Question

Topic: Animal Internal Transport Systems

1. Compare a plant: would you describe the overall vascular tissue as an open or closed system? Xylem and Phloem?

2. What molecules are moved in an animal’s circulatory system? Compare and contrast animals and plants for molecules transported internally.

3. Describe the different types of force used to move fluids in plant internal transport systems and animal internal transport systems.

Answer 1

This is a very interesting topic, both Kingdoms posses developed vascularity, at least in the majority of their species.

- Would you describe the overall vascular tissue as an open or closed system? Xylem and Phloem?

In plants the vascular system is divided into 2 subsystems, the xylem and the phloem. The xylem is an open system, because it is actually connected to the environment in both ends. The entrance end is in the roots, where water is constantly entering along with some dissolved molecules in it, the water travels all the way up to the leaves where there is another oppening (stomata) that allows it to escape (only in the case of non being used for light dependant reactions). Phloem on the other hand, transports organic molecules produced in the leaves that travel to the rest of the plant, this system has no conspicuous entrance nor exit, thus it is a closed system.

- What molecules are moved in an animal’s circulatory system? Compare and contrast animals and plants for molecules transported internally.

Animals have one single vascular system that transports water, salt ions, cells and organic molecules. We could say that plants achieve all those transport functions but separating them into 2 different subsystems, that we already discussed. Xylem in in charge of water and salt ions, while phloem is in charge of organic molecules. The only exception is for cell transport, since plants never transport their cells through their vascular systems, and that is because plant cells cannot move due to their cell wall interactions.

- Describe the different types of force used to move fluids in plant internal transport systems and animal internal transport systems.

Animals need the use of a conspicuous pump to actively maintain vacularity, such pump is known as heart, but plants don't need such an organ. In xylem, plants use the force of capilarity to transport the water from the roots all the way up to the leaves, but this is not the force used for phloem. In the case of phloem, the force used is called pressure flow, and it consists of osmotic pressure, the tissue near the leaves is a place with high osmotic concentrations and the target destinations have low osmotic concentrations, this difference pushes the water and the organic molecules in it to the destination tissues. This osmotic gradient is created by the active transport of sugars out of the leaf cells and the active transport of the sugars into the destination cells