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Biology - Basic Biology (Cell Structure, Plant and Animal Tissues)

Grade 9ICSE

Review the key concepts, formulae, and examples before starting your quiz.

🔑Concepts

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The Cell Theory: Proposed by Schleiden and Schwann, and later expanded by Rudolf Virchow, it states that all living organisms are composed of cells and that all cells arise from pre-existing cells (Omnis cellula e cellulaOmnis \: cellula \: e \: cellula).

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Protoplasm: The 'living matter' of the cell, which includes the cytoplasm and the nucleus. It is primarily composed of elements like Carbon (CC), Hydrogen (HH), Oxygen (OO), and Nitrogen (NN).

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Nucleus: The control center of the cell containing genetic material in the form of Chromatin. During cell division, chromatin condenses into chromosomes which carry DNADNA (Deoxyribonucleic Acid).

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Mitochondria: The 'powerhouse' of the cell where aerobic respiration occurs to release energy in the form of ATPATP (Adenosine Triphosphate).

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Plastids: Found only in plant cells. Chloroplasts contain chlorophyll for photosynthesis, represented by: 6CO2+12H2O→ChlorophyllSunlightC6H12O6+6O2+6H2O6CO_2 + 12H_2O \xrightarrow[Chlorophyll]{Sunlight} C_6H_{12}O_6 + 6O_2 + 6H_2O.

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Meristematic Tissues: Plant tissues with actively dividing cells found at growth regions like root and shoot tips (Apical MeristemApical \: Meristem).

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Permanent Tissues: Tissues that have lost the ability to divide. Simple types include Parenchyma, Collenchyma, and Sclerenchyma. Complex types include Xylem (water transport) and Phloem (food transport).

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Epithelial Tissues: Animal tissues that form protective layers. Examples include Squamous, Cuboidal, and Columnar epithelium.

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Connective Tissues: Tissues that bind or support other tissues. This includes Fluid Connective Tissue like Blood, which contains Plasma, RBCsRBCs, WBCsWBCs, and Platelets.

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Nervous Tissue: Consists of specialized cells called Neurons that transmit electrical impulses across the body.

📐Formulae

Total Magnification=Magnification of Eyepiece×Magnification of Objective Lens\text{Total Magnification} = \text{Magnification of Eyepiece} \times \text{Magnification of Objective Lens}

Surface Area to Volume Ratio of a Cube=6L2L3=6L\text{Surface Area to Volume Ratio of a Cube} = \frac{6L^2}{L^3} = \frac{6}{L}

Cellular Respiration: C6H12O6+6O2→6CO2+6H2O+38 ATP\text{Cellular Respiration: } C_6H_{12}O_6 + 6O_2 \rightarrow 6CO_2 + 6H_2O + 38 \text{ ATP}

Photosynthesis: 6CO2+6H2O+light energy→C6H12O6+6O2\text{Photosynthesis: } 6CO_2 + 6H_2O + \text{light energy} \rightarrow C_6H_{12}O_6 + 6O_2

💡Examples

Problem 1:

Explain why a cell's size is limited by its surface area to volume ratio using a mathematical approach where the side of a cubic cell is ss.

Solution:

As the side ss of a cell increases, the volume (s3s^3) increases much faster than the surface area (6s26s^2). The ratio 6s\frac{6}{s} decreases as ss increases.

Explanation:

A smaller ratio means the cell surface (plasma membrane) cannot efficiently transport enough nutrients (O2O_2, glucose) or remove wastes (CO2CO_2) to support the large internal volume, leading to cell division or limited growth.

Problem 2:

Calculate the magnification if a student uses an eyepiece of 10x10x and an objective lens of 45x45x.

Solution:

10×45=450x10 \times 45 = 450x

Explanation:

The total magnification of a compound microscope is the product of the individual magnifications of the lenses used.

Problem 3:

Identify the tissue responsible for the movement of food in plants and state its components.

Solution:

The tissue is Phloem. Its components are: 1. Sieve tubes, 2. Companion cells, 3. Phloem parenchyma, 4. Phloem fibres.

Explanation:

Phloem is a complex permanent tissue that conducts organic food (sucrose) synthesized during photosynthesis from leaves to other parts of the plant.

Basic Biology (Cell Structure, Plant and Animal Tissues) Revision - Class 9 Science ICSE