Lecture 4 Evolution and Natural Selection: Discovery 1: Concept of fixed species: LAMARCK'S GIRAFFE Original short-necked ancestor Keeps stretching neck to reach leaves higher up on tree and stretching and stretching until neck becomes progressively longer - Idea that nothing changed through time. - There were 6 days of creation in which all of the species were formed Discovery 2: Transmutation: - Theory proposed by Jean Baptiste de Lamarck (1744- 1829) the theory was proposed in 1801. - Involves the idea of change through use and disuse- anatomical characters could be inherited Discovery 3: Smith and Geology: Driven by inner "need" - William Smith mapped British geology and fossils. - He was hired by canal diggers to investigate geology - was able to show that rocks were laid down in certain orders and in different layers, with different fossils representing different geological eras. - A Yorkshire hyena den: 1821: Buckland recognised bones from Kirkdale Cave as a fossil hyena den - this was evidence of antediluvian occupation (diluvian - flood) Discovery 4: The voyage of HMS Beagle: - Charles Darwin's circumnavigation of the globe which took place from 1831-1836 - This event was a commercial event and it was a cruise of biological discovery. - Darwin's finches - alterations in beak morphology to adapt to different kinds of food (seeds, nuts) - FOUNDER EFFECT - a few finches were perhaps blown off course and landed on Galapagos - found empty niches and evolved to eat different types of seeds. However they are still all one species, despite very different appearances - Fossil relatives - giant ground sloth, camelid etc - giant macro-fauna that dot exist in the world today Survival of the fittest: - Malthus' essay on human population growth - concept that population growth would increase exponentially and would increase beyond the food supply available - Where food was limited, only the fittest would survive - Darwin applied ideas to biology and devised the principle of Natural Selection - the concept that an organisms with a characteristic that improved its survival would pass it on to the next generation. - Development is an issue in the poorest of poor countries - Development of technology has improved food resource availability, but the principle of survival of the fittest is still in place. Natural Selection: - Differential survival and reproduction of particular physical traits - For adaptions to evolve: Differences in the trail must cause differences in fitness (ability to survive and reproduce) · Differences in the trait must be heritable - Relative fitness of offspring compared to others because of better adapted phenotypes - Humans originated in Africa with darker skin. Moved out of Africa and moved Northward, skin became paler. - Fitness is the ability to survive and reproduce - Phenotype are the observed characteristics rather than the genetic ones - Those most suited to their environment with advantageous characteristics will survive better - e.g. Inuits and Massai comparison.
Summary of Darwin's Theory: - Organisms in nature produce more