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APES STUDY GUIDE
Chapter 4
Biodiversity and Evolution
Key Concepts
4-1 The biodiversity found in genes, species, ecosystems, and ecosystem processes is vital to sustaining
life on earth.
4-2A The scientific theory of evolution explains how life on the earth changes over time due to changes in
the genes of populations.
4-2B Populations evolve when genes mutate and give some individuals genetic traits that enhance their
abilities to survive and to produce offspring with these traits (natural selection).
4-3 Tectonic plate movements, volcanic eruptions, earthquakes, and climate change have shifted wildlife
habitats, wiped out large numbers of species, and created opportunities for the evolution of new species.
4-4A As environmental conditions change, the balance between the formation of new species and the
extinction of existing species determines the earth’s biodiversity.
4-4B Human activities are decreasing biodiversity by causing the extinction of many species and by
destroying or degrading habitats needed for the development of new species.
4-5 Species diversity is a major component of biodiversity and tends to increase the sustainability of some
ecosystems.
4-6A Each species plays a specific ecological role called its niche.
4-6B Any given species may play one or more of four important roles—native, nonnative, indicator, or
keystone—in a particular ecosystem.
Key Questions and Case Studies
CORE CASE STUDY: Why Are Amphibians Vanishing?
Amphibians were among the earliest vertebrates to emerge from the earth’s waters and live on land.
Historically, they have been able to adjust to and survive environmental changes more effectively than
any other species. The amphibian world is now changing rapidly. Many scientists believe that the threats
to amphibians present a warning about a number of environmental threats to biodiversity.
4-1 What is biodiversity and why is it important?
A. Biodiversity is the variety of species, genes, ecosystems, and ecosystem processes.
1. Species are individuals that can make and produce viable offspring.
2. Species diversity, genetic diversity, ecosystem diversity, and functional diversity.
a. Biomes are large regions with distinct climates and certain species that are adapted to them.
SCIENCE FOCUS: Insects Play a Vital Role in Our World
Insects often have a bad reputation and are considered pests. However the ecological roles they play
in pollinating flowering plants and controlling other insect populations make them invaluable to
humans.
4-2 How does the earth’s life change over time?
A. Most of what we know of the history of life comes from the fossil record.
B. Evolution is the change in a population’s genetic makeup over time.
C. All species descend from earlier, ancestral species—the theory of evolution.
1. Natural selection occurs when members of a population have genetic traits that improve their
ability to survive and produce offspring with those specific traits.
Instructor's Manual: Chapter 4
CASE STUDY. How Did Humans Become Such a Powerful Species?
Humans have thrived so well as a species because of their strong opposable thumbs, ability to walk
upright and complex brain. These adaptations may not prove as beneficial as the environment
continues to change, though our powerful brain may allow us to live more sustainably in the future.
4. Natural selection can only act on existing genes and is limited by reproductive capacity.
5. Three common misconceptions about evolution:
a. Fitness is a measure of strength.
b. Organisms develop certain traits because they need them.
c. Evolution works according to some grand plan.
4-3 How do geological processes and climate change affect evolution?
A. Processes such as the shifting of tectonic plates, volcanic eruptions, and earthquakes influence
earth’s climate and in turn affect evolution by removing and/or isolating habitats and species.
B. Long-term climate changes relocate ecosystems, thus determining where certain species can live.
C. Asteroids and meteorites have caused environmental stress and mass extinctions.
4-4 How do speciation, extinction, and human activities affect biodiversity?
A. Natural selection can lead to development of an entirely new species.
In speciation, two species arise from one when some members of a population cannot breed with
other members to produce fertile offspring. Speciation occurs in two phases:
1. Geographic isolation: physical separation for long time periods
2. Reproductive isolation
B. When population members cannot adapt to changing environmental conditions, the species
becomes extinct.
1. Endemic species (those found in only one place) are especially vulnerable.
C. When local environmental conditions change, some species will disappear at a low rate; this is
called background extinction.
D. Mass extinction is a significant rise in extinction rates above the background extinction level.
Usually, 25–95% of species are lost. There appear to have been at least three and perhaps five
mass extinctions on the earth.
SCIENCE FOCUS: Changing the Genetic Traits of Populations
Artificial selection involves crossbreeding between genetic varieties of the same species to give rise
to populations with desirable traits. Now, scientists can use genetic engineering to produce desirable
traits or eliminate undesirable ones.
4-5 What is species diversity and why is it important?
A. Species diversity is the number of species (richness) combined with their relative abundance
(evenness).
B. Species rich communities tend to be more stable and more productive.
4-6 What roles do species play in ecosystems?
A. Ecological niche is a species’ way of life in an ecosystem – everything that affects its survival
and reproduction.
B. Some species have broad ecological roles and are termed generalist species.
C. Some species have narrow ecological roles and are termed specialist species.
SCIENCE FOCUS: Scientists Are Searching for the Causes of Amphibian Declines
Herpetologists study amphibians. Some scientists hypothesize viral and fungal diseases are killing
amphibians. Others hypothesize habitat fragmentation, prolonged drought, high levels of UV
radiation, pollution and overhunting.
D. Niches can be occupied by native or non-native species.
Evolution and Biodiversity
E. Indicator species provide early warning of ecosystem damage because they have a narrow range
of tolerance.
H. Keystone species have a large affect on maintaining balance within an ecosystem.
1.
CASE STUDY: The American Alligator—A Keystone Species That Almost Went Extinct
Alligators act as a keystone species, yet their numbers were seriously compromised by over-hunting.
Their activities provide important habitat for fish and avian species. They also control populations
by their feeding behaviors. In 1967 the alligator was placed on the endangered species list and has
made a dramatic recovery.
1. Foundation species create and enhance habitats that benefit other species.
Key Terms
adaptation
adaptive trait
background extinction
biological diversity
biological evolution
differential reproduction
ecological niche
endemic species
extinction
Instructor's Manual: Chapter 4
fossils
foundation species
generalist species
geographic isolation
indicator species
keystone species
mass extinction
mutations
native species
natural selection
niche
nonnative species
reproductive isolation
specialist species
speciation
species
species diversity
theory of evolution