What is a deep steep sided valley formed by weathering and erosion called

Plants that have reproductive structures called cones are?

Aplant may open end close its stomata to prevent excess water loss and maintain

Which scientific design has both practical limitations and limitations due to scale? studying the effect of bleach on the growth of mold spores exposing cultures of duckweed to different intensities of light observing the replication of dna molecules with a hand lens using colored marbles to model a cross between two colors of rabbits