Evolution in Action

What is a Species?

• Morphological definition – a species is defined by its structure and appearance

• Biological definition – a species is defined by whether or not a population of organisms

that can interbreed, or not with other groups(& produce fertile offspring). This was proposed by Biologist Ernst Mayr in 1942.

Modern definition of species includes components of both morphological and biological definitions.

Is the Red Wolf a Separate Species (from Glenco: Biology, The Dynamics of Life)

• The red wolf (Canis rufus) can breed with the coyote (Canis lantrans) and the gray wolf (Canis lupus). Despite this fact, the three animal types have been classified as separate species.

• The red wolf skull is midway between gray wolves and coyotes. Based on these data biologists classified them as different species.

• Geneticists found shared DNA sequences in all three.• Geneticists concluded that the red wolf is a hybrid of the

gray wolf and the coyote.

Coevolution – The change in two or more species in close association with each other Examples may include: parasite & hostrelationships, prey-predator relationships, orflower-pollinator)

The flower & the beak of the hummingbird is an example of coevolution.

The long-nosedfruit bat, and theflower it feedsfrom, have bothcoevolved.

• Some microbes have evolved to live within certain animals, while these animals have adapted to either benefit from or avoid the microbes. (example – the protozoan Trichonympha and the termite)

Convergent Evolution “Sometimes organisms that appear to bevery similar, are not closely related at all.”

Convergent evolution is the process by which different species evolve similar traits.

It may occur when unrelated species become more and more similar as they adapt to similar environments.

Example of Convergent Evolution: Sharks and whales have very different

origins. Sharks are fish and whales are mammals, yet they have adapted similar traits to their environments.

They both have fins, and streamlined shapes.

Anole Lizards & Convergent Evolution (Modern Biology pg 308-309)Anole lizards (Genus Anolis) are found on the

Caribbean Islands of Cuba, Hispaniola, Jamaica, and Puerto Rico. Body types correspond to the habitat of each species.

These Anolis lizards live on the Island of Hispaniola in the Caribbean

It seems that there are distinct species of twig-dwelling lizards on each Island.

Biologists analyzed the DNA of various species and found that twig-dwelling species evolved independently on each island. In other words, they had different ancestors but evolved similar adaptations.

The is an example of convergent evolution.

Divergent Evolution – the descendents of a single ancestor diversify into species that each fit different parts of the environment.

Caribbean Anole lizards evolution must also explain how the lizards became adapted to their particular habitats.

Adaptive radiation is one important type ofdivergent evolution. (Many related speciesevolve from a single ancestral species)

If Adaptive Radiation occurs: A new population in a new environment will

undergo divergent evolution until the populations fills many parts of the environment.

Example of Adaptive Radiation:Galapagos Island Finches & Anole lizards

Example of divergent radiation:Galapagos Island Tortoises

Artificial Selection: This can speed theprocess of divergent evolution.

Example: Humans have bred domestic dogs for years. Dogs are bred for certain phenotypic characteristics.

Due to the actions of dog breeders, the process ofdivergence among domestic dogs has occurredmany times faster that would have been possiblein nature.

• In the 2000s, geneticists analyzed DNA from 654 dog breeds, including ancient dog remains and found that all breeds of dogs share DNA similarities with wolves in East Asia.

• These findings support the hypothesis that humans first selected domestic dogs from a wolf population about 15,000 years ago.