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Transcript
Chapter 12 & 13 History of Life on Earth & Evolution Mrs. Cook Biology Hypothesis for How life Began •1920’s- Russian Scientist A.I.Oparin, and British Scientist J.B.S. Haldam •Suggested that the early Earth’s oceans contained large amounts of organic molecules. •Known as “Primordial Soup” model. •Thought that oceans were filled with many different organic molecules, like a pot of soup. •Hypothesized that there molecules formed spontaneously in chemical reactions activated by energy from solar radiation, volcanic eruptions, & lightening. Hypothesis for How life Began • Operin and American Scientist, Harold Urey, proposed that Earth’s early atmosphere lacked oxygen. • Instead believed it was rich in -Nitrogen (N) -Hydrogen gas (H2) -Water vapor (H2O) -Ammonia (NH3) -Methane (CH4) Hypothesis for How life Began • 1953- Primordial Soup Model was tested by Stanley Miller, who was working with Urey. • Miller placed the gases that he and Urey proposed existed on early Earth into a device. Hypothesis for How life Began • To stimulate Lighting- provided an electrical spark • After a few days Miller found a complex collection of organic molecules in his apparatus. - amino acids - fatty acids - hydrocarbons * Supported Hypothesis that some basic chemicals of life could have formed spontaneously. Hypothesis for How life Began • Reevaluating the Miller-Ulery Model - Now know that some of the molecules were not abundant when earth began such as ozone (O3), which protects Earth from UV radiation. - UV radiation would have destroyed ammonia and methane. - Without ammonia and methane key molecules that Miller-Ulery proposed could not have been made. *Scientists don’t yet know where these molecules came from. http://www.youtube.com/watch?v=j9ZRHoawyOg show 1st 3 min Hypothesis for How life Began • 1986- geophysicist Louis Lerman suggested that the key process that formed the chemicals needed for life took place within bubbles on the ocean’s surface. 1. Gases were trapped in underwater bubbles ammonia, methane… 2. Gases underwent chemical reactions & were protected within the bubbles- resulting in amino acids. 3. Gases were ejected into the atmosphere when they burst on the ocean surface 4. Gases underwent further reactions when exposed to UV radiation and lightening 5. Simple and complex compounds fell into the oceans with rain. How to Determine Earth’s Age • Earth is around 4.5 billion years old. • Measuring Earth’s Age • Radiometric Dating- use radiometric isotopes in a substance to estimate its age. - Radioisotopes release energy in the form of charged particles. - The time it takes for these particles to be given off helps to determine a substance’s age. - Half Life- the time it takes for one-half of a given amount of radioactive decay. How to Determine Earth’s Age • When did the first organisms form? Fossil- is a preserved or mineralized remains (bone, tooth, or shell) or imprint of an organism that lived long ago. • Oldest know fossil, which are microscopic prokaryotes, come from rock that is 2.5 billion years old. Fossils http://www.youtube.com/watch?v=1920gi3swe4 First Cells on Earth • Cyanobacteria - first prokaryotic cells on earth - photosynthetic - released oxygen in oceans - after hundreds of millions of years, oxygen escaped into the air First Cells on Earth • Evolution of Prokaryotes • Two Groups • Eubacteria - contain a chemical called peptidoglycan in their cell walls - include bacteria that cause disease and decay • Archaebacteria- prokaryotes that lack peptidoglycan in their cell walls & have unique lipids in their cell membranes. - still found today First Cells on Earth • The Evolution of Eukaryotes • 1.5 billion years ago the first Eukaryotes appeared • Much larger than Prokaryotes • Complex system of internal membranes • DNA in a nucleus • Have mitochondria • Plants and Protists have Chloroplasts • Mitochondria & Chroloplasts have their own DNA First Cells on Earth • The Origin of Mitochondria and Chloroplasts - 1966- American Biologist Lynn Margulis- proposed the Theory of Endosymbiosis. - states that mitochondria are the descendants of symbiotic, aerobic (oxygen required) eubacteria and chloroplasts are the descendants of symbiotic, photosynthetic eubacteria. - bacteria entered larger cell as a parasite or an undigested prey. - instead of being digested, the bacteria began to live inside the host cell. First Cells on Earth • Support of theory for Mitochondria & Chloroplasts: 1. Same Size and Structure as bacteria 2. Genetic Material- circular DNA present 3. Ribosomes- present 4. Reproduction- produced with in eukaryotic cells by binary fission. http://www.youtube.com/watch?v=RaAM8qQcs6E Multicellular Organisms • Protists: make up a large, varied group that includes both multicellular and unicellular organisms. • Fungi, Plants and Animals: make up half the biomass (total weight of all living things) on earth. • Most organisms that exist today probably originated during a relatively short time (10-100 million years). - Precambian and Early Cambian periods known as the Cambian Explosion. Mass Extinctions • About 440 million years ago, a large percentage of the organisms on Earth suddenly became extinct. -Extinction- is the death of all members of a species. -Mass Extinction- is an episode where large numbers of species become extinct. • There are 5 major extinctions recorded. The latest was 65 million years ago & brought the extinction of about 2/3 of all land species & the dinosaurs. • Scientists believe we are in the mist of another extinction due to human activity- ex. Destruction of the Tropical Rain Forests will lead to extinction of vegetation, birds, insects & other wild life. http://www.youtube.com/watch?v=ON-m4Yqd7ds The Ozone Layer • Before the Ozone layer was formed, organisms were sequestered to the ocean, where they were protected from UV radiation. • 2.5 billion years ago, photosynthesis by cyanobacteria began adding oxygen to Earth’s atmosphere. O2 reacted with the sun’s radiation to form O3 or ozone. • The upper atmosphere blocks the Ultra Violet radiation of the sun. • After millions of years Ozone has made Earth a safe place to live…. ….But you Still need to wear sunscreen! Life on Earth • First Multicellular Organisms was Fungi living together with plants and algae. • 100 million years after first union with fungi, plants covered the earth forming large forests. • Land plants provided food source for land-dwelling animals. • Arthropods- first animals to successfully make land. -hard outer skeleton, segmented bodies, and paired, jointed limbs. (lobsters, crabs, insects, spiders.) Life on Earth • First Vertebrates- (animals with a backbone) • 530 million years ago, small, jawless fish • 430 million years ago, small jawed fish • Fish are most successful living vertebrates • 370 million years ago- Amphibians -today include frogs, toads & salamanders • 340 Million Years ago- Reptiles -today includes snakes, lizards, turtles, & crocodiles • 65 Million years ago- birds and small mammals Continental Drift • The movement of Earth’s land masses over Earth’s surface through geologic time. • Results in the present day position of the continents. http://www.youtube.com/watch?v=uGcDed4xVD4 http://www.youtube.com/watch?v=TzzGPfVx32M PART II- Evolution Chapter 13 Pre-Darwin Ideas • 18th Century Europe: Most scientists believed that all species were permanent and unchanging. • They also believed that the Earth was only thousands (and not billions) of years old. • By 1800s, scientists in Europe began to study Strata- or Rock Layers Pre-Darwin Ideas • Georges Cuvier (1769-1832) reconstructed unique organisms from fossils that he found in the layers • He suggested that the lower the level, or older, the more different these organisms were to modern organisms. • He found sudden changes in the organisms and suggested extinctions occurred in the past • Not all of his explanations are still accepted, but he contributed to scientific evidence that geological change and extinction had occurred. Pre-Darwin Ideas • Charles Lyell (1797-1875) Worked with the idea of uniformitarianism. That geological processes have changed the shape of Earth’s surface in the past & continue to work in the same ways today. • Pangaea Pre-Darwin Ideas • Jean Baptiste Lamark (1744-1829) Supported the idea that populations change over time. • He thought that simple organisms could arise from nonliving matter • And that simple forms of life inevitably develop into more complex forms • He also thought individuals could acquire traits in their lifetime and pass those traits on to their offspring. The ideas of Charles Darwin (1809-1882) • Mid 1800’s, Charles Darwin and Alfred Russel Wallace formed a new theory to explain how evolution took place. • Darwin began his theory while on his voyage on the HMS Beagle, which he noticed the locations of similar organisms around the world. He also noticed that species varied based on their environment. • He spent much of his time at the Galapagos islands off the coast of South America • He studied 13 species of Finches on the different islands and used this as his argument for Natural Selection The ideas of Charles Darwin • In 1859, Darwin Published a book entitled On the Origin of Species by Means of Natural Selection. • He wanted to give evidence that evolution occurs • And to explain the variety and distribution of organisms on Earth in the terms of Natural Processes that are observable everyday. • Darwin used the phrase decent with modification to describe evolution- he said that every species, living or extinct must have descended from a previous species (or a common ancestor) and that species must be able to change over time. Natural Selection • Natural Selection• Process by which individuals that are better adapted to their environment survive and reproduce more successfully than less well adapted individuals do • It is also a theory to explain the mechanism for evolution. Four Main Parts of Darwin’s Reasoning 1. Overproduction- more offspring can be produced than can survive to maturity; the environment limits the populations of all organisms by causing deaths or by limiting births. http://www.youtube.com/watch?v=3AZKixtQz_Q Four Main Parts of Darwin’s Reasoning 2. Genetic Variation- within a population, individuals have different traits; occasionally new traits may appear in a population due to mutations, crossing over, random fertilization, independent assortment. 3. Struggle to Survive- individuals must compete with each other in a “struggle for existence”. Some traits improve and individual’s chance to survive while other traits reduce this chance. • A trait that makes an individual successful in its environment is called an Adaptation. Four Main Parts of Darwin’s Reasoning 4. Differential Reproduction- organisms with the best adaptations are most likely to survive and reproduce and through inheritance, the adaptations will become more frequent in the population. • Populations may begin to differ as they become adapted to different environments, even if they descend from the same ancestors. Natural Selection • The theory of Natural Selection proposes that nature changes species by selecting traits • Darwin sometimes used the phrase “Survival of the Fittest” to explain Natural Selection. • In evolutionary terms, Fitness is a measure of an individual’s hereditary contribution to the next generation. Evidence of Evolution 1. Biogeography is the study of the locations of organisms around the world. Fossil Records and live organisms are used. Evidence of Evolution 2. Anatomy and Embryology • Anatomy is the study of the body structure of organisms • Embryology is the study of how organisms develop Evidence of Evolution 3. Homologous Structures- are the anatomical structures that occur in different species and that originate by heredity from a structure in the most recent common ancestor of the species • Often have a related structure even if their functions differ between species • Example: the forelimbs of vertebrates Evidence of Evolution 4. Analogous structures- have closely related functions but do not derive from the same ancestral structure. • Examples: wings of birds, bats, and moths Evidence of Evolution 5. Vestigial Structures- seem to serve no function but that resemble structures with functional roles in related organisms. • Examples: human tailbone, pelvic bones of modern whales, and the human appendix. Evidence of Evolution 6. Biological Molecules- in all species, DNA and RNA are the molecular basis for inheritance of traits. • You can compare the DNA and RNA of different species- the greater the number of similarities between any given species, the more closely the species are related through a common ancestor. Types of Evolution 1. Convergent Evolution- is the process by which different species evolve similar traits. Types of Evolution 2. Divergent Evolution- is a process in which the descendents of a single ancestor diversify into species that each fit different parts of the environment • Example: Darwin’s finches Types of Evolution • Sometimes a new population in a new environment will undergo divergent evolution until the population fills many parts of the environment. This pattern of divergence is called Adaptive Radiation or founders affect. • Example: Caribbean anole lizards http://www.youtube.com/watch?v=9x8lFXgXmZI Types of Evolution 3. Artificial Selection- is a process when a Human Breeder chooses individuals that will parent the next generation with select desirable traits • Example: breeding dogs, cats, horses • AKA- Selective Breeding Types of Evolution 4. Coevolution is when two or more species have evolved adaptations to each other’s influence • Evolution is ongoing and many species can be evolving at once • Each species is part of the forces of natural selection that act upon the other species • Examples: humans have developed and used antibiotics but many bacteria have evolved adaptations to resist the effects of some antibiotics.