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SOLAR SYSTEM LIFE-capacity for growth, metabolism, reproduction, reaction to stimuli SOLAR SYSTEM-Big Bang theory- one mass of matter blew apart 12-15 billion years ago Smaller H and He atoms fused to form heavier elementsstars huge masses of interstellar gases; sun formed 6 billion years ago Planets formed 4.6 billion years ago by the condensing of peripheral gases and matter around the sun. FORMATION OF EARTH Earth formed about 4.6 billion years ago Four layers of earth formed by the effect of heat from gravitation and radioactivity: Inner solid core- mostly of iron and nickel Outer molten core- of iron and sulfur A plastic mantel – iron, magnesium, aluminum, silicon, oxygen silicate compounds A thin crust which solidified 4.1 billion years ago The earth’s diameter is 12,742 KM (7,900 miles) compared with that of the sun –(1,391,000 KM) and an object on the sun’s surface would weigh 28 times as much as it does on earth’s surface. Atmosphere- due to the earth size under a gravitational field Gases in atmosphere- nitrogen, carbon dioxide, hydrogen Water vapor due to intense heat- in thick clouds; when cooled forms rain collected in rivers, lakes, oceans etc. ORIGIN OF LIFE CHEMICAL EVOLUTION – complexity of chemicals led to first cells Oparin (1938) – postulated that reducing atmosphere coupled with free energy from volcano activity, lightening, radioactive minerals and the sun (devoid of ozone layer) facilitated the formation of organic molecules. Miller (1953) – duplicated the early conditions in the lab by creating an artificial ‘atmosphere’ and ‘ocean’ and introducing hydrogen, methane, ammonia, and water into the system with electric spark as energy supply, to obtain after one week, the formation of amino acids and small organic molecules. Other scientists repeated their work, eventually producing amino acids, ATP, glucose and other sugars, lipids, and the bases which form RNA and DNA, and adenine the key component of ATP and NAD. Over a long period of time the lack of oxidation and decay allowed organic molecules to form a thick, warm organic “primordial soup”. PROTOCELLS PROTOCELL – cell-like structure with a lipid-protein membrane developed from coacervate droplets. Coacervate droplets – are complex spherical units formed spontaneously when concentrated mixtures of macromolecules (like RNA, DNA, amino acids, phospholipids, clay etc.) are held at the right temperature, ion composition, and pH. They absorb and incorporate various substances from the surrounding solution. A protocell could have contained only RNA to function as both genetic material and enzymes. First protocells were heterotrophs using ATP as energy and carrying out a form of fermentation. Heterotroph – an organism unable to synthesize organic compounds from inorganic substances and therefore must take in preformed organic compounds, e.g. animals Autotroph – an organism that make organic molecules from inorganic nutrients, e.g., plants HISTORY OF LIFE - 1 PRECAMBRIAN encompasses 87% of geological time scale and based on this, life began from 570 million to 4.6 billion years ago. Early bacteria resembled archaea that live in hot springs today. Archaeans resemble bacteria but developed separately from common ancestor nearly 4 billion years ago. They thrive under extreme conditions and are labeled as ‘extremophiles’. Bacteria and archaea are termed as PROKARYOTES –organisms whose DNA is not enclosed in a nucleus of the cell. EUKARYOTIC cells are aerobic and arose 2.1 billion years ago. They contain nuclei and organelles. Plants appeared on land (mud flats) during the ‘Paleozoic’ period, about 440 million years ago. They provided food for higher animals to evolve. HISTORY OF LIFE - 2 MESOZOIC PERIOD-ruled by dinosaurs; sub-divided into 3 categories. Triassic – 245-208 million years ago; appearance of ferns, gingkophytes, cycads, conifers Jurassic – 208-146 million years ago (mya)- birds, dinosaurs Cretaceous – 146- 65 million years ago – angiosperms (flowering plants and extinction of dinosaurs CENOZOIC PERIOD – 66-24 million years ago – mammals and tropical forests; 24 mya – appearance of monkeys apes and humans; major climatic shift; grasslands replaced forests 6-24 mya – grazing animals flourished; 2-6 mya - herbaceous flowering plants flourished and first homonids ( intermediate between apes and people e. g. genus Australopithecus ) appeared PLEISTOCENE EPOCH (0.01-2 mya)- ice age caused mammalian extinction; herbaceous plants spread and the RISE OF MODERN HUMANS. PROKARYOTES Prokaryotes are single celled micro-organisms characterized by: i. the lack of a membrane-bound nucleus and ii. membrane bound organelles. There are two domains of prokaryote: i. ii. the Eubacteria/Bacteria the Archaebacteria/Archaea Cont… Differences between bacteria and archaea: Eubacteria have cell walls composed of peptidoglycan, Archaebacteria have cell walls composed of various different substances. Eubacteria have ester-linked straight-chain membrane lipids (fatty acids). Archaebacteria have ether-linked branched-chain member lipids. Eubacteria and Archaebacteria have differences in their DNA replication and transcription systems that suggest independent elaboration in these two groups Eubacteria usually use N-formylmethionine as the initial amino acid of a protein, while Archaebacteria use plain methionine. The translation apparatus of Eubacteria is inhibited by such antibiotics as chloramphenicol, cycloheximide, tetracycline, streptomycin, and kanamycin, while the translation apparatus of Archaebacteria is not. The translational apparatus of Archaebactera is inhibited by diphtheria toxin, while the translational apparatus of Eubacteria is not. PROKARYOTE CELL BIOLOGY A) B) Cell = fundamental unit of biology, building block of all organisms Organisms range from unicellular to multicellular 1) 2) Unicellular: 1 cell = 1 organism Multicellular: 1036 cells = 1 organism, different cells for different functions, exhibit division of labor Diversity of cells 1) Different types of unicellular organisms (Paramecium & Amoeba) 2) Different types of cells in multicellular organisms (muscle, skeletal, immune, lungs, epithelium, etc...) D) Classification of cells 1) Two major groups - Prokaryotes and Eukaryotes 2) Differences: Prokaryotes - smaller size, simple structure (no membrane bound organelles, no nucleus, DNA in a single strand), primitive (old group of organisms, nearest relatives of first living organisms) C) EUKARYOTES Cells having a membrane-bound nucleus, membrane-bound organelles and chromosomes Includes all other cells from other origins EUKARYOTES CELL STRUCTURES EUKARYOTES ORGANELLES DNA-associated with chromosomes, chromatin, nucleolus, ATP-ase; synthesizes RNA and ribosomes RIBOSOMES-protein synthesis ER-protein transport (rough ER); regulates Ca levels; breaks down toxic substances (smooth ER) GOLGI APPARATUS- process and packages substances produced by the cell LYSOSOMES- digests old molecules and foreign substances CYTOSKELETON (microfilaments/tubules) contributes to support, movement and division of cell CILIA- propels cell MITOCHONDRION- transfers energy from ATP Vacuole- (in plants) stores enzymes and waste products Plastids- (in plants) stores pigments Function Eukaryotes Prokaryotes Isolation (plants and) cell wall (plants) phospholipid bilayer cell membrane with proteins same but minor chemical differences Support cytoskeleton none Energy (production) chloroplasts (plants) mitochondrion (Krebs cycle) chlorophyll but no covering none (fermentation) Energy (digestion) lysosomes (aging??) None Protein Synthesis animals Rough ER ribosomes only Fat Synthesis Smooth ER none Refine Chemical and Storage Golgi apparatus none Movement cilia and flagella psuedopod movement flagella (different) Reproduction and Control DNA DNA on chromosomes inside nucleus DNA in single strand, DNA floating freely, no nucleus