Biological Science - Inquiring Into Life (1987)

thank you foreign [Music] it appears chaotic a scramble of organisms all sizes all kinds but underneath all of this incredible diversity there is a kind of orderly progression from simple to complex from individuals to vast populations oh from ecosystems to the biosphere and Beyond biologists view Life as a chain of interconnecting levels beginning with the molecules that produce life's incredible chemistry [Music] molecules lie far beyond the reach of a laboratory microscope the smallest spec seen here would have to be further enlarged ten thousand times to see even a hint of its molecular structure however with a little imagination you can picture the frenzied dance as molecules are coupled and uncoupled in the countless chemical reactions that go on within each living cell research in molecular biology has given biologists a powerful insight into the nature of life like the discovery of special proteins that catalyze each of the chemical reactions taking place within a living cell it turned out that the instructions for assembling these controlling enzymes were encoded in giant information molecules contained in the cell's nucleus molecules of DNA DNA has been isolated and studied in hundreds of Laboratories where biologists are learning to read the molecular instructions for life they have even learned to rewrite instructions and to inject new messages into living systems [Music] molecules to the next level jump in size a million times into the realm of the cell the smallest cells are bacteria simple when compared to the complex cells of plants and animals but amazing nonetheless [Music] each tiny bacterium digests nutrients transforms energy and manufactures enzymes and other proteins from DNA instructions bacteria share their drop of pond water with protozoans like paramecium but the difference between these two kinds of cells is great [Music] for example paramecium is filled with all sorts of complex organelles some carry out food getting and digestion others oxidize the digested products for energy but the most obvious difference is that paramecium like the cells of plants and animals has a nucleus and within it a number of chromosomes containing its DNA foreign bacteria show none of the complexity seen in the larger cells in fact they don't even have a nucleus the difference between bacteria and more complex cells splits the living world into two branches organisms made of cells with nuclei and organelles the eukaryotes and those without them the prokaryotes there are single cell eukaryotes like paramecium and multicellular eukaryotes are familiar plants and animals the cells of these larger organisms form tissues tissues form organs and organs make up the working parts of the individual it may seem like the individual is the highest level of biological order but individuals are parts of a larger unit called a population biologists Define population as all of the individuals in a given region capable of mating and producing fertile offspring all of the Lions spread across the continent of Africa make up a population the region can be large or small populations that share the same living area tend to interact even microorganisms for example paramecium and bacteria paramecium eats them [Music] the wigglers eat the paramecium fish eat the wigglers and all become links in a food chain [Music] populations of interacting species form ecological systems or ecosystems like a pond ecosystem the physical environment and the populations of organisms living there are what define an ecosystem some examples would be Forest a grassland or an ocean ecosystem and all of our planet's ecosystems are linked together as parts of a larger system the biosphere Earth's thin shell of life within the biosphere life and the physical world interact and over great stretches of time this interaction brings about change analysis of gases trapped deep in our planet's interior indicate that Earth's original atmosphere was made up almost entirely of carbon dioxide with no oxygen microorganisms are believed to be responsible for lowering the original high levels of carbon dioxide by incorporating carbon molecules into their bodies [Music] process that took place over a very long span of Earth history oxygen on the other hand went from almost none in the original atmosphere to around 20 percent today this change is thought to have been brought about by microorganisms particularly a kind of blue-green prokaryote that first appeared around 2 billion years ago there is evidence that these strings of blue-green cells were the first living things to release oxygen from water through photosynthesis biological Innovation that changed our world the discovery that life is responsible for our modern atmosphere is one of the exciting new ideas in biology we have been exploring the way life is organized in space but life's Roots also reach back through time evolutionary biology is the science that explores life's Origins and the mechanisms of change [Music] some investigators working in this area attempt to unravel Earth's biological history tracing out evolutionary Pathways that explain how our modern day organisms came to be others use carefully designed experiments to probe the genetic processes that produce change these investigations shed light on the difficult question of why some populations spawn new species While others become extinct [Music] it's often rapidly reproducing organisms that have improved our understanding of life the fruit flies 12-day life cycle allows geneticists to make experimental crosses that show how traits are passed from one generation to the next [Music] its large chromosomes make it possible to actually locate the genes that govern a particular trait all Fields draw on genetics developmental biologists want to know how genes are turned on and off as a fertilized egg develops into an individual behavior of biologists are attempting to discover connections between genes and behavior molecular biologists are learning how to manipulate genes in order to create new traits in living things they have already put microorganisms to work producing a growing list of genetically engineered products for medicine and Industry the controlled manipulation of genes is one of the great scientific achievements of our time but such achievements are only possible if there is a huge research base to build on improving this knowledge base often depends on the development of new tools just as the light microscope turned tiny specks into amazing single cell beams the electron microscope reveals structures within these cells that could not be imagined by an earlier generation of biologists and although it was the electron microscope that showed life's hidden structure it was the biochemists who isolated cell parts and discovered how they performed their life-giving reactions but biochemists and just about all of the other fields of biology owe a special thanks to these organisms and to the microbiologists who 100 years ago worked out the techniques for culturing them in the laboratory [Music] under laboratory conditions bacteria will double their numbers every 30 minutes making them ideally suited for experimental studies for example evolutionary biologists can use microorganisms to follow changes through hundreds of generations the equivalent of twenty thousand years if humans were the subjects even ecologists have found that they can use microorganisms to model the larger world in this study a single cell Predator is introduced into a population of paramecia [Music] it attacks one and in less than a minute swallows it whole [Music] thank you [Music] by studying how these rapidly reproducing organisms interact ecologists have developed theories about how predators and prey coexist [Music] but biologists also ask questions that can only be tackled using larger organisms the trick is to choose a subject that is suited for their particular line of inquiry for example in order to study brain function this investigator is taking advantage of the highly simplified brain of a sea slug thank you the mollusk's brain has but four lobes each with less than 100 large brain cells making it possible to probe and listen in on the electrical activities of individual cells the cells involved in a particular Behavior pattern the Escape reaction triggered by the touch of a predatory starfish [Music] from such studies biologists are learning how the brain controls Behavior but to what extent can the results gain by studying simple organisms be extended to complex ones do brains with billions of cells also have wiring diagrams for Behavior and what will we ultimately discover about life as biologists push further into the Mysterious World of molecules and cells or explore the vast networks of interrelationships that govern the biosphere knowledge leads to new questions and investigations and we can be sure that our understanding of The Marvelous process of life will continue to advance on all its levels [Music]