Estimated Average Requirement (EAR) and Recommended Dietary Allowance (RDA) for amino acids (protein) for healthy adults 19 y and older, mg/kg/day:
- Estimated Average Requirement (EAR): average, estimated to meet the requirements of 50%.
- Recommended Dietary Allowance (RDA): average, sufficient to meet the nutrient requirements of nearly all.
|phenylalanine + tyrosine
|methionine + cysteine
A tree is a plant with an elongated stem, or trunk, supporting branches and leaves in most species. Trees tend to be long-lived, some reaching several thousand years old. Trees have been in existence for 370 million years.
A variety of plant species have independently evolved a woody trunk and branches to compete for sunlight. In more general sense, tall palms, tree ferns, bananas and bamboos are also trees. The roots branch out under the ground to anchor the tree and to extract moisture and nutrients from the soil. Above ground, the branches usually bear leaves, which capture light.
Trees reduce erosion and moderate the climate. Trees and forests provide a habitat for many species of animals and plants. Some trees provide edible fruit.