Speciation

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

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

Changes in the Gene Pool 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 A species is a group of organisms that breed with one another and produce fertile offspring. This population will share a common gene pool.

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

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

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

Temporal Isolation Two or more species reproduce at different times.

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

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

Human Evolution

Primates The evolutionary history of primates began about 85 million years ago. Fossils have been found primarily in North America, however they were widespread throughout Eurasia and Africa Notharctus Discovered in Germany ~ 16.5 million years old

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

Becoming Human Savannah Theory Aquatic Ape Hypothesis 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 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 Homo habilis 2.4 to 1.4 million years ago (mya) Found in Africa Possessed small molars and large brains Was surrounded by stone and bone tools Nicknamed “Handy Man”

Hominids Homo rudolfensis and Homo georgicus 1.9-1.6 million years ago H. rudolfensis Incomplete skull found in Kenya. Scientists debate whether this is another species, or another H. habilis H. georgicus Found in Georgia (near Russia) Thought to be an intermediate form between H. habilis and H. erectus

Hominids Homo ergaster and Homo erectus H. ergaster H. erectus Discovered in Indonesia 1.8-1.25 mya, seen as a subspecies of H. erectus H. erectus 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 Homo cepranensis and Homo antecessor Both thought to be intermediate forms between H. erectus and H. heidelbergensis H. cepranensis 1.2 mya-500,000 ya Based on fossils found in Spain and England H. antecessor 800,000 ya Based on a single skull cap found in Italy

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

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

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

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

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

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