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G. Tyler Miller’s
Living in the Environment
13th Edition
Evolution and Biodiversity:
Origins, Niches, and Adaptations
Chapter 5
Evolution and Adaptation
Natural selection
• Process in by which individuals of a population acquire
genetically based traits that increase their chances of
survival and their ability to produce offspring.
Adaptation (n.)
– A heritable trait that enables an organism to better
survive and reproduce under a given set of
environmental conditions
Artificial selection
• Humans select one or more desirable genetic traits in
the population of a plant or animal.
Natural Selection
Conditions necessary for natural
selection:
– variability
– heritability
– differential reproduction
Fig. 5-5 p. 101
Climate Change and Natural
Selection
• Changes in climate throughout the earth’s history
have shifted where plants and animals can live.
Figure 4-6
Limits on Adaptation through
Natural Selection
• A population’s ability to adapt to new
environmental conditions through natural
selection is limited by its gene pool and how
fast it can reproduce.
– Humans have a relatively slow generation time
(decades) and output (# of young) versus some
other species.
Evolution and Adaptation
• Co-Evolution
– Populations of two different species
interacting over a long period of time
– Changes in the gene pool of of one species
changes the gene pool of another species
• Predator-Prey Relationships
• Plant defense mechanisms
Ecological Niches and Adaptation
Occupation
• Ecological niche
– Total way of life or functional role of a
species in an ecosystem.
Address
• Habitat
– Physical location of a species
Ecological Niches and Adaptation
• Fundamental niche
– Full potential range of the physical, chemical,
and biological factors a species can use if
there were no direct competition from other
species.
• Realized niche
– Part of a species fundamental niche that are
actually used.
Broad and Narrow Niches
• Generalist species
– Species with a broad ecological niche.
• Live in many different places.
• Eat a variety of food.
• Tolerate a wide range of environmental conditions.
(flies, mice, deer, catfish, humans)
• Specialist species
– Species with a narrow ecological niche.
• Live only in one type of habitat
• Use only a few types of food
• Tolerate only a narrow range of climatic and other
environmental conditions.
(tiger salamander, red-cockaded woodpecker,
spotted owls, pandas)
Generalist and Specialist Species:
Broad and Narrow Niches
• Generalist
species
tolerate a
wide range of
conditions.
• Specialist
species can
only tolerate a
narrow range
of conditions.
Speciation, Extinction, and Biodiversity
Speciation - formation of two species
from one species because of
divergent natural selection
1) Geographic isolation – groups
of the same species become
physically separated
Geographic Isolation
…can lead to reproductive isolation, divergence
of gene pools and speciation.
Speciation, Extinction, and Biodiversity
2) Reproductive Isolation – isolated
populations become so genetically
different they cannot . . .
Interbreed, or
produce live, fertile offspring
Extinction: Lights Out
• Extinction occurs
when the
population
cannot adapt to
changing
environmental
conditions.
The
golden toad of Costa Rica’s
Monteverde cloud forest has
become extinct because of
changes in climate.
Figure 4-11
Extinction: Lights Out
• 99.9 % of all
species that
ever existed
are now
extinct
Figure 4-11
How do speciation and
extinction affect biodiversity?
Speciation – Extinction =
Biodiversity
Effects of Humans on Biodiversity
• The scientific consensus is that human activities
are decreasing the earth’s biodiversity.