When a Stickleback fish feels threatened, it will flare out its pair of pelvic spines and three dorsal spines, making it difficult for predators to swallow them.
Lying generally between the foot of acontinental rise and a mid-ocean ridge,abyssal plains cover more than 50% of the Earth's surface. the zone of theocean floor that separates the thinoceanic crust from thick continentalcrust. ... the slope between the outer edge of the continental shelf and thedeep ocean floor.
The second stage of prenatal development begins at about two weeks after conception. at this point, the growing bundle of cells is called an embryo.
It just depends what you are studing:
