Darwin and Speciation Notes

Meet Charles Darwin 1809-1882 Published On the Origin of Species in 1859 Fun fact! Darwin dropped out of medical school after seeing his first cadaver

Darwin’s Findings Darwin observed many species during his voyage on the HMS Beagle In the Galapagos, Darwin observed the variations of animals and plants from island to island. This eventually led to his theory of evolution by natural selection

Building on Earlier Science Darwin built his theory off the work of Jean-Baptiste Lamarck Lamarck wrote that living things change over time Lamarck thought that organisms passed on their most-used traits to their offspring Is this true? No!

Macroevolution 6/10/2018 What is a Species? A species is a group of similar individuals capable of interbreeding to produce fertile offspring. G. Podgorski, Biol. 1010

How Many Species Are There? Macroevolution 6/10/2018 How Many Species Are There? We don’t know Estimates range from 4 to 100 million ~2 million species have been described G. Podgorski, Biol. 1010

Macroevolution 6/10/2018 How Do Species Arise? Speciation- evolutionary process by which reproductively isolated biological populations evolve to become distinct species. Let’s break that down, shall we? First things first: Evolution = ? Change over time! G. Podgorski, Biol. 1010

Macroevolution 6/10/2018 How Do Species Arise? The key to speciation is reproductive isolation of populations. Geographic isolation is most common G. Podgorski, Biol. 1010

Process of speciation: Macroevolution 6/10/2018 Process of speciation: Parent species 2 separate species III. No Longer Able to interbreed II. Diverge and Mutate I. Barrier G. Podgorski, Biol. 1010

Two Types of Speciation Macroevolution 6/10/2018 Two Types of Speciation 1. Allopatric speciation: geographic isolation creates a reproductive barrier (an extrinsic mechanism). G. Podgorski, Biol. 1010

Allopatric Speciation Example Macroevolution 6/10/2018 Allopatric Speciation Example Harris’ antelope squirrel White-tailed antelope squirrel Two species of ground squirrel are thought to have descended from a common ancestral population that was separated by formation of the Grand Canyon. G. Podgorski, Biol. 1010

Two Types of Speciation Sympatric speciation: reproductive barrier is created by something other than geographic isolation (intrinsic mechanism).

Sympatric Speciation Example Ancestors of apple maggot flies laid their eggs on hawthorns, a plant species native to North America. When immigrants came from Europe, they brought apple seeds. Apple maggot flies now had a choice of where to lay their eggs—hawthorns or apples. Flies hatched on apples only mate with apple-hatched flies, while flies hatched in hawthorns only mate with hawthorn-hatched flies.

How Fast Does Speciation Occur? Macroevolution 6/10/2018 How Fast Does Speciation Occur? It depends! Speciation relies on many factors Examples: A slow rate of speciation evidenced by a living horseshoe crab (13 extant species) and a 300 million year-old fossil species. In contrast, Galapagos finches have diversified into 13 species within the last 100,000 years. G. Podgorski, Biol. 1010

What do we mean by “better?” Better for survival and reproduction Macroevolution 6/10/2018 Does Evolution Create the Perfect Organism? No, only better organisms as evolution is constrained by history and buffeted by random events. What do we mean by “better?” Better for survival and reproduction G. Podgorski, Biol. 1010