Why is a hypothesis called an educated guess?

Why does the shell of a birds egg have microscopic holes in it?

Polar bears, when they are not hibernating, need an average of 2 kg of fat per day to obtain enough energy to survive. The polar bear's primary food source is seals and they prefer seal blubber over the rest of the animal.

Chloroplasts are unable to survive without the energy they receive from cell respiration. What conclusion can be drawn from this fact? It is not possible that chloroplasts ever existed as free-living bacterial cell and endosymbiotic theory is flawed.

Is pain a sign or symptom

In addition to providing food why are plants important to human society give three examples

Structures through which conduction impulses pass, in sequential order, causing the heart to contract:

When a river or stream flows downward into a basin that is surrounded by high ground on all sides, what can form a. a lake b. a creek c. a sinkhole d. a delta

Is groundwater a renewable or nonrenewable resource? what are the consequence of drought or overpumping?

Which of these explains why deletion of an imprinted gene can be a dominant mutation?

Which of the following has yielded compounds with the most antimicrobial activity? water air volcanoes soil