Theories on the Origin of Life PDF

Theories on the Origin of Life LESSON OBJECTIVES 01 enumerate theories that explain how life emerged on Earth; and 02 explain how life formed and evolved. Theories on the Origin of Life Theories that describe how life on Earth first existed include the following: Special Creation Theory Theory...

Theories on the Origin of Life LESSON OBJECTIVES 01 enumerate theories that explain how life emerged on Earth; and 02 explain how life formed and evolved. Theories on the Origin of Life Theories that describe how life on Earth first existed include the following: Special Creation Theory Theory of panspermia Spontaneous generation theory Primordial soup theory Biogenesis Theory  Special Creation Theory NOT based on facts, but rather on faith Life is created by a Supreme Being This theory emphasizes that everything that you see came from the Almighty God/ Creator. This one is not about from the facts but rather on FAITH.  Panspermia Cosmozoic Theory AKA Panspermia  Panspermia Fertilization (Earth was fertilized) Cosmozoa (Alien material that fertilized the Earth) Its either from comet, asteroid or from our neighboring planets (Venus and Mars)  Panspermia The theory was proposed by astronomer Fred Hoyle in the 19th century. It states that life on Earth was seeded from a celestial source. The theory of panspermia is also called exogenesis, as some of its hypotheses suggest that building blocks of life came from another planet.  Panspermia These include comets colliding the Earth and depositing living cells or the precursors of life, and aliens making life-essential materials in a laboratory. Most scientists who believe in panspermia stick to the origin of life from comets.  Panspermia This particular theory does not focus on the origin of life itself but on the possible transmission of life that allowed it to be distributed to different parts of the planet. Organisms like bacteria and other microorganisms might have travelled in dormant stages within comets and asteroids that heated the Earth.  Panspermia These dormant organisms became activated and started colonizing the Earth, which served as their new environment. Until now, the integrity of the theory remained in question as there is no evidence supporting its hypothesis.  Spontaneous Generation Theory  ‘ABIOGENESIS’ Spontaneous Generation  Spontaneous Generation The theory of spontaneous generation described that life comes from lifeless or nonliving material through a mysterious process.  Spontaneous Generation The idea of abiogenesis, or the formation of life from nonliving materials, had popularized this theory. Abiogenesis is the process by which life emerges naturally from inanimate or nonliving materials.  Spontaneous Generation Anaximander, a Greek philosopher in the 6th century BCE. Other philosophers, including Aristotle, adapted and expanded Anaximander’s idea. Aristotle explained in his writing, The History of Animals that was written in 350 BCE, that some organisms appeared from inanimate objects spontaneously.  Spontaneous Generation For instance, when hay was piled, mice appeared. When garbage was left for some time, maggots appeared. From these coincidences, he assumed that clutter gave rise to vermin through spontaneous generation, a process that transmuted lifeless objects to living organisms by supernatural means.  ARISTOTLE ”On the Generation of Animals or also known as The History of Animals” The theory suggests that organisms do not descend from other organisms or from a parent.  ARISTOTLE He suggested that animals and plants could arise from earth and liquid, because there was “vital heat” within all air, there is air/gas in water, and there is water in earth, meaning there is “vital heat” or “soul” within everything.  ARISTOTLE Wet soil after a flood was believed to create amphibians such as frogs and toads.000 Garbage in the streets was thought to create rats. Salamanders were thought to be borne within fire (they often hide inside logs and were probably trying to escape the blaze!).  ARISTOTLE Oyster shells were believed to form as the earth solidified around them and the “vital heat” grew the creature within. Crocodiles in Egypt were thought to have emerged from the mud with the sunshine as a catalyst.  Spontaneous Generation Francesco Redi (1668) challenged the idea by using the concept that maggots came from rotting meat. Disproving:  Spontaneous Generation He insisted that maggots will not be formed (or appear) in totally and partially sealed containers. However, results of this experiment did not convince the scientific community during that time.  Spontaneous Generation John Needham (1745) conducted an experiment on boiled broths to support spontaneous generation theory. He believed that boiling kills microorganisms in the broth.  Spontaneous Generation He actually conducted an experiment with boiled broth and sealed it afterwards. He hypothesized that the broth would become cloudy and still form microorganisms, thus supporting the belief in spontaneous generation. Proving:  Spontaneous Generation Lazzaro Spallanzani In 1768, Lazzaro Spallanzani made some modifications on Needham’s experiment by excluding the possibility of contamination factor prior sealing the bottle after boiling. He boiled the broth in a partially sealed jar with the air partially evacuated to avoid explosions while boiling. He did not observe any growth, although the issue of the role of air remains in question to disprove spontaneous generation theory. Lazzaro Spallanzani  Spontaneous Generation Lastly, in 1859, a French scientist, Louis Pasteur made an experiment to totally disprove the spontaneous generation theory. In his experiment, Pasteur boiled a meat broth in a goose-like flask having a long curved neck.  Spontaneous Generation He explained that the bend in the neck prevented particles from reaching the meat broth and still allowed free air to flow. In his observation, the flask remained clear and there was no cloud formation observed for an extended period. Conclusion: Boiling broth will NOT spontaneously give rise to new life, unless directly exposed to air. This experiment of Pasteur convinced a lot of scientists during his time and led to the exclusion of spontaneous generation theory as a valid idea to explain the origin of life. Louis Pasteur  LIFE from INORGANIC and ORGANIC MOLECULES The conditions of the early Earth changed these inorganic molecules to complex organic molecules which are necessary to life. And from these complex organic molecules the primitive life emerged.  Primordial Soup Theory It was proposed by Alexander Oparin and John Haldane. Life started in a primordial soup of organic molecules from inorganic materials. This theory explains how the catalysts for nonliving things became living cells from the chemical compounds abundant on the early Earth. A.PROTEIN WORLD Metabolism occurred first as networks that supported the formation of living things. EUrey-Miller experiment simulated the conditions of the early years of Earth. Proved that organic molecules can be formed from inorganic molecules (Water, Methane, Ammonia and Nitrogen Gas) Urey-Miller Experiment B. RNA WORLD As we know cells needs both: DNA - store genetic informations Proteins - for replication, growth and development, and survival - this keeps the cells alive and healthy but cannot store information. B. RNA WORLD In short, (1)DNA needs protein to function (2)Protein needs DNA to exist (storage of genetic material) WHICH CAME FIRST? B. RNA WORLD RNA may hold the answer. Scientists hypothesized that RNA came first. RNA can do 2 jobs: (1)Store information (DNA role) (2)Perform functions that keep cells alive (Protein role) B. RNA WORLD HOW RNA WAS FORMED? (1)Billions of years ago, in some primordial soup of molecules a self-replicating RNA was formed. (2)Early RNA was formed in Mars and hits a ride on asteroid to our planet. B. RNA WORLD HOW RNA WAS FORMED? Strong RNA survived and became protein. RNA mutated and became DNA. Today, RNA can slice, dice, catalyze, build, destroy, code, replicate and transform. Present: Central Dogma of Life BIOGENESIS THEORY Life comes from life BIO means LIFE, GENESIS means BEGINNING Complex living beings emerged from simpler living beings. “Life produces life.” Biogenesis Theory All living things appear similar in their early stages of development (embryonic stages), leading to the idea that there is one common ancestor or a primordial cell of all living things.