Answer:
Transport in both plants and mammals is by a system of specialised tubes. ... In mammals this forms a circulatory system of arteries, capillaries and veins. In flowering plants, transport is not circulatory and occurs in microscopic xylem and phloem.
Explanation:
Mammals:
ºSpecialised tubes - arteries, capillaries and veins.
ºAll tubes are composed of living cells.
ºThe concentration of substances transported is controlled (see homeostasis). The ºconcentration of the substances being transported is not controlled.
ºThe heart controls the circulatory system. The heart is controlled by the nervous system.
ºThe rate of flow is moderate and is regulated by vasoconstriction and vasodilation.
ºUses water as a medium in which to transport substances (it is a good solvent, it has a high specific heat capacity, has good surface tension but is not viscous, and is unreactive).
º The substances being transported are: respiratory gases, glucose, amino acids, fatty acids, glycerol, vitamins, minerals, hormones.
Plants:
º Specialised tubes - xylem vessels and tracheids and phloem sieve tubes.
º Some tubes are composed of living cells, e.g. phloem. Others are composed of dead cells, e.g. xylem.
º The concentration of the substances being transported is not controlled.
º There is no such control in plants.
º The rate of flow in the xylem and phloem is quite slow. The rate of flow in the xylem is controlled by external factors via the stomata (e.g. temperature, wind, humidity).
º Uses water as a medium in which to transport substances.
ºSubstances being transported are: sucrose, amino acids, fatty acids, glycerol, vitamins, hormones (in the phloem) and minerals and water (in the xylem). Respiratory gases are not transported by this system but move via a series of inter-connecting air spaces.
