BIO 1130 Lecture Notes - Lecture 1: Anagenesis, Cladistics, Paraphyly
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Major events in the history of Biology: Modern theory of
evolution and more 2.
Two different ways of how species arise
Anagenesis:Organism that gradually over time is replaced by a different one
Disappeared over time , no increase in species but change in species
Cladogenesis: Darwin told us about , when you get lineage that has in its population two
distinct morpheologies one may evolve where it becomes a new species . Splitting where
it becomes new or additional ones to create them.
Biologists on species:
-Biologists don’t agree on how to define species although it is fundamental to what we
-Species is a fundamental species , if we don’t understand what is invlolved or whos there
then we cannot to conservation etc
Ernest Mayer gave the idea that species are groups or potentially interbreeding
populations, which are reproductively isolated from other such groups.
-His concept is interbreeding and all switching alleles
-Creates 2 major problems: cant be used with fossils only living organisms, whole group
that use sexual reproduction which is the prokaryotes which means we cant use biological
species on prokaryotes.
-Dominated taxonomy ever swince Linnaeus developed his scheme, can be identifies
morphologically and have a different appereance
-Often doesent give us idea of what we have in species.
-Works in well isolated groups.
Potential for interbreeding
Slowly developing into unique species but still potential for hybridization
But in process of isolating
Morphology doesen’t work for them
-Interbreed on their own boundaries bat at the far end they aren’t since they have
-Adapting into habitat and they morphologically change
-Two populations come together
-Gradual changes in population , can potentially mate but we know they are on their way
to separate species.
Second Contact-Hybridization outcomes
-Fusion of populations-When two populations mix , population differences disappear and
-Reinforcement-Reinforcing differences because hybrids aren’t viable
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