Organisms exchange substances with their environment

Question 1

Every organism needs to exchange things with its environment

Answer 1

• Cells need to take in oxygen (for aerobic respiration and nutrients),
• excretion of waste (Carbon dioxide, urea),
• heat needs to be exchanged so it stays the same temp,
• in cells these substances can be diffused directly through the cell surface membrane, it’s quick bc substances only travel a small distance. The rate of exchange depends on sa:v which is high for small animals

Question 2

Multicellular organisms need exchange organs and mass transport systems

Answer 2

• In multicellular organisms diffusion across an outer membrane is too slow bc some cells are v deep w/in the body so the distance between them and the outside environment is too big,
• larger animals have a high sa:v, it’s difficult for enough substances to fill the volume through the smaller sa.
• multicellular organisms need Exchange Organs like lungs, as well as an efficient system to carry substances to and from their individual cells (mass transport)
• In mammals it’s usually the circulatory system (blood to carry glucose, oxygen, hormones, antibodies, and waste like co2)
• In plants, mass transport usually involves the transport of water and solutes in the xylem and the phloem.