NUSH BL2131 Notes

BL2131 Notes Foundations in Biology II Topics 1 to 7 This is a compilation of topics taught in BL2131. Made by LQ “Double the initial number of the module code, double the pain!” ~Einstein or someone idk Links of All LQ Notes: LQ Notes Links Document Topic Page Topic 1: Transport in Plants 2 Topic 2: Transport in Hoomanz 22 Topic 3: Respiration 40 Topic 4: Heredity 48 Topic 5: Reproduction in Plants 56 Topic 6: Reproduction in Hoomanz 66 Topic 7: Homeostasis and Thermoregulation 85 Sources 95 Author’s Note Please use at your own discretion, information in this set of notes may not be correct (im not good at bio okay) , do confirm with your Lovely Biology Teachers if you have any doubt, and if you can, drop a comment in the notes if you find a mistake. Information marked with [confirm] need further clarification, if you have knowledge on the content, pleeeeeaaaassse help. Everything that says “FYI” is purely for additional reading, and is not tested (at this level). Thanks for reading and good luck! :D Note: Topic 1 - Transport in Plants is NOT tested for EOY Exams. ~Page 1 of 100~

Topic 1: Transport in Plants Recap: If you need a Recap for Y1 Biology BL1131, consider referring to BL1131 NotesTopic 7: Nutrition in Plants before continuing. 1.1 Parts of a Leaf Consider the transverse section of a Privet ( ligustrum ) plant below, in Figure 1 . 1 . Figure 1.1: A Transverse Section of a Ligustrum Leaf This is a typical dicotyledonous (or dicot, for short) leaf. We can label this transverse section as such: Figure 1.2: Labelled Transverse Section of Ligustrum Leaf However, as you might notice, the stoma and vascular bundles are not labelled. ~Page 2 of 100~

Figure 1.3: Labelled Stoma of Ligustrum Leaf Figure 1.3 above shows the stoma of the Ligustrum Leaf. For clarity’s sake, here’s a clearer image of what the stoma looks like, from an Alfalfa ( Medicago Sativa ) plant: Figure 1.4: Labelled Stoma of Medicago Sativa Leaf ~Page 3 of 100~

Figure 1.5: Labelled Vascular Bundle of Ligustrum Leaf Note that the xylem is always above the phloem (when the leaf is positioned naturally, i.e. stomata on the bottom). ~Page 4 of 100~

1.2 Vascular Tissues in the Stem Figure 1.6: Longitudinal Section of Cucurbita Stem Figure 1.6 above shows the Longitudinal Section of Vascular Tissues of a Squash ( Cucurbita) Plant Stem. The xylem is always positioned closer to the centre of the stem than the phloem, as in Figure 1.7 below: Figure 1.7: Cross Section of a Plant Stem ~Page 5 of 100~

1.3 Vascular Tissues in the Roots Figure 1.8: Cross Section of a Ranunculus Plant Root Figure 1.8 above shows the xylem and phloem of a Buttercup ( Ranunculus ) Plant Root. As you can see, we can observe that the phloem and xylem are not packed into vascular bundles like they are in the stem or leaves. The xylem is also shaped in the shape of a star (or X, or cross, or whatever you call it) . The xylem and phloem alternate with each other. 1.4 Xylem Vessels Xylems are the water-carrying tubes of a plant. 1.4.1 Function of Xylem The xylem has 2 main functions: 1. Providing mechanical support for the plant; and 2. Conducting water and dissolved mineral salts from the roots to the stem and leaves. The xylem is a long, continuous, hollow tube , similar to a straw, that is made up of dead cells fused together. It contains no cross-walls or protoplasm . But what are cross-walls? Refer to Figure 1.9 below. ~Page 6 of 100~

Figure 1.9: Formation of Xylem 1.4.2 Lignin Lignin is a hard and rigid substance that is found on the walls of the xylem, which strengthens it and provides mechanical support for the plant. Deposits of lignin are formed on the walls of the xylem through a process called lignification . Figure 1.10 below shows three lignification patterns that we need to know, where the red parts denote lignin deposits: Figure 1.10: Lignification Patterns The benefits of lignification are that the plant gets mechanical support , ensuring that the vessels do not collapse and hence helps in the transport of water and mineral salts . ~Page 7 of 100~

1.5 Processes Involved in Transport of Water There are three main processes involved in the transport of water - Root Pressure , Capillary Action , and finally Transpiration Pull . 1.5.1 Root Pressure Root Pressure is the pressure resulting from the constant entry of water (by osmosis) through the roots. Figure 1.11 below is an illustration of this: Figure 1.11: Root Pressure As illustrated, the water molecules “push” the entire stream of water upwards as they try to enter by osmosis, as shown by the red arrows. Illustrated by Figure 1.12 below is the effect of root pressure. ~Page 8 of 100~

Figure 1.12: Effect of Root Pressure 1.5.2 Capillary Action Capillary Action is dependent on the forces of cohesion and adhesion . It is defined as the tendency of water molecules to move up inside very narrow tubes called capillaries. Cohesion is the attraction of water molecules to other water molecules held together. When one molecule goes up, the others are pulled up by cohesion. Refer to Figure 1.13 below. ~Page 9 of 100~

Figure 1.13: Cohesion of Water Adhesion is the attraction of water molecules to other molecules (like the glass test tube, or the xylem walls). Refer to Figure 1.14 below. Figure 1.14: Adhesion of Water ~Page 10 of 100~