Lesson Notes By Weeks and Term v4 - SHS 3
PLANT SYSTEMS
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PLANT SYSTEMS
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Subject: Biology
Class: SHS 3
Term: 2nd Term
Week: 19
Grade code: 3.4.2.LI.2
Strand code: 4
Sub-strand code: 2
Content standard code: 3.4.2.CS.1
Indicator code: 3.4.2.LI.2
Theme: SYSTEMS OF LIFE
Subtheme: PLANT SYSTEMS
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This lesson explores one of the most fundamental processes on Earth: sexual reproduction in flowering plants. This is not just a topic for examinations; it is the process that gives us the food we eat every day, from the maize for our *banku* and *kenkey*, to the mangoes we enjoy, and the cocoa beans that are the backbone of our economy. By understanding how plants reproduce, we can better appreciate their critical role in our survival, our environment, and our nation's prosperity. We will investigate the key stages of this process and, most importantly, discuss why life as we know it would be impossible without it.
This topic focuses on the "why" – the importance of reproduction. However, to understand *why* it is important, we must first master *how* it happens. Part 1: The Process of Sexual Reproduction in Flowering Plants
A. Structure of a Typical Flower A flower is the reproductive organ of a flowering plant (angiosperm). A perfect, or bisexual, flower contains both male and female parts. A good local example is the Hibiscus flower (*shoe flower*). Whorls of the Flower: Calyx: The outermost whorl, made up of sepals. *Function:* Protects the flower bud before it opens. Usually green. Corolla: The whorl inside the calyx, made up of petals. *Function:* Often brightly coloured and scented to attract insects and other pollinators. Androecium (Male Part): The whorl inside the corolla, made up of stamens. Each stamen consists of: Anther: Produces and stores pollen grains. Filament: A stalk that holds the anther in a suitable position to disperse pollen. Gynoecium / Pistil (Female Part): The innermost whorl, made up of one or more carpels. Each carpel (or a fused pistil) consists of: Stigma: The receptive tip, which is often sticky to trap pollen grains. Style: A tube-like structure that connects the stigma to the ovary. Ovary: The swollen base that contains one or more ovules. Each ovule contains the female gamete (egg cell).
![A simple labelled diagram of a flower with all parts clearly indicated would be drawn on the board here.]
B. Pollination This is the first critical step. Definition: The transfer of pollen grains from the anther to the stigma of a flower. Types of Pollination: Self-pollination: Pollen from the anther of a flower lands on the stigma of the *same flower* or *another flower on the same plant*. (e.g., Tomatoes, groundnuts) . Cross-pollination: Pollen from the anther of a flower on one plant lands on the stigma of a flower on *another plant of the same species*. (e.g., Pawpaw, Maize). This promotes genetic variation. Agents of Pollination (Ghanaian Context): Insects (Entomophily): Bees pollinating mango or orange flowers. Butterflies on flamboyant flowers. Wind (Anemophily): Maize plants release huge amounts of light pollen, which is carried by the wind to the silky tassels (stigmas) of other maize plants. Birds (Ornithophily): Sunbirds pollinating flowers with long tubes to get nectar. Water (Hydrophily): Occurs in some aquatic plants.