Reproduction in Plants & Humans
Master asexual and sexual reproduction, gamete adaptation, human hormone control, and STI transmission
What This Chapter Is About
- Asexual Reproduction: One parent, no variation, fast (bacteria, plant bulbs)
- Sexual Reproduction: Two parents, variation, slower but adaptive (gametes fuse)
- Plant Reproduction: Pollination (transfer) → Fertilization (fusion) → Seed development
- Human Reproduction: Specialized reproductive systems, gamete adaptations, menstrual cycle control
- Hormonal Control: FSH, LH, oestrogen, and progesterone orchestrate the menstrual cycle
- STIs: HIV attacks lymphocytes → AIDS. Prevented by safe sex, testing, education
Asexual Reproduction
What Is It?
Asexual reproduction is a process resulting in genetically identical offspring (clones) from a single parent. No sex cells are involved, no fertilization occurs.
Think of it as photocopying: one original makes an exact duplicate. Fast, reliable, but no variation.
Binary Fission (Bacteria)
Bacteria reproduce asexually by copying their circular chromosome, then splitting into two genetically identical daughter cells. This is called binary fission.
PARENT BACTERIAL CELL
↓
(chromosome duplicates)
↓
CELL CONTENTS DOUBLE
↓
(cell divides by binary fission)
↓
TWO IDENTICAL DAUGHTER CELLS
Result: Population can double every 20 minutes under ideal conditions. Incredibly fast reproduction.
Vegetative Reproduction in Plants
Plants can reproduce asexually using underground storage organs:
Bulbs
A bulb is a short stem surrounded by fleshy leaves that store food. The bulb produces lateral buds, which grow into new plants. Example: daffodils, tulips.
Tubers
Swollen underground stems with buds. Example: potatoes. Each potato tuber can sprout multiple eyes (buds) that become new plants.
Runners
Horizontal stems that grow along the ground, producing small plantlets at nodes. Example: strawberries. The plantlets root and develop into independent plants.
Key Point: All offspring from asexual reproduction are genetically identical to the parent. No genetic variation = no adaptability to new conditions.
Advantages & Disadvantages
| Type |
Advantages |
Disadvantages |
| Wild Species |
• Rapid population growth
• Exploit suitable environments quickly
• Energy efficient |
• Zero genetic variation
• Vulnerable to climate change
• Disease affects all (no immunity diversity) |
| Crop Plants |
• Desired traits preserved
• Uniform characteristics (commercial sale)
• Faster production
• Lower cost |
• Can't adapt to climate change
• Requires human management
• If parent diseased → offspring diseased
• Vulnerability to pests = big financial loss |
Practice Question
A farmer grows potatoes by planting tubers. Explain why this method is fast but risky if disease spreads.
Sexual Reproduction: The Basics
Definition
Sexual reproduction is a process involving the fusion of two gamete nuclei to form a zygote, producing offspring that are genetically different from each other and their parents.
Gametes and Zygotes
What Are Gametes?
gamete
Key difference:
haploid
n