and prepare for exams. processConsider the great diversity of dog breeds (Figure 3.4a). sprouts. Our entire agricultural system is based on artificial
People generated every type of dog alive today by starting
selection. We depend on a working understanding of evolution
• Because organisms produce excess young, individuals vary • Natural selection can act as a diversifying force as species
with a single ancestral species and selecting for particular
in their traits, and many traits are inherited, some individu- adapt to their environments in myriad ways. (pp. 52–53)
for the very food we eat.
desired traits as individuals were bred together. From Great
als will prove better at surviving and reproducing. Their • Speciation by geographic isolation (or other means) pro-
Dane to Chihuahua, all dogs are able to interbreed and pro-
genes will be passed on and become more prominent in duces new species. (pp. 53–54)
duce viable offspring, yet breeders maintain striking differ-
future generations. (p. 68) Evolution generates biodiversity
ences among them by allowing only like individuals to breed
• Mutations and recombination provide the genetic variation • The branching patterns of phylogenetic trees reflect the
historical pattern in which lineages of organisms have
Just as artificial selection helps us create new types of pets,
for natural selection. (p. 68) diverged. (p. 54) 71
direction is termed artificial selection. farm animals, and crop plants, natural selection serves to
Artificial selection has given us the many crop plants we
697 depend on for food, all of which people domesticated from elaborate and diversify traits in wild organisms. Over the long
term, natural selection helps lead to the formation of new spe-
52 wild ancestors and carefully bred over years, centuries, or cies and whole new types of organisms. Life’s complexity can
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