Lesson Notes By Weeks and Term - Senior Secondary 3

TERM – 1^ST TERM

WEEK THREE

Class: Senior Secondary School 3

Age: 17 years

Duration: 40 minutes of 5 periods each

Date:

Subject: Biology

Topic: Development of seeds and fruits

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

1. Discuss the stages involved in the process of zygote development in flowering plants
2. Define germination
3. Identify and explain the two types of germination
4. Identify conditions necessary for germination
5. Identify the types and structure of a fruit
6. Differentiate between fruits and seeds

INSTRUCTIONAL TECHNIQUES: Identification, explanation, questions and answers,

demonstration, videos from source

INSTRUCTIONAL MATERIALS: Videos, loud speaker, textbook, pictures

INSTRUCTIONAL PROCEDURES

PERIOD 1-2

NOTE

DEVELOPMENT OF SEEDS AND FRUITS

Process of development of Zygote in flowering plants

In flowering plants, the process of zygote development involves several stages, including pistil formation, stem growth, and fertilization.

1. Pistil Formation: The pistil is the female reproductive organ of a flower, typically consisting of the stigma, style, and ovary. The ovary contains ovules, each housing an egg cell.
2. Stem Growth: The stem supports the flower and facilitates the transport of nutrients and water. Within the stem, specialized tissues conduct substances between the roots, leaves, and reproductive organs.
3. Fertilization: Pollination is the transfer of pollen (containing male gametes) from the anther to the stigma. Once pollen reaches the stigma, it grows a pollen tube down the style and enters the ovary. Fertilization occurs when a sperm cell from the pollen fuses with an egg cell in an ovule, forming a zygote.

After fertilization, the zygote develops into an embryo within the ovule. The ovule transforms into a seed, and the ovary develops into a fruit. This entire process ensures the continuation of the plant's life cycle, involving the production of seeds that can germinate into new plants.

Germination of Seeds

 Germination is the process by which a seed develops into a new plant. It involves the activation of metabolic processes leading to the emergence of a seedling from the seed. Key stages include water absorption, activation of enzymes, and the growth of the embryonic plant.

Types of Germination

1. Epigeal Germination: The cotyledons (seed leaves) emerge above the soil surface, and the shoot develops before the cotyledons fully expand. Examples include beans and sunflowers.
2. Hypogeal Germination: The cotyledons remain below the soil surface as the shoot emerges. The cotyledons may or may not eventually appear above ground. Examples include peas and peanuts.

Conditions Necessary for Germination

1. Water: Adequate moisture is crucial to initiate metabolic processes within the seed.
2. Oxygen: Seeds require oxygen for cellular respiration during germination.
3. Temperature: Optimal temperature varies among plant species, but generally, a moderate temperature range is favorable for germination.
4. Light (for some seeds): While some seeds require light for germination (photoblastic), others germinate in darkness.
5. Soil or Substrate: A suitable planting medium provides physical support and the necessary nutrients for seedling growth.

Fruits

Fruits are mature ovaries of flowering plants that typically contain seeds. They develop from the fertilized ovules after pollination and fertilization. The structure of fruits includes three main parts: the pericarp (ovary wall), the seed(s), and often an accessory tissue like the fleshy pulp or outer skin.

Types of Fruits

1. Simple Fruits: Develop from a single ovary. Examples include, Apple, cherry.
2. Aggregate Fruits: Develop from multiple ovaries in a single flower. Examples are, Strawberry, raspberry.
3. Multiple Fruits: Form from the ovaries of multiple flowers that are closely packed together. Examples are, Pineapple, fig.

Seed Structure

Seeds are the mature ovules of flowering plants and typically consist of an embryo, a seed coat, and often a stored food reserve (endosperm).

Agents of Dispersal

1. Wind: Seeds adapted for wind dispersal are often lightweight with structures like wings or parachutes.
2. Animals: Seeds may attach to fur or feathers, be eaten and excreted, or buried by animals.
3. Water: Seeds that float can be dispersed by water currents.
4. Explosive Mechanisms: Some plants have mechanisms to forcefully eject seeds.

Difference between fruits and seeds

Below is a tabulated summary of the differences between fruits and seeds:

EVALUATION: 1. Give 4 differences between fruits and seeds

2. Identify the 4 agents of dispersal.
3. Identify 4 conditions necessary for plants germination
4. Define germination and identify the types of germination.

CLASSWORK: As in evaluation

CONCLUSION: The teacher commends the students positively