Answer:
Wolves are a keystone species because they are so important to the ecosystem that their removal causes a catastrophic disequilibrium.
Explanation:
Wolves are the predators available in the environment but they exist in relatively less number while comparing it with another species of animals. Wolves influence their pray which are influenced by plants. Thus, They are so important to the ecosystem that their removal causes a catastrophic disequilibrium.
The average speed <em>appears to be</em> (distance) / (time) =
(length of the cable) / (time from when a pulse goes in until it comes out the other end) .
That's 1,200,000 meters/ 0.006 second = 2 x 10^8 = <em>2 hundred million m/sec</em>
That figure is about 66.7% of the speed of light in vacuum.
The reason I went through all of this detail was to point out that this is
NOT necessarily the speed of light in this glass, for two reasons.
1). The path of light through an optical fiber is not straight down the middle. In the original fibers of 20 or 30 years ago, the light bounced back and forth off the inside walls of the fiber, and zig-zagged its way along the length. In current modern fibers, it still zig-zags, but it's a more gentle, up-and-down curved path. In either case, the distance covered by the light inside the fiber is more than the straight length of the cable, and the time it takes it to come out the other end is more than its actual speed inside the glass would have meant if it could have traveled straight through the pipe.
2). This problem talks about an optical fiber that's 1,200km long. There is loss in optical fiber, and you're NOT going to get light all the way through a single piece of it that's something like 745 miles long. It takes electronic repeaters, "boosters", and regenerators every few miles to keep it going, and these devices add "latency" or time delay in the process of going through them. That delay in the electronics shows up as apparent delay through the fiber-optic cable, and it makes the speed through the glass appear to be slower than it actually is.
The ball takes 0.2 sec to travel the height of the window, which is 2 m.
Then the speed of the ball at that time was
We know that:
Where 
is the initial velocity.
So:
Then we have the equation for the position as a function of time.
Where
= initial position
r = position as a function of time
= initial velocity
g = acceleration of gravity
t = time.
If the ball is thrown from the ground then:
= 0 m
We want to find now the distance between the window and the ground.
When the ball reaches the bottom of the window t = 1.8s
So:
m
The window is 37,404 m high
Finally, to know how high the ball rises we must know at what moment the vertical velocity of the ball is zero.
Now we replace t in the position equation
The ball reaches up to 44.70 m in height.
It is basically shielding a magnetic field. This can be done with rubber or any other material that is thick. Normally small magnets already block the shield.
Fruit trees are important because they can make more trees from the seeds of their fruit. regular trees just drop leaves and pollen
