Anatomy Of Life

[Music] The Science Screen Report bringing you each month the latest discoveries, developments, and applications science, engineering, and medicine made to help solve the problems of modern life. [Music] Man has long wondered if he is alone in the universe. Today, the search for other forms of life and even civilizations beyond the Earth is becoming. Space probes have been launched to sun Mars. And similar missions have been planned to probe Saturn's moon Titan. The Pioneer spacecraft traveling beyond the solar system carry greetings to hypothetical extraterrestrial life. [Music] Simultaneously, the world's radio astronomers are scanning the universe, seeking evidence of possible civilizations far out in space. Researchers hypothesize such communicating civilizations are an eventual consequence of evolution. [Music] to better understand living things on Earth and the possible discovery of life forms beyond our planet. This issue of the Science Screen Report is an introduction to the anatomy of life as we identify it today. [Music] [Music] We see living things around us every day. But which characteristics do scientists use to actually define life? For example, is something alive because it moves? Like these microscopic [Music] parramiums, there is movement on a soap bubble partly because of surface tension, but a bubble is not alive. [Music] Gravity or the tides can move oil over water, but oil is not alive. or one liquid may diffuse through another. But neither is this a living [Music] system? Do growth and reproduction define life? The offspring of this stentor is growing directly out of the parent during the process of budding, a type of sexual reproduction. [Music] But growth and reproduction are subtle concepts. These crystals grow, but they are not life as biologists define it. [Music] [Applause] [Music] Or consider a very advanced computer equipped with machine tools and mining equipment which might be programmed to grow and even build a copy of itself. Would such a selfreplicating machine be truly alive? [Music] Can life be defined in terms of its biochemistry? Studies have sought to define the chemical nature of life as we recognize it on Earth. This film animation suggests how all Earth life is composed of molecules, some as simple as water. Biochemists have determined that on Earth the double helix spiral molecule DNA holds the genetic code of the heredity pattern of future generations. This DNA control process via self-replication is similar in all forms of life. Here documentary microphotography shows mitosis cellular reproduction by DNA replicating the DNA molecules. But neither is this universal. For example, this bacteriaage is parasitic upon DNA of other life for its replication is a basic feature of life. the ability to collect and store energy. Plants do this through photosynthesis. Most animals, like this amoeba shown ingesting a stentor, gather energy by capturing other living organisms, digesting them, and assimilating the nutrients they contain. [Music] Many feeding techniques have evolved. This rotifer uses its whirling psyia to bring in food and a grinding mechanism to tear it apart. The dragonfly larve has a specialized mouth to capture and ingest its prey. Tentacles and stinging cells called pneumaticists are used by the hydra to paralyze this small [Music] shrimp. Is water fundamental to life as we know it? Life thrives when water is present. But take away water and in many cases you take away life. Some organisms like shrimp become immobile even before they become dehydrated and the metabolic activities cease. Dehydration here is proceeding from left to right. [Music] [Music] However, other life forms can survive drastic changes in the availability of water. Rotifers like this one have adapted to survive with a minimum of moisture. [Music] [Music] Many round worms like rotifers can also survive a drastic loss of water in a dried up resistant state. [Music] Can life therefore be defined by limiting environmental factors? The microscopic water bear, often found in the thin layer of water covering mosses, can also survive when over 95% of its body water is removed. In addition, it has been known to survive at temperatures from near absolute zero to above 100° C and when exposed to highintensity radiation. [Music] Bacteria, the microscopic unicellular organisms which exhibit both plant and animal characteristics also can survive many environmental extremes. Some can live in concentrated salt solutions. Others endure extreme cold, and still other varieties thrive in hot springs at 90° C. Strains of bacteria found in the Antarctic, which had been dormant for at least 10,000 years, have resumed their life activities when exposed to air and then been grown in active colonies. [Music] Could life as we know it exist on other planets such as Mars? Life forms there would be exposed to environmental conditions such as temperatures reaching 50° C, a minimum of water and exposure to ultraviolet radiation. Moreover, if Mars is currently passing through an ice age, as some scientists believe, one hypothesis is that life forms might be dormant, waiting for the long winter to end before they resume their life [Music] processes. or a subsurface perafrost layer of the planet may hold ancient or living organisms deep within it. In either case, the first life-seeking missions to Mars have not been equipped to detect such hidden or dormant life forms. [Music] In search of the beginnings of life, scientists have simulated conditions that may have existed on Earth billions of years ago, no atmospheric oxygen, simple inorganic and organic compounds such as methane and carbon dioxide and water, and energy, including heat and ultraviolet radiation. The products of such tests have included amino acids, the building blocks of proteins, and nucleic acids, the constituents of DNA. What then defines life? Life cannot be explained in terms of a simple life function, but as an intricate balance of many life processes, each one unique and basic in sustaining a living organism. [Music] [Music] Perhaps the basic characteristic of life is its ability to evolve, to adapt, diversify, and survive in a wide and everchanging variety of forms. [Music] [Music] Seeking life beyond the earth is another important step along the road that man has traveled since his beginnings, looking for his place in the universe. [Music]