hey everybody its mr. speeds and today we'll be covering topic 3.3 that survivorship curves so today's concept is going to build on topic 3.2 which is R and K selected species so if you haven't seen that video yet make sure to take a look at it the link is in the description below so you want to make sure to check that out first so like I said we'll be building on our understanding of reproductive strategies here today since are selected and K selected species differ and how much parental care they give their offspring they also differ in the survivorship of their offspring or how likely they are to survive infancy and reach adulthood a survivorship curve shows a group of individuals of the same species and it plots how many of them are still alive at each age the group reaches so we have a survivorship on the y-axis that's going to be the number of individuals or the proportion that are still alive and then as we go out on the x-axis we have time so the further out we go here the older the individuals are as you can see in this graph most humans are going to survive infancy childhood and we're going to reach adulthood but then we're going to die off pretty rapidly once we hit old age trees on the other hand have really low survivorship early in life barely any tree seedlings survive and that's because they don't get the parental care that humans do they're likely to get stepped on or eaten or shaded out by other trees and so a much much much lower proportion of them are going to survive early in life so let's take a look at our objectives essential knowledge and skills for the day our objective is to be able to explain survivorship curves and in order to do that we need to know that they show survival rates for a cohort or a group of individuals that are all born at about the same time we also need to know that there are three different basic trends in survivorship that we can see type 1 type 2 and type 3 and finally we should know that K selected species are going to show type 1 survivorship due their high parental care for offspring whereas our selected species are going to show type 3 survivorship due to their lack of parental care but remember they have many more offspring to account for this low survivorship the skills we'll be practicing in the frq at the end of the video today we'll be data analysis so here we have our classic survivorship graph and you'll want to note that the three lines or curves represent the three basic types of survivorship so remember that the survivorship curve is just a line on a graph and it shows the survivorship or how many individuals are still alive in a cohort or group of individuals all born at the same time so the faster the curve decreases such as these type 3 survivorship organisms like the dandelion the faster they're dying off so the fewer of them are surviving early in life the longer the individuals are surviving the less dramatic that drop-off is so if we look at type 1 like the whale many of those individuals are surviving early in life in the middle in life and then we have a really sharp decline later in life as old age kind of sits in so with type 1 survivorship these are our K selected species for the most part they have high survivorship early in life because their parents take such good care of them and so you could think about like a mother grizzly bear fiercely defending her cubs or a mother chimpanzee who's gonna breastfeed her offspring and keep us safe from danger by carrying it around with her they also have high survivorship in midlife because once they're fully developed they're often large organisms that are capable of defending themselves either with behavioral adaptations like living in herds or escaping from predators or even fighting them off however they do have a rapid decrease in survivorship late in life as old age sets in type 2 are somewhere in the middle between type 1 and type 3 so just like there's a spectrum of parental care there's also a spectrum of survivorship type 2 species our organisms like birds or rodents and they typically have a little bit of parental care early in life but they're usually smaller organisms that are less capable of protecting their young from predators or they have young that are more sensitive to disease or temperature so think about a baby chick or a small rodent without fur type 2 species experience a pretty constant and steady decline all throughout life so just because a bird survives its fledged fledgling stage when it's in the nest it doesn't I guarantee that it will reach full sexual maturity or full adulthood type three now our our selected species and these are going to be organisms like insects fish and plants so they provide little to no parental care which means they experience very high mortality or very high death rate early in life they have to offset this low survivorship or this high death rate by having lots and lots of offspring so remember that their strategy still works they just have to have a lot of offspring to compensate for that low survivorship so as I said very few type three individuals in a population will make it to middle age most of them die in infancy or in childhood once they do there's a relatively slow decline in survivorship as time goes on so unlike the type one species who generally experience a sharp decrease in survivorship once they hit old age and one thing I want to point out here before we move on is that when we look at this graph the units at the bottom here age these are relative units so this graph does not mean that dandelions are going to live the same age as whales it just means that relative to the total maximum lifespan of a dandelion this percentage of them will reach their maximum age same thing with the squirrel and same thing with the whale so we can show them all on the same x-axis here because we should know that these are relative units of age so even though the whale lives far longer than a squirrel which generally looks far longer than a dandelion this is going to represent comparative units of age all right our frq practice for topic 3.3 today will be data analysis and specifically we'll be describing patterns or trends and data so you will need to describe the trend in survivorship shown in this graph and justify which type of survivorship curve these data represent all right everybody thanks for tuning in today don't forget to like this video if it was helpful subscribe for future apes video updates and check out other notes over here to the side and as always think like a mountain right like a scholar