What is survivorship? What does a survivorship curve show?...

Key Concepts

Type III Survivorship Curve

This curve shows very high mortality rates among young individuals, with only a few surviving to older ages. This pattern indicates that species produce a large number of offspring with little parental investment, such as oysters, where only a small fraction of the offspring survive to maturity.

Type II Survivorship Curve

This curve displays a relatively constant mortality rate throughout an organism's life, resulting in a steady, linear decline in survival. It suggests that the risk of death is fairly uniform across different ages, a pattern seen in some animal populations like certain small mammals or birds.

Survivorship

Survivorship is a concept in population ecology that describes the proportion of individuals in a cohort that survive to different ages. It provides insight into the life history and survival strategies of species by tracking mortality rates over time.

Survivorship Curve

A survivorship curve is a graphical representation that shows the number or proportion of individuals surviving at each age. It helps ecologists visualize and compare patterns of mortality and survival among different species or populations over their lifespans.

Type I Survivorship Curve

This curve is characterized by high survival rates during early and middle life stages with a steep decline in survival at older ages, reflecting low juvenile mortality and high old age mortality. It is typically associated with species that invest heavily in offspring care, such as humans.

Transcript

00:01 So for this problem, we are going to be looking at some different terms and graphing them to try and demonstrate how there can be some differences.

00:08 But what we need to talk about first is the term of the day, which is survivorship.

00:14 And based on our understanding of english language and the words that we could see in front of us, we should already have somewhat of an indication of what this term is referring to.

00:23 So survivor means essentially not dying.

00:26 It means that you are continuing to live.

00:27 And i mean, there's different contexts for surviving.

00:31 It doesn't always have to be death.

00:32 But in this context, we're talking about just surviving, keeping on living.

00:38 So, and particularly what this term means in this context is we're going to be looking at the number or percentage.

00:48 We can say percentage or fraction.

00:50 Those are just two different ways of viewing an amount of a total amount, right? so we're going to be looking at as the fraction of individuals.

01:00 In a given age interval.

01:04 So we'll say within a certain age.

01:08 So for an example, we could look at 0 to 10.

01:11 We could look at 10 to 20, 20 to 30, different intervals that makes it to the next interval.

01:26 Which means in this instance is surviving, right? because if you don't die from ages of 0 to 10, congratulations, you meet it to the 10 to 20 interval.

01:34 You survived.

01:35 Then, oh, 10 to 20, you didn't die.

01:37 You made it to the next interval, 20 to 30.

01:39 So that's what that's just telling us when we're looking at survivorship.

01:43 And we can actually graph this as a survivorship curve where we're going to see let's try and draw these lines a little straighter we're going to see a graph where we see on the y axis you see survivorship so survivor running on a space a little bit survivorship and this is normally a percentage where we can see this is going to be 100 % survive and this is going to be 0 % survive and then on the x -axis we're going to have maximum life capacity.

02:29 So how possible is it for that organism to survive? so if nothing were to happen and they were able to just live as long as physically possible, how long would they live? then we have different life capacities for different animals.

02:44 But either way, that's what we're looking at when we see this survivorship curve.

02:49 And what we can do is you can plot different organisms and see how survivorship varies from organism to organism.

02:54 The first organism we're going to draw.

02:56 We're going to be humans.

02:58 And humans have, we have through technology and building these wonderful civilizations and environments, we've pretty much mastered...

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