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Early History of Earth

Early History of Earth. What was early Earth like? Some scientists suggest that it was probably very hot . The energy from colliding meteorites could have heated its surface , while both the compression of minerals and the decay of radioactive materials heated its interior.

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Early History of Earth

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  1. Early History of Earth What was early Earth like? • Some scientists suggest that it was probably very hot. • The energy from colliding meteorites could have heated its surface, while both the compression of minerals and the decay of radioactive materials heated its interior.

  2. Early History of Earth • Volcanoes might have frequently spewed lava and gases, relieving some of the pressure in Earth’s hot interior. These gases helped form Earth’s early atmosphere.

  3. The Origin of Life – Early Ideas In the past, the ideas that decaying meat produced maggots, mud produced fishes, and grain produced mice were reasonable explanations for what people observed occurring in their environment. Such observations led people to believe in spontaneous generation— the idea that nonliving material can produce life. In 1668, an Italian physician, Francesco Redi, disproved a commonly held belief at the time—the idea that decaying meat produced maggots (immature flies). Time Control group • Redi’s well-designed, controlled experiment successfully convinced many scientists that maggots, and probably most large organisms, did not arise by spontaneous generation. Experimental group Time

  4. The Origin of Life – Early Ideas • However, during Redi’s time, scientists began to use the latest tool in biology—the microscope (invented by Anton Van Leeuwenhoek ) • Although Redi had disproved the spontaneous generation of large organisms, many scientists thought that microorganisms were so numerous and widespread that they must arise spontaneously-probably from a vital force in the air. • In the mid-1800s, Louis Pasteur designed an experiment that disproved the spontaneous generation of microorganisms. • Pasteur set up an experiment in which air, but no microorganisms, was allowed to contact a broth that contained nutrients. • Pasteur’s experiment showed that microorganisms do not simply arise in broth, even in the presence of air. • From that time on, biogenesis, the idea that living organisms come only from other living organisms, became a cornerstone of biology.

  5. Pasteur’s Experiment The flask’s S-shaped neck allowed air to enter, but prevented microorganisms from entering the flask. Each of Pasteur’s broth-filled flasks was boiled to kill all microorganisms. Microorganisms soon grew in the broth, showing that they come from other microorganisms. Pasteur tilted a flask, allowing the microorganisms to enter the broth.

  6. The Evolution of Cells • Fossils indicate that by about 3.4 billion years ago, photosynthetic prokaryotic cells existed on Earth. But these were probably not the earliest cells.The first forms of life may have been prokaryotic forms that evolved from a “protocell”. • Because Earth’s atmosphere lacked oxygen, scientists have proposed that these organisms were most likely anaerobic. • For food, the first prokaryotes probably used some of the organic molecules that were abundant in Earth’s early oceans. • Over time, these heterotrophs would have used up the food supply. • Heterotrophs are organisms which obtain their food from other heterotrophs or autotrophs (plants).

  7. The First True Cells • Autotrophs are organisms that can make their own food (i.e. plants). These first autotrophs were probably similar to present-day archaebacteria. • Archaebacteria are prokaryotic and live in harsh environments, such as deep-sea vents and hot springs. • The earliest autotrophs probably made glucose by chemosynthesis rather than by photosynthesis. • In chemosynthesis, autotrophs release the energy of inorganic compounds, such as sulfur compounds, in theirenvironment to make their food (they use chemicals instead of sunlight). Bill Nye Video Segment – Life As We Know It

  8. The Endosymbiont Theory (Endosymbiosis) • Complex eukaryotic cells probably evolved from simple prokaryotic cells. • The endosymbiont theory, proposed by American biologist Lynn Margulis in the early 1960s, explains how eukaryotic cells may have arisen. • The endosymbiont theory proposes that eukaryotes evolved through a symbiotic relationship between ancient prokaryotes. • New evidence from scientific research supports this theory and has shown that chloroplasts and mitochondria have their own ribosomes that are similar to the ribosomes in prokaryotes. • In addition, both chloroplasts and mitochondria reproduceindependently of the cells that contain them. • The fact that some modern prokaryotes live in close association with eukaryotes also supports the theory. (i.e. E.coli in human gut)

  9. The Discovery of Cells • Anton Van Leeuwenhoek= Dutch scientist who invented the first light microscope. • Robert Hooke = English scientist who identified and named the “cell”while observing cork cells with a light microscope. • Robert Brown = English scientist who identified and named the nucleusof the cell. • Matthias Schleiden = German scientist that noted all plants are made of cells. • Theodor Schwann = German scientist who noted that all animals are made of cells. • Rudolf Virschow = Russian scientist who stated that cells come from pre-existing cells.

  10. Schleiden Schwann The Cell Theory The cell theory (proposed independently in 1838 and 1839) is a cornerstone of biology. All plants are made of cells. All animals are made of cells

  11. The Cell Theory 1. All organisms are made of one or more cells. 2. The cell is the basic unit of structure and organization of organisms. 3. All cells come from pre-existing cells. Modern Additions: 4. All cells contain hereditary information which is passed from cell to cell during cell division. 5. All cells are basically the same in chemical composition. 6. All energy flow (metabolism and biochemistry) of life occurs within cells.

  12. A prokaryotic cell A eukaryotic cell Comparing Cells Two Fundamentally Different Types of Cells • PROKARYOTES • All lack a nucleus • Contain DNA • Contain cytoplasm • All lack organelles • All have a cell membrane • Only bacteria are made of prokaryotic cells • EUKARYOTES • All have a nucleus • All contain organelles • All contain cytoplasm • All have a cell membrane • All contain DNA inside a nucleus

  13. “Us vs. Them” - Eukaryotes and Prokaryotes

  14. CELLS!

  15. CELLS! PROKARYOTE vs. EUKAROTE Common Features

  16. EUKARYOTES ★ Greek = “true nucleus” ★ Compartmentalized with organelles (membrane-bound structures) ★ Eukaryotic cells include: plant, animal, fungi, protist

  17. EUKARYOTES PLANT vs. ANIMAL Electron Micrograph

  18. EUKARYOTIC ORGANELLES PLANTANIMAL ★Cell Wall★Centriole ★Chloroplast ★Cilia or Flagella ★Large central vacuole★ Many small vacuoles ★Cell/Plasma Membrane ★Cell/Plasma Membrane ★Cytoplasm/Cytosol ★Cytoplasm/Cytosol ★Mitochondria ★Mitochondria ★Ribosomes ★Ribosomes ★Nucleus ★Nucleus ★Nucleolus ★Nucleolus ★Nuclear Envelope/Membrane ★Nuclear Envelope/Membrane ★Rough Endoplasmic Reticulum (E.R.)★Rough Endoplasmic Reticulum ★Smooth E.R. ★Smooth E.R. ★Lysosomes ★Lysosomes ★Golgi Body/Apparatus ★Golgi Body/Apparatus ★Cytoskeleton ★Cytoskeleton

  19. Animal vs. Plant Cells – Chloroplasts Are a Big Part of the Difference

  20. Two Other Unique Features of Plant Cells The central vacuole may occupy 90% of a plant cell.

  21. EUKARYOTIC ORGANELLES

  22. EUKARYOTIC ORGANELLES

  23. EUKARYOTIC ORGANELLES THE NUCLEUS ★Latin = “kernel” or “nut” ★First described by Robert Brown (1831) ★Most eukaryotic cells contain one central nucleus ★Fungi have many nuclei ★Contains Nucleolus (where synthesis of ribosomal RNA takes place) ★ Nucleus protected by Nuclear Envelope/Membrane (which contains nuclear pores)

  24. EUKARYOTIC ORGANELLES THE NUCLEUS http://www.cartage.org.lb/en/themes/Sciences/Zoology/AnimalPhysiology/Anatomy/AnimalCellStructure/Nucleus/Nucleus.htm http://www.frontiers-in-genetics.org/en/pictures/nucleus_1.jpg

  25. The Nucleus “The Control Center of the Cell” Think of the nucleus as the cell’s control center. • Regulates all cell activity • Contains chromatin composed of DNA. Two meters of human DNA fits into a nucleus that’s 0.000005 meters across.

  26. EUKARYOTIC ORGANELLES THE ENDOPLASMIC RETICULUM ★Endoplasmic = “within the cytoplasm” • Reticulum = Latin for “a little net” • Usually connected to nuclear envelope ★ ROUGH E.R.: Contain many ribosomes, which appear pebbly or “rough”, and are destined to be exported from the cell; synthesizes, moves and proofreads proteins. • SMOOTH E.R.: Relatively few or no ribosomes; may contain enzymes which can 1) storage and synthesis of lipids and steroids (testes, intestine, and brain) or; 2) carry out detoxification of drugs (liver)

  27. EUKARYOTIC ORGANELLES THE ENDOPLASMIC RETICULUM http://www.ccs.k12.in.us/chsBS/kons/kons/eukaryotic%20cell/cytoplasm_and_its_associated_str_files/image002.jpg http://academic.brooklyn.cuny.edu/biology/bio4fv/page/rougher.htm

  28. EUKARYOTIC ORGANELLES THE GOLGI BODY/APPARATUS ★ Flattened stacks of tubular membranes ★ Smooth, membranous structure located near the middle of the cell • Receives proteins and lipids from the E.R. • Modifies and sorts proteins • Creates lysosomes ★ Packages proteins into membrane-bound structures, called vesicles, to be sent to appropriate destinations ★ Similar to a “post office”

  29. EUKARYOTIC ORGANELLES THE GOLGI BODY/APPARATUS http://www.bu.edu/histology/i/20303ooa.jpg http://media-2.web.britannica.com/eb-media/52/116252-004-9615DB80.jpg

  30. EUKARYOTIC ORGANELLES THE CENTRIOLES ★ Important in animal Cell Division ★ Composed of 9 triplets of microtubules ★ Microtubules = long, hollow cylinders which influence cell shape, move the chromosomes in cell division, and provide structure for flagella and cilia ★ Barrel-shaped organelles found in animals and most protists ★ Plants and fungi lack centrioles ★ Occur in pairs, usually at right angles

  31. EUKARYOTIC ORGANELLES CENTRIOLES http://upload.wikimedia.org/wikipedia/commons/4/49/Plagiomnium_affine_laminazellen.jpeg http://images.protopage.com/view/721389/3ydo50yjpdnqy8ag4flqbd1un.jpg

  32. EUKARYOTIC ORGANELLES THE LYSOSOME ★ Membrane-bounded digestive vesicles ★ Arise from the Golgi Apparatus ★ Contain degrading enzymes which break down (recycle) old organelles ★ Enzymes also function to eliminate harmful or foreign cells through phagocytosis • Called “suicide sacs” • In plants, called peroxisomes

  33. EUKARYOTIC ORGANELLES THE LYSOSOME http://www.stolaf.edu/people/giannini/cell/lys/autophag.jpg http://www.cartage.org.lb/en/themes/sciences/zoology/AnimalPhysiology/Anatomy/AnimalCellStructure/Lysosomes/lysosome.jpg

  34. EUKARYOTIC ORGANELLES Endocytosis = into the cell Exocytosis = exiting the cell

  35. The Lysosome

  36. The Lysosome This bacterium is about to be eaten by a white blood cell and will spend the last minutes of its existence within a lysosome.

  37. EUKARYOTIC ORGANELLES FLAGELLA/CILIA ★ Made of microtubules • Aid the cell in locomotion or feeding • Motion is similar to that of oars in a rowboat • Flagella are longer projections that move with a whip-like motion • Cilia are shorter, numerous projections that look like hairs. • Some protists use a pseudopod(“false foot”) to crawl; similar to squeezing a water balloon at one end forces the balloon to bulge out at the other end.

  38. EUKARYOTIC ORGANELLES http://www.ibri.org/RRs/RR051/51cytoskeleton.gif CILIAFLAGELLA Flagella = tails (move with whip-like action) Cilia = tiny hairs (move like oars in a boat)

  39. EUKARYOTIC ORGANELLES THE MITOCHONDRION ★ Plural = Mitochondria ★ Peanut-shaped with outer membrane and highly folded inner membrane (cristae) ★ Have their own DNA (mitochondrial DNA or mDNA) important for oxidative metabolism (inherited by you mother) ★ Supply ATP (energy) to the cell; “powerhouse” of the cell • Similar to a battery, generator or power plant • Where cellular respiration occurs ★ Cells have many mitochondria (ex: liver cells have up to 2000!) ★ Each time the cell divides, a mitochondrion divides in two

  40. EUKARYOTIC ORGANELLES MITOCHONDRIA http://academic.brooklyn.cuny.edu/biology/bio4fv/page/mito.gif

  41. The Mitochondrion * Responsible for Apocytosis = programmed cell death * A class of diseases that causes muscle weakness and neurological disorders are due to malfunctioning mitochondria. Worn out mitochondria may be an important factor in aging.

  42. EUKARYOTIC ORGANELLES THE CYTOSKELETON ★ Interior framework of the cell ★ Network of protein fibers that support the shape of the cell and anchor organelles to fixed locations ★ Stretches the plasma membrane like the poles on a circus tent! ★ Allows cells to rapidly alter shape

  43. EUKARYOTIC ORGANELLES http://www.ibri.org/RRs/RR051/51cytoskeleton.gif CYTOSKELETON http://www.noble.org/press_release/plantbio/blancaflornasa/cytoskeleton.jpg http://migration.files.wordpress.com/2007/07/cytoskeleton02.jpg

  44. An animal cell cytoskeleton The Cytoskeleton The name is misleading. The cytoskeleton is the skeleton of the cell, but it’s also like the muscular system, able to change the shape of cells in a flash.

  45. The Cytoskeleton in Action A white blood cell using the cytoskeleton to “reach out” for a hapless bacterium.

  46. EUKARYOTIC ORGANELLES THE CHLOROPLAST ★ Greek: chloro = “green”; plasts = “form “ or “entitiy” ★ Commonly in plant cells ★ Contain pigment called chlorophyll (gives plants their green color) ★ Carry out photosynthesis ★ Typically contain one to several hundred ★ Contain two membranes; closed compartment of stacked membranes called grana which have disk-shaped structures called thylakoids ; surrounding thylakoid is a fluid matrix called stroma ★ A type of plastid which contains it’s own DNA

  47. The Chloroplast Think of the chloroplast as the solar panel of the plant cell. Only plants have chloroplasts, but animals reap the benefits too.

  48. EUKARYOTIC ORGANELLES CHLOROPLAST http://upload.wikimedia.org/wikipedia/commons/4/49/Plagiomnium_affine_laminazellen.jpeg http://virtualbiologytutor.co.uk/images/chloroplast.jpg

  49. Cells In a Leaf

  50. A Consequence of Cell Walls – the Great Strength of Woody Plants

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