4.6.5Additional lessons
Plant Reproduction — IB Biology SL Revision Notes & Topical Questions
5 min read 5 parts Lesson 120 of 142
Curriculum Equation Key قوانين الرقم الهيدروجيني والاتزان الأيوني - pH & Acid-Base Equilibrium FormulasFast Exam Solution
pH = -log[H⁺] | pOH = -log[OH⁻] | pH + pOH = 14 | [H⁺][OH⁻] = 10⁻¹⁴
Word Equation & Conditions: الرقم الهيدروجيني = -لوغاريتم تركيز أيون الهيدروجين | pH + pOH = 14
Location & Specifications: الاتزان الأيوني، كيمياء 3 ثانوي، التحصيلي، و AP Chemistry.
Part 1 of 5Flower Structure
A flower is a reproductive shoot carrying male and female organs, often in the same flower.
Sepal
- Sepal Sepals are leaf-like structures that enclose and protect the flower bud before it opens.
Petal
- Petal Petals are often brightly coloured or scented in insect-pollinated flowers, and attract pollinators to the flower.
Stamen
- Stamen The male part: an anther that makes pollen grains on top of a filament that holds the anther up.
Carpel
- Carpel The female part: a stigma that receives pollen, a style that supports it, and an ovary that contains ovules.
Nectary
- Nectary Glands at the base of the flower produce sugary nectar as a reward for visiting animals.
Part 2 of 5Gametes in Flowers
Gametes in Flowers
Pollen grain
- Pollen grain Each pollen grain contains the male gamete nuclei and has a tough outer wall that protects it during transfer.
Ovule
- Ovule Each ovule sits inside the ovary and contains an egg cell, the female gamete, within a structure called the embryo sac.
Meiosis sites
- Meiosis sites Meiosis happens in the anthers to make pollen and in the ovules to make the egg cell.
Haploid gametes
- Haploid gametes Both the male and the female gamete are haploid, so fertilisation restores the diploid number.
Part 3 of 5From Pollination to Seed
One pollen grain fertilises one ovule, so the number of seeds depends on the number of ovules fertilised.
1
Pollen lands on the stigma of a compatible flower during pollination.
2
A pollen tube grows from the pollen grain down through the style towards the ovary, carrying the male nucleus.
3
The pollen tube enters an ovule, and the male nucleus fuses with the egg cell nucleus in fertilisation.
4
The fertilised egg becomes a zygote and divides to form an embryo plant inside the ovule.
5
The ovule matures into a seed, and the surrounding ovary wall develops into the fruit.
Part 4 of 5Linking Structure and Function
Stigma
- Stigma A sticky or feathery surface traps pollen effectively so that more grains are captured.
Anther position
- Anther position Anthers placed where visiting insects brush against them transfer pollen onto the insect.
Style length
- Style length A long style positions the stigma where it can receive pollen and provides a path for the tube.
Fruit
- Fruit Fruit protects the seeds and often helps in seed dispersal.
| Part | Becomes after fertilisation |
|---|---|
| Ovule | Seed |
| Ovary | Fruit |
| Zygote | Embryo in the seed |
Part 5 of 5Exam Checklist & Tips
4.6.5 – Key Points for the Exam
- Anther Part of the stamen that produces pollen.
- Stigma Surface of the carpel that receives pollen.
- Ovule Structure in the ovary containing the egg cell, which becomes the seed.
- Pollen tube Tube growing from a pollen grain to carry the male nucleus to the ovule.
- Fruit Structure developed from the ovary that encloses the seeds.
Common Mistakes
- Confusing pollination with fertilisation;
- pollination is transfer of pollen, fertilisation is fusion of gametes.
- Saying that pollen grains are the male gametes; they contain the male gametes.
- Mixing up anther and stigma, or stamen and carpel.
- Stating the ovule becomes the fruit; it becomes the seed and the ovary becomes the fruit.
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