Aim: How did species evolve ?

HW 13

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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

DIVERGENT EVOLUTION

•"One ancestral stock evolves into two species, which continue to evolve and become less and less alike over time."

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.

• "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."

• 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?

Aim: How did speciation occur?

• Patterns of evolutionA.

B.

C.

Hawaiian Honeycreepers

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

results from

which include

produced by produced byproduced by

which result in

which result in

Reproductive Isolation

Isolating mechanisms

Behavioral isolation Temporal isolationGeographic isolation

Behavioral differences Different mating timesPhysical separation

Independentlyevolving populations

Formation ofnew species