| Answer | Crossword Clue |
|---|---|
| ESTRUS | Stage when an animal is in heat |
| blastula | An animal embryo at the early stage of development when it is a hollow ball of cells |
| blastulas | An animal embryo at the early stage of development when it is a hollow ball of cells |
| ectotherms | An animal that is dependent on external sources of body heat |
| ectotherm | An animal that is dependent on external sources of body heat |
| endotherm | An animal that is dependent on or capable of the internal generation of heat; a warm-blooded animal |
| endotherms | An animal that is dependent on or capable of the internal generation of heat; a warm-blooded animal |
