JAMB Biology: Internal Anatomy of Plants and Mammals
To excel in this section, you must move beyond the surface. Understanding the internal “plumbing” of plants and the “layout” of mammalian organs is non-negotiable.
Table of Contents
- 1. Internal Structure of Flowering Plants
- 2. Supporting Tissues in Plants
- 3. Internal Structure of a Mammal
- 7 Essential JAMB Past Questions (Internal Structure)
1. Internal Structure of Flowering Plants
Flowering plants (Angiosperms) have specialized tissues for support, transport, and photosynthesis. JAMB frequently tests the Transverse Section (T.S.) of roots and stems.
A. The Leaf (The Factory)
The leaf is designed for gas exchange and photosynthesis.
- Epidermis: Transparent layer to let light through; contains stomata for gas exchange.
- Mesophyll: * Palisade Mesophyll: Closely packed, vertically arranged cells with many chloroplasts (Primary site of photosynthesis).
- Spongy Mesophyll: Loosely packed with air spaces for gas diffusion.
- Vascular Bundles: Contain Xylem (water) and Phloem (food).
B. Root and Stem (The Support & Transport)
You must be able to differentiate between Dicot and Monocot arrangements:
- Dicot Stem: Vascular bundles are arranged in a regular ring around the pith.
- Dicot Root: Xylem usually forms an “X” or star shape in the center, with Phloem in the “arms.”
2. Supporting Tissues in Plants
Plants don’t have bones, so they rely on specialized cells for mechanical strength:
- Collenchyma: Living cells with thickened corners (cellulose). Provides flexibility and support in young, growing stems.
- Sclerenchyma: Dead cells with very thick, lignified walls. Provides rigid mechanical support (found in coconut shells and pear grit).
- Xylem Vessels/Tracheids: Provide both water transport and structural support due to lignin.
- Phloem Fibres: Provide tensile strength to the vascular bundles.
3. Internal Structure of a Mammal
JAMB expects you to know the relative positions of organs within the body cavities (Thoracic and Abdominal).
A. The Thoracic Cavity (Chest)
- Heart: Located centrally (slightly left) between the lungs.
- Lungs: Spongy organs occupying most of the chest cavity.
- Diaphragm: A muscular sheet separating the chest from the abdomen.
B. The Abdominal Cavity (Belly)
- Digestive Organs: Stomach (top left), Liver (top right/largest gland), Intestines (filling most of the lower cavity).
- Excretory Organs: Kidneys (Bean-shaped, located against the back wall/dorsal side).
- Reproductive Organs: Located in the lowest part (Pelvic region).
7 Essential JAMB Past Questions (Internal Structure)
1. In a transverse section of a dicotyledonous stem, the vascular bundles are arranged:
- A. Scatted throughout the ground tissue
- B. In a definite ring near the periphery
- C. In an X-shape at the center
- D. Only in the pith
2. Which of the following tissues provides the main mechanical support to a fully grown woody stem?
- A. Parenchyma
- B. Collenchyma
- C. Sclerenchyma
- D. Epidermis
3. The palisade mesophyll is a specialized tissue for photosynthesis because its cells:
- A. Are loosely packed with large air spaces
- B. Contain many chloroplasts and are vertically arranged
- C. Form a transparent layer on the leaf surface
- D. Are dead at maturity and lignified
4. In the mammalian body, the kidneys are located on the:
- A. Ventral side of the abdominal cavity
- B. Dorsal side of the abdominal cavity
- C. Thoracic cavity above the diaphragm
- D. Pelvic cavity near the bladder
5. The tissue responsible for the translocation of manufactured food in plants is the:
- A. Xylem
- B. Phloem
- C. Cambium
- D. Cortex
6. Which of these is a living supporting tissue characterized by cellulose thickening at the corners of the cells?
- A. Sclerenchyma
- B. Xylem fibres
- C. Collenchyma
- D. Phloem parenchyma
7. The muscular partition that separates the thoracic cavity from the abdominal cavity in mammals is the:
- A. Pleura
- B. Pericardium
- C. Diaphragm
- D. Peritoneum
Answer Key:
1-B, 2-C, 3-B, 4-B, 5-B, 6-C, 7-C
Study Tip: JAMB loves to show a diagram of a Dicot stem and label the Cambium (the layer between Xylem and Phloem). Remember: Cambium = Secondary Growth (increase in girth/thickness).
