Bozeman science: Response to external environments

hi it's mr. Andersen and welcome to biology essentials video number 19 this is on response to external environment of all the animals that I love my favorite is the water bear their name is tardigrade but we in general just calm water bears on this is a picture of a couple of them under electron microscopy um they're about the biggest ones or maybe like one and a half millimeters in length so they're pretty small but they get their name from the way that they walk they kind of move back and forth almost like a bear they live everywhere on a planet so you'd find them in the Himalayas you'd find them deep in the ocean you find them everywhere but what makes them interesting is that they're able to survive incredible harsh environment so they can survive near absolute zero 304 degrees Fahrenheit they can survive for decades without water they seem to replace the water inside them with some kind of a sugar and recently they've been studied in space so they kept a population of water bears in space for ten days just exposed to low Earth orbit and not only did they survive but they laid a number of eggs which also survived and so water bears our world record holders as far as surviving harsh environments but a lot of animals on our planet have to survive an organism with changing environments and so they do that through two types of responses first type is behavioral so example of to that I'll talk about our hibernation and migration and those are response to changes in climate not climate but in temperature and then physiological are going to be changes within an organism themselves a couple i'll talk about in humans are shivering and sweating to keep ourselves a little warmer and to keep ourselves cooler and so a behavioral response is an organism or a group of organisms doing that but physiological is going to be within that organism itself okay and so behavioral responses let me talk about a few let's say it gets cold so let's say it gets cold during the winter what can you do well you can either stay or you can go and if you choose to stay you're going to have to tough it out or you could enter into something called hybrid and so hibernation you're probably familiar with in true hibernation what you do is you lower your body temperature you lower your metabolism and so a true hibernator a great example would be like a ground a groundhog which is the type of a moment and what they do is they'll actually crank their metabolism down so it's almost the same as their environment so right around freezing their body temperature is torpor is a type of hibernation it's essentially doing that on a daily scale so lowering the metabolism probably at night to survive that and then it's kind of a continuum and so there's a continuum from torpor to hibernation and so things that we think of as hibernators are probably not true hibernators like a bear because a bear even though they turn their they slow down their metabolism crank down their body temperature a little bit they're easily aroused and it doesn't go near zero so there's this continuum from just daily torpor to hibernation but essentially what you're doing is cranking down your metabolism so you're able to survive during a period of time where it's cold another way that we can survive during a period of cold is to just leave and so migration is an example of that so caribou will migrate to a calving area or to an area where they can they don't get such harsh environment during the winter but probably the most famous migrators of all are birds and of all of those the bartell got wood is the record holder they will migrate from the northern hemisphere during the summer they'll spend time there northern Asia some of them all the way up in Australia in Alaska and then they'll migrate all the way down to New Zealand and Australia during the what would be their summer there and so instead of having to deal with that harsh climate they're simply moving and so this is a group of individuals or a population that is that is doing that now that that can be a mate you could be born with it or it could be something that you inherit but one thing is that that's probably not fast enough in other words if it gets really cold or if it gets really hot we also have to have physiological responses so physiological responses are within you so a couple of examples in humans could be shivering and sweating this is during the Napoleon withdraw from Russia thousands of people died from hypothermia and so if you're an endotherm warm-blooded critter like we are once your body's temperature starts to drop off then you can quickly die and so as a response for that we could get goosebumps we could have our hair try to stand up on end we could you know have clothes for sure but one thing that we start to do very quickly when we get cold as we start to shiver and the reason we do that it's its muscles especially muscles around the vital organs in our body will start to move very very quickly and the reason they're doing that is they're expending energy they're generating ATP but the other thing that they're they're generating is heat and that heat is being generated to keep that keep us alive keep us warm so we don't go hypothermic on the other side let's say we get too hot then we'll start to sweat and the reasons that we sweat is that water on our skin is quickly going to evaporate and when it evaporates it's going to carry heat with it and so that's evaporative cooling now if you can't sweat other organisms will paint like a dog for example will pan a funny story I remember reading about the marathon is that they used to think that if you drank water during the marathon it would slow you down add weight to you but if you're running a marathon you also have to get rid of the heat so this is highly debris Salah sees the world record holder in the marathon right now and they constantly are taking in water throughout the run that's to replace water that they've lost through sweating just to keep that core body temperature low and so these are physiological responses and we constantly are doing this to maintain homeostasis but remember we can have behavioral responses and all of these lead to the fitness of the individual and are selected through natural selection and so those are responses to environment and I hope that's helpful