Well, the thing is: we don't really know, as we don't even know how many species there are on earth.
If we take a look at the estimates of <span>World Wide Fund for Nature, an organization that works toward combating species extinction, their estimates vary from 200 to 100 000 - but a probable number is 20 000 (d). </span>
<span />
Answer:
¹/₃₈₇ second
Explanation:
<em>The period of a wave is the reciprocal of its frequency.</em>
So, simply, the frequency is ¹/₃₈₇ second(s), as that is the reciprocal of the frequency, 387 Hz.
Answer:
a. wavelength of the sound, 
b. observed frequecy, 
Given:
speed of sound source,
= 80 m/s
speed of sound in air or vacuum,
= 343 m/s
speed of sound observed,
= 0 m/s
Solution:
From the relation:
v =
(1)
where
v = velocity of sound
= observed frequency of sound
= wavelength
(a) The wavelength of the sound between source and the listener is given by:
(2)
(b) The observed frequency is given by:


(3)
Using eqn (2) and (3):


<span>Thermocline is a layer between
warm water from the ocean’s surface and cool water from below the ocean. In here,
the temperature decreases rapidly from the warmer layer to the colder layer. A thermocline forms due to the heat of the sun
heating the ocean’s surface. Because of the difference in density between warm
and cooler ocean water, cooler ocean water sinks and warmer ocean water floats.
This is caused due to the heat and mass transfer between particles of the
ocean. The answer is letter C. The sun’s radiation does not extend below a
certain depth; therefore, deeper ocean water is colder than surface water.</span>