They respond to danger by diving rather than flying, and are in any case much less wary than ducks. Extant species range in size from the least grebe, at 120 grams (4.3 oz) and 23.5 cm (9.3 inches), to the great grebe, at 1.7 kg (3.8 lbs) and 71 cm (28 inches).hey respond to danger by diving rather than flying, and are in any case much less wary than ducks. Extant species range in size from the least grebe, at 120 grams (4.3 oz) and 23.5 cm (9.3 inches), to the great grebe, at 1.7 kg (3.8 lbs) and 71 cm (28 inches).
Noun. 1. productivity-the quality of being productive or having the power to produce. productiveness. fruitfulness, fecundity-the quality of something that causes or assists healthy growth.
Net Productivity - The gain in energy or biomass per unit area per unit time after accounting for respiratory losses. This can be divided into Net Primary Productivity (Producers) and Net Secondary Productivity (Consumers). The NPP is potentially what is available for consumers in an ecosystem.