Unit 11 – Origin of Life and Types of Evolutionary Change Lesson Overview Unit 11 – Origin of Life and Types of Evolutionary Change

Mechanisms of Evolution Four key processes influence evolution: Natural Selection Mutation – just happens randomly Genetic drift Gene flow

Mechanisms of Evolution Genetic Drift - occurs when random or chance events determine which alleles are passed to the next generation What is an allele? one of a number of different forms of a gene - Genetic drift is significant only for small populations – problem for small sample size – happens by chance

Examples of Genetic Drift Examples: (1) A population of ten wildflowers in a field and the moose stepping on only the white flowers. (2) A population of beetles and a human stepping on only the green ones.

Mechanisms of Evolution Gene Flow - occurs when alleles are transferred from one population to another via movement of individuals (migration) or gametes (plant pollen dispersal) - Gene flow has two effects: Populations become more similar New alleles can be introduced into a population.

Examples of Gene Flow Examples: (1) Two different colored beetles. One beetle migrates to another population and passes down his alleles that are different from the other colored beetles.

Origin of Life Video - NOVA http://www.pbs.org/wgbh/nova/evolution/origins-life.html

The Mysteries of Life’s Origins This infant planet was very different from Earth today. Earth’s early atmosphere contained little or no oxygen(anaerobic). It was principally composed of carbon dioxide, water vapor, and nitrogen, with lesser amounts of carbon monoxide, hydrogen sulfide, and hydrogen cyanide.

The First Organic Molecules In 1953, chemists Stanley Miller and Harold Urey tried recreating conditions on early Earth to see if organic molecules could be assembled under these conditions. They filled a sterile flask with water, to simulate the oceans, and boiled it.

The First Organic Molecules To the water vapor, they added methane, ammonia, and hydrogen, to simulate what they thought had been the composition of Earth’s early atmosphere. They passed the gases through electrodes, to simulate lightning.

The First Organic Molecules Next, they passed the gases through a condensation chamber, where cold water cooled them, causing drops to form. The liquid continued to circulate through the experimental apparatus for a week. After a week, they had produced 21 amino acids—building blocks of proteins.

The First Organic Molecules Miller and Urey’s experiment suggested how mixtures of the organic compounds necessary for life could have arisen from simpler compounds on a primitive Earth. We now know that Miller and Urey’s ideas on the composition of the early atmosphere were incorrect. But new experiments based on current ideas of the early atmosphere have produced similar results.

Production of Free Oxygen At first, the oxygen(aerobic) combined with iron in the oceans, producing iron oxide, or rust. Iron oxide, which is not soluble in water, sank to the ocean floor and formed great bands of iron that are the source of most iron ore mined today. Without iron, the oceans changed color from brown to blue-green. Next, oxygen gas began to accumulate in the atmosphere. The ozone layer began to form, and the skies turned their present shade of blue. Over several hundred million years, oxygen concentrations rose until they reached today’s levels

Origin of Eukaryotic Cells One of the most important events in the history of life was the evolution of eukaryotic cells from prokaryotic cells. Eukaryotic cells have nuclei, but prokaryotic cells do not. Eukaryotic cells also have complex organelles. Virtually all eukaryotes have mitochondria, and both plants and algae also have chloroplasts.

Endosymbiotic Theory Over time a symbiotic relationship evolved between primitive eukaryotic cells and prokaryotic cells in them.

Endosymbiotic Theory One hypothesis proposes that mitochondria evolved from endosymbiotic prokaryotes that were able to use oxygen to generate energy-rich ATP molecules. Without this ability to metabolize oxygen, cells would have been killed by the free oxygen in the atmosphere.

Endosymbiotic Theory Another hypothesis proposes that chloroplasts evolved from endosymbiotic prokaryotes that had the ability to photosynthesize. Over time, these photosynthetic prokaryotes evolved within eukaryotic cells into the chloroplasts of plants and algae.

Evidence of Evolution (1.) biogeography (2.) fossil record 6 areas of evidence that support the scientific theory of evolution: (1.) biogeography (2.) fossil record (3.) comparative anatomy (4.) comparative embryology (5.) genetics (6.) natural selection

Evidence of Evolution Go to Power point on Infinity

A random change in a small population’s allele frequency is known as Question #1 A random change in a small population’s allele frequency is known as a. A gene pool b. Genetic drift c. Variation d. Fitness

A random change in a small population’s allele frequency is known as Question #1 A random change in a small population’s allele frequency is known as a. A gene pool b. Genetic drift c. Variation d. Fitness

Question #2 Over time, the climate of an island became drier, which resulted in changes to the populations of various island finch species. Finch populations with a certain beak shape thrived, while those not having that beak shape decreased. Which of the following describes a necessary condition for these changes in the finch populations to occur? fewer mutations limited food resources limited beak variations overproduction of offspring

Question #2 Over time, the climate of an island became drier, which resulted in changes to the populations of various island finch species. Finch populations with a certain beak shape thrived, while those not having that beak shape decreased. Which of the following describes a necessary condition for these changes in the finch populations to occur? fewer mutations limited food resources limited beak variations overproduction of offspring

Question #3 Polyploidy may instantly produce new types of organisms that are larger and stronger than their diploid relatives in a. Animals b. Plants c. Bacteria d. Fungi

Question #3 Polyploidy may instantly produce new types of organisms that are larger and stronger than their diploid relatives in a. Animals b. Plants c. Bacteria d. Fungi

Question #4 A small population of chimpanzees lives in a habitat that undergoes no changes for a long period. How will genetic drift probably affect this population? A. It will accelerate the appearance of new traits. B. It will promote the survival of chimpanzees with beneficial traits. C. It will increase the number of alleles for specific traits. D. It will reduce genetic diversity.

Question #4 A small population of chimpanzees lives in a habitat that undergoes no changes for a long period. How will genetic drift probably affect this population? A. It will accelerate the appearance of new traits. B. It will promote the survival of chimpanzees with beneficial traits. C. It will increase the number of alleles for specific traits. D. It will reduce genetic diversity.