By Subhash Kumar | Science Educator | UREducator
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Reproduction in Plants
Complete Teaching Resource for CBSE Class 7 Science Chapter 8
Class: VII
Subject: Science
Chapter: 8
Duration: 4 Hours
What Students Will Achieve
Knowledge
- Understand different modes of plant reproduction
- Describe asexual reproduction methods in plants
- Explain the process of sexual reproduction in flowering plants
- Identify different parts of a flower and their reproductive functions
Understanding
- Compare asexual and sexual reproduction in plants
- Explain the process of pollination and fertilization
- Understand the significance of seed dispersal
- Analyze adaptations of different plants for reproduction
Skills
- Conduct vegetative propagation experiments
- Dissect flowers to study reproductive parts
- Observe and document seed dispersal mechanisms
- Create models of plant reproductive processes
Prior Knowledge Assessment
Starter Questions:
- How do plants create new plants without seeds?
- What are the male and female parts of a flower called?
- Why is it important for seeds to be dispersed away from the parent plant?
Plant Reproduction Without Seeds
Methods of Asexual Reproduction
Vegetative Propagation
- New plants from roots, stems, leaves
- Examples: Potato (stem), Bryophyllum (leaves), Sweet potato (roots)
- Faster than seed reproduction
- Identical to parent plant
Budding
- Small outgrowth develops into new organism
- Example: Yeast cells
- Bud detaches or remains attached forming chains
- Common in unicellular organisms
Fragmentation
- Organism breaks into pieces, each grows into new individual
- Example: Spirogyra (algae)
- Requires moist environment
- Rapid multiplication
Spore Formation
- Tiny, protected reproductive cells
- Examples: Fungi, ferns, mosses
- Can survive harsh conditions
- Dispersed by wind, water, animals
Vegetative Propagation Examples
| Plant Part | Example Plants | Special Feature |
|---|---|---|
| Stem | Potato, Ginger, Sugarcane | Nodes with buds (eyes) |
| Leaf | Bryophyllum, Begonia | Marginal buds on leaves |
| Root | Sweet potato, Dahlia | Adventitious buds on roots |
| Bulb | Onion, Garlic | Underground stem with fleshy leaves |
Experiment: Growing Plants from Cuttings
Objective: Demonstrate vegetative propagation
- Take stem cuttings of rose/money plant with nodes
- Plant some in soil, others in water
- Observe daily for root development
- Compare growth rates in different media
- Record time taken for new leaves to appear
Flower Structure and Function
Flower Reproductive Parts
Male Parts (Stamen)
- Anther: Produces pollen grains
- Filament: Supports the anther
- Pollen contains male gametes
- Found in both bisexual and unisexual male flowers
Female Parts (Pistil)
- Stigma: Receives pollen
- Style: Tube leading to ovary
- Ovary: Contains ovules with female gametes
- Found in both bisexual and unisexual female flowers
Flower Types
- Bisexual: Contains both stamen and pistil
- Unisexual: Only male or female parts
- Examples: Mustard (bisexual), Papaya (unisexual)
- Some plants have both male and female flowers
Pollination and Fertilization
| Stage | Process | Result |
|---|---|---|
| Pollination | Transfer of pollen from anther to stigma | Pollen lands on compatible stigma |
| Pollen Tube Growth | Tube grows down style to ovary | Pathway for male gametes |
| Fertilization | Fusion of male and female gametes | Formation of zygote |
| Seed Formation | Ovule develops into seed, ovary into fruit | New generation plant embryo |
Activity: Flower Dissection
Objective: Identify reproductive parts of flowers
- Collect different types of flowers (bisexual/unisexual)
- Use magnifying glass to examine parts
- Dissect to separate stamen and pistil
- Compare structures of different flowers
- Sketch and label all reproductive parts
How Seeds Travel to New Locations
Methods of Seed Dispersal
Wind
- Lightweight seeds with wings/hairs
- Examples: Maple, Dandelion, Cotton
- Adaptations: Winged structures, parachute-like hairs
- Can travel long distances
Water
- Buoyant seeds/fruits
- Examples: Coconut, Lotus, Water lily
- Adaptations: Fibrous coats, air pockets
- Can survive water immersion
Animals
- Hooked or sticky seeds
- Examples: Xanthium, Urena, Burrs
- Adaptations: Hooks, spines, sticky surfaces
- Also through animal droppings
Explosion
- Mechanical dispersal
- Examples: Balsam, Castor, Pea
- Adaptations: Tension in fruit walls
- Sudden bursting propels seeds
Importance of Seed Dispersal
| Benefit | Explanation |
|---|---|
| Prevents Overcrowding | Reduces competition among seedlings |
| Reduces Disease Risk | Prevents spread of plant-specific diseases |
| Colonizes New Areas | Helps plants spread to new habitats |
| Genetic Diversity | Promotes cross-pollination and variation |
Project: Seed Dispersal Hunt
Objective: Collect and classify seeds by dispersal method
- Gather different seeds from school grounds/park
- Examine each seed's adaptations
- Classify by dispersal method (wind, water, animal, explosion)
- Create a display showing classification
- Present findings to class
Evaluation Strategies
Formative Assessments
- Labeling diagrams of flower parts
- Quiz on reproduction methods
- Experiment report evaluation
- Class participation in discussions
Summative Assessments
- Chapter test (MCQs + short answers)
- Project on seed dispersal mechanisms
- Practical exam on flower dissection
- Case study on importance of pollination
Extended Learning: Visit to Botanical Garden
Objective: Observe plant reproduction in natural settings
- Identify plants showing different reproduction methods
- Document flower structures and pollination mechanisms
- Collect samples of different seed types
- Interview gardeners about propagation techniques
- Prepare a field report with photographs
Frequently Asked Questions
Why do some plants reproduce both sexually and asexually?
Plants use both methods for different advantages:
- Asexual: Quick, no mate needed, preserves successful genetics
- Sexual: Genetic diversity, adaptation to changing environments
- Some plants use asexual reproduction when conditions are stable
- They switch to sexual reproduction when stressed to create variation
- This dual strategy maximizes survival chances
How do seedless fruits like bananas reproduce?
Seedless fruits typically reproduce through:
- Vegetative propagation (suckers, rhizomes, cuttings)
- Being sterile hybrids created by human cultivation
- Bananas reproduce through suckers (lateral shoots)
- Commercial varieties are clones of parent plants
- Wild bananas do have seeds but are less edible
