Mules are considered to have many superior characteristics compared to the horse or burro. Mules are often stronger, agile, and can jump higher than either of their parents. Why are mules considered to be a weak hybrid and not a separate species?

Because they are sterile

Explanation:

Mules are considered to be a weak hybrid and not a separate species because they are sterile and cannot produce progeny of their own.

Mules are hybrid products from two separate species - a donkey and a horse.

A species is generally defined as a group of organisms that are capable of breeding to produce fertile offspring. Hence, in order for them to have the potential of being categorized as a separate species, they must be able to produce their own progeny but this is not the case.

when the displaced particles are perpendicular to the direction the wave travels, is called a transverse wave, whereas in longitudinal wave the displace practices are parallel to the direction of the wave.

in the given image:

first image shows - longitudinal wave

second image shows - transverse wave

third image shows - longitudinal wave

fourth image shows - longitudinal wave