Developing a Theory to Explain Change Scientific evidence to support the Theory of Evolution QuestionsQuestions toto Ponder?Ponder?

„ Can you compare different explanations for changes in populations over time?

„ Can you describe the evidence to support the theory of evolution?

„ Can you explain how scientific knowledge is accumulated and organized to develop theories?

„ Can you analyze data to determine relatedness among organisms? ¾ Plato (427-347 B.C.E.) and Aristotle (384-322 B.C.E.) believed that all life existed in a perfected and unchanging form

¾ Buffon’s Histoire Naturelle ¾George-Louis Leclerc, Comte de Buffon challenged this idea. In 1749, he published a 44-volume Histoire Naturelle. ¾In this publication, he noted similarities between humans and apes. Speculated that we may have a common ancestor ¾Also said that earth was older than 6000 years (at the time that was considered the age of earth) ¾ Cuvier’s Fossils: ¾ George Cuvier is credited for developing the science of Paleontology ¾ Examined rocks and noticed that each stratum (layer of rock) was characterized by a unique group of fossil species ¾ He noticed that species would be in one strata and then disappear in the next- ¾ Proposed idea of extinction- organisms alive after the catastrophe would populate the world (Revolutions) ¾ Time and Nature act to destroy species – not create them! ¾ Lyell’s Principles of Geology ¾ Didn’t like idea of revolutions ¾ Reasoned that geological changes are slow and continuous ¾ If Earth is changing, could slow, subtle changes also occur in populations?

¾ Lamarck: Inheritance of Acquired Characteristics ¾Proposed that species evolve by acquiring characteristics of their parents and thus increased in complexity over time until they were perfect (for their niche) ¾ Lamarck: Inheritance of Acquired Characteristics ¾The Environment is the key factor in evolution (True) but the rest of the theory is wrong! ¾1. Theory of Need: organisms need or WANT to change ¾2. Theory of use and Disuse: organs or appendages remain strong when the used – when not they weaken and disappear ¾3. Theory of Aquired traits can be passed on to offspring : organism with arm cut off – has offspring WITH appendage ¾Proposed that species evolve by acquiring characteristics of their parents and thus increased in complexity over time until they were perfect (for their niche) ¾ Charles Darwin- gets the credit to develop the concept of “natural” selection even though they were both publishing at the same time! Theory includes: 1. All organisms produce more offspring than can actually survive in the environment 2. Every organism face a constant struggle to survive- competition 3. The characteristics of individuals of a GIVEN species vary ( think bell-curve) 4. Individuals with characteristics best adapted to an environment will survive- survival of the fittest 5. These individuals will pass on their traits to their offspring

DarwinDarwin gotgot it!it!

„ Organisms produce more offspring than survive to reproduce.

„ Their offspring vary slightly.

„ Characteristics can be passed on from generation to generation.

„ Those most suited to their environment survive at the expense of those less 'fit'. Trilobite fossil found in Burgess Shale „ FOSSILS – are the mineralized remains or traces (tracks, imprints) of animals, plants or other organisms

„ THE FOSSIL RECORD –fossils found in rock strata that show a sequence or history of life on Earth Some of the fossils found here are now long extinct and are unlike „ The Burgess Shale is a anything presently existing middle Cambrian site (~540 MYA)

„ One of the few places in the world where difficult-to-preserve soft- bodied organisms of our past were preserved „ Fossils found in young layers of rock (ie closer to the surface) tend to be more similar to present day organisms „ Fossils appear in chronological order (oldest ancestors in deepest layers „ Not all organisms appear in the fossil record at the same time – ie fish are the oldest vertebrates – then in subsequent layers amphibians, reptiles, mammals and birds „ Transitional fossils are fossils that show intermediary links between groups of organisms

„ They can provide a link between the past and Archaeopteryx – a transitional fossil present because of its characteristics of both reptiles (dinosaurs) and birds ARCHAEOPTERYX – transitional fossil

„ Example: Basilosaurus and Dorudon were ancient whales with tiny hind limbs – living entirely in water

„ Ambulocetus – a more recent ancestor, had heavier leg bones and lived in both water and on land - The tiktaalik was an ancient -- They lived in oxygen-poor water tetrapod - - used their lobe fins to live partly on - It was thought to have descended land-possibly gave rise to amphibians from lobe-finned fishes

The study of the past and present geographical distribution of organisms

„ Darwin and Wallace observed that many species evolve in one location and spread out to other areas ADAPTIVE RADIATION „ Darwin found 14 different species – Diversification of a of finch – he theorized all evolved common ancestral species from one common ancestral finch into a variety of species -left: cactus from S.America -right: cactus from Australia Top: Canary Island lizard Bottom: West African lizard -a depiction of the Earth 250 MYA – continents were joined together

„ Fossils of the same species can be found on the coastline of neighboring continents

„ Example: Cynognathus has been found in Africa and S.America

„ At one time, all continents were joined (Pangea – 250 MYA) -distribution of ancient Cynognathus crateronotus organisms Vertebrate forelimbs

can be used for many different functions:

„ Flying (birds, bats)

„ Swimming (whales)

„ Brachiation (monkeys)

„ Running (horses, dogs) Homologous structures: HOWEVER: they ALL contain the same set of bones organized in similar Similar in structure but often differ in ways – WHY? function

Homologous structures provide evidence for a common ancestor amongst all vertebrates Analogous Structures Structures that evolve separately to perform a similar function are analogous. The wings of birds, bats, •Bird: feathers and insects, for example, have • different embryological origins but Bat: skin are all designed for flight. •Butterfly: chitin VESTIGIAL STRUCTURES

Vestigial structures are thought to have had a purpose at one time in our ancestry, but no longer have a specific function (eg) human appendix VESTIGIAL STRUCTURES

“c” indicates the The muscles connected to the ear of a human do not develop enough Underdeveloped hind legs to have the same mobility as those Of the baleen whale of the monkey „ The embryos of different vertebrates show similar stages of embryonic development

„ Neck pouches – in humans become ears & throat

- in fish become gills

- Similarities among embryos point to a common ancestor

Can you tell which embryo is which?

A – cat B – cow C – horse D - human

„ Many organisms share similar cellular components such as:

„ Proteins – long chains of amino acids used for building & repair

„ Enzymes – made from proteins – they control many biochemical reactions in the cell

„ DNA – genetic material found The DNA of chimpanzees & in the nucleus humans is ~ 98% identical „ Hemoglobin—the oxygen-transport protein that gives blood its red color— got its start at about the time life hemoglobin (found in RBCs) is used to bond to O originated on earth, nearly four billion 2 years ago. Now it is almost ubiquitous, appearing in the cells of plants, animals and even bacteria, and a study of this protein affords scientists a rare glimpse back as well as forward in time. A look at the ancestral hemoglobins indicates that newly arising proteins co-opt the chemistry of older ones and gain new functions through structural alterations. But these studies have revealed an additional way to modify function. Scientists are coming to the realization that changes in a protein's regulation— the when and how of its expression— can also give rise to functional differences. The surprise, says the author, is that these regulatory changes outpace structural ones—an important lesson for students of molecular evolution and a possible indicator of http://adsabs.harvard.edu/abs/1999AmSci..87 where protein evolution will go in the .....H future. Below:hominid evolution EvidenceEvidence forfor Evolution?Evolution?

1. Fossils

2. Radiometric Dating – decay of isotopes

3. Plate Tectonics

4. Phylogeny- classifying organisms due to its genetic similarities

5. Homologous and Analogous structures

6. Vestigial organs

7. Embryological Studies

8. DNA studies

9. Speciation