1.2 The Concept of Circulatory System

  1. The circulatory system is an organ system that permits blood and lymph circulation to transport nutrients, oxygen, carbon dioxide, hormones, blood cells, etc. to and from cells in the body.
  2. The circulatory system in human and animals consists of blood, blood vessels and heart.
  3. Blood is the medium of transport in the circulatory system in human and animal.
  4. In SPM, you need to know
    1. the composition of human blood
    2. the function of blood and haemolymph in transport
    3. the types of circulatory system
    4. the circulatory system in humans
    5. the regulation of blood pressure

1.1 The Importance of Transport System in Multicellular Organisms

  1. The transport system in humans and animals is the circulatory system.
  2. The transport system in plants is the vascular tissues.
  3. The vascular tissues consist of 
    1. xylem tissues and 
    2. phloem tissues.

Live Process of Cells

  1. Every cell in an organism need to obtain nutrients and oxygen from the environment and at the same time, is able to remove the waste products from the cell.
  2. Unicellular organisms obtain their nutrients and oxygen across the plasma membrane directly from the environment by diffusion.
  3. Unicellular organisms are small in size. As a result, they have a large total surface area to volume (TSA/V) ratio. This enables the exchange of substances to occur rapidly by diffusion.

Why the Transport System is Important for Multicellular Organism?

  1. Multicellular organisms are bigger and hence have a small total surface area to volume (TSA/V) ratio. As a result, the rate of diffusion of substances is low. The larger the organism, the more difficult it is for the substances to diffuse in and out of the body cells.
  2. Also, as the size of an organism increases, the amount of nutrients and oxygen gas needed also increases. So does the metabolic waste products. As such, diffusion alone is not sufficient to fulfill the needs of the body cells and to remove the waste products from the body.
  3. Other than that, for a multicellular organism, the cells are located further in the body. They are not directly in contact with the environment.
  4. Therefore, multicellular organisms need special transport systems to transport the nutrients to all the body cells and at the same time to remove the metabolic waste from the body cells. 

7.10.1 The Formation of Images by Plane Mirrors and Lenses (Structured Questions)

Question 1:
Diagram 1.1 and Diagram 1.2 show an experiment to measure the focal length of two convex lenses.

(a) Measure and write down the focal length in Diagram 1.1. [1 mark]

(b) Observe Diagram 1.1 and 1.2.
What is the difference between the focal lengths of the two convex lenses? [1 mark]

(c) State one inference for this experiment. [1 mark]

(d) State the variables in this experiment.
(i) Constant variable [1 mark]
(ii) Manipulated variable [1 mark]

(a) 7.0 cm

The convex lens shown in Diagram 1.1 has a shorter focal length than the convex lens shown in Diagram 1.2.

The thicker a convex lens is, the shorter its focal length will be.

Parallel light rays from a distant object passing through the convex lens.

Convex lenses with different thicknesses.