NCEA Biology Scholarship: patterns of macro-evolution speciation

Punctuated equilibrium

Where one species gradually evolves into a new species overtime

• Very long and slow process

• Very slow changes to the environment

• Slow, steady rate of change

Phyletic Gradualism

Long periods of stasis punctuated by rapid speciation events

• Change in selective pressures, forces species to adapt

• Long period of stasis—nothing changes until all of a sudden drastic event occurs causing species to adapt to differing selective pressures

Parallel evolution

Where two related species arise from a common ancestor. The two species then evolve in the same way over time, likely in response to similar environmental selection pressures.

• Often comes from divergent evolution

• Both species evolve at the same time and rate

• Gradualism—occurs over a long period of time

• Shared homologous structures proof that two species share common ancestors

Homologous structures

Evidence two species have a common ancestor is that they share similar features, such as an organ, system, or body part—these features are called homologous structures

• E.g. all mammals share a common ancestor as they all share homologous structures

Convergent evolution

Where two unrelated species evolve similar features due to similar selection pressures

• Analogous features evident

Divergent evolution

Where two seperate species evolve from one common ancestor.

• Homologous structures are evidence of this type of evolution

Adaptive radiation

Where more than one species evolve from one common ancestor

• Occurs due to the opening up of new niches and rapid bursts of evolution (punctuated)

• Occurs as punctuated event opened up lots of new niches, empty habitats + food sources, adapted to fill these spaces

Co-evolution

Where two unrelated species that have a close relationship become selection pressures for each other—when one evolves, the other does too

• If one becomes extinct, the other will become extinct

• Mutualism—both individuals in species gain a survival advantage

• Survival advantage—e.g. no other bird species to compete with in taking nectar from flower