Speciation Speciation in Darwins Finches l Speciation in

Speciation

Speciation in Darwin’s Finches l Speciation in the Galapagos finches occurred by founding of a new population, geographic isolation, changes in the new population’s gene pool, reproductive isolation, and ecological competition.

Founder’s Arrive l Finches from the mainland of South America arrive on the Galapagos islands. l As finches do not usually fly over open water, it is assumed they were blown off course by a storm.

Separation of Populations l As finches do not fly over open water, they remained on whatever island they landed on.

Changes in the Gene Pool l Each island of the Galapagos has its own unique flora and fauna (plants and animals)—the finches slowly adapted to their islands through natural selection.

Species l A species is a group of organisms that breed with one another and produce fertile offspring. l This population will share a common gene pool.

Reproductive Isolation l When members of two populations cannot interbreed and produce fertile offspring,

Behavioral Isolation l Occurs when two populations are capable of interbreeding but have differences in courtship rituals or other reproductive strategies.

Geographic Isolation l Two populations are separated by a geographic barriers such as rivers, mountains, or bodies of water.

Temporal Isolation l Two or more species reproduce at different times.

Ecological Competition l All organisms compete for limited resources. l The finches evolved specialized beaks for particular foods to limit the competition.

Continued Evolution l The process of isolation, genetic change, reproductive isolation, most likely repeated itself over and over again. l As a result, there are 13 different species of Galapagos finches.

Human Evolution

Primates l The evolutionary history of primates began about 85 million years ago. l l Fossils have been found primarily in North America, however they were widespread throughout Eurasia and Africa Notharctus l l Discovered in Germany ~ 16. 5 million years old

Primates to Humans l Nakalipithecus (Kenya) & Ouranopithecus (Greece) Last common ancestors between gorillas, chimpanzees, and humans. l Between 8 -4 mya, chimpanzees and gorillas split from the line leading to humans. l

Becoming Human l Savannah Theory l l l Proposed by Raymond Dart Stated that hominids began to stand on two legs to peer over savannah grasses to hunt and hide from predators. Aquatic Ape Hypothesis l l States that early hominids lived around water and often dove, waded, and swam. Accounts for our lack of hair, subcutaneous fat, and abundance of sebaceous glands.

Hominids l Homo habilis 2. 4 to 1. 4 million years ago (mya) l Found in Africa l Possessed small molars and large brains l Was surrounded by stone and bone tools l Nicknamed “Handy Man” l

Hominids l Homo rudolfensis and Homo georgicus l 1. 9 -1. 6 million years ago l H. rudolfensis l l Incomplete skull found in Kenya. Scientists debate whether this is another species, or another H. habilis H. georgicus l l Found in Georgia (near Russia) Thought to be an intermediate form between H. habilis and H. erectus

Hominids l Homo ergaster and Homo erectus l H. ergaster l l l Discovered in Indonesia 1. 8 -1. 25 mya, seen as a subspecies of H. erectus l l l 1. 5 -1 mya, found in Africa, Asia, and Europe Used elaborate stone tools First human ancestor to truly walk upright May have used fire Peking Man

Hominids l Homo cepranensis and Homo antecessor l l Both thought to be intermediate forms between H. erectus and H. heidelbergensis H. cepranensis l l l 1. 2 mya-500, 000 ya Based on fossils found in Spain and England H. antecessor l l 800, 000 ya Based on a single skull cap found in Italy

Hominids l Homo heidelbergensis lived from 800, 000 ya to 300, 000 ya l Heidelberg Man l

Hominids l Homo rhodesiensis l l l 300, 000 -125, 000 ya—disputed separation from H. Heidelbergensis Rhodesian Man Gawus Cranium l l l Discovered in 2006 in Gawis, Ethiopia 500, 000 -250, 000 ya Might possibly be an intermediate species between H. erectus and H. sapiens

Hominids l Homo neanderthalensis 300, 000 ya to 30, 000 ya l Mitochondrial DNA studies suggest that H. neanderthalensis is a separate species from H. sapiens l Neanderthals are NOT our ancestors l

Hominids l Homo sapiens l l 250, 000 ya to the present Direct evidence suggests we migrated out of Africa However, this does not preclude multiregional speciation H. sapiens idaltu l l Oldest known anatomically modern human 160, 000 years old, found in Ethiopia

Hominids l Homo floresiensis 100, 000 -12, 000 years old l Skeleton of a 30 year old woman found (~18, 000 yo) l l One meter (3 feet) tall l Nicknamed “Hobbit”

Hominids l Homo floresiensis l Separate Species or Homo Sapien? l At first scientists thought that H. florensis was a separate species l Now, they believe that H. floresiensis is a H. sapien that has insular dwarfism l Modern day people on the island of Flores are pygmies