EK 1B2 Phylogenetic trees and cladograms are graphical representations (models) of evolutionary history that can be tested.
Difference between Phylogenetic Trees and Cladistics • http://www.youtube.com/watch?v=fQwI90bkJl4 • http://www.youtube.com/watch?v=fQwI90bkJl4
Convergent Evolution • Describes the independent evolution of similar features in different species. • Example – wings
Different means of obtaining evidence to create Phylogenetic trees and cladograms 7 Definitions
Definitions • Homoplastic evolutionary changes:acquisition of a similar form or structure between species of different lineages as a result of convergent evolution • Biogeography: the study of the geographical distribution of species and their evolutionary relationships. Species appear to have colonized island habitats from mainland areas and then been modified by natural selection • Fossil Record: the fossilized remains of organisms provide a historical record of life on earth. Reveals the vast time scale over which the process of evolution has occurred
Homology: structures in closely-related species have been a similar underlying structure that appears to have been modified by natural selection in different environments • Analogy: Structures in distantly-related species have no similarity in underlying structure but have a similar function. These structures appear to have evolved under natural selection in similar environments. • Embryology: similarities and differences in embryological stages indicate evolutionary relationships among organisms. • Molecular biology: similarities and differences in the structures of DNA and protein indicate evolutionary relationships among organisms.
Phylogenic trees and cladograms are constantly being revised • New research with biological data • New mathematical and computational ideas • Current knowledge compared to emerging knowledge
HARDY WEINBERG EQUILIBRIUM • Requirements for H/W equilibrium • No mutation takes place • No migration (emigration or immigration) • Random mating • Very large population • No selection occurs (leaving more offspring than competing organisms) • If all five are met, the allele and genotypic frequencies will remain the same from generation to generation.