HumanDiversity 2010

HumanDiversity 2010 - HUMAN DIVERSITY What is a species?...

Info iconThis preview shows pages 1–9. Sign up to view the full content.

View Full Document Right Arrow Icon
HUMAN DIVERSITY What is a species?
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Species a population or group of populations that is capable of interbreeding and is reproductively isolated from other populations. The members can produce viable offspring that can live and reproduce How does speciation occur? Basically, when gene flow is interrupted and genetically isolated subgroups are maintained, new species may arise if the subgroups become incapable of interbreeding
Background image of page 2
Two models for the rate of speciation: Gradualism: new species arise gradually over time through accumulation of small modifications Punctuated equilibrium: a species remains stable (in equilibrium or oscillating) for a long period of time, punctuated by sudden changes or evolutionary leaps Think how the fossil record reflects these models
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Gradualism Expect to see transitional forms between species We see a lot of transitional forms between Homo erectus and Homo sapiens . These transitional forms are called Archaic Homo
Background image of page 4
Punctuated equilibrium: Mutation of large numbers of genes, Or mutation of genes that code for important phenotypic traits When combined with founder effect, can result in a new species fairly quickly A burst of change forms a speciation event when a portion of a species is physically or genetically isolated We expect NOT to see transitional forms between species We don’t see transitional forms between quadrupedalism and bipedalism, for example
Background image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Natural selection should be viewed as a conservative force, Eliminating what doesn’t work adaptively Allowing to reproduce what does work adaptively So long as the environment or other selective forces remain the same, there is no change in what does or does not work adaptively
Background image of page 6
Variation in species Some species are more variable than others: depends on its geographic distribution and the variety of environments to which its members are adapted. i.e., narrow niche or different niches. If adapted to a narrow niche, species will be fairly homogeneous = specialized. Example: koala Australia eucalyptus
Background image of page 7

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
many niches = generalized . Examples: dogs; grizzly bears Generalized species are probably polymorphic (species with alternative alleles, or species with variation). http://yp.bellsouth.com/sites/petgrooming/images/dogs.jpg
Background image of page 8
Image of page 9
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 33

HumanDiversity 2010 - HUMAN DIVERSITY What is a species?...

This preview shows document pages 1 - 9. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online