Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Mate choice wikipedia , lookup
Acquired characteristic wikipedia , lookup
Sociobiology wikipedia , lookup
Evolutionary mismatch wikipedia , lookup
Sexual selection wikipedia , lookup
The Descent of Man, and Selection in Relation to Sex wikipedia , lookup
Theistic evolution wikipedia , lookup
Saltation (biology) wikipedia , lookup
Hologenome theory of evolution wikipedia , lookup
Natural selection wikipedia , lookup
Topic 8 – Natural Selection DAY 1 THEORY OF EVOLUTION Natural Selection: A Mechanism of Change WHAT ARE WE LEARNING TODAY? Benchmarks SC.912.L.15.13 – Describe the conditions required for natural selection, including: overproduction of offspring, inherited variation, and the struggle to survive, which result in differential reproductive success. Learning Objectives I will analyze the reasoning in Darwin’s theory of evolution by natural selection. I will relate the concepts of adaptation and differential reproductive success to the theory of natural selection. WHAT IS THE ESSENTIAL QUESTION? “It is not the strongest of the species that survives, nor the most intelligent that survives. It is the one that is most adaptable to change.” Charles Darwin After reading the quote above and learning about Darwin’s theory of natural selection, what do you think he meant by it? WHO IS CHARLES DARWIN? Greatest contributor to our understanding of evolution. Evolution is: the change of allele frequencies in a population over time. process by which modern organisms have descended from ancient organisms. DARWIN’S TRAVELS TO THE GALAPAGOS ISLANDS • 1831: voyage on the HMS Beagle • 5 year voyage around the world to Australia, S. America, Galapagos Islands, and Africa • Made several observations on the different species he found • He noticed 3 patterns of biodiversity 1. Species vary Globally 2. Species vary locally 3. Species Vary over time OTHER SCIENTISTS THINKING ABOUT EVOLUTION Jean-Baptiste Lamarck • Suggested organisms change during their lifetime Where did Lamarck go wrong in is theory? • Suggested individuals pass on acquired traits to offspring • We now know individuals do not evolve in their own life time • Recognized a link to an organism’s environment and its body structures • We also know that acquired traits cannot be passed on to offspring. ACQUIRED TRAIT VS. INHERITED TRAIT Acquired traits Inherited Traits • are obtained by the individual in their life time • Are passed on from the genes of parents to offspring If you were to get a tattoo, that would be an acquired trait Will affect the traits of future generations of offspring OTHER SCIENTISTS THINKING ABOUT EVOLUTION James Hutton and Charles Lyell Thomas Malthus • Concluded that earth was extremely old • Reasoned that is populations grew unchecked, there would not be enough space, food, resources for everyone • Processes that changed earth in the past are the same ones changing the earth now • Principles of Geology • English Economist WHAT IS AN ADAPTATION? Eyes with light reflective retina to see in the dark Stripes to help them hide Loose abdomen skin to reduce injury when kicked Long, sturdy tail to help with balance Razor sharp teeth with muscular jaws to kill prey Long, retractable claws to grab prey An adaptation is any inherited characteristic that increases an organism’s chance of survival. WHAT ADAPTATIONS IMPROVE THIS ORGANISM’S ABILITY TO SURVIVE? DARWIN’S 4 TENETS OF NATURAL SELECTION • Natural Selection: process by which organisms with variations most suited to their environments survive and leave more offspring • Natural selection is the driving force, the mechanism, of evolution • Darwin proposed that in order for evolution to occur by natural selection, 4 conditions must be met (4 tenets) 1. Overproduction of Offspring 2. Inherited variation within the population 3. Struggle for existence 4. Differential reproduction WHAT IS OVERPRODUCTION OF OFFSPRING? What is taking place in this picture? o Grasshoppers can lay over 200 eggs at a time. o Only a small fraction of these offspring survive to reproduce. Organisms produce more offspring than can survive. WHAT IS INHERITED VARIATION? What are some of the differences you see in the population of grasshoppers? What do you think causes these variations? Inherited variations are the heritable differences that exists in every population. Mutations Recombination Where this variation comes from WHAT IS THE STRUGGLE TO SURVIVE? How would you describe the environment in which the grasshopper lives? Which grasshopper is better adapted to survive in this environment? What would happen to this population if a drought caused the grass to turn brown? WHAT IS THE STRUGGLE TO SURVIVE? Certain heritable variations, called adaptations, increase an individual’s chance of surviving and reproducing. o Heritable variation includes brown and green body color. o Green coloration is an adaptation that allows grasshoppers to blend into their environment to be less visible to their predators. WHAT IS DIFFERENTIAL REPRODUCTIVE SUCCESS? What do you think it means that “green grasshoppers have a greater differential reproductive success than brown grasshoppers?” Green grasshoppers survive and reproduce more often than do brown grasshoppers in this environment. DIFFERENTIAL REPRODUCTIVE SUCCESS Organisms whose traits are best suited to the environment experience better reproductive success and become more common 1) more grasshoppers are born than can survive, 2) individuals vary in color, a heritable trait, and 3) green individuals have a higher differential reproductive success in the current environment SUMMARY OF DARWIN’S THEORY (NATURAL SELECTION) Individuals organisms within a species are different. Some of these differences are passed down from parent to offspring, or heritable. Individuals produce more offspring that can survive due to limited resources creating a struggle for existence. Individuals best suited, or adapted, to their environment survive to experience higher differential reproductive success.