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Download Chapter 19 The Origin of Life and the Evolution of Cells
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Chapter 19 The Origin of Life and the Evolution of Cells Biology 100 Early Ideas of Origin of Life • Spontaneous generation was a concept proposed by Aristotle around mid-300 B.C. which is the hypothesis that living things arise from non-living material – Widely accepted theory for a long period of time – Believed maggots arose from decaying meat, lice formed from sweat, and frogs originating from mud • An opposing theory was biogenesis is the concept that life originates only from preexisting life Disproving Spontaneous Generation • In 1668, Francesco Redi, performed an experiment where he set up two sets of jars with decaying meat, one which was covered by gauze, the other one left exposed – Redi saw that the gauze blocked their access • Flies arose from the open jar, so Redi concluded that maggots arose from the eggs of flies Disproving Spontaneous Generation • In 1861, Louis Pasteur placed a fermented sugar solution and yeast mixture in a flask with a long swan neck and boiled. The flask was left open, and for a control, one flask was neck was broken off. Endosymbiotic Theory • Biologists generally believe that eukaryotes evolved from prokaryotes – Eukaryotes have their DNA in a nucleus and membrane bound organelles • The Endosymbiotic Theory states that present day eukaryotic cells evolved from the uniting of several types of primitive prokaryotic cells – Some organelles (mitochondria and chloroplasts) might have been were originally prokaryotes that were involved in a symbiotic relationship Endosymbiotic Theory Chapter 20 The Classification and Evolution of Organisms Biology 100 Classification of Organisms • Common names vary from culture to culture, as well as varying between region to region • Taxonomy is the science of naming organisms and grouping them into local categories • In 1758, Swedish doctor Carlos Linnaeus, introduced the binomial system of nomenclature uses two Latin names to identify an organism – Genus is a group of closely related organisms – Species word added to the genus name to identify which one of several species within the genus Classification of Organisms • So, the binomial system of nomunclature is in the order Genus species – In order to identify it as a scientific name, the names are italicized in computer for of the genus font, and underlined when hand-written – The first letter of the genus is capitalized, while species name is in lowercase • Homo sapiens Three Domains of Life • There was a need for placing organisms into groups. • At first, there Linnaeus proposed plant and animal kingdoms. Later on, the groups were bacteria, plants and animals. • The three major categories of organisms called domains. – Today, these three domains are Eubacteria, Archaea, and Eucarya Three Domains of Life • Divided into these three domains are based on specific structural and biochemical features of cells – Prokaryotes • Eubacteria • Archaea – Eukaryotes • Eucarya Classification • In order to classify organisms, biologists see how a species fits into different categories – – – – – – – – Domain Kingdom Phylum Class Order Family Genus Species • Mnemonics for classification: King Phyl Came Over For Good Spaghetti, King Philip Came Over From Germany Swimming Classification of Humans Taxonomic Category Human Characteristics Classification Other Represenatives Domain Eucarya Nucleus in cells, other kinds of organelles Plants, Animals, Fungi, Protozoa, Algae Kingdom Animalia Eukaryotic heterotrophs Sponges, jellyfish, insects, cats Phylum Chordata Animals with type of backbone Fish, reptiles, mammals Class Mammalia Animals with hair/mammary gland Kangaroos, mice, whales, monkeys Order Primates Mammals with large brain, opposable thumbs Monkeys, gorillas, baboons Family Homindae Primates lack tail and have upright posture Humans and extinct relatives Genus Homo Hominids with large brains Humans only surviving member Species Homo sapiens Humans Eubacteria Domain • Eubacteria, “true bacteria” are small, prokaryotic, single-celled organisms • Most Eubacteria are saprophytes, decomposing dead organic matter for energy • Some live in anaerobic environments (anoxic mud, guts of herbivores), while others are aerobic. Archaea Domain • The Archaea are the extremophiles, many living in some of the least hospitable habitats on Earth. • They have been discovered living in hot springs as hot as 140176oF in hot springs at Yellowstone National Park • Others live as symbionts or free-living cells at deep seas hydothermal vents at over 212oF. • Some Archaea are decomposers in very anaerobic environments, such as marshes • Some live in the digestive systems of animals and produce methane. • Other species live in very salty environments like Great Salt Lake. Eucarya Domain • Eukaryotes are much larger than prokaryotes, that allow them to have specialized membranous organelles. There are several different divisions (kingdoms) in the Domain Eucarya. – Kingdom Protista – Kingdom Fungi – Kingdom Plantae – Kingdom Animalia Kingdom Protista • Traditionally, most single-celled eukaryotes were lumped together in a group called the Protista. • The Protista also contains a few multicellular colonial members. • There are three major lines of evolution within Protista. – Plantlike autotrophs (Algae) – Animal-like heterotrophs (Protozoa) – Fungus-like heterotrophs (Slime molds) Kingdom Fungi • More commonly known as fungus and are multicellular and non-motile. • They form networks of multicellular filaments which penetrate their environment. • Most species are decomposers • They secrete hydrolytic enzymes which digest dead organic matters into smaller molecules which the fungus absorbs. • A few fungi are parasites, especially of plants, sometimes animals. Kingdom Plantae • About 500 million years ago, a group of green algae developed adaptations that enabled them to invade the land. These are knownas plants. • Plants are nonmotile, terrestrial, and multicellular organisms. They contain chlorophyll and produce their own organic compounds. All plant cells have a cellulose cell wall. Kingdom Animalia • In this kingdom, all animals are motile, heterotrophic, and multicellular. Acellular Infectious Particles • In order to be considered living, an organism must have certain characteristics: – Metabolism – Reproduce independently – Cellular organization – Homeostasis – Heredity Acellular Infectious Particles • Viruses are not considered “living” because they do not meet the criteria of reproducing independently – Viruses are literally “parasitic” chemicals, segments of DNA (or RNA) wrapped in a protein coat Structure of Viruses • A virus is simply put, a protein with a core of nucleic acid – The protein sheath is known as a capsid which surrounds their nucleic acid core – In addition, some viruses form a membranelike envelope, rich in proteins, lipids and glycoprotein molecules around the capsid Structure of Viruses • Viruses vary in complexity and shape. – Most animal and plant viruses are simpler in appearance and are either helical or isometric – Bacteriophages are generally more complex, looking like a lunar lander Bacteriaphages • Bacteriophages are viruses that infect bacteria – During the process of bacterial infection, one of the tail fibers, contacts the lipoproteins of the host bacterial cell wall. – Then the contents of the head (DNA) are injected into the host cytoplasm – The virus infecting and killing the host cell is known as the lytic cycle. Lytic Cycle http://bioinfo.bact.wisc.edu/themicrobialw orld/lysogeny.jpg
