Some unicellular organisms are similar to because they have the ability to

reptiles, lay eggs
plants, produce sound
animals, move
birds, fly

Some unicellular organisms are similar to animals because they have the ability to move.
Third option

Because the earth is not round ,but it may seem round when viewed from ,our planet but true some points earth is not round was an oblate spheroid -a square that it squashed as globe however is not even a perfect oblate spheroid.in fact isaac newton's first proposed that earth was not perfectly round but it was an oblate spheroid instead.that mean a square that is squashed as its poles and swollen at the