WEBVTT 00:00:00.984 --> 00:00:01.738 So... 00:00:01.971 --> 00:00:04.816 in your book in Chapter 17 00:00:05.918 --> 00:00:08.769 the importance of wolves to the Yellowstone ecosystem 00:00:09.579 --> 00:00:11.242 is the main topic. 00:00:12.532 --> 00:00:16.344 And we have talked already about the connections between living things 00:00:16.631 --> 00:00:17.949 and their environment; 00:00:18.120 --> 00:00:19.951 and how there are different 00:00:20.379 --> 00:00:21.902 types of interactions. 00:00:22.396 --> 00:00:24.435 We also found out that wolves fulfill 00:00:25.036 --> 00:00:26.925 a very important role in the community: 00:00:26.925 --> 00:00:28.553 they're a keystone species. 00:00:28.867 --> 00:00:30.859 Which means that they have a really 00:00:31.248 --> 00:00:34.565 big influence for their population size on the community structure; 00:00:35.209 --> 00:00:38.768 and their presence or absence can really change that community structure. 00:00:39.615 --> 00:00:41.364 Wolves occupy 00:00:41.902 --> 00:00:45.361 a very important niche in the Yellowstone ecosystem. 00:00:45.901 --> 00:00:48.410 And a niche simply refers to, 00:00:48.770 --> 00:00:51.208 what is an organisms role in its environment? 00:00:51.505 --> 00:00:52.655 What does it do? 00:00:52.895 --> 00:00:55.105 Who does it interact with, and how? 00:00:55.105 --> 00:00:56.609 What are its needs? 00:00:56.825 --> 00:00:59.640 So, really, the needs and the... 00:01:00.064 --> 00:01:01.746 interactions of an organism 00:01:01.746 --> 00:01:02.870 in an ecosystem 00:01:03.193 --> 00:01:05.060 describe this concept of a niche. 00:01:05.407 --> 00:01:07.057 Basically, everything about how 00:01:08.030 --> 00:01:09.869 it acts in that ecosystem. 00:01:10.435 --> 00:01:12.675 If there is overlap of a niche, 00:01:13.103 --> 00:01:15.397 a place where needs and roles overlap, 00:01:15.742 --> 00:01:20.011 then we get our last type of biological interaction: competition. 00:01:20.841 --> 00:01:22.604 Competition is going to take place 00:01:22.801 --> 00:01:24.336 when two organisms, 00:01:24.965 --> 00:01:26.152 two species, 00:01:26.590 --> 00:01:29.020 or two members of the same species 00:01:29.601 --> 00:01:34.977 are interacting in a way that indicates that they are competing for a resource. 00:01:35.490 --> 00:01:38.418 So, for example, here we have a little parakeet 00:01:38.936 --> 00:01:42.053 and a starling that are fighting over a french fry. 00:01:43.385 --> 00:01:45.238 Now, hypothetically... 00:01:46.343 --> 00:01:47.967 in the case of competition, 00:01:48.177 --> 00:01:52.640 one competitor will usually manage to exclude the other competitor for that 00:01:52.640 --> 00:01:53.957 --from that resource-- 00:01:53.957 --> 00:01:56.273 and we refer to this as competitive exclusion. 00:01:56.976 --> 00:01:58.997 Organisms can compete for lots of things. 00:01:59.705 --> 00:02:01.375 They can compete for space, 00:02:01.599 --> 00:02:03.079 like these corals. 00:02:03.310 --> 00:02:04.220 Um... 00:02:04.585 --> 00:02:06.828 the corals are also competing for sunlight. 00:02:07.053 --> 00:02:10.417 There is some algae sort of growing here in the corner of the picture; 00:02:10.421 --> 00:02:14.199 and as that algae grows over the coral it takes up the sunlight and the coral 00:02:14.199 --> 00:02:15.206 can't get it. 00:02:15.441 --> 00:02:18.044 So organisms can compete for physical resources like: 00:02:18.044 --> 00:02:20.793 space, sunlight, nutrients, water, things like that. 00:02:22.152 --> 00:02:24.151 Organisms can compete for food. 00:02:24.702 --> 00:02:27.321 The lions and hyenas are competing for food here. 00:02:27.885 --> 00:02:30.723 You saw some competition in the "Battle At Krueger" video. 00:02:31.035 --> 00:02:34.536 There was some very interesting competitive interactions taking place. 00:02:35.798 --> 00:02:37.614 Organisms can compete for mates. 00:02:37.794 --> 00:02:39.859 These are two male elephant seals, 00:02:40.003 --> 00:02:42.613 uh, who are competing to become the "beach master." 00:02:42.926 --> 00:02:47.850 And that is a real term that describes the male elephant seal that has control of 00:02:47.850 --> 00:02:49.556 all the females on the beach. 00:02:49.821 --> 00:02:52.275 Elephant seals have a harem mating system 00:02:52.693 --> 00:02:55.392 where one male mates with the females, and, of course, 00:02:55.700 --> 00:02:59.758 for that evolutionary fitness, for that reproductive success, 00:03:00.263 --> 00:03:04.152 that is a very hotly contested position. 00:03:04.621 --> 00:03:08.476 You can see they are battling pretty hard. They are bloody and fighting, uhm... 00:03:08.476 --> 00:03:11.996 What's really interesting about the elephant seal situation is that you do 00:03:11.996 --> 00:03:14.053 have a little bit of disruptive selection. 00:03:14.053 --> 00:03:16.760 There are "sneaker males," as well, in that system. 00:03:17.583 --> 00:03:20.404 But, there is very intense competition for mates. 00:03:23.401 --> 00:03:25.056 When organisms compete 00:03:25.056 --> 00:03:27.246 they can compete in different ways. 00:03:27.726 --> 00:03:32.364 Some organisms compete by taking up, using up a resource. 00:03:32.905 --> 00:03:35.898 And we refer to this as exploitation competition. 00:03:35.898 --> 00:03:39.398 Now, this is different from the exploitation that we talked about earlier 00:03:39.398 --> 00:03:42.955 when we talked about how parasites and predators exploit other organisms. 00:03:43.571 --> 00:03:47.549 In the case of exploitation competition, you can also think of it as "scramble." 00:03:48.136 --> 00:03:49.837 This squirrel is hoarding nuts. 00:03:50.424 --> 00:03:54.305 He's gathered up nuts and he is sitting on them and he's com--com--com... 00:03:54.985 --> 00:03:58.841 um, taking up that resource and keeping other organisms from getting it. 00:03:59.820 --> 00:04:03.621 So exploitation competition can happen when an organism uses up a resource 00:04:04.164 --> 00:04:06.656 and doesn't allow other organisms to access it. 00:04:07.653 --> 00:04:09.936 Interference competition, on the other hand, 00:04:10.375 --> 00:04:14.706 is when you have organisms that are physically competing, or interfering, 00:04:14.706 --> 00:04:16.525 with one another for a resource. 00:04:16.770 --> 00:04:19.443 This is sometimes referred to as "contest competition." 00:04:19.689 --> 00:04:21.596 So, in this case you have a, uh... 00:04:22.227 --> 00:04:26.158 a little ground squirrel and some starlings that are competing for nuts. 00:04:26.678 --> 00:04:30.068 And, instead of--instead of the ground squirrel hogging all the nuts 00:04:30.068 --> 00:04:31.742 and just setting them aside, 00:04:32.081 --> 00:04:35.211 instead what we have is an actual, physical altercation, 00:04:35.627 --> 00:04:37.692 a fight if you will, for that resource. 00:04:38.443 --> 00:04:41.574 So, exploitation competition: using up the resources. 00:04:42.103 --> 00:04:45.825 Interference competition: physically competing over them and--and 00:04:46.340 --> 00:04:48.872 physically keeping other organisms from having them. 00:04:49.944 --> 00:04:52.634 So those are two different strategies for competition. 00:04:52.634 --> 00:04:55.883 And depending on the organism and the resource, you might see either 00:04:55.883 --> 00:04:56.992 of those take place. 00:04:58.613 --> 00:05:02.401 The coral example here, we have the algae is engaging 00:05:02.401 --> 00:05:04.839 in exploitation competition by 00:05:04.839 --> 00:05:07.629 covering up the coral and keeping it from getting light. 00:05:08.222 --> 00:05:11.983 The elephant seals are engaging in interference competition 00:05:12.398 --> 00:05:14.250 by physically battling one another 00:05:14.439 --> 00:05:15.571 for the mates. 00:05:17.074 --> 00:05:17.865 Okay... 00:05:18.594 --> 00:05:20.153 When competition occurs 00:05:20.909 --> 00:05:22.360 one of the things that we see 00:05:22.838 --> 00:05:25.125 is that one competitor, 00:05:27.487 --> 00:05:29.786 if they have the same exact needs, 00:05:30.268 --> 00:05:32.397 will often out compete the other predator. 00:05:32.889 --> 00:05:34.330 So here are two protists. 00:05:34.881 --> 00:05:37.614 Um , Paramecium aurelia and Paramecium caudatum. 00:05:38.101 --> 00:05:40.032 That, if grown in separate flasks, 00:05:40.384 --> 00:05:41.605 in separate conditions, 00:05:41.605 --> 00:05:44.782 we see almost the exact same population growth curves. 00:05:44.782 --> 00:05:46.352 They grow in the same way. 00:05:47.650 --> 00:05:50.448 If, however, we put them in the same flask 00:05:51.029 --> 00:05:56.004 Paramecium aurelia ultimately out competes Paramecium caudatum 00:05:57.456 --> 00:06:02.147 because two organisms cannot occupy the same niche simultaneously 00:06:02.147 --> 00:06:03.661 and continuously. 00:06:04.421 --> 00:06:06.903 This is known as competitive exclusion. 00:06:07.250 --> 00:06:10.129 So, the parrot and the starling competing for a french fry, 00:06:10.129 --> 00:06:13.311 if they lived in the exact same environment and only ate the same 00:06:13.311 --> 00:06:17.717 food, over time what we would see is one competitor would be a superior 00:06:17.717 --> 00:06:21.418 competitor; out compete the other one. and we would get competitive exclusion. 00:06:23.252 --> 00:06:26.596 How organisms get around this is through resource partitioning. 00:06:27.568 --> 00:06:28.379 For example: 00:06:28.779 --> 00:06:30.885 this is a group of birds, warblers, 00:06:30.885 --> 00:06:32.329 a closely related species, 00:06:32.799 --> 00:06:34.944 that are engaging in resource partitioning. 00:06:34.944 --> 00:06:36.536 They use different resources 00:06:37.510 --> 00:06:38.980 to allow them 00:06:38.980 --> 00:06:40.649 to effectively coexist. 00:06:42.193 --> 00:06:45.262 So, some of the warblers use different parts of the tree. 00:06:45.663 --> 00:06:49.613 The myrtle warbler, for example, is found in the mid-section, the lower mid-section 00:06:49.613 --> 00:06:50.429 of the tree. 00:06:50.429 --> 00:06:53.523 While the cape may warbler is found at the tops of the trees. 00:06:54.155 --> 00:06:55.485 They eat different things. 00:06:55.485 --> 00:06:58.771 Black throated warblers that live sort of near the tops are eating 00:06:58.771 --> 00:07:00.705 small worms and grubs. 00:07:00.705 --> 00:07:04.507 Where cape may warblers are actually uh, eating flying insects. 00:07:05.510 --> 00:07:09.769 So we have different forms of competition 00:07:10.071 --> 00:07:12.999 different types of resources being used here. 00:07:13.436 --> 00:07:15.565 Different spaces, different food items... 00:07:16.286 --> 00:07:19.736 And so these birds have engaged in resource partitioning 00:07:20.182 --> 00:07:23.511 where they take advantage of different resources 00:07:24.041 --> 00:07:27.067 so that they can still gain a foothold in the ecosystem. 00:07:27.797 --> 00:07:30.424 One of the things we might see here though is that 00:07:30.424 --> 00:07:35.039 some areas of this tree, or some types of insect prey may not be as desire-- 00:07:35.039 --> 00:07:36.389 as desirable as others. 00:07:37.140 --> 00:07:41.722 So that when one resource is removed, or one competitor is removed 00:07:42.014 --> 00:07:43.485 we might see changes. 00:07:43.705 --> 00:07:47.306 And so competition really can influence distributions in time and space. 00:07:47.713 --> 00:07:49.785 Here is an example from the Oregon Coast. 00:07:51.174 --> 00:07:54.765 We have two different species that are living on the coastline here, 00:07:55.002 --> 00:07:56.222 we have barnacles 00:07:56.609 --> 00:07:57.888 and we have mussels. 00:07:58.216 --> 00:08:01.360 And these two organisms both like to live in the inner tidal zone. 00:08:01.360 --> 00:08:05.367 This is an area between the high and low tides that is partially covered by water 00:08:05.367 --> 00:08:07.330 during a portion of the day . 00:08:08.183 --> 00:08:11.134 And mussels tend to be very quickly growing. 00:08:11.366 --> 00:08:14.606 They grow fast, they are a little bit bigger, and they can actually 00:08:14.606 --> 00:08:16.275 -and you see this happening here- 00:08:16.275 --> 00:08:18.460 they can crush and squeeze out barnacles. 00:08:19.036 --> 00:08:23.148 They are engaging in some exploitation competition where they are physically 00:08:23.148 --> 00:08:26.343 taking up a resource and keeping other organisms from getting it. 00:08:27.436 --> 00:08:29.022 The problem that mussels have 00:08:30.862 --> 00:08:31.862 is that... 00:08:33.814 --> 00:08:37.193 while they are competitively excluding these barnacles 00:08:38.549 --> 00:08:41.230 they are limited to the area 00:08:41.831 --> 00:08:44.910 that is covered by water for much of the day. 00:08:45.749 --> 00:08:50.631 They have a much lower tolerance for drying out than the barnacles do. 00:08:51.150 --> 00:08:52.876 And so we see this very distinct, 00:08:52.876 --> 00:08:55.018 what's called a zonation line, 00:08:56.330 --> 00:08:58.821 that's separating the mussels and the barnacles 00:08:58.824 --> 00:09:01.768 because barnacles can live in those higher, inner tidals 00:09:02.077 --> 00:09:04.942 where there is less wave splash, but mussels can't survive. 00:09:05.474 --> 00:09:08.434 So this is a good example of resource partitioning. 00:09:09.375 --> 00:09:13.805 The mussels have excluded the barnacles from the--the wet zone down here 00:09:14.604 --> 00:09:18.098 but he barnacles, because they can last a little bit longer out of water, 00:09:18.451 --> 00:09:22.517 have been able to engage in resource partitioning and use this space up 00:09:22.517 --> 00:09:24.000 in the high inner tidal. 00:09:24.861 --> 00:09:26.296 What's kind of exciting 00:09:27.905 --> 00:09:31.599 is that if mussels are removed in some way 00:09:33.311 --> 00:09:35.097 then barnacles will spread 00:09:35.423 --> 00:09:37.005 to fill the available space. 00:09:37.243 --> 00:09:40.031 So perhaps we have a sea star predator that comes up here, 00:09:41.077 --> 00:09:42.960 removes and eats the mussels, 00:09:43.683 --> 00:09:46.403 barnacles will then spread to fill that available space 00:09:46.403 --> 00:09:48.858 and this is known as "competitive release." 00:09:49.538 --> 00:09:52.958 Basically if a superior competitor is removed 00:09:54.338 --> 00:09:58.233 then the other competitor may take advantage of that better resource. 00:09:58.674 --> 00:10:00.922 They don't have to resource partition anymore. 00:10:02.405 --> 00:10:06.574 And so this the reason that sea stars are, themselves, considered a keystone 00:10:06.574 --> 00:10:08.533 species on the Oregon Coast 00:10:09.018 --> 00:10:10.952 and throughout the Pacific Northwest 00:10:10.952 --> 00:10:15.027 because they wipe out big mussel populations and allow other kinds of 00:10:15.027 --> 00:10:16.963 organisms to live in the inner tidal. 00:10:17.714 --> 00:10:20.115 So, competition has a really big influence here, 00:10:20.617 --> 00:10:24.342 but if our sea star comes along and removes that superior competitor, 00:10:24.702 --> 00:10:26.104 it changes the community-- 00:10:26.109 --> 00:10:29.262 making the sea star another example of a keystone species. 00:10:31.692 --> 00:10:35.887 And you can see that here in this actual picture of the, um, these sea stars 00:10:35.887 --> 00:10:38.838 that come up to a certain level of the inner tidal 00:10:39.128 --> 00:10:41.512 they've eaten a whole bunch of these mussels. 00:10:42.782 --> 00:10:45.152 Remember from our example of co-evolution, 00:10:45.152 --> 00:10:49.757 sea stars are great at eating shellfish because they pry open that shell 00:10:49.757 --> 00:10:50.800 just a little bit 00:10:50.800 --> 00:10:54.853 and push their stomachs inside out and inside that shell and--and dissolve those 00:10:54.853 --> 00:10:57.143 nutrients in there and then [clicks tongue] 00:10:57.143 --> 00:10:59.243 pull their stomachs back into their bodies. 00:10:59.908 --> 00:11:04.168 So, here they have created this line of mussels and if you look below 00:11:04.168 --> 00:11:07.343 the mussel line you can see all these different kinds of seaweed, 00:11:07.343 --> 00:11:09.202 there's some other shells downs here, 00:11:09.202 --> 00:11:10.113 some barnacles. 00:11:10.113 --> 00:11:12.458 And they have really changed the community. 00:11:13.563 --> 00:11:16.730 And we have different populations taking part in that community. 00:11:16.824 --> 00:11:17.991 We have mussels, 00:11:17.991 --> 00:11:19.416 we have sea stars, 00:11:19.618 --> 00:11:21.112 we have barnacles, 00:11:21.112 --> 00:11:22.560 we have algae, 00:11:22.560 --> 00:11:24.298 all of those populations, 00:11:24.298 --> 00:11:27.114 all the members of a species that are living together in a place 00:11:27.114 --> 00:11:28.593 are interacting... 00:11:29.107 --> 00:11:30.496 in this community. 00:11:30.496 --> 00:11:31.920 And what we are going to see 00:11:31.920 --> 00:11:33.636 is that competition 00:11:33.636 --> 00:11:36.092 can occur between members of a community. 00:11:36.661 --> 00:11:38.742 Like a lion and a crocodile. 00:11:40.410 --> 00:11:44.031 And, in this case, what are a lion and a crocodile gonna compete for? 00:11:44.121 --> 00:11:46.544 Well, they're certainly competing for food. 00:11:46.544 --> 00:11:49.521 But, they may not be competing for all of the same things. 00:11:50.048 --> 00:11:52.700 So here we have niche overlap that is just partial . 00:11:52.779 --> 00:11:54.800 In this case, the lion and the crocodile 00:11:54.800 --> 00:11:57.192 they're not competing for the same place to live; 00:11:57.192 --> 00:12:00.296 the crocodile prefers an aquatic environment, the lion does not. 00:12:00.296 --> 00:12:02.365 They're certainly not competing for mates. 00:12:03.595 --> 00:12:04.668 However... 00:12:05.261 --> 00:12:10.402 lions are going to have 100% niche overlap with other members of the same species. 00:12:11.246 --> 00:12:16.052 And so competition tends to be much more intense between members 00:12:16.052 --> 00:12:17.629 of the same species. 00:12:17.629 --> 00:12:21.210 That's the difference between interspecific competition: 00:12:21.210 --> 00:12:24.612 competition that takes place between members of a different species 00:12:25.436 --> 00:12:30.734 and intraspecific competition that takes place between members of the same species. 00:12:31.366 --> 00:12:34.026 And the real difference here is complete niche overlap. 00:12:34.460 --> 00:12:35.895 If you're in the same species 00:12:35.895 --> 00:12:37.559 you're competing for food, 00:12:37.559 --> 00:12:38.734 for living space, 00:12:38.734 --> 00:12:39.797 for mates, 00:12:39.797 --> 00:12:41.667 because you have the exact same needs. 00:12:41.667 --> 00:12:45.297 So one of the things that we see with competition that's really interesting 00:12:45.297 --> 00:12:51.104 is that intraspecific competition tends to be the most intense competition 00:12:51.291 --> 00:12:53.152 and is going to be much more intense, 00:12:53.152 --> 00:12:54.042 in many cases, 00:12:54.042 --> 00:12:56.207 than interspecific competition. 00:12:59.569 --> 00:13:03.868 We are going to be focusing more next week on other kinds of dynamics that 00:13:03.868 --> 00:13:05.315 influence the shape, 00:13:05.315 --> 00:13:07.245 and size of these pop... 00:13:09.245 --> 00:13:13.697 We are going to be looking in much more detail next week at other kinds 00:13:13.697 --> 00:13:17.962 of interactions that influence the shape and size of these populations. 00:13:19.152 --> 00:13:25.041 In the meantime, don't forget to do the "Battle At Krueger" online exercise for 00:13:25.041 --> 00:13:28.665 your 5 activity points and to also participate in the discussion 00:13:28.665 --> 00:13:31.575 forum for this week where you can ask and answer questions. 00:13:31.805 --> 00:13:34.626 I will also be asking and answering questions 00:13:34.626 --> 00:13:38.655 and that is going to help us keep up on these community interactions.