Species and Speciation BIOL 1407. Biological Species Concept A group of organisms that can...
-
Upload
hector-pierce -
Category
Documents
-
view
217 -
download
0
Transcript of Species and Speciation BIOL 1407. Biological Species Concept A group of organisms that can...
Species and Speciation
BIOL 1407
Biological Species Concept
• A group of organisms that can interbreed and produce viable, fertile offspring
• Photo Credit of Galápagos Marine Iguanas: Putneymark, 2008, Wikimedia Commons
Biological Species Concept
• Assumes – Common
characteristics – Genetically compatible– Interbreed under
natural conditions– Sexual Reproduction
• Photo Credit of Iguana iguana: Ianare, 2007, Wikimedia Commons
Drawbacks of Biological Species Concept
• Cannot be used with exclusively asexual organisms – Prokaryotes– Amoeba & some
other protists– Some animals,
plants & fungi• Photo Credit of Amoeba proteus: Angel, BIOL 1407
student, fall 2008
Drawbacks: Isolated Populations
• How do you test for interbreeding under natural conditions?
• Can a deer in Florida interbreed with one in Wisconsin?
• Photo Credit of Key Deer: Scott Bauer, 2006, USDA• Photo Credit of Deer Running: Paul Frank, 2006, USFWS
Drawbacks
• Can a Great Dane interbreed with a Chihuahua?
• Photo Credit: David Shankbone, 2006, Wikimedia Commons
Drawbacks• Some species look
and behave differently
• Can interbreed and have viable, fertile offspring
• Example: coyotes, wolves, dogs
• Picture Credits: Courtesy of Smithsonian National Zoo @ nationalzoo.si.edu (coyote and wolf); Pam Wolfe (dog)
Drawbacks:Horizontal Gene Transfer
• Vertical gene transfer Parents offspring
• Horizontal gene transfer Individual individualNot parent-offspring
• Diagram Credit: Gregorius Pilosus, 2009, Wikimedia Commons
Horizontal Gene Transfer
• Can occur between organisms:– Different species – Different kingdoms– Different domains
• Diagram Credit: Barth F. Smets, Ph.D., with permission, 2005, Wikimedia Commons
Horizontal Gene Transfer in Bacteria
(1) Transformation
Horizontal Gene Transfer
in Bacteria
(2) Transduction
Horizontal Gene Transfer in Bacteria
(3) Conjugation
Horizontal Gene Transfer
• E. coli 0157:H7 has picked up Shiga toxin gene from Shigella
• Up to 25% genetic difference among E. coli strains
• Photo Credit of E. coli 0157:H7: E. H. White, Centers for Disease Control, 1995, Wikimedia Commons
Horizontal Gene Transfer
• Normally, 25% genetic diversity different species
• Human and chimp genomes differ by only 1.2%
• Photo Credit: Thomas Lersch, 2005, Wikimedia Commons
Drawbacks: Fossil Species
• Cannot tell if fossil organisms were capable of interbreeding
• Photo Credit of Harlan’s Ground Sloth: Doyle Cross, 2006, UT Memorial Museum
Fossils
• Normally can’t compare genes of different fossil species
Morphological Species Concept
• Group of individuals that share common characteristics
• Used for:• Fossils • Exclusively asexual• Traditional method
for sexual organisms• Photo Credit of Orchid: Bernd Haynold, 2004, Wikimedia
Commons
Biological Species Concept:Reproductive Isolation
• Barriers between species• Prevent viable fertile
offspring• Photo Credit (Lesser Bird of Paradise): Roderick Eime, 2005; (Greater
Bird of Paradise): Andrea Lawardi, 2008, Wikimedia Commons
Reproductive Isolating Mechanisms
• Prezygotic mechanisms – Before fertilization
• Postzygotic mechanisms – After fertilization
Prezygotic Mechanisms
• Prevents: – Prevent mating from
occurring – Prevents gametes
from forming a zygote
• Photo Credit for Sperm fertilizing an ovum: Wikimedia Commons, 2008
Prezygotic Mechanisms: Temporal Isolation
• Isolated by time• May breed:
– Different times of day– Different seasons – Different years
• Photo Credit: Alan Zomerfeld, 2006, Wikimedia Commons
Temporal Isolation
Late Winter Late Summer
Prezygotic Mechanisms: Habitat Isolation
• Same geographic area• Different habitats
Prezygotic Mechanisms: Behavioral Isolation
• Different courtship rituals
• Blue-Footed Booby Video: http://www.youtube.com/watch?v=4MPfTzXEZdY
• Photo Credit: Richard001, 2007, Wikimedia Commons
Behavioral IsolationEastern and Western Meadowlarks
• Isolated by Songs• Listen to both species (Links to songs are below the picture):• http://www.lewis-clark.org/content/content-article.asp?ArticleID=401
Prezygotic Mechanisms: Mechanical Isolation
• Structural differences prevent mating
• Example:
Genital openings (arrows) not aligned No Mating
Prezygotic Mechanisms: Gametic Isolation
• Sperm cannot fertilize eggs
• Very important in aquatic species (broadcast spawners)
• Example: Sea Urchins
Postzygotic Mechanisms
• Prevents hybrid zygotes from developing into viable, fertile adults
• Photo Credit of Zeedonk: Ondrejk, 2004, Wikimedia Commons
Postzygotic Mechanism: Reduced Hybrid Viability
• If Sheep and goats mate Hybrid zygotes
• Die before birth.• Photo Credit: Missouri NRCS Photo
Gallery
Postzygotic Mechanism: Reduced Hybrid Fertility
• Male donkey x Female horse Mule
• Mules:– Healthy (viable)– Sterile.
Postzygotic Mechanism: Hybrid Breakdown
• First generation hybrids are viable and fertile.
• Offspring of hybrids are feeble or sterile.
Speciation
• Process of species formation
• Two main mechanisms:
– Allopatric speciation
– Sympatric speciation
Allopatric Speciation
Geographic separation Genetic
exchange Populations
become genetically different
Reproductive isolation
Sympatric Speciation
• Populations not geographically separated
• Can be due to rapid genetic changes:– Alter morphology – Alter behavior– Alter habitat
preferences
Example: Sympatric Speciation
• Euhadra snails• Mutation in one
gene Shell spirals in opposite direction
• Instant mechanical isolation
Two species
Adaptive Radiation
• A common ancestor Many new species
• Relatively rapid• Common in island
chains– Isolated– Numerous habitats &
resources• Map Credit: M. Minderhoud, 2006, Wikimedia Commons
Galápagos Finches
• Ancestral finch from South America Several finch species– Different diets– Different beak
shapes – Different beak sizes
Galápagos Finches
Hawaiian Silverswords
• Tarweed arrived from North America ~ 5 mya
• Common ancestor Silverswords
• Map Credit: M. Minderhoud, 2006, Wikimedia Commons
Hawaiian Silverswords
The End
Unless otherwise specified, all images in this presentation came from:
Campbell, et al. 2008. Biology, 8th ed. Pearson Benjamin Cummings.