Causes of speciation
<span>Geographic isolation
In the fruit fly example, some fruit fly larvae were washed up on an island, and speciation started because populations were prevented from interbreeding by geographic isolation. Scientists think that geographic isolation is a common way for the process of speciation to begin: rivers change course, mountains rise, continents drift, organisms migrate, and what was once a continuous population is divided into two or more smaller populations.
</span>Reduction of gene flow
<span>However, speciation might also happen in a population with no specific extrinsic barrier to gene flow. Imagine a situation in which a population extends over a broad geographic range, and mating throughout the population is not random. Individuals in the far west would have zero chance of mating with individuals in the far eastern end of the range. So we have reduced gene flow, but not total isolation. This may or may not be sufficient to cause speciation. Speciation would probably also require different selective pressures at opposite ends of the range, which would alter gene frequencies in groups at different ends of the range so much that they would not be able to mate if they were reunited.</span>
Answer:
The correct option is B.
Explanation:
Muscle tissues of the heart refers to a group of cells that are carrying out similar functions in the heart. There are three different types of muscles, these are skeletal, cardiac and smooth muscles. The cardiac muscles are found in the heart, they form the contractile wall of the heart. These muscle contract involuntarily ( that is, without any external stimulation) and they are single nucleus, striated and short.
The volume of the cube of unknown substance is 
. The length of one side of the cube is 9 cm
<u>Explanation:</u>
As per the formula of mass and density, Mass / Density equals to volume. Therefore as the mass of the cube was given to be 81 g and the density of the cube is known to be 3.0 g/
,, to help Bill find out the volume. It is the ratio of mass and density and can be calculated as
As it is a cube, the volume is product of length, breadth, and height. Here, all sides are same as it is the cube.
The iris focuses light rays before they enter the posterior portion of the eye
Answer:
In the physical sciences, subatomic particles are smaller than atoms. They can be composite particles, such as the neutron and proton; or elementary particles, which according to the standard model are not made of other particles.
Explanation:
