Bio 004, College of the Desert
Capacity of organisms to change over time through reproduction.
Point #1: Individual organisms may develop certain traits, by using or disusing body parts, that are in turn passed on to their offspring.
Flaw: Acquired characteristics are NOT inherited, but acquired after birth!
1. Species tend to overproduce offspring.
2. There exists variation among individuals within a population.
Group of organisms of the same species living in the same area at the same time
Smallest unit of evolution : Only populations evolve, not individuals
Random generation of new alleles
Specifically synapsis, crossing-over, segregation, independent assortment.
Allele frequency – or the relative occurrence of certain traits –remain constant from one generation to the next.
1. Populations must be extremelylarge. Small populations increase allele fluctuations.
Genetic additions to and/or sub-tractions from a population resulting from the movement of fertile individuals or gametes.
Contribution an individual makes to the gene pool relative to the contributions of other individuals.
Natural selection that favors individuals at one end of the phenotypic range.
Example: black bear size in Europe during the ice ages - increased during glaciation, decreased during warming.
Natural selection that favors individuals on both extremes of a phenotypic range over intermediates.
Black-bellied seedcracker finches of Cameroon - small bills for soft seeds, large bills for hard seeds – intermediate bills ineffective on both seed types.
Example: Human birth weights – if the newborn is under or overweight, infant mortality increases
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