Or, for a medical example, suppose smoking multiplies the risk of lung cancer by some number R: then the Wald test can be used to test whether R = 1 (i.e. there is no effect of smoking) or is greater (or less) than 1 (i.e. smoking alters risk).
There are more than 900 species of Tardigrade or Water Bear, pictured. They're found everywhere in the world, from the highest mountains to the deepest oceans. Boil the 1mm creatures, freeze them, dry them, expose them to radiation and they're so resilient they'll still be alive 200 years later.
Though they are excellent swimmers, polar bears spend most of their time atop Arctic sea ice. Sea ice is an ecosystem in itself, supported at its base by plankton and algae at the bottom of the food chain. Polar bears share this habitat with seals, whales, Arctic foxes, birds and even people.