BSCI 124 Lecture Notes
Undergraduate Program in Plant Biology, University of Maryland
LECTURE 14 - ADAPTATIONS
I.
Definitions:
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A. Adaptation: the process by which genetic changes occur
B. Microevolution: genetic changes at the population level
C. Speciation: the successful divergence of populations into independent,
reproductive distinct kinds the consequence of microevolutionary processes
D. Macroevolution: broad, major patters of evolutionary changes in species,
genera, and families coupled with changes in the environment the consequence
of speciation events
II. Adaptations occur as a result of an increase in those genes that
allow individuals in a population to better survive and reproduce in a changing
environment
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A. Natural selection is the processes where, as a result of a number of factors
(e.g., environment, size of population, types of reproduction, etc.), individuals
with a particular genotype has a rate of reproductive success greater than
other individuals with different genotypes in the same population
B. Artificial selection is the process whereby human, for a particular reason
(color, size, shape, etc.) differentially select individuals with the desired
characteristics
C. The study of evolution is thus a study of adaptation.
III. Universality of adaptations
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A. Life occurs essentially everywhere on and in the earth
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1. Microorganisms dwell well within the earth s crust, in boiling water of
thermal springs, inside other organisms, and from the depths of the oceans
to the highest elevations on earth
2. Algae and fungi occur in an equally broad array of habitats, in glaciers,
inside rocks, on deserts and in the tropics
3. Higher plants, such as the mosses, ferns, gymnosperms and flowering plants,
are less broadly distributed but occur from the margins of the oceans to
the highest mountains
B. Each organism is adapted to its own niche (e.g., place in the environment)
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1. Adaptation to a particular niche is the result of natural selection
2. Numerous complexes of adaptations for performing life functions is required
for any organism to exist, survive, adapt and evolve, via speciation processes,
into new and different kinds capable of surviving an every changing environment
- read about
carnivorous
plants, an unusual form of adaptation, and
desert plants, and
adaptation to hot and dry conditions
C. Without adaptations species might become extinct
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1. Change is never ending in a biological world
2. Change is constantly occurring on the earth
3. Without change and a multitude of resulting environmental niches, life
on earth would be reduced to a single kind
4. Change drives evolution
IV. Adaptation and Heredity
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A. All organisms response to changes in their environment
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1. Individuals respond in a wide variety of ways, most unsuccessfully
2. Populations respond more generally, most successfully
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a. Genotype: all of the genes of an organism; determines the general parameters
within which the organism may adapt
b. The course of development is influenced by the environment
c. Phenotype: the morphological and/or physiological features that are the
result of environmental influences
B. Phenotypic variation
C. Genotypic variation
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1. Variation due to differences in genes among individuals in a population
2. Populations often have differ sets of genes
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a. Some organisms have exceedingly little genotypic variation (cheetah
essentially no variation in the entire species)
b. Other exceedingly variable (individual plants of desert gold (Dedeckera
eurekensis) share less than 70% of their genes
D. Population Genetics
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1. Darwin was not aware of genetics; early evolutionist ignored genetics
until the 1920s
2. R.A. Fisher (1890-1962), J.B.S. Haldane (1892-1964) and Sewall Wright
(1889-1988) formulated mathematical theories on how alleles behave in
populations
3. They defined adaptation as an increase in fitness of an organism to a
particular environment; this was expressed with an increase in the number
of offspring with a particular advantageous genotype
V. Causes for Change in Populations
VI. Examples of Adaptation
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A. Perdation
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1. Desert plants, often a source of water, frequently are armed with thorns
or spines to retard grazing
2. The growth point of grasses is at the base of the plant rather that at
the tips of branches as in most plants
3. Specialized leaves of tropical plants often are the homes of ants; the
ants raise aphids on the plant (aphids are insects that produce sugar as
a by-product) and attack any grazing animal (or plant collector) who might
disturb the plant
4. The fruits of the
persimmon are readily edible by numerous animals late in the season when
the seed is fully mature; prior to that the fruit is highly astringent. Think
of the sour taste of an unripe/non-mature blackberry, or blueberry.
B. Coloration
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1. The pepper moth (Biston betularia) of Europe became darker during
the industrial revolution as a fine layer of coal dust covered tree trunks
where the moth rested during the day, the whitish color against the darker
background allow birds to more readily find the moth. Since the advent of
modern pollution control equipment, the coal dust has disappeared and the
moths are becoming lighter in color
2. Different flower colors attract different classes of pollinators; red-flowered
Indian paintbrushes (Castilleja) tend to be visited by butterflies
and hummingbirds whereas those with brownish-yellow flowers tend to be visited
by bees and ants.
C. Morphology
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1. Strawberries have underground stems ("stolons") which readily break so
that a new plant can result from just a portion of the parent plant (asexual
reproduction)
2. Leaves of desert plants are often hairy (to reduce water loss) whereas
those in the tropics are mostly smooth; likewise fruits in temperate regions
tend to be hard (nuts, acorns) whereas those of the tropics are often fleshy
(banana)
3. Flowers tend to be large and solitary in tropical plants; smaller and
more numerous in temperate regions
4. Flowers of the desert centaury (Centaurium exaltatum) are essentially
identical to those of the Great Basin centaury (C. namophilum var.
nevadense), and both grow together around small pools of water in
Nevada. Both are pollinated by the same bee, yet they remain distinct as
the former has 34 chromosomes and the latter has 80 chromosome.
VII. Coevolution
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A. Definition:
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1. "The long-term evolutionary adjustment of one group of organisms to another"
Raven & Johnson; "a reciprocal process in which characteristics of one
organism evolve in response to specific characteristics of another" Moore
et al.
2. Criteria for coevolution
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a. Traits involved in both organism are genetically based
b. Variation of these traits vary in a tandem pattern in both organism
c. Traits and variation are mutually induced
3. Kinds of coevolution
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a. Gene-for-gene: host and parasite have complementary genes
b. Specific: two interacting species, as in mimicry
c. Guild: Coevolution among a group of interacting species in the same
environment (e.g., succulent plants such as New World cacti and Old World
euphorbs)
d. Sequential: One species adapts and becomes dependent upon another, but
the latter s evolution is not impacted by the actions of the former (e.g.,
butterflies on certain plants).
B. Examples:
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1. Of a: Moth &
Yucca and ants
& Acacia
2. Of b: Bluejays and monarch & viceroy butterflies
3. Of c: Columnar cacti and arborescent euphorbs
4. Of d: Eriogonum (wild buckwheat, a plant) and Euphilotes
(blues, the butterfly)
VIII. Symbiosis
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A. Definition: The intimate association of two species, living together in
a relationship that can be beneficial to one or both organisms
B. Examples:
NOTE: While there are no required readings for this lecture, students
are strongly encouraged to review the two items listed below.
Other important sites
Predation
and competition
Interaction
between organisms
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Delwiche Last revised:July 19, 1999