13, 1781: British astronomer William Herschel discovers Uranus—the first new planet discovered since ancient times - while searching for faint stars. 1787-1851: Four Uranian moons are discovered and named Titania, Oberon, Ariel and Umbriel. 1948: Another moon, Miranda, is discovered. Mar.
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Answer: The correct answer is option a.
Explanation:
Prezygotic isolation is a mechanism by which mating and fertilization is prevented. Thus, it prevents the formation of a zygote.
It can be achieved by various reasons such as temporal differences (difference in mating seasons), habitat isolation, behavioural differences (different mating rituals such as different dance patterns, voice calls, et cetera), mechanical isolation, et cetera.
Thus, different breeding calls prevent the species to interbreed with each which ultimately prevent the formation of zygote formation.
Hence, it is a type of prezygotic isolation.
Threatened means they are lowering in numbers and nearing to be endangered.
Endangered means they are dangerously close to being extinct
Extinct means there is none of them left in the wild.
I hope this is what you meant.
Stressor due it comes from an external condition or event.
