Download Evolutionary Patterns Guided Notes

Name ___________________________________________
Period _____ Date __________
Evolutionary Patterns, Rates, and Trends
Reproductive Isolation, Maybe New Species
 ________________ is a macroevolutionary process.
 It starts when a population becomes ________________________________ from others of the species and ends
when daughter species have formed.
What is a New Species?
 A species is…
 one or more groups of individuals that
________________, produce fertile
________________, and are reproductively
________________ from other such groups.
 Many organisms have variations in traits,
can thrive in different environments, and
may even have different appearances but
be part of the same species.
Reproductive Isolating Mechanisms
 Gene flow is the movement of alleles into and out of a population.
 Speciation begins when ________________, or the potential for it, ________________ between natural populations.
 Once it stops, gene pools start to change and populations undergo genetic divergence, because mutation,
natural selection, and genetic drift are free to operate independently in each one.
 There are six main types of isolating mechanisms:
 Mechanical Isolation
 Temporal Isolation
 Behavioral Isolation
 Ecological Isolation
 Gamete Isolation
 Geographic Isolation
Mechanical Isolation
 This is when the ________________ of a species are ________________ a physical
________________ with those of a species that could otherwise serve as a mate or pollinator.
Temporal Isolation
 This is when reproductive ________________________________, as when one organism is fertile in the
fall and the other in the spring.
 Cicada species that differ in form and behavior often live in the same habitat in the eastern United
States.
 They all mature underground and feed on juicy roots, emerging every 17 years to
reproduce.
 There is a sibling species of similar form and behavior that emerges every 13 years.
 That means that the two species will not meet except once every 221 years.
Behavioral Isolation
 Behavioral differences ________________________________ between related species.
 Before male and female birds copulate, they may engage in courtship displays.
 A female bird is genetically prewired to recognize singing, wing spreading, prancing, or
head bobbing of a male of her species as an overture to sex.
 Females of different species usually do not.
Ecological Isolation
 Populations occupying ________________________________________________ may be ecologically
isolated.
 Two manzanita species live in seasonally dry foothills of the Sierra Nevada,
one at elevations between 600 and 1850 meters, the other between 750 and
3350 meters.
 They hybridize rarely, and only where the two ranges overlap.
Gamete Isolation
 Gametes of different species may have ________________________________.
 For example: if pollen lands on a plant of another species, it usually does not
respond to the plant’s molecular signals to germinate.
 Unsuitable interactions among genes or gene products can cause early
death, sterility, or weak hybrids with low survival rates.
 Certain hybrids are sturdy, but sterile.
 Mules, which are the offspring of a female horse and
male donkey, are infertile hybrids.
The Main Model for Speciation
 The genetic changes leading to a new species usually begin with
________________________________ between populations.
 This is called ________________ speciation.
Start With Geographic Isolation
 In allopatric speciation, ________________________________ stop
________________________________ among populations or subpopulations of a species.
 These physical barriers can come from sudden earthquakes that re-route waterways, or
through the movement of glaciers, or even the slow colossal movements of entire
continents.
 In any case, the now separated groups of organisms can
________________________________________________ one another.
 In both groups, reproductive isolating mechanisms develop.
 In time, speciation is complete and interbreeding is no longer possible
even if daughter species come into contact with one another.
Isolation Within the Home Range
 With ________________________________ speciation, a species may form within the home
range of an existing species, in the absence of a physical barrier.
 This may happen when a species ________________, ________________, or
________________ preferences are dramatically different.
 Evidence from Cichlids in Africa
 When Cichlids from Barombi Mbo lake (a small crater lake in Africa) were genetically tested, it
showed that there were eleven separate species of cichlids.
 There are no barriers to separate the species, and chemical conditions are the same
throughout the lake.
 However, there is feeding separation (ecological isolation).
 Some cichlids feed in open waters, some at the lake bottom.
 This may have lead to their speciation.
Isolation at Hybrid Zones
 ________________________________ speciation occurs when ________________
selective ________________ affect populations that are in contact along a
________________________________.
 Hybrids that form in the ________________________________ are less fit
than individuals on either side of it, and appear in the hybrid zone only.
Gradual Model of Speciation
 This model holds that species originate by ________________________________
changes over long time spans.
 The model fits with many fossil sequences.
 Vertical sequences of fossils can reflect gradual morphological change.
Punctuation Model of Speciation
 This model holds that many morphological changes happen during
________________________________________________, followed by long periods of ________________.
 The fossil record shows that stability prevails for all but 1% of the history of most species, followed by abrupt
changes.
 Both models are ________________.
 Changes have been gradual, abrupt, or both.
 Species originated at different times and have differed in how long they last.
 Some did not change much over millions of years, others were the start of adaptive radiations.
Convergent Evolution
Different species must often adapt to similar environments.
▫ Evolution toward ________________ characteristics in
________________ species is called convergent evolution.
 The giant armadillo, the giant pangolin, the giant anteater, and
the spiny anteater, all live in similar environments across the
world, and have evolved similar characteristics.
Divergent Evolution
•
 When ________________________________ species evolve in ________________
directions, they become increasingly different through divergent evolution.
 Though closely related, the two species have different appearances that have resulted
from adapting to different environments.
Coevolution
Coevolution is the process by which ________________________________ evolve in
________________ to changes in each other
▫ Example:
 The bull-thorn acacia is a plant species with branches covered in hollow thorns.
 Although the thorns protect the plant from being eaten by large animals, small herbivores such as
caterpillars can fit between them.
 Stinging ants live inside the thorns and feed on the plant’s nectar.
 The ants protect the plant by stinging animals that try to eat the leaves.
• Although the relationship between the bull-thorn acacia and ants may
seem like simple cooperation, it is much more than that.
▫ The acacia and ants share an evolutionary history.
▫ The hollow thorns and nectar producing leaves of the acacia
and the stinging of the ants have evolved due to the
relationship between the two species.
 Close relatives of these species that are not
involved in this type of relationship do not have
these traits.
Evolutionary Arms Race
•
•
•
Coevolution can also occur in ________________________________ relationships.
Evolutionary arms races are situations in which each species responds to pressure from the other through better adaptations
through many generations.
▫ For example

The thick shells and spines of murex snails are an adaptive response to predation by crabs. In turn, crabs
have evolved powerful claws strong enough to crack the snail’s shells.
Adaptive Radiations
 An adaptive radiation is a burst of ________________ from a ________________________________ that leads to many
new species.
 This is the pattern that gave rise to the family of Hawaiian honeycreepers.
 It requires adaptive zones, or a set of niches that come to be filled by a group of related species.
 A species may take ________________ of ________________ or ________________ niches or develop a
key innovation.
 A ________________________________ is a
chance modification in some body structure or
function that gives an organism the opportunity
to exploit the environment more efficiently or in
a novel way.
 Once a species has entered an adaptive zone,
it can give rise to other species.
The Inviting Archipelagos
 An archipelago is an island chain some distance from a continent.
 The islands are only the tops of volcanoes that starting
building up on the seafloor, which in time broke the
surface of the ocean.
 Winds or currents may carry a few individuals
from the mainland to such islands.
 ________________ and selection
________________ differ within and
between these islands, so allopatric
________________ occurs.
 The big island of Hawaii formed less than 1 million years ago, and its habitats range from old lava beds, rain forests, and
grasslands to snow-capped volcanoes.
 The first birds to colonize it found a buffet of fruits, seeds, nectars, tasty insects, and few competitors.
 This absence of competition spurred rapid speciation.
 The Hawaiian islands combined make up less than 2% of the world’s land masses, but they are the
original home of 40% of all species of fruit flies.
Extinctions—The End of the Line
 Extinctions are the ________________________________ of a
species.
 By some estimates, more than 99% of all species that
ever lived are extinct.
 ________________ extinctions are on-going, smallscale extinctions.
 For example: The Tasmanian tiger.
 ________________ extinctions are catastrophic
losses of entire families or other major groups.