The Unity and Diversity of Life

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  • 1. The Unity of Life •Biologists define life through a set of observable characteristics that are not shared by nonliving things (). Because all living organisms possess these properties, this concept is referred to as the unity of life. Complexity and Organization Growth and Development Metabolism Homeostasis Movement Responsiveness Reproduction Heredity and Variation
  • 2. Complexity and Organization •Living organisms are both complex and organized. oSomething is complex if it has a lot of parts, and organized if its parts are arranged in a specific order or pattern. A crystal of table salt is highly organized but consists of only 2 elements, sodium and chlorine. Seawater is complex, containing atoms of 92 elements, but they are disorganized and distributed randomly.
  • 3. •Yet even a single cell contains dozens of different elements, forming compounds that combine to form even higher levels of organization. Levels of biological organization. The cell is the lowest level that is able to carry out all the functions of life. Not all organisms have tissues; some lack organs; and others lack body systems. Biosphere Ecosystem Community Population Organism Body system Organ Tissue Cell
  • 4. Growth and Development •Living organisms grow and develop. oGrowth occurs by an increase in the size of the individual cell(s), by an increase in the number of cells, or by both. oSome organisms stop growing when they reach a certain size, while others continue to grow indefinitely.
  • 5. Metabolism •Metabolism is the ability to obtain energy from various sources and to use it to do biological work. oIt consists of chemical reactions, each of which releases or absorbs energy. oThese reactions are organized into metabolic pathways, in which a product of one reaction becomes a reactant (substrate) in the next. A B C D Reaction 1 Reaction 2 Reaction 3 Starting Chemical End Product
  • 6. Homeostasis •Homeostasis is the tendency of living organisms to maintain a relatively stable internal environment.
  • 7. Movement •All living things have the property of movement. oThe living material within all cells is constantly in motion. Some cells can also move from place to place. oMost plants and animals transport fluids through the body. oEven sedentary adult animals such as sponges and corals have free- swimming larvae. When a fly alights on a Venus fly trap’s sticky leaf, within seconds its leaves close over the fly.
  • 8. Responsiveness •Responsiveness is the ability of an organism to perceive and respond to stimuli in its internal and external environments. oAn animal seeks food when the level of blood sugar is low and the stomach is empty. oIntestinal bacteria produce different enzymes depending on the food eaten by their host. oA plant grows toward light. Mammals shiver when their body temperature falls.
  • 9. Reproduction •Living organisms produce offspring of their own kind, or species.
  • 10. Heredity and Variation •Heredity is the transmission of traits from parent(s) to offspring. oGenes, which are composed of DNA, carry hereditary information. oMutations, which are permanent changes in the DNA of the genes, may be passed from generation to generation. They are the ultimate cause of variation among individuals. A gene is a part of a DNA molecule.
  • 11. Viruses •Viruses are not living things. Simply stated, they are merely hereditary information surrounded by a protein coat – “parasitic chemicals” that require host cells to reproduce.
  • 12. Q: How is the unity of life – the fact that all living things share the same fundamental characteristics – explained?
  • 13. •Estimates of the total number of species on earth range from 10 million to 100 million – this vast variety of life is known as biodiversity. The Diversity of Life
  • 14. •All living organisms are composed of one or more cells. Thus, a living organism may be: oUnicellular – it consists of just one cell. The cells may be able to live together, as colonies or filaments, but they are still identical and can survive on their own. oMulticellular – it consists multiple cells that are functionally specialized and cannot survive on their own. The unicellular organism Chlamydomonas reinhardtii. Unicellular vs. Multicellular
  • 15. •Two major types of cells and types of organisms exist on earth. oA prokaryotic cell never contains a nucleus during its lifetime. A eukaryotic cell contains a nucleus, at least during some part of its life— some cells contain multiple nuclei. oA unicellular organism may be a prokaryotic cell or a eukaryotic cell. A multicellular organism contains only eukaryotic cells. oAn organism made of a prokaryotic cell is a prokaryote. An organism made of one or more eukaryotic cells is a eukaryote. The unicellular organism Paramecium containing two nuclei. Notice the “mouth”. Prokaryotic/Prokaryote vs. Eukaryotic/Eukaryote
  • 16. The Six-Kingdom System •Many biologists classify living organisms into six groups, called kingdoms. oA eukaryote which is not a plant, animal, or fungus (pl., fungi) is included within the protists. Prokaryotes Bacteria Archaeans Eukaryotes Plants Animals Fungi Protists
  • 17. Prokaryote Eukaryote Unicellular Bacteria and Archaeans Yeasts and most Protists Multicellular Fungi (except yeasts), Plants, Animals, and some Protists (such as seaweed) oBacteria and archaeans are superficially very similar. oSeaweed is a colloquial term used to describe multicellular algae, including the red, brown, and green algae. oThe only unicellular fungi are the yeasts.
  • 18. Major Modes of Nutrition •The way a living organism obtains energy and the element carbon is called its mode of nutrition: oEnergy can be obtained from light or from chemical compounds oCarbon can be obtained from carbon dioxide (CO2) or from organic compounds. Organic compounds are built around chains of carbon atoms and contain hydrogen atoms; all other compounds (including CO2) are called inorganic compounds. •Some organisms can switch modes of nutrition depending on environmental conditions.
  • 19. MAJOR MODES OF NUTRITION ENERGY SOURCE Light Chemical compounds CARBON SOURCE Carbon dioxide • Plants • Algae • Some prokaryotes • Some prokaryotes Organic compounds • Some prokaryotes • Animals • Fungi • Protists • Most prokaryotes
  • 20. A hydrothermal vent in the Pacific Ocean. All the hot, mineral-rich water attracts bacteria that get their energy from chemicals such as H2S instead of the sun (as there is no sunlight on the seafloor), which in turn attract organisms that graze on the bacteria.
  • 21. Thousands of white vent crabs exemplify the abundance of life found around deep sea thermal vents, these in the Antarctic Ocean.
  • 22. The Godzilla Hydrothermal Vent (23 July 2011) http://vimeo.com/diogenesii/godzilla
  • 23. Q: How is the diversity of life explained?