All animals are multicellular. Multicellular organisms are organis that are made up of many cells and most of the cells are specialized to perform various functions. Sponges are animals but they lack true tissues. There are some animals that also lack organs, this includes the simple animals e.g sponges, sea cucumbers etc. All animals are heterotrophic eukaryotes ie they obtain their food and derive energy from autotrophs and other heterotrophs.
Explanation: All animals are Eukaryotic, I.e they are multicellular organims which means they posses different organs and cells that helps in the survival of the animal.
It is useful for an ecologist to identify the keystone species in an ecosystem because the keystone species is important to maintaining the stability of an ecosystem, and any changes in the keystone species population shows that there is changes in ecosystem health.
