Lesson Notes By Weeks and Term - Senior Secondary 2

TERM – 1^ST TERM

WEEK SEVEN

Class: Senior Secondary School 2

Age: 16 years

Duration: 40 minutes of 5 periods each

Date:

Subject: Biology

Topic: EXCRETORY SYSTEM

SPECIFIC OBJECTIVES: At the end of the lesson, pupils should be able to

1. Define excretory system
2. Identify excretory organs of various organisms
3. Describe how excretion is carried out.

INSTRUCTIONAL TECHNIQUES: Identification, explanation, questions and answers, demonstration, videos from source

INSTRUCTIONAL MATERIALS: Videos, loud speaker, textbook, pictures

INSTRUCTIONAL PROCEDURES

PERIOD 1-2

NOTE

EXCRETORY SYSTEM

The excretory system is responsible for removing waste and excess substances from the body, maintaining a balance of fluids and electrolytes. Key components include the kidneys, which filter blood to produce urine, and other organs like the bladder, ureters, and urethra, involved in storing and eliminating urine. This system helps regulate the body's internal environment and maintain homeostasis.

Contractile vacuole

A contractile vacuole is a cellular structure found in certain protists, including some single-celled organisms like amoebas and paramecia. Its primary function is to regulate water content within the cell. The contractile vacuole collects excess water that enters the cell through processes like osmosis and then contracts, expelling the water from the cell to prevent it from bursting due to overhydration. This mechanism helps these organisms adapt to varying environmental conditions, particularly changes in water availability.

Flame cells

Flame cells are specialized cells found in the excretory system of some invertebrates, particularly in flatworms (Platyhelminthes). These cells are involved in osmoregulation and the removal of metabolic wastes. Flame cells have a distinctive flickering, flame-like appearance due to the movement of cilia (hair-like structures) on their surfaces.

The cilia create currents that propel fluids through tubules, ultimately leading to the expulsion of waste from the organism. Flame cells play a role in maintaining the internal balance of fluids and electrolytes in these simpler organisms, helping them excrete excess water and waste products.

Malpighian tubules

Malpighian tubules are excretory organs found in insects and some other arthropods. These tubules are an essential part of the insect's excretory system, serving to remove metabolic wastes and maintain the insect's internal balance.

Unlike vertebrates, insects do not have kidneys. Instead, they rely on Malpighian tubules, which are typically attached to the digestive system. These tubules extract waste products, including nitrogenous compounds, from the hemolymph (the insect's equivalent of blood). The collected waste is then released into the insect's hindgut, from which it is expelled as solid feces.

Malpighian tubules play a crucial role in osmoregulation and the elimination of nitrogenous waste, contributing to the overall homeostasis of the insect's internal environment.

Kidney

The kidney is a vital organ within the excretory system, responsible for filtering blood and eliminating waste products from the body. As part of this system, kidneys play a central role in maintaining homeostasis by regulating the balance of fluids, electrolytes, and other essential substances. The excretory function of the kidneys involves the formation of urine, which contains the waste products that are removed from the bloodstream. Additionally, the kidneys contribute to the regulation of blood pressure and the production of certain hormones, making them a crucial component of the overall excretory and regulatory functions within the body.

Stomata and Lenticels

Stomata are microscopic pores found on the surface of plant leaves and stems. They play a crucial role in gas exchange, allowing plants to take in carbon dioxide for photosynthesis and release oxygen.

Lenticels, on the other hand, are openings in the bark of woody plants. They facilitate gas exchange and are essential for the respiration of underlying tissues. Unlike stomata, lenticels are more prominent in woody stems and provide a pathway for gases like oxygen to enter and exit the plant.

NOTE: Neither stomata nor lenticels are directly involved in excretion in plants. Excretion in plants typically occurs through processes like the secretion of waste substances into vacuoles or through the shedding of older leaves.

EVALUATION: 1. Define excretory system

2. How do the kidney facilitates the excretion of waste from the body
3. What is the organ responsible for excretion in insects?

CLASSWORK: As in evaluation

CONCLUSION: The teacher commends the students positively