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Lecture 3

Lecture 3 & 4 readings.docx

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Biological Sciences
Maydianne Andrade

Lecture 3 & 4 readings: Chapter 2 pg. 37-49 and 53 – 65 Chapter 2 – The Pattern of Evolution 2.1 Evidence of Change through Time Evidence from living species - By monitoring natural populations, we can directly observe small scale change (microevolution) - Examining bodies of organisms can show dramatic change: macroevolution Example of observed change: Scott Carroll  soapberry bug (Jadera haematoloma) These bugs use their long beaks to inflate a balloon like fruit (tries to reach the seed) The seed would be located deep within the fruit (near the center) Soon people began to plant a flat-podded golden rain tree (relative of the balloon vine) but the fruit is quite flat (not sphere like). The researchers collected the soap bugs found on the different plants and measured the length of their beak. The soap bugs living on the flat-podded golden rain tree had shorter beaks than the bugs living on the balloon vine. The short beaked bugs were relatives of the long beaked bugs and they most likely evolved to be short beak bugs. Another possibility is that they develop their beak size depending on which plant seeds they eat. To rule this out they experimented and found that the beak size stayed the same regardless of which plant they fed on. Vestigial Organs Vestigial structures – useless or rudimentary version of a body part that has an important function in another (closely allied) species North Island brown kiwi is a flightless bird with tiny wings Rubber boa has the remnant hind limbs Humans’ vestigial structure is our tailbone known as the coccyx (tail) We also have muscles on our hair follicle that will allow our hair to stand up, if we had more hair than it would make us look bigger or keep us warm Vestigial structures can also occur at a molecular level. Evidence from the fossil record Fossil – trace of any organism that lived in the past Worldwide collection of fossils  fossil record Fossils argue that life has changed throughout time 3 specific observations that helped Darwin The fact of Extinction – 1801 Baron George Cuvier listed some extinct species. At first it was thought that the organisms were out of our detection but taking into consideration their size as well as the fact that they’ve explored all around the world and it was highly improbable that these organisms went passed our detection He studied the fossil remains of the Irish elk and through careful analysis found that it had no living relatives The law of Succession – 18 century William Clift  fossils and living organisms in the same geographical region are related to each other and are distinctly different from organisms found in other areas. Today’s species are descended with modification from ancestors that lived in the same region; it is to be expected that they would bear a stronger resemblance to their recent ancestors than to their distantly related kin in other parts of the world Transitional forms Fossil records should capture evidence of transformations in progress: transitional species showing a mix of features, including traits typical of ancestral populations and novel traits seen later in descendants The most famous transition form is Archaeopteryx, which lived 145 to 150 million years ago in Germany. It was identified as a bird since it had feathers. Its skeleton resembled a reptile (claws, teeth, long bony tail). Birds developed first before the change in skeletal structure. Birds evolved from dinosaurs. The ambulocetus natus existed 50 million years ago and was an excellent swimmer, which had large hind limbs, and it later evolved into a whale (whales still have a femur and pelvis) Evidence of Decent with modification Species change over time on a small, or microevolutionary scale (soapberry bug) species also change over time on a large, or macroevolutionary scale (birds from dinosaurs) 2.2 Evidence of Common Ancestry Ring species – Siberian greenish warbler (Phylloscopus trochiloides) the species forms a ring around Tibetan Plateau. Although their songs are a little different depending on region they still recognize the other as the same species and interbreed. Exception = central Siberia where the northeastern form meets the northwestern form and refuse to mate. Greenish warblers show that with space and time one species can gradually divide into two. Homology – the study of likeness Richard Owen defined homology as the same organ in different animals under every variety of form and function Structural and developmental homology Owen and Baron Georges Cuvier descri
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