Aim: How did species evolve ? HW 13 Text read chapter 16 Do Analyzing Data Activity page 408

Patterns of Evolution Natural selection can ultimately lead to the formation of new species. Sometimes many species evolve from a single ancestral species. Similarities in skeletal and muscular structure of Hawaiian honeycreepers led scientists to conclude that the 23 species of honeycreepers evolved from one ancestral species

Hawaiian Honeycreepers Adaptive radiation is one example of divergent evolution. Divergent evolution is the process of two or more related species becoming more and more dissimilar The Hawaiian Islands are of volcanic origins, and have a variety of habitats. Adaptive radiations have occurred in Hawaiian Honeycreepers . In the absence of other bird species, they radiated to fill numerous niches. Location, location, location and environmental niches Divergent evolution is the process of two or more related species becoming more and more dissimilar

Discuss with your group what environmental changes could promote speciation (evolution of new species) Food, type of food, geographic isolation (species are separated and do not interbreed).

DIVERGENT EVOLUTION "One ancestral stock evolves into two species, which continue to evolve and become less and less alike over time." The ancestral mammal probably existed about 190 million years ago. It was around at the time of the dinosaurs, but with the extinction of the dinoasurs, the mammals were able to undergo extensive adaptive radiation to fill a wide range of ecological niches.

Patterns of Evolution In convergent evolution, on the other hand, unrelated species become more and more similar in appearance as they adapt to the same kind of environment. http://cas.bellarmine.edu/tietjen/Evolution/convergent_evolution_examples.htm

"CONVERGENT EVOLUTION occurs when two or more groups that are not closely related come to resemble each other more and more as time passes. This is usually the result of occupation of similar habitats and the adoption of similar environmental roles.."

Patterns of Evolution Punctuated Equilibrium attempts to explain abrupt transitions in the fossil record Gradualism explains evolution as proceeding in small gradual steps

PARALLEL EVOLUTION "In PARALLEL EVOLUTION two related species arise from a common ancestor. The two species then evolve in much the same way over time, probably in response to similar environmental selection pressures." In this example, both the wooly mammoth, which occupied parts of North America, and the elephant, still found in Asia and Africa are presumed to have evolved from a common ancestor. Their geographical isolation and environmental selection pressures caused further evolution of the species, but each, in its own location, occupies(d) a similar niche.

Punctuated equilibrium This type of diagram reflects the theory that evolution has not occurred at a constant rate, rather it has occurred in short bursts with long periods of stability between. This theory explains the absence of the infinite range of intermediate fossils in branches of evolution such as the vertebrates.

Cladograms show evolutionary 'closeness' This simple mammalian cladogram shows that dingos (placental) and koalas (marsupial) are more closely related than either are to the platypus (monotreme).

What does this cladogram show? This more complex cladogram shows not only the relationships between bears, panda and dogs, but it gives an idea of time since these animals shared common ancestors. What does this cladogram show?

Aim: How did speciation occur? Patterns of evolution A. B. C.

Hawaiian Honeycreepers Divergent evolution is the process of two or more related species becoming more and more dissimilar The Hawaiian Islands are of volcanic origins, and have a variety of habitats. Adaptive radiations have occurred in Hawaiian Honeycreepers . In the absence of other bird species, they radiated to fill numerous niches. Location, location, location and environmental niches Divergent evolution is the process of two or more related species becoming more and more dissimilar

Factors that contribute to the formation of a new species ? Section 16-3 Reproductive Isolation results from Isolating mechanisms which include Behavioral isolation Temporal isolation Geographic isolation produced by produced by produced by Behavioral differences Different mating times Physical separation Discuss with your group http://www.pbs.org/wgbh/evolution/darwin/origin/index.html which result in Independently evolving populations which result in Formation of new species