Development & Evolutionary Theory PDF

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ABIO 121 (Now 131) - Dr. Elise Gervais...

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Development & Evolutionary Theory Monday, January 27, 2020

2:43 PM

> Changes in Developmental Gene Expression Can Drive Evolutionary Change ○ What is Evolution? ▪ Change over a period of time ▪ Evolution by natural selection is one of the best supported theories in modern biology

○ Lamarck & Evolution as Change Through Time ▪ 1809 - Lamarck was the first to propose a formal theory of evolution □ Based on Aristotle's great chain of being, simple organisms originate at the base of the chain by spontaneous generation □ Organisms evolve by moving up the chain over time ▪ Lamarck suggested that the process responsible for this pattern was the inheritance of acquired characteristics □ As individuals develop, their phenotype changes in response to environmental challenges. These phenotypic changes are then passed on to their offspring ▪ OFFSPRING WILL NEVER INHERIT CHANGES TO THE PARENTS' PHYSICAL BEING ○ Common Misconceptions of Evolution ▪ "Evolution is just a theory" □ A scientific theory is not just a guess or simple idea ▪ "Darwin invented evolution"

□ Darwin combined many previous ideas with his own observations and mechanism to propose his theory of evolution and then popularized it ▪ "Humans come from apes" □ We share a common ancestor with apes and some of the offspring of those ancestors went down evolutionary paths ▪ "Survival of the fittest" □ The biggest, strongest and most aggressive individuals are not necessarily the most biologically fit. Biological fitness is all about how many babies you have! ▪ "Evolution perfects organisms" □ Perfection isn't possible with changing environments. What makes you better fit in one environment may be a detriment in another environment

○ Evolution by Natural Selection ▪ Darwin and Wallace proposed that change in species through time does not follow a linear, progressive pattern

□ Evolution is based on variation among individuals in populations  A population consists of individuals of the same species living in the same area at the same time

▪ This view uses population thinking to describe descent with modification □ Darwin claimed that variation among individuals in a population was the key to understanding evolution - Change over time produced modern, modified species from ancestral species ▪ The pattern component of the theory of evolution by natural selection predicts that: □ Species change over time □ Species are related by common ancestry (phylogenetic trees)

▪ Evolution by Natural Selection Definition: □ Start here ▪ Darwin's inspiration □ Artificial selection in pigeon breeding  Darwin crossbred pigeons and observed how characteristics were passed on to offspring  He concluded that the diverse pigeon breeds all descended from wild pigeons

□ Similar species in the same geographic area  There are often striking similarities among island species ◊ For example, birds that Darwin collected from the Galapagos Islands  A phylogenetic tree is a diagram that illustrates the ancestor-descendant relationships among taxa (groups)  Researchers compared bird DNA and placed the birds on a phylogenetic tree, which shows that the different Galapagos species are each other's closest living relatives and they share a single common ancestor □ Extinction - Loss of Species...