Which of the following is an r-selected species?

a)rat
b)humpback whale
c)eagle
d)elephant

it is a)

The correct answer is- A) Rat.

R selected species are those species that can survive in unstable, unpredictable environmental conditions and produce large number of small size offspring ( with low survival rate and no parental care).

These species grow very rapidly and attain reproductive maturity at early stage in their lives.

Example- Insects, rats.

On the contrary, B) , C), and D) are K selected species that survive under stable environmental conditions and produce large size offspring with very few number ( having long life span and parental care).

several tissues working together form an organ, and several organs together make up an organisms.

the group of cell that carries out special jobs are tissue.