History and Theory of Evolution

Evolution Introduction Definition: – Change in a population over time Specifically: – Evolution is the frequency of heritable traits in population changing from one generation to the next

Evolution Introduction Allele = several variety of changes Alleles code for traits to establish form or structure, physiology, or behavior Descent = subsequent generations with modifications

Evolution Introduction Explains: – Ways organisms suited for environment – Shared characteristics of life (unity) Genetic code – Diversity of life Life became many different forms

2 Views of Evolution Microevolution – Small changes over short periods of time – Supports improvements in existing species Macroevolution – Small changes accumulating over long periods of time result in major changes – Supports the formation of new speices

History of Evolution Paved the way for Darwin’s thinking

History of Evolution Some Greek philosophers suggested life may change gradually over time Aristotle ( B.C.) viewed species as fixed – Ordered all organisms based on complexity

History of Evolution Carolus Linnaeus – Developed binomial nomenclature system of naming organisms “nested” classifications system (not linear) – Opposed the idea of evolution Classification

History of Evolution Georges Cuvier – Studied fossils in strata Fossils in older strata have changed from current life-forms Some species appeared and disappeared – His explanation: catastrophism = events in past occurred suddenly Boundary between strata represented a local catastrophe (ex. flood); area repopulated by immigration Paleontology

History of Evolution Charles Lyell – Came up with gradualism or uniformitarianism Change is constant over time Same process, same rate – Sediment deposition is constant – Catastrophes are common Geology

History of Evolution Erasmus Darwin – Grandfather of Charles Darwin – Life evolves as environments change Pattern of Evolution

History of Evolution Jean-Baptiste de Lamarck – Organisms adapt to their environments by acquiring traits – Changes in their lifetime Disuse: organisms lost parts because they did not use them Perfection with use and need: the constant use of an organ leads that organ to increase in size – Transmit new characteristics to next generation Pattern of Evolution

Lamarck Observation of giraffes: – In order to reach higher vegetation, giraffes stretched their neck to acquire longer necks Using Darwin’s ideas: Giraffes born with longer necks survive better and leave offspring that will inherit their long necks

History of Evolution Charles Darwin (1809 – 1882) British naturalist (tried medicine and clergy) Proposed evolution by natural selection – Differences in survival and reproduction in accordance to their interaction with environment Naturalist

Charles Darwin Invited to travel around the world in the HMS Beagle – – Made many observations of nature Robert Fitzroy

Voyage of the HMS Beagle Observing the origin of the fauna on the Galapagos

Observations Succession of Types – Current species resemble fossils in same area Glyptodont fossils are also unique to South America. Why should extinct armadillo-like species & living armadillos be found on the same continent?

Observations Modern sloth (right) Mylodon (left) Giant ground sloth (extinct) “This wonderful relationship in the same continent between the dead and the living will…throw more light on the appearance of organic beings on our earth, and their disappearance from it, than any other class of facts.”

Observations

Darwin collected and found birds on Galapagos islands – Thought they were very different kinds – However…14 birds species were different types of finches – Only one species of finch found on the mainland How did one species of finches become so many different species now?

Observations Descendant species Ancestral species

Observations Correlation of species to food source Seed Eaters Flower Eaters Insect Eaters

Darwin’s Finches Found differences in beaks – Associated with different foods

Darwin’s Finches Conclusions: – Small populations of original South American finches landed on islands Variation in beaks enabled individuals to gather food successfully in different environments – Over generations, population of finches changed anatomically and behaviorally Accumulation of advantageous traits in population Emergence of different species

Darwin’s Finches Differences in beaks: – Successfully compete – Successfully feed – Successfully reproduce Pass on successful traits – Natural selection

More observations Correlation of species to food source Whoa, Turtles, too!

…perhaps these are the first steps in the splitting of one species into several? Many islands also show distinct local variations in tortoise morphology More Observations

Darwin’s Return Returned to England in 1836 – Wrote papers describing observations – Wrote his theory of species formation in 1844 Instructed his wife to publish his ideas after his death Reluctant to publish but did not want his ideas to die with him

But… 1858 = Darwin received letter from Alfred Russel Wallace Wallace published article similar to Darwin’s unpublished idea of natural selection – Asked Darwin to evaluate his ideas and pass it along for publication

It was time!!! Became a race of who will publish first and what will be better accepted Wallace published his article on “The Tendency of Varieties to Depart Indefinitely from the Original Type” (1858) Darwin published “The Origin of Species by Means of Natural Selection” (1859)

Patterns of Evolution 3 types of evolution (describing organisms in relation to one another): 1. Divergent (adaptive radiation) = similar organisms become increasingly different because of different types of environments

Patterns of Evolution 2. Convergent evolution = different organisms become increasingly similar because of similar types of environments

Patterns of Evolution 3. Coevolution = two nonrelated species change because of close interaction Predator-prey (disease & host) Competitive species Mutualism (pollinators & flowers)