CMC 1º BACHILLERATO A/D BILINGUAL SECTION UNIT 3. ORIGIN AND EVOLUTION OF LIFE

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Damon Payne
5 years ago
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1 A) What is Life? For scientists there is not a unique concept for life but there are some common characteristics that allow us to distinguish the most essential of this phenomenon. Life is a system that uses an environment for reproduction and perpetuation of species. B) The chemical basis of Life: Immediate Principles Immediate principles are biomolecules that are part of living being. They consist of about 70 chemical elements that are also called bioelements. Bioelements can be classified into: Primary or essential (CHONPS). Constitute 96% by mass of living matter. They are the key components of the water and organic biomolecules. Secondary. Are less abundant (approximately 4 %) but play an essential role in the physiology of living being. Are calcium (Ca), magnesium (Mg), sodium (Na), potassium (K) and chlorine (Cl). Tertiary. They are part of living being in a small proportion (0.1%), but they are essential for life as they are involved in many biological processes. Examples: iodine (I), iron (Fe), manganese (Mn), cobalt (Co), selenium (Se), fluoride (F), copper (Cu), etc. Biomolecules, in turn, can be divided into two groups: INORGANIC: water and mineral salts. ORGANIC: carbohydrates, lipids, proteins and nucleic acids, made up of chains of carbon and hydrogen and they can be found exclusively in living beings C) First Theories about the Origin of Life Creationism This is a philosophical doctrin which considers that from the beginning, man has sought explanation of the origin of life. The first cultures linked this to the presence of an omnipotent being (God), although this hypothesis is not scientific by not testing any observable fact that can verify it, however, creationism have survived to this day.

Spontaneous generation Experiments conducted between the XVII and XVIII centuries eventually banish this idea. Here is the most important experiment: Redi's experiment.

2 Spontaneous generation Experiments conducted between the XVII and XVIII centuries eventually banish this idea. Here is the most important experiment: Redi's experiment. Francesco Redi, an Italian physician, performed an experiment in 1668 in which he placed four glasses in which respectively put a piece of snake, fish, eels and a piece of beef. Then prepared another four glasses with the same materials and left open, while the first ones remained sealed. Soon some flies were attracted by food left in open vessels and went to eat and lay eggs; after a period of time, in this series of vessels began to appear some larvae. This is not verified, however, in closed vessels, even after several months. Therefore, Redi concluded that the larvae (maggots) were originated because of flies and not by spontaneous generation. Some people objected to Redi saying in closed vessels had lacked air circulation (which, they said, lay the "vital principle") and that had prevented spontaneous generation. Redi made a second experiment, this time the experiment vessels were not sealed, but only coated gauze. The air, therefore, could circulate. The result was identical to the previous experiment, because the gauze obviously prevented insect access to the vessels and subsequent deposition of eggs and therefore not given birth larvae. With these simple experiences, Redi showed that putrefying flesh was developed by a larvae action and not by a meat processing, as was claimed by supporters of spontaneous generation.

D) Modern theories about the Origin of Life Prebiotic Synthesis: The Origin of Life upon Alexander Oparin Oparin postulated that 4,000 million years ago, about the time the Earth s crust cooled,

3 D) Modern theories about the Origin of Life Prebiotic Synthesis: The Origin of Life upon Alexander Oparin Oparin postulated that 4,000 million years ago, about the time the Earth s crust cooled, small molecules of atmospheric gases (H 2 O, methane [CH 4 ] and ammonia [NH 3 ]) resulted in a organic molecule called prebiotic, thanks to the energy provided primarily by ultraviolet radiation from the Sun and the constant shock of storms. These prebiotic molecules, more complex, would become amino acids (protein constituent of elements) and nucleic acids. According to Oparin, these first molecules would be trapped in shallow pools formed in the early ocean coastline, forming a prebiotic soup. Afterwards these simple compounds forming polymers were grouped into forming more complex organic molecules. At some point, somewhere a molecule capable of replicating itself would appear and lead the formation and appearance of the first cell. E) The Cell The Eucaryotic Cell: Eucaryotic Animal Cell

Eucaryotic Plant Cell Organelle Function Nucleus The brain of the cell, the nucleus directs cell activities and contains genetic material called chromosomes made of DNA.

4 Eucaryotic Plant Cell Organelle Function Nucleus The brain of the cell, the nucleus directs cell activities and contains genetic material called chromosomes made of DNA. Mitochondria Cell structures responsible for supplying energy from food Ribosomes Cell structures responsible for protein production. Golgi Apparatus Process and package proteins Lysosome Contains digestive enzymes to help break food down Endoplasmic Called the "intracellular highway" because it is for transporting all sorts of Reticulum items around the cell. Vacuole Used for storage, vacuoles usually contain water or food. Plant cells also have: Chloroplasts Use sunlight to create food by photosynthesis Cell Wall To support and protect the cell

5 Prokaryotic Cells Prokaryotic cells are not as complex as eukaryotic cells. They have no true nucleus as the DNA is not contained within a membrane or separated from the rest of the cell, but is coiled up in a region of the cytoplasm called the nucleoid. Organelle Capsule Cell Wall Cytoplasm Function Found in some bacterial cells, this additional outer covering protects the cell when it is engulfed by other organisms, assists in retaining moisture, and helps the cell adhere to surfaces and nutrients. Outer covering of most cells that protects the bacterial cell and gives it shape A gel-like substance composed mainly of water that also contains enzymes, salts, cell components, and various organic molecules. Surrounds the cell's cytoplasm and regulates the flow of substances in and Cell Membrane out of the cell. Pili Flagella Ribosomes Plasmids Nucleiod Region Hair-like structures on the surface of the cell that attach to other bacterial cells. Help bacteria attach to surfaces. Long protrusion that aids in cellular locomotion. Cell structures responsible for protein production. Gene carrying, circular DNA structures that are not involved in reproduction. Area of the cytoplasm that contains the single bacterial DNA molecule.

6 F) Main Theories of Evolution Until the early nineteenth century, theories attempting to explain the origin and diversity of living things were type of Fijism (species had remained static and unvarying since Creation). Linnaeus and Cuvier were known as scientists who had followed the ideas of fijism; but precisely Cuvier, ironically, contributed decisively to the beginning of the evolutionary theories, through its work on the fossil record. For this reason he is called the father of paleontology. Lamarckism Lamarck explains that evolution occurs by accumulation of acquired characters in the course of several generations. So his theory is also known as the theory of acquired characteristics. The main criticisms of Lamarckism are: - There is no evidence that organisms need their bodies to be transformed, or that changes necessarily involve an increase in complexity. - Today we know that as much as individuals change their customs, they can not transfer those changes to the genotype. Darwinism Charles R. Darwin was considered the father of the current theory of evolution, as he published The Origin of Species (1859) after five years of navigation on the HMS Beagle ( ). Darwin got the basic ideas for the formulation of his theory on the observation of the diversity of animals and plants during this trip. As a result of readings and observations, Darwin developed a theory explaining the origin and diversity of living beings; he called this theory as "Common Descent with Modification whose engine was natural selection. These are its basic ideas: 1) Evolution is gradual and it is explained by selective accumulation of favorable variations over many generations. 2) There are minor variations between organisms that are inherited. 3) Some of these inherited variations provide advantages to survive and / or to leave more descendants. Consequently, over several generations advantageous characters have to rise and who are not likely to disappear. 4) In nature more individuals are born than can survive. Consequently, organisms must compete for survival with limited resources. 5) The engine of evolution is adaptation to the environment, resulting from the combined effect of natural selection and random mutations.

7 Neodarwinism This new theory consists essentially of an enrichment of Darwinism with Mendelian inheritance, chromosomal theory of inheritance and population genetics, so for this reason is also called Neodarwinism. It is based on the following principles: 1) The evolutionary unit is not the individual but the population. That is, the environment makes the process of natural selection on the set of genes in a population. 2) The mechanism by which natural selection occurs is produced by differential reproduction resulting from the interaction between genetic variation and ambient pressure. Given a set of possible variants (alleles) for the gene encoding for a given character, only some of them will be selected by the environment, which will be key in making the population, and others disappear. 3) The evolution occurs by a gradual change in the genes of species.

prokaryotic eukaryotic

prokaryotic eukaryotic Cell Basics Two Basic Cell Types All cells are either prokaryotic or eukaryotic Prokaryotic Cells a.k.a. Bacteria Prokaryotes, which includes all bacteria. They are the simplest cellular organisms. They