The most abundant animal
species on Earth?

mammals

Explanation:

theres no explanation but technically humans are likely the most numerous species of mammal on earth at the moment.

any abiotic or biotic factor in an ecosystem that causes a population's size to slow or decrease is a limiting factor.

thrombocytopenia, which is a deficiency in blood platelets, can cause bleeding and bruising in the dermis similar to senile purpura. other possible causes include: exposure to ultraviolet rays and aging skin are common causes of senile purpura. senile purpura may also be a sign of collagen loss in the skin and bones.