Chapter 16 The Origin of Species

“Species” Definitions: Pre-Darwin: –_______________ of organisms (based on appearance) Biological species concept: –Species are groups of actually or potentially ___________________________, which are reproductively isolated from other such groups. –Appearance Can Be Misleading

Appearance Can Be Misleading Same species? –Cordilleran flycatcher and Pacific slope flycatcher –They __________

Appearance Can Be Misleading Same species? –The myrtle warbler and Audubon’s warbler used to be classified as different species –__________ where their ranges overlap

Species Limitations of species definition –_________reproducing organisms or ______ –Often _______ to observe whether members of two different groups interbreed

Speciation Process by which new species form. It depends on 2 factors: –A. __________ –B. __________ __________ When populations are isolated, gene flow between them is __________ Isolated populations subsequently _____ genetic differences large enough to prevent interbreeding –Differences arise by _______ (genetic drift) or through __________ __________

Hypothetical mechanisms of speciation: __________ speciation occurs when two populations of a species become separated by a __________ barrier –Colonization of remote ______ by mainland organisms –__________________ such as volcanism, earthquakes, continental drift, and rivers changing course –speciation occurs when isolated populations diverge __________

Allopatric Speciation Is believed to be the ___________ type of speciation, especially among animals Two allopatric populations, the Kaibab squirrel and Abert’s squirrel, may be evolving into two separate species

Hypothetical mechanisms of speciation: __________ speciation occurs when –Two populations of a species living in the same geographical area become _______ to different _________ –Isolated populations __________

Sympatric Speciation Two sympatric populations of fruit flies (Rhagoletis pomonella) may be evolving into two separate species. –One population lays its eggs in _______ fruit, while the other prefers __________ –The two populations experience very little interbreeding –Males and females prefer the same type of fruit in which they developed –Apples mature two or three weeks ____ than hawthorn fruit (flies mature and mate at different times)

New Species Mechanisms of speciation and reproductive isolation lead to _______ branches in the __________ _____ of life, as one species splits into two

Adaptive Radiation Adaptive radiation is the rise of _____ __________ over a relatively _____ period of time

Adaptive Radiation Occurs when populations of one species invade a variety of __________ –Cichlid fish colonization of Lake Malawi –__________ in the Galapagos Islands

Adaptive Radiation –Tarweed plant colonization of the Hawaiian Islands

Maintenance of Reproductive Isolation Between Species __________ isolating mechanisms (prevents the mating between 2 organisms) –__________ isolation –__________ isolation. –__________ isolation –__________ incompatibility

Premating Isolating Mechanisms __________ isolation occurs when populations cannot mate because of physical barriers –In nature, lions do not mate with tigers Lions live in __________ Savanna Tigers live in __________ lands.

Premating Isolating Mechanisms …Geographical isolation Kaibab and Abert squirrels; in different areas of the Grand Canyon. Very similar, but have they diverged?

Premating Isolating Mechanisms __________ isolation occurs when species might live in the _____ area, but use different __________ of the habitat: –White-crowned sparrows inhabit fields and meadows, while white-throated sparrows inhabit __________

Premating Isolating Mechanisms …Ecological isolation –Each species of fig wasp breeds in the fruits of a particular species of fig

Premating Isolating Mechanisms _________ isolation occurs when species can’t mate because they _____ at ______ __________ In nature, Bishop pines and Monterey pines do not interbreed –Bishop pine pollination occurs in summer –Monterey pine pollination occurs in early spring

Premating Isolating Mechanisms __________ isolation occurs when species can’t mate because they have different courtship and mating rituals ____ and ________ of male songbirds are species specific –Attract females of the same species –Females of other species are unresponsive

Premating Isolating Mechanisms …Behavioral isolation Male frogs embrace ___ female regardless of species –Female frogs encountering males of a different species utter the “_______ call”

Premating Isolating Mechanisms Mechanical incompatibility. In plants or animals: Size or ________ of reproductive organs __________. –e.g., snails of species whose shells have left- handed spirals may be unable to successfully copulate with snails whose shells have right-handed spirals

Maintenance of Reproductive Isolation Between Species __________ isolating mechanisms (prevents the production of vigorous and fertile offspring) –__________ incompatibility –Hybrid __________

Postmating Isolating Mechanisms __________ incompatibility occurs when sperm from one species __________ eggs of another –In animals, fluids of the female reproductive tract my ________ or __________ of another species –In plants, ______ from one species may ____ to __________ when it lands on the stigma of another species

Postmating Isolating Mechanisms Hybrid __________ occurs when hybrid offspring ________________ to maturity Hybrid may _______ early in development Hybrid may be unable to reproduce because it display behaviors that are __________ of the two parental types –Lovebird hybrids have great difficulty learning to carry nest materials during flight

Postmating Isolating Mechanisms Hybrid __________ occurs when hybrid offspring are ______ or have reduced _____ Horse + donkey  sterile __________ Lion + tiger  sterile __________ Infertility is caused by the failure of chromosomes to _____ properly during _______, so eggs and sperm never develop

R.M.L. Lulu born Very active Bay with black legs, mane and tail. Molly Mule Foal. Very good conformation. Mother is dark brown/black quarter horse mare, 15-1 hands. Sire is Knute's Centinela Gomez Black Catalonian Mammoth Jack, 14.2 Hands. $1,650.00

Ligers Ecological isolation: liger only in captivity

Extinction Extinction is the ______________ __________ ______ At least ____% of all species that ever existed are now extinct Factors that can cause extinction: –__________ Distribution –__________ –Competition for __________ __________ –________ __________ (living and non-living)

Localized Distribution Species inhabiting extremely limited ranges may become extinct if the area is __________ –Devil’s Hole pupfish is found in only one spring-fed water hole in the Nevada desert

Overspecialization Species that develop __________ that favor survival in a _________ __________ are at risk of becoming extinct –The Karner blue butterfly feeds ___ on the blue lupine plant –Lupine’s habitat is now reduced. –Loss of the lupine will lead to extinction of the Karner blue butterfly

Competition Among Species Species that are __________ to exploit __________ more efficiently and effectively than their competitors may become extinct After formation of land bridge between North and South America 2.5 million years ago, many species in South America were displaced and became extinct.

Habitat Destruction Habitat destruction is the single _______________ of extinction ______ activities are the primary cause of present-day habitat destruction –Clearing of tropical rainforests could lead to loss of up to half of all current species over the next ___years The Ethiopian wolf - the most endangered canid in the world - faces a variety of threats due to conflict with Ethiopia's ever-expanding human population. The EWCP works with local herders and communities to reduce conflict with livestock, protect wolves from hunting, and to reduce disease transfer from, and inbreeding with, local domestic dogs. With only an estimated Ethiopian wolves left in a few isolated populations throughout the country, research and community involvement are crucial to the survival of this unique wolf.

Other notes on speciation 1. Polyploidy in plants can lead to speciation fertilization meiosis meiosis fails; no viable gametes viable, diploid gametes Case 1: Self- fertilization Case 2: Breeds with normal diploid parent meiosis Speciation by polyploidy