Because there is little leaching.
I believe it is 13 m towards the origin position, or just 13 m south.
Veins carry deoxygenated blood from the body to the heart so it can be sent to the lungs, pulmonary veins takes oxygenated blood from the lungs to the heart.
Frogs are insectivores. If the frogs prey on the gnats and their numbers are decreased, this allows the gnats to proliferate because the competition for survival is lessened. Gnats, being lower on the food chain, have adapted to lay large numbers of eggs due to the environmental pressures under which they evolved (being eaten in large quantities). Therefore, fewer gnats being eaten = more gnats surviving.
