Section 15.2 Summary– pages 404-413 a group of organisms that look alike and can interbreed to...
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Transcript of Section 15.2 Summary– pages 404-413 a group of organisms that look alike and can interbreed to...
a group of organisms that look alike and can interbreed to produce fertile offspring in nature.
• The evolution of new species, a process called
speciation.
-But HOW are new species made?
SPECIATION• What is a species?
Tree Kangaroo! ->
• In nature, physical barriers can break large populations into smaller ones.
• Geographic isolation occurs whenever a physical barrier divides a population.
• A new species can evolve when a population has been
geographically isolated.
SPECIATION
• When geographic isolation divides a population of tree frogs, the individuals no longer mate across populations.
• Tree frogs are a single population.
SPECIATION
• Over time, the divided populations may become two species that may no longer interbreed, even if reunited.
SPECIATION
• Reproductive isolation occurs when formerly interbreeding organisms can no longer mate and produce fertile offspring.
SPECIATION
• For example, if one type of tree frog mates in the fall and the other mates in the
summer, these two populations will not mate with each other and are reproductively isolated.
DIVERSITY
• Divergent evolution is the pattern of evolution in which species that were once similar to an ancestral species diverge, or become increasingly different.
• Divergent evolution occurs when populations change as they adapt to different environmental conditions, eventually resulting in new species.
Possible AncestralLasan finch
Amakihi Extinct mamo
Crestedhoneycreeper
Akialoa
Akepa
Akiapolaau LiwiMaui parrotbill
Apapane
Ou
Grosbeak finch
PalilaAkikiki
Niihau
Kauai
Oahu
Lanai
Molokai
Maui
KahoolaweHawaii
• When an ancestral species evolves into an array of species to fit a number of diverse habitats, the result is called adaptive radiation.
• A pattern of evolution in which distantly-related organisms evolve similar traits is called convergent evolution.
• Convergent evolution occurs when unrelated species occupy similar environments in different parts of the world.
DIVERSITY
Which type of natural selection does NOT favor the evolution of new species?
Question 1
D. directional
C. stabilizing
B. disruptive
A. divergent
Which of the following rarely affects a population’s genetic equilibrium?
Question 2
D. disruptive selection
C. gene flow
B. lethal mutations
A. beneficial mutations
The answer is B. Organisms with lethal mutations do not survive. Therefore, organisms with lethal mutations cannot produce enough offspring to affect a population’s genetic equilibrium.
Why are the Galapagos Islands rich in unique species of organisms?
Question 4
D. The island species have been subjected to stabilizing selection.
C. Lots of species constantly move in and out of the islands.
B. The islands are geographically isolated.
A. The islands have an abnormal number of mutations.