Living And Non-living Things (2nd Ed, 1978)

[Music] okay 40 when astronauts first  went to the moon they found a world without life it's a world far different  from the earth which is filled with living things what do we mean by life how can you decide  if something is alive or if it is not alive most of the time you wouldn't have any trouble  telling living and non-living things apart but you might have trouble with this the patches of  color on these rocks look like paint but they are really very simple living things called lyen  you might also be puzzled by this coral Coral is found in the ocean and looks like a rock but  what Clues do you see that tell you that Coral is alive you can see that it's not always easy to  tell whether something is living or not if you want to be sure you need to know what living  things do that non-living things do not do let's start by looking at what living things  are made of a pond is full of living things some of them are too small to see let's collect  a sample of pond water and look at a drop through a microscope a microscope makes it possible to  see very small things every drop of pond water contains many living things most of them are  made of only one cell cells are the building blocks of living things plants we can see are  made of many cells together and animals we can see are made of many cells together in fact all  living things are made of cells whether they're as big as an elephant or so small that hundreds  can live in a drop of water non-living things don't have cells this is a very thin slice  of rock we are going to look at under the microscope the rock is not made of cells but  some non-living things are made of cells once this piece of wood was part of a living tree but  now it is dead if you were to take a small slice of the wood and look at it under a microscope  you'd see that it has cells even though it is now a non-living thing so being alive means  more than just having cells it also means making new living things all new living things come  from other living things just as you came from your parents this is called reproduction  animals reproduce they make new living things plants reproduce on this orange  tree there are oranges that have [Music] seeds when a ripe orange falls to the ground a  a new tree May grow from a seed that was in the orange do non-living things reproduce what else do living things do that  non-living things don't [Music] do all living things grow growth usually happens when cells  like this one split in two making more and more cells and as living things grow they make special  parts for example as these bean sprouts grow some of their cells become Roots other cells become  the stem and others become leaves what about growth in non-living things like this Crystal  watch what happens to it when we put it in a special liquid for a day the crystal grows  but is it growing special Parts the way the plant did no it isn't because the crystal  is not a living thing even though it can grow what happens to living  things when they get [Music] hurt living things can repair themselves can non-living things repair  them themselves when they're damaged here is something else most  living things do most living things move with special cameras we can see how  green plants move as they grow some living things can move from one place to another  also there is movement inside their bodies for instance the movement you see here  is caused by blood flowing through an arm clouds move too so does water and so do bicycles  but are they alive what made the bicycles move in order to move grow repair themselves  and reproduce living things need food all living things depend on the sun's energy for food  green plants use the energy of sunlight to change water and carbon dioxide from the air into their  food all other living things get their food from plants or from animals that eat plants food  gives living things energy to turn food into energy most living things must have oxygen  we can't see oxygen but it's in the air we breathe the harder we work the more energy we  use the more energy we use the more oxygen we need some non-living things use oxygen too the  candle burns with the help of oxygen in the air as soon as all the oxygen under the cover  is used up the flame goes [Music] out the candle is a non-living thing that needs oxygen  to burn but does the candle do anything else that living things [Music] do living things  also can tell when there are changes in the world around them and they can do something  about these changes what they do is called a response some responses seem very simple  like your response when you step on a sharp object this plant responds when it's touched other responses are not  simple they're very complicated in human beings responses often  involve what we call thinking living things often can respond to  the same situation in many different ways sometimes it seems as though non-living  things also have responses throw a rock in a pond and the water responds with ripples but can  the water respond to the Rock in any other way you've seen that non-living things sometimes  act like living things some can grow some use oxygen some move but only living things have  cells reproduce and grow only living things move on their own repair themselves you use  food to keep going and respond to the world around them there is one other thing living  things do they die dead things like this tree slowly break down into smaller and smaller  pieces after a while the dead tree becomes part of the soil later the same bits of soil may  be used by a new tree so living and non-living things form a circle in which living things die  and non-living things can become part of living things sometimes it's not clear what is  living and what is not we can show you what we mean with this electron microscope  which is used to see things too small to be seen by an ordinary microscope like these  viruses by themselves viruses don't use food don't move and don't reproduce in  other words they seem to be non-living but when viruses meet up with the right kind  of cell the viruses move into the cell and reproduce then they often cause diseases like  colds and flu viruses are on the borderline between living and non-living things our world  is filled with many forms of life and what about other worlds is there life in other plaxces in  the universe we are searching for the answer with the help of spacecraft and with our knowledge  of the differences between living and non-living things