This is the 634th most frequent Japanese word.
動物
Animal.
Here, '動物' is used to generalize animals as beings that require kindness and respect.
動物を大切に扱うことが必要です。
It is necessary to treat animals with care.
Here, '動物' is used as the subject of the sentence, referring broadly to animals as living creatures.
動物は自然の中で自由に生きています。
Animals live freely in nature.
In this sentence, '動物' is used to specify the entities housed in the zoo, emphasizing its variety.