A dolphin can breathe while sleeping because _________.

How are cactus spines like leaves?

Birds migrate when the food supply changes.

Birds leave the north when days get longer.

Birds help pollinate flowers.

Flowers are able to _____ with the help of insects.

Insects carry ________ from one flower to another.

A flower's color and scent are _____ that invite the insects.

Dolphins and humans are both_____.

However, they breathe differently. Humans breathe _________ without thinking

dolphins must open and close their _________ to breath.

A cactus has _____ that allow it to sore large amounts of water.

The cactus's _____ keep away thirsty animals.

The cactus also has a thick, waxy skin so that water doesn't __________________.

Many birds must________ to find food.

They fly the same______ every year.

Birds fly the same route every year, moving between their summer and winter ________.