chapter 17 processes of evolution (sections 17.11 - 17.14)
Post on 21-Mar-2016
33 Views
Preview:
DESCRIPTION
TRANSCRIPT
www.cengage.com/biology/starr
Albia Dugger • Miami Dade College
Cecie StarrChristine EversLisa Starr
Chapter 17Processes of Evolution
(Sections 17.11 - 17.14)
17.11 Allopatric Speciation
• In allopatric speciation, a geographic barrier arises and ends gene flow between populations – genetic divergences then give rise to new species
• allopatric speciation • Speciation pattern in which a physical barrier that
separates members of a population ends gene flow between them
Barriers to Reproduction
• Whether a geographic barrier can block gene flow depends on whether and how an organism travels (e.g. by swimming, walking, or flying), and how it reproduces (e.g. by internal fertilization or by pollen dispersal)
• Example:• When the Isthmus of Panama formed, it cut off gene flow
among populations of aquatic organisms in the Pacific and Atlantic oceans
Allopatric Speciation in Snapping Shrimp
Fig. 17.20, p. 272
Isthmus of Panama
Alpheus millsae (Pacific)
Alpheus nuttingi (Atlantic)
Allopatric Speciation in Snapping Shrimp
Fig. 17.20a, p. 272
Isthmus of Panama
Columbia
Atlantic Ocean
Mexico
Pacific Ocean
Allopatric Speciation in Snapping Shrimp
Fig. 17.20b, p. 272
Alpheus nuttingi (Atlantic)
Allopatric Speciation in Snapping Shrimp
Fig. 17.20b, p. 272
Alpheus millsae (Pacific)
Allopatric Speciation in Snapping Shrimp
Speciation in Archipelagos
• Archipelagos are isolated island chains formed by volcanoes, such as the Hawaiian and Galápagos Islands
• Archipelagos were populated by a few individuals of mainland species whose descendants diverged over time
• Selection pressures within and between the islands can foster even more divergences
The Hawaiian Islands
Hawaiian Honeycreepers
• The first birds to colonize the Hawaiian Islands found a near absence of competitors and predators and an abundance of rich and vacant habitats, which encouraged rapid speciation
• The many species of honeycreepers, unique to the Hawaiian Islands, have specialized bills and behaviors adapted to feed on certain insects, seeds, fruits, nectar, or other foods
Honeycreeper Diversity
Fig. 17.21a, p. 273
Akepa (Loxops coccineus)
Insects, spiders, nectar; high mountain rain forest
Honeycreeper Diversity
Fig. 17.21b, p. 273
Akekee (Loxops caeruleirostris)
Insects, spiders, nectar; high mountain rain forest
Honeycreeper Diversity
Fig. 17.21c, p. 273
Nihoa finch (Telespiza ultima)
Insects, buds, seeds, flowers, seabird eggs; rocky or shrubby slopes
Honeycreeper Diversity
Fig. 17.21d, p. 273
Palila Maui (Loxioides bailleui)
Mamane seeds, buds, flowers, berries, insects; high mountain dry forests
Honeycreeper Diversity
Fig. 17.21e, p. 273
Maui parrotbill (Pseudonestor xanthophrys)
Insect larvae, pupae, caterpillars; mountain forests, dense underbrush
Honeycreeper Diversity
Fig. 17.21f, p. 273
Apapane(Himatione sanguinea)
Nectar, caterpillars and other insects, spiders; high mountain forests
Honeycreeper Diversity
Fig. 17.21g, p. 273
Poouli (Melamprosops phaeosoma)
Tree snails, insects in understory; last one died in 2004
Honeycreeper Diversity
Fig. 17.21h, p. 273
Maui Alauahio(Paroreomyza montana)
Bark or leaf insects, high mountain rain forest
Honeycreeper Diversity
Fig. 17.21i, p. 273
Kauai Amakihi (Hemignathus kauaiensis)
Bark-picker; insects, spiders, nectar; high mountain rain forest
Honeycreeper Diversity
Fig. 17.21j, p. 273
Akiapolaau(Hemignathus munroi)
Probes, digs insects from big trees; high mountain rain forest
Honeycreeper Diversity
Fig. 17.21k, p. 273
Akohekohe (Palmeria dolei)
Mostly nectar from flowering trees, some insects, pollen; high mountain rain forest
Honeycreeper Diversity
Fig. 17.21l, p. 273
Iiwi (Vestiaria coccinea)
Mostly nectar (ohia flowers, some nectar; lobelias, mints), some insects; high mountain rain forest
Honeycreeper Diversity
ANIMATION: Allopatric speciation on an archipelago
To play movie you must be in Slide Show ModePC Users: Please wait for content to load, then click to play
Mac Users: CLICK HERE
ANIMATION: Models of speciation
To play movie you must be in Slide Show ModePC Users: Please wait for content to load, then click to play
Mac Users: CLICK HERE
17.12 Sympatric and Parapatric Speciation
• Populations sometimes speciate even without a physical barrier that bars gene flow between them
• In sympatric speciation, populations in physical contact speciate
• With parapatric speciation, populations in contact along a common border speciate
Sympatric Speciation
• Sympatric speciation can occur instantly with a change in chromosome number – many plants are polyploid (e.g. wheat)
• Sympatric speciation can also occur with no change in chromosome number (e.g. mechanically isolated sage plants)
• sympatric speciation • Pattern in which populations inhabiting the same
geographic region speciate in the absence of a physical barrier between them
Sympatric Speciation in Wheat
Fig. 17.22, p. 274
C Emmer probably hybridized with a wild goatgrass having a diploid chromosome number of 14 (two sets of 7 DD). The resulting common bread wheat has six sets of 7 chromosomes (42 AABBDD).
B About 8,000 years ago, the chromo-some number of an AB hybrid plant spontaneouslydoubled. The resulting species, emmer, is tetraploid: it has two sets of 14 chromosomes (28 AABB).
A Einkorn has a diploid chromosome number of 14 (two sets of 7, shown here as 14 AA). Wild einkorn probably hybridized with another wild species having the same chromosome number (14 BB) about 11,000 years ago. The resulting hybrid was diploid (14 AB).
Triticum mono-
coccum (einkorn)
Unknown species of Triticum
spontaneous chromosome doubling T. turgidum
(emmer)T. tauschii (goatgrass)
T. aestivum (common
bread wheat)
42 AABBDD28 AABB14 BB14 AA 14 DD X14 ABX
Sympatric Speciation in Wheat
Examples of Sympatric Speciation
• Lake Victoria cichlids (sexual selection)• In the same lake, female cichlids of different species
visually select and mate with brightly colored males of their own species
• Warblers around the Tibetan plateau (behavioral isolation)• Two populations overlap in range, but don’t interbreed
because they don’t recognize one another’s songs
Male Cichlids of Lake Victoria
Parapatric Speciation
• Parapatric speciation may occur when one population extends across a broad region with diverse habitats
• Example: Two species of velvet walking worm with overlapping habitats in Tasmania: Where they interbreed, their hybrids are sterile
• parapatric speciation • Speciation model in which different selection pressures
lead to divergences within a single population
Comparing Speciation Models
Key Concepts
• How Species Arise• Speciation varies in its details, but it always involves the
end of gene flow between populations• Microevolutionary events that occur independently lead to
genetic divergences, which are reinforced by reproductive isolation
ANIMATION: Sympatric Speciation in Wheat
To play movie you must be in Slide Show ModePC Users: Please wait for content to load, then click to play
Mac Users: CLICK HERE
17.13 Macroevolution
• A central theme of macroevolution is that major evolutionary novelties often stem from the adaptation of an existing structure for a completely different purpose (exaptation)
• exaptation • Adaptation of an existing structure for a completely
different purpose; a major evolutionary novelty
Patterns of Macroevolution
• Macroevolution includes patterns of evolution above the species level, such as one species giving rise to multiple species, origin of major groups, and major extinction events
• Four patterns of macroevolution:• Stasis• Adaptive radiation• Coevolution• Extinction
Stasis
• With the simplest macroevolutionary pattern, stasis, a lineage persists for millions of years with little or no change
• Example: Coelacanths
• stasis • Evolutionary pattern in which a lineage persists with little
or no change over evolutionary time
Coelacanth: Fossil and Living
Mass Extinctions
• More than 99% of all species that ever lived are now extinct
• There have been more than twenty mass extinctions, which are simultaneous losses of many lineages, including five catastrophic events in which the majority of species on Earth disappeared
• extinct • Refers to a species that has been permanently lost
Adaptive Radiation
• In adaptive radiation, a lineage rapidly diversifies into several new species
• Adaptive radiation can occur after individuals colonize a new environment that has a variety of different habitats with few or no competitors (e.g. Hawaiian honeycreepers)
• adaptive radiation • A burst of genetic divergences from a lineage gives rise to
many new species
An Example of Adaptive Radiation
• This evolutionary tree diagram shows how one ancestral species gave rise to the Hawaiian honeycreepers
• Only 41 of many hundreds of species are represented here (orange are extinct)
Adaptive Radiation (cont.)
• Adaptive radiations also occur after geologic or climatic events eliminate some species from a habitat
• Example: Mammals were able to undergo an adaptive radiation after the dinosaurs disappeared
Adaptive Radiation (cont.)
• A key innovation can result in an adaptive radiation, or rapid diversification into new species
• Example: evolution of lungs opened the way for an adaptive radiation of vertebrates on land
• key innovation • An evolutionary adaptation that gives its bearer the
opportunity to exploit a particular environment more efficiently or in a new way
Coevolution
• In coevolution, close ecological interactions between two species cause them to evolve jointly
• Over evolutionary time, two species may become so interdependent that they can no longer survive without one another (e.g. the large blue butterfly (Maculinea arion) and red ant (Myrmica sabuleti))
• coevolution • Joint evolution of two closely interacting species• Each species is a selective agent for traits of the other• Each adapts to changes in the other
Coevolved Species
• The ant eats honey exuded by the butterfly larva and carries it to its nest
• The caterpillar lives in the ant nest and eats ant larvae until it pupates
Evolutionary Theory
• Many biologists disagree about how macroevolution occurs
• Dramatic jumps in morphology may be the result of mutations in homeotic or other regulatory genes
• Macroevolution may be an accumulation of many microevolutionary events, or it may be an entirely different process
Key Concepts
• Macroevolution• Patterns of genetic change that involve more than one
species are called macroevolution• Recurring patterns of macroevolution include the origin of
major groups, one species giving rise to many, and mass extinction
ANIMATION: Adaptation to What?
To play movie you must be in Slide Show ModePC Users: Please wait for content to load, then click to play
Mac Users: CLICK HERE
ANIMATION: Animal evolution in Phyla
To play movie you must be in Slide Show ModePC Users: Please wait for content to load, then click to play
Mac Users: CLICK HERE
ANIMATION: Evolution of Horses
To play movie you must be in Slide Show ModePC Users: Please wait for content to load, then click to play
Mac Users: CLICK HERE
17.14 Phylogeny
• Instead of trying to divide the diversity of living organisms into a series of taxonomic ranks, most biologists are now focusing on evolutionary connections
• Cladistics allows us to reconstruct evolutionary history (phylogeny) by grouping species on the basis of their shared characters
Key Terms
• phylogeny• Evolutionary history of a species or group of species
• cladistics • Method of determining evolutionary relationships by
grouping species into clades based on shared characters
• character • Quantifiable, heritable characteristic—any physical,
behavioral, physiological, or molecular trait of a species
Examples of Characters
Ranking Versus Grouping
• The result of a cladistic analysis is a cladogram, a type of evolutionary tree used to visualize evolutionary patterns
• Each line represents a lineage, which may branch into two sister groups at a node, which represents a shared ancestor
• Every branch ends with a clade, a species or group based on a set of shares characters
• Ideally, each clade is a monophyletic group that comprises an ancestor and all of its descendants
Key Terms
• evolutionary tree • Type of diagram that summarizes evolutionary
relationships among a group of species
• cladogram• Evolutionary tree that shows a network of evolutionary
relationships among clades
• clade • A species or group of species that share a set of
characters
Key Terms
• sister groups • The two lineages that emerge from a node on a cladogram
• monophyletic group• An ancestor and all of its descendants
Cladograms
Fig. 17.27, p. 278
earthworm
multicellular with a backbone, legs, and fur or hair
multicellular with a backbone and legs
multicellular with a backbone
multicellular
A human
mouse
lizard
tuna
B
earthworm
human
mouse
lizard
tuna
Cladograms
ANIMATION: Interpreting a cladogram
To play movie you must be in Slide Show ModePC Users: Please wait for content to load, then click to play
Mac Users: CLICK HERE
How We Use Evolutionary Biology
• Hawaiian honeycreepers illustrate how evolution works:• Isolation that spurred honeycreepers’ adaptive radiations
also ensured they had no built-in defenses against predators or diseases from the mainland
• Specializations became hindrances when habitats suddenly changed or disappeared
• At least 43 species of honeycreeper that thrived on the islands before humans arrived were extinct by 1778 -- today, 32 of the remaining 71 species are endangered, and 26 are extinct
Going, Going, and Gone
• Destruction of food sources and avian malaria decimated the palila and akekee
• The poouli is probably now extinct
Key Concepts
• Cladistics• Evolutionary tree diagrams are based on the premise that
all species interconnect through shared ancestors• Grouping species by shared ancestry better reflects
evolutionary history than do traditional ranking systems
Rise of the Super Rats (revisited)
• The allele that makes rats resistant to warfarin is adaptive when warfarin is present, and maladaptive when it is not
• Periodic exposure to warfarin maintains a balanced polymorphism of the resistance gene in rat populations
top related