Notes, summaries, assignments, exams, and exercises for Biology for Secondary education

Bioelements in Living Organisms

Bioelements are chemical elements essential to living things, including oxygen, nitrogen, hydrogen, and carbon.

• Calcium (Ca): Supports bone and tooth development, muscle function, and blood clotting. Deficiency: Rickets.
• Phosphorus (P): Component of bones, cell membranes, and nucleic acids. Deficiency: General weakness.
• Magnesium (Mg): Activates energy production and regulates muscle and nerve function. Deficiency: Weakness and stunted growth.
• Sulfur (S): Component of proteins in hair and nails. Deficiency: No major disruption.
• Sodium (Na) and Potassium (K): Regulate body fluids, blood pressure, and nerve impulses. Deficiency: Muscle cramps, loss of appetite, and weakness.
• Chlorine (Cl): Component of gastric juice and

Respiratory System

This system oxygenates the blood and removes carbon dioxide. It consists of the lungs and airways.

Components of the Respiratory System

• Nostrils: Two cavities that warm and humidify the air.
• Pharynx: Common tube leading to the larynx.
• Larynx: Contains the vocal cords.
• Trachea: Carries air to the lungs.
• Lungs: Facilitate gas exchange.
• Bronchi: Two conduits that branch into smaller bronchioles, eventually forming pulmonary alveoli.

Oxygen and carbon dioxide exchange occurs in the pulmonary alveoli by diffusion, moving from areas of high concentration to low concentration.

The Internal Environment

The fluids surrounding the cells of an organism provide nutrients and oxygen to the cells and remove waste products. These fluids consist of:...

Blood Circulation and Waste Removal Processes

The exchange of substances occurs between blood plasma and tissue cells through a network of arteries and veins.

The Heart's Chambers

Atria

The atria receive blood from the veins coming from the body's organs. They communicate with the ventricles through valves (mitral and tricuspid).

Ventricles

The ventricles are connected to arteries that pump blood from the heart throughout the body. Semilunar valves between the ventricles and arteries prevent backflow.

Blood Flow Dynamics

Blood always flows in the same direction: from veins to arteries.

• Atrial Systole: Atrial contraction pushes blood into the ventricles.
• Ventricular Systole: Ventricles contract, closing the mitral and tricuspid valves, and forcing blood

Biological Macromolecules

• Carbohydrates: Quick (short-term) energy source. Found in foods like; built from simple sugars (monosaccharides).
• Lipids: Long-term energy. Provide insulation and protection. Make up cell membranes. Include fats, oils, and waxes.
• Proteins: Made of amino acids. Help build structures (muscles, tissues). Act as enzymes to speed up reactions.
• Nucleic Acids: Store and transmit genetic information. Examples: DNA and RNA. Made of nucleotides.

Practice Questions

Energy Use During a Sprint

1. Which macromolecule would your body use first during a sprint? Why? Your body uses carbohydrates first because they provide quick, easily accessible short-term energy.

Macromolecules in Cell Membranes

2. Which macromolecule helps form your cell...

Master Exam Manual: CB 1.3 Genetic Variation

Chapter 1: Genetic Variation

1. Cells and Chromosomes

• The Nucleus as the Command Center: Eukaryotic cells isolate genomic material inside a double-membrane nucleus. This structure protects DNA from chemical damage caused by cellular metabolism.
• Chromosome Condensation: DNA does not float as loose strands. It wraps around spool-like proteins called histones. This complex coils into chromatin. During cell division, chromatin packs into visible, X-shaped structures called chromosomes.
• Karyotypes and Chromosome Pairs: Humans possess 46 chromosomes in total. They form 23 homologous pairs. One chromosome of each pair comes from the sperm (paternal); the other comes from the egg (maternal).
• Autosomes vs. Sex

Human Reproduction

1. Key Concepts in Reproduction

• (a) Ovulation is induced by: Luteinizing hormone (LH)
• (b) Acrosome of sperm is formed from: Golgi apparatus
• (c) Cessation of menstrual cycle in female is called: Menopause
• (d) Progesterone is secreted by: Corpus luteum
• (e) Connection between foetus and uterus: Placenta
• (f) Acrosome of sperm is formed from: Golgi body
• (g) Release of ovum from a mature follicle: Ovulation
• (h) Cells that nourish sperm: Sertoli cells
• (i) Genes located in Y chromosome: Holandric genes
• (j) Anterior part of sperm: Head
• (k) Germinal epithelium of gonads: Germ epithelium
• (l) Function of interstitial cells: Secretion of testosterone
• (m) Ovulation is induced by: Luteinizing hormone (LH)
• (n) Acrosomal vesicle contains: Hyaluronidase

Molecular Basis of Inheritance

1. Which enzyme transcribes hnRNA?

Answer: RNA polymerase II.

2. Why is the genetic code considered 'degenerate'?

Answer: Because more than one codon can code for the same amino acid.

3. What are Okazaki fragments?

Answer: Short DNA fragments synthesized discontinuously on the lagging strand during DNA replication.

4. Which two basic amino acids are abundant in histone proteins?

Answer: Lysine and Arginine.

5(a). What is the function of mitochondria in sperm?

Answer: It provides energy (ATP) for sperm motility.

5(b). Which codon is the starting codon?

Answer: AUG.

5(c). What is the genetic code?

Answer: The genetic code is the sequence of codons in mRNA that determines the sequence of amino acids in a protein.

5(d). What is

Kingdom Monera

• Prokaryotic organisms: Includes Archaebacteria and Eubacteria.
• Archaebacteria: Includes Methanogens (found in marshes), Thermoacidophiles (heat-resistant), and Halophiles (salt-tolerant).
• Eubacteria: True bacteria.

Kingdom Protista

• Single-celled eukaryotes: Diverse group of microscopic organisms.
• Chrysophytes: Includes diatoms with soapbox-like shells; their gritty soil is used in oil filters.
• Dinoflagellates: Possess two flagella and cellulose plates.
• Euglenoids: Have a pellicle; can be both autotrophic and heterotrophic.
• Slime Moulds: Saprophytic organisms that form aggregates called Plasmodium (e.g., Physarum).
• Protozoans: Includes amoeboid, flagellated, ciliated, and sporozoan types.

Kingdom Fungi

• Examples: Wheat rust (Puccinia) and

Absorption by the Roots

Key Biological Definitions

1. Imbibition: It is the phenomenon by which a living or a dead cell absorbs water through surface attraction.
2. Diffusion: It is the free movement of molecules of a substance from a region of higher concentration to lower concentration when the two are in direct contact.
3. Osmosis: It is the process of movement of water molecules from a region of higher concentration to a region of lower concentration through a semi-permeable membrane.
4. Endosmosis: It is the inward diffusion of water through a semi-permeable membrane when the surrounding solution is less concentrated.
5. Exosmosis: It is the outward diffusion of water through a semi-permeable membrane when the surrounding solution is more concentrated.
6. Osmotic

Fundamental Biological Processes

What is Germination?

Germination is the process of seeds developing into new plants.

What is Growth?

An increase in the size of an organism or part of an organism, usually as a result of an increase in the number of cells.

What is Respiration?

The transfer of oxygen from the outside environment to cells within tissues, as well as the removal of carbon dioxide in the opposite way.

What is Photosynthesis?

The process by which green plants and some other organisms use sunlight to synthesize foods from carbon dioxide and water. Photosynthesis in plants generally involves the green pigment chlorophyll and generates oxygen.

What is Interdependence?

Organisms depend on each other for survival. This is called interdependence....