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Animal Populations and Habitats

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Subido el 28 de mayo de 2007 por EducaMadrid

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In the third segment of the Case of the Zany Animal Antics the tree house detectives simulate population growth with an experiment and learn how to estimate populations with random sampling from a NASA explorer school. In the last part of the Animal Populations and Habitats segment the tree house detectives learn what makes up a good habitat.

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So what's up? Will the treehouse detectives find any endangered animals in Jacob's backyard? 00:00:00
Will Kaylee get her Girl Scout badge? 00:00:06
What else should the detectives do to help Jacob get a certified habitat? 00:00:09
Find out in the next exciting chapter of The Case of the Zany Animal Antics. 00:00:13
Be sure to look for answers to the following questions. 00:00:20
What is carrying capacity? 00:00:23
Why is it important to randomly sample a population? 00:00:25
What makes a good habitat? 00:00:28
What does territorial mean? 00:00:30
Thanks for helping me on my bat project, Dr. D. 00:00:34
Helping an endangered species is one of the requirements for my wilderness badge. 00:00:37
No problem. I'm glad that your project involves bats, 00:00:41
because over 40% of bat species are endangered or threatened. 00:00:44
It's especially important because the eastern big-eared bat, 00:00:47
which is native to southeastern Virginia, is endangered. 00:00:51
I heard that as well. 00:00:54
Did you know that one bat can eat up to 3,000 insects in one night? 00:00:56
It can also help to disperse seeds and pollinate fruits. 00:01:01
So by providing the bats with shelter and a place to raise their young, 00:01:04
the number of bats in the area should increase. 00:01:08
It will certainly help, but a lot of factors affect the growth of a population. 00:01:11
Isn't a population a group of the same species that's living in a particular area? 00:01:15
I see that you've been doing some research. 00:01:20
Let's do an experiment with pennies that simulates population growth. 00:01:22
If I throw down eight pennies to represent eight bats, how many will turn up heads? 00:01:26
On the average, four should turn up as heads. 00:01:31
That's right. Let's say that the bat population as a whole 00:01:33
averages one baby or pup per bat couple per year. 00:01:36
That means that with four bat couples or eight bats, 00:01:40
they would produce a total of four pups per year, 00:01:43
which means after one year you would have 12 bats. 00:01:46
Excellent. We can then add four pennies and throw down a total of 12 00:01:48
to see how many bats we'll have in the next year. 00:01:52
Let's try to experiment five times to see how many bats we'll have in five years. 00:01:54
We've got five heads. 00:02:01
Add five pennies to mine. 00:02:05
I get 45. The population increased rapidly. 00:02:19
I have 62. It's different because you don't always get the average when you throw down pennies. 00:02:23
Shouldn't we subtract a few pennies to represent the bats that died or left the area? 00:02:28
That's a good point. Under ideal conditions where bats only die of old age and no bats immigrate, 00:02:33
the population will eventually reach what's called its biotic potential as it grows very rapidly. 00:02:38
I guess that means that the animals' needs are met and that they have a healthy habitat. 00:02:43
That's right. In the real world, the population will eventually reach an equilibrium situation 00:02:47
where the number of births equal the number of deaths. 00:02:52
I guess that's because the population gets so big there's just not enough food to feed everyone. 00:02:55
That's one factor, but there are a lot of other factors. 00:03:00
A lot of animals in a small area is called a high density. 00:03:03
High densities of prey attract more predators. 00:03:06
And I would think that diseases would spread more easily through high density populations. 00:03:09
Plus, I guess that animals just need a certain amount of space. 00:03:14
That's right. All of these factors affect the maximum number of a species that a given environment can support. 00:03:17
That's called the carrying capacity. 00:03:22
I just hope we can help increase the bat population. 00:03:25
I hope so, too. So how can you tell if the population is shrinking or growing? 00:03:28
We would have to count them, but I would think it would be almost impossible to count all of the animals. 00:03:33
Yes, it would be difficult. In order to estimate the population of a species, 00:03:38
scientists will capture some of them, mark them with a tag, and then release them. 00:03:42
Some time later, they will capture some more of the same species and see what fraction are tagged. 00:03:46
I bet there's some mathematical way to figure out the size of the total population. 00:03:50
There are some other techniques to measure populations. 00:03:54
Right on the Internet, the Carroll City Elementary School in Miami, Florida is investigating a random sampling technique. 00:03:57
Aren't they a NASA Explore School? 00:04:02
To find out how you can get your school to become a NASA Explore School, visit the NASA Sci-Files website. 00:04:05
Yes, and they're working with the Society of Women Engineers. 00:04:11
Here they are now. 00:04:15
Hi, I'm Ta'Quinn, and I'm from Ms. Belanco's class. 00:04:17
And I'm Anita, and I'm in Ms. Gant's class here at Carroll City Elementary School in Miami, Florida. 00:04:21
Hi, Dr. D told us about your investigation. Can you tell us about it? 00:04:26
Sure. With the help from our mentors from the Society of Women Engineers, 00:04:30
we begin by looking at this critter page and trying to predict how many critters are on it. 00:04:33
It looks like it has a lot of critters. 00:04:37
Yes, it's a lot to count, so we brainstormed some ways to estimate the number. 00:04:40
We decided to use a random sampling technique. 00:04:44
Right, we used a sampling square and randomly dropped it on the page of critters. 00:04:47
Why did you drop it randomly? 00:04:51
Randomly dropping the square gives a better sample of the population. 00:04:53
If you choose where to count the critters, you may pick areas with lots of them. 00:04:57
Then your estimate will be too high. 00:05:00
Next, we outlined the square and then counted the number of critters in it. 00:05:02
What do you do if a square cuts a critter in half? How do you count it? 00:05:05
Good question. For our sample, we only used critters that were at least half in the square. 00:05:09
So how many samples did you take? 00:05:14
Remember, in a random sample, the more data you collect, the more accurate your estimate. 00:05:16
We dropped the square four more times. 00:05:21
Next, we found the average number of critters per square unit. 00:05:23
How did you find the total number of critters? 00:05:26
We counted the number of square units on the page, and there were 63. 00:05:29
So we multiplied our average number by 63 and recorded it on our chart. 00:05:33
To give us an even more accurate estimate, we used each group's average and calculated the class average. 00:05:37
How do you know if your estimates are accurate? 00:05:43
Don't you need to know the total number of critters on the page? 00:05:45
Yes, we each counted the critters and compared our answers. 00:05:48
There were 393 critters on the page. 00:05:51
How did your estimates compare with the actual numbers? 00:05:54
Our group estimated 433, so we were off by 40. 00:05:57
However, when we compared the class estimate to the actual, it was 412, a lot closer. 00:06:00
That's why it's important to take lots of samples and gather plenty of data. 00:06:05
It is very difficult to count a large population of animals, 00:06:09
but by sampling and finding an estimate, you can get pretty close to the number. 00:06:13
Next, we're going outside to do a sample of some real critters, like grasshoppers. 00:06:17
Sounds like fun. Maybe we should do that for Jacob's backyard. 00:06:21
Be sure to post your results on the website so we can see what you found. 00:06:25
Will do, and let us know about the animal population in your preserve. 00:06:29
Goodbye from Carroll City Elementary School in Miami, Florida. 00:06:33
I'm not sure that Jacob will want to know the population of critters in his backyard. 00:06:38
Probably not, but at least you have an idea of how to find the size of a population. 00:06:42
I wonder how Jacob's doing. Maybe I should go see if he needs some help. 00:06:47
Well, this will take some time to dry. 00:06:51
Whoa! 00:07:17
Have you heard from Jacob? 00:07:42
I wonder if he's working in his backyard. 00:07:44
No, but Kaylee's report on populations was very helpful. 00:07:47
She's almost done all of her work to earn her badge. 00:07:50
All she needs is to find out about an endangered species in our state. 00:07:53
I wonder if there's one in Jacob's backyard. 00:07:56
I think everything in Jacob's backyard is endangered. 00:07:59
I know, but if we could find a species that his backyard could support, maybe we could help Kaylee. 00:08:02
That would be awesome. Let's go to the problem board. 00:08:07
Good idea. 00:08:09
So what do we know? 00:08:11
We know that animals belong to the animal kingdom and are divided into two separate divisions. 00:08:13
Right, vertebrates and invertebrates. 00:08:17
We know that animals have basic needs and that they will migrate to find new food sources. 00:08:19
We also know that animals reproduce based on the amount of food available and the right conditions. 00:08:23
That's why populations will vary so much. 00:08:28
So what do we need to know? 00:08:30
We need to know what makes a good habitat. 00:08:32
We also need to learn more about how habitats can help endangered species. 00:08:34
So where do we go? 00:08:38
Dr. Mota mentioned that Dr. Brenninger studies and protects the wildlife at NASA Kennedy. 00:08:40
I'll see if he can help. 00:08:44
Great. Since we're going to be creating a habitat that can support wildlife and possibly even an endangered species, 00:08:46
we'll need to know what makes up a good one. 00:08:51
Exactly. Here's Dr. Brenninger now. 00:08:53
Hi, I read your email and I understand that Jacob wants to turn his backyard into a nature preserve. 00:08:55
Yes, but we need to learn more about habitats before he does. 00:09:01
What exactly is a habitat? 00:09:05
An area with specific habitat features that allows a specific species to survive. 00:09:07
For example, this area has loess trees and a sparse tree canopy and is called scrubby flatwoods. 00:09:12
So what makes a good habitat? 00:09:18
Lots of things. Habitat should provide enough food, shelter, and protection from predators. 00:09:20
When all these things are present, animals can produce enough young for their population to survive. 00:09:26
Does a species ever produce too many young? 00:09:32
Yes, and that makes the habitat overcrowded. 00:09:35
In fact, some animals will leave and find less crowded areas, while others will stay but will produce fewer young. 00:09:37
So the size and health of a habitat can determine the population of a species? 00:09:45
Exactly. Each individual or family of animals needs enough habitat to survive. 00:09:49
Depending on the amount of food, water, and shelter in a habitat, only a certain number of individuals can be supported. 00:09:55
If the habitat cannot provide for a large enough population, the species faces extinction. 00:10:02
What do you mean? 00:10:09
In a species, there are years when there are more deaths than births. 00:10:10
There are also times when the habitat is disrupted by disease, fire, and storms. 00:10:14
But won't they just reproduce once the habitat is restored? 00:10:20
If the disruption causes the population to decrease, then the probability that enough individuals will survive to reproduce is less likely. 00:10:24
How much habitat does each species need? 00:10:34
That varies among species. Florida scrub jays need about 25 acres, and they're very territorial. 00:10:37
What is territorial? 00:10:43
Territorial means that they claim a specific area of their own. If other scrub jays try to live in their area, they will defend it. 00:10:45
I never thought of birds defending their home. 00:10:55
Scrub jays live within the same territory with their mate for life. Their young also often stay with them for many years. 00:10:58
So how are habitats destroyed or disrupted? 00:11:06
Fires and storms regularly can change habitat but seldom destroy them. 00:11:10
Humans, however, regularly destroy habitats to build houses and grow food. 00:11:16
They also disrupt natural processes such as wildfires. 00:11:22
Why is fire so important? 00:11:26
Fires keep the shrubs low and add nutrients back into the soil. 00:11:28
How do you help NASA protect the environment? 00:11:32
I use field studies, remote sensing, and computer models to study animal populations and their habitat. 00:11:35
I then advise NASA on how to take care of the environment. 00:11:42
NASA sure is concerned about the environment. 00:11:47
That's right, and we want to make sure that endangered animals such as scrub jays are around for a long time. 00:11:50
Thanks, Mr. Brenninger. This has been helpful. 00:11:57
You're welcome, and good luck on your nature preserve. 00:12:00
Wow, I never realized how difficult it was to protect habitats and endangered species. 00:12:03
That's why it's such a great idea to create a backyard habitat. 00:12:08
Just think of what you can do to help animals. 00:12:11
Do you really think we can actually help an endangered species? 00:12:13
Well, we can try. 00:12:16
In fact, now that we've done the research, we may be ready to start learning about protecting animals in the backyard habitat. 00:12:18
Great, I hope we can help. 00:12:24
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Idioma/s:
en
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Autor/es:
NASA LaRC Office of Education
Subido por:
EducaMadrid
Licencia:
Reconocimiento - No comercial - Sin obra derivada
Visualizaciones:
751
Fecha:
28 de mayo de 2007 - 15:34
Visibilidad:
Público
Enlace Relacionado:
NASAs center for distance learning
Duración:
12′ 27″
Relación de aspecto:
4:3 Hasta 2009 fue el estándar utilizado en la televisión PAL; muchas pantallas de ordenador y televisores usan este estándar, erróneamente llamado cuadrado, cuando en la realidad es rectangular o wide.
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480x360 píxeles
Tamaño:
74.67 MBytes

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