lecture_24__05 - Humans can also create selection that...

Info iconThis preview shows pages 1–6. Sign up to view the full content.

View Full Document Right Arrow Icon
Humans can also create selection that influences the survival of populations: Fig. 22.12 insecticide treatment: drug treatment:
Background image of page 1

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

View Full DocumentRight Arrow Icon
organisms other than humans can have very significant effects on the survival of other species: Example: leaf-cutting ants and their fungus farms. Survival of the ants affects the fungus, and survival of the fungus affects the ants Parasite-host relationships are another example of this interdependency: mosquito carrying the Plasmodium falciparum malaria parasite
Background image of page 2
Sexual dimorphism : secondary sex characteristics of males vs. females Example: sockeye fish; males are much larger and have more extreme coloring This is representative of many species where the male is more brightly colored in comparison to the female Most sexual dimorphism features are not adaptive per se, but contribute to the mating choices (usually made by females) Mating preferences and rituals affect reproductive success and therefore also evolutionary fitness Example: peacocks sexual dimorphism is very common among bird species
Background image of page 3

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

View Full DocumentRight Arrow Icon
Modes of selection: Selection can have different effects on a population with respect to a particular trait Fig. 23.12
Background image of page 4
Example: The number of receptors expressed on the outside of a lymphocyte cell is determined by the alleles present at loci A, B, and C such that some combinations of alleles lead to high numbers of the receptor, while other combinations lead to little or no receptor expressed on the cell surface. The receptor is recognized by virus X. Binding of virus X to high numbers of receptors on a single cell induces an anti-viral response, but binding of the virus to only a few receptors does not elicit the response. Cells lacking the receptor are not infected by the virus.
Background image of page 5

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

View Full DocumentRight Arrow Icon
Image of page 6
This is the end of the preview. Sign up to access the rest of the document.

This document was uploaded on 09/06/2009.

Page1 / 14

lecture_24__05 - Humans can also create selection that...

This preview shows document pages 1 - 6. Sign up to view the full document.

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