Origin of Species

How much time does natural selection have to act? Earth history as one day

A. What is a species?

1. Linnaeus

cactus      euphorb

2. Ernst Mayr-1940

-Biological Species Concept

populations whose members are capable of interbreeding in nature

reproductively isolated from other species

Problems: asexually reproducing organisms; artificial environments

B. Methods for Reproductive Isolation (How do species keep their genetic distinctiveness?)

1. Prezygotic






2. Postzygotic

-hybrid inviability

-hybrid sterility

C. Modes of Speciation (How could populations become reproductively isolated?)

1. Allopatric speciation

-adaptive radiation

-kingfisher example

2. Sympatric speciation

-meiosis review; polyploid speciation in plants

D. Speciation and Macroevolution

How did the major characteristics that define taxonomic groups evolve?

1. Characteristics of extant groups are modified versions of older structures

-versions of the eye limpet planaria nautilis murex loligo

2. Genes that control development play a major role in macroevolution


-allometric growth: chimpanzee and human skull growth

E. Evolution is Not Goal Oriented

-evolution of the horse1

-evolution of the horse2