Anthro2050 1st Edition Lecture 5 Outline of Last Lecture I Charles Darwin II Natural Selection and Adaptation Outline of Current Lecture I More on Natural Selection II Evidence for Evolution Current Lecture More on Natural Selection Constraints on selection Character correlation selecting for one trait or character that happens to be related to another trait as well For example when selecting for beak depth in birds beak width is automatically selected for as well Physical constraint something that can t evolve due to basic physical properties For example there are no land mammals the size of a blue whale because the mass wouldn t be able to be supported on land and needs the buoyancy of water to be supported properly Developmental constraint When a trait is set early in development it is difficult to alter For example the vast majority of animals have a set 7 neck vertebrae To make a longer or shorter neck selection can t just add more bones so the bones must be bigger or smaller to change the length Genetic constraint not enough genetic variance in a population to evolve This happens when a species loses a vast majority of the population relying on very few individuals to repopulate Types of Selection Directional selection selecting for one trait over others Stability selection selecting against the extremes in a population These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute Disruptional selection selection against the average in a population leaving only the extremes can sometimes lead to speciation Evidence For Evolution Artificial Selection domesticated animals and plants changed over time due to selection for specific desired traits Example domesticated wolf ancestor bred through the years resulting in the different types of dogs we have today selected for specific traits such as hunting herding working and companionship Nested Hierarchy natural world groups into ever bigger categories I e humans and apes with other primates and primates with other mammals if not for evolution there would be no grouping as the natural world would be random Homology Similarities among various species due to common ancestry From the basic components of DNA to similar bone structure in the limbs Vestigial Structures Common structures from a common ancestor that some species no longer use and therefore are fading i e Tail bone in humans and hind limbs in sea mammals such as dolphins and whales Living Organisms that Breed Fast Since change occurs over the course of many generations it is difficult to see these changes in our on average 80 year human lives However in single celled organisms insects and some fishes the life spans are short enough we can track hundreds of generations as well as observe changes as they evolve For example the reason we need new flu shots every season is that they flu virus evolves rapidly throughout the year and we have to change the antiviral formula to match the new generation Fossils Show terrestrial forms through millions of years and scientists can trace through the fossil record to examine and identify ancient ancestors of modern species
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