BIOLOGY STUDENTS, I NEED UR HELP.. Substances transported in the phloem are carried upwards in the stem at some time of the year and downwards at other times. Explain why substances are transported in the phloem upwards at one time of the year and downwards at another. *

economic impact of malaria is estimated to cost africa $12 billion every year. this figure factors in costs of health care, absenteeism, days lost in education, decreased productivity due to brain damage from cerebral malaria, and loss of investment and tourism.

a. seed plant structure. 1. the three main plant organs are roots, stems, and leaves. a fourth kind of tissue, meristematic tissue, is responsible for plant growth. meristematic tissue is the only plant tissue that produces new cells by mitosis. plants can lose water out of their leaves as they exchange gases with the air

explanation: