As multicellular organisms scale up in size, simple diffusion across their outer surface becomes insufficient to supply cells with essential nutrients and oxygen. Various structural and physiological adaptations have evolved to overcome this limitation.
Which row in the table below correctly describes the features of these transport and exchange systems?
Insect tracheoles deliver O2Counter-current flow in fishLarge organisms have a higherdirectly to respiring cellsgills maintains oxygen gradientSA:V ratio, requiring specializedwithout blood transportacross the entire lamellainternal transport systemsAYesYesYesBYesYesNoCNoYesNoDYesNoNo \begin{array}{|c|c|c|c|} \hline & \text{Insect tracheoles deliver } \text{O}_2 & \text{Counter-current flow in fish} & \text{Large organisms have a higher} \\ & \text{directly to respiring cells} & \text{gills maintains oxygen gradient} & \text{SA:V ratio, requiring specialized} \\ & \text{without blood transport} & \text{across the entire lamella} & \text{internal transport systems} \\ \hline \textbf{A} & \text{Yes} & \text{Yes} & \text{Yes} \\ \hline \textbf{B} & \text{Yes} & \text{Yes} & \text{No} \\ \hline \textbf{C} & \text{No} & \text{Yes} & \text{No} \\ \hline \textbf{D} & \text{Yes} & \text{No} & \text{No} \\ \hline \end{array} ABCDInsect tracheoles deliver O2directly to respiring cellswithout blood transportYesYesNoYesCounter-current flow in fishgills maintains oxygen gradientacross the entire lamellaYesYesYesNoLarge organisms have a higherSA:V ratio, requiring specializedinternal transport systemsYesNoNoNoRow A\textbf{A}A
Row B\textbf{B}B
Row C\textbf{C}C
Row D\textbf{D}D
82 exam-style questions on OCR GCSE Biology 2.1 Supplying the cell, covering 2.1.1 Transport across cell membranes, 2.1.2 Mitosis and the cell cycle, 2.1.3 Importance of cell differentiation, and 2.1.4 Stem cells. Each one has a worked solution and a mark scheme showing where the marks go.