Science (EVS K-5) · Class 7 · Reproduction in Plants · Term 3

Fertilisation: From Pollen to Zygote

Understand what happens after pollination: the fusion of male and female gametes to form a zygote, which develops into an embryo within a seed.

TL;DR:We know how pollen makes its journey from one flower to another, but what magical process happens inside the flower to create a seed?

• CBSE Learning Outcomes
• NCERT Class 7 Science: Chapter 12 - Reproduction in Plants

About This Topic

This topic, 'Fertilisation: From Pollen to Zygote', is a fundamental concept within the Class 7 Science curriculum, directly following the study of flower structure and pollination, as outlined in the NCERT framework. It shifts the focus from the external mechanism of pollen transfer to the internal, cellular events that lead to the creation of a new life. For Indian students, this process is visibly demonstrated in the agriculture and horticulture that surrounds them, from the mango orchards of Uttar Pradesh to the spice gardens of Kerala. The core of this lesson is to explain how the male gamete, carried within the pollen grain, travels down a specially grown tube to fuse with the female gamete in the ovule. This fusion, or fertilisation, results in a zygote.

Understanding this microscopic journey is crucial for grasping the complete life cycle of a flowering plant. The lesson then extends to the macroscopic changes that are easily observable: the transformation of the fertilised ovule into a seed and the development of the surrounding ovary into a fruit. This connects cellular biology to everyday experiences of eating fruits and sowing seeds. By contextualising this process, teachers can highlight its immense importance in food security, biodiversity, and the Indian economy, which is heavily reliant on agriculture. The topic lays the groundwork for more complex concepts in genetics and plant breeding that students will encounter in higher classes.

Key Questions

1. Explain the process of fertilisation in a flowering plant.
2. Identify the parts of the flower that develop into the fruit and the seed.
3. Analyse the journey of the male gamete from the stigma to the ovule.

Learning Objectives

• Describe the process of fertilisation in a flowering plant, starting from the germination of the pollen grain.
• Differentiate between the terms pollination, fertilisation, zygote, and embryo.
• Illustrate the path of the pollen tube from the stigma to the ovule in a diagram of a pistil.
• Identify the ovary as the part of the flower that develops into the fruit and the ovules as the parts that develop into seeds.

Key Vocabulary

Fertilisation	The process of fusion of the male gamete (from pollen) with the female gamete (in the ovule) to form a zygote.
Zygote	The single cell formed as a result of fertilisation, which develops into an embryo.
Embryo	The young, developing plant contained within a seed.
Pollen Tube	A tube that grows from a pollen grain after it lands on the stigma, creating a path for the male gamete to reach the ovule.
Ovule	The structure inside the ovary that contains the female gamete and becomes a seed after fertilisation.

Watch Out for These Misconceptions

Common Misconception

Pollination is the same thing as fertilisation.

What to Teach Instead

Pollination is only the first step, where pollen is transferred to the stigma. Fertilisation is the next, separate step where the male and female gametes actually fuse inside the ovule.

Common Misconception

The entire pollen grain travels down to the ovule.

What to Teach Instead

The pollen grain itself stays on the stigma. It grows a very thin tube, called the pollen tube, which travels down the style to deliver the male gamete to the ovule.

Common Misconception

All parts of the flower, like petals, grow into the fruit.

What to Teach Instead

After fertilisation, parts like petals, sepals, and stamens usually wither and fall off. Only the ovary develops into the fruit, and the ovules inside it become the seeds.

Active Learning Ideas

Simulation Game

Pollen Tube Journey Model

Students use chart paper to draw a large cross-section of a pistil. They then use a string to represent the pollen tube, guiding it from a paper pollen grain on the stigma down to a bead representing the ovule.

25 min·Small Groups

Simulation Game

Dissect a Hibiscus Flower

Provide students with a common local flower like a hibiscus (gurhal). Guide them to carefully remove the petals and stamens to expose the pistil, then make a careful incision in the ovary to observe the small ovules inside with a magnifying glass.

30 min·Pairs

Simulation Game

From Flower to Fruit Sorting

Create cards with images of flowers (e.g., tomato, brinjal, mango) and their corresponding fruits. Students work in groups to match the flower to the fruit and identify the part of the flower that developed into the fruit.

15 min·Small Groups

Real-World Connections

• Understanding fertilisation is key for farmers to ensure good crop yields, as no fruit or grain will form without it.
• The creation of hybrid plant varieties, like new types of rice or wheat, is done by manually controlling pollination and fertilisation.
• It explains why the presence of pollinators like bees and butterflies is so crucial for growing many fruits and vegetables in our kitchen gardens.
• The entire fruit and seed industry, from selling mangoes and apples to packaging rice and dal, depends on the successful completion of this natural process.

Assessment Ideas

Quick Check

Ask students to draw a flowchart showing the sequence of events from pollination to fruit formation.

Quick Check

A short test with a diagram of a pistil showing fertilisation. Students must label the pollen tube, zygote, and ovule, and answer questions about post-fertilisation changes.

Quick Check

Provide a checklist with 'I can' statements, such as 'I can explain the role of the pollen tube' or 'I can tell the difference between an ovary and an ovule'.

Frequently Asked Questions

What is the difference between a zygote and an embryo?

A zygote is the very first single cell formed right after the male and female gametes fuse. This zygote then divides many times to grow into a multi-cellular structure, which is called the embryo.

Why do some fruits like mango have one seed, but others like watermelon have many?

This depends on how many ovules were present in the flower's ovary. If a flower has only one ovule, its fruit will have one seed. If a flower has many ovules, its fruit will have many seeds.

Does fertilisation happen instantly after pollination?

No, it takes some time. After the pollen grain lands on the stigma, it has to grow the pollen tube all the way down to the ovule. This can take a few hours or even a few days, depending on the plant.