---
title: "From Flower to Fruit"
book: "Primary & Middle School Biology"
subject: biology
language: en
chapter: 31
exercises: 11
source: https://one-course.com/books/biology/1/en/chapter/31-from-flower-to-fruit
---

# Chapter 31 — From Flower to Fruit

[Chapter 16](https://one-course.com/books/biology/1/en/chapter/16-flowers-fruits-and-seeds#ch-g3-flowers-fruits-seeds) watched the cherry blossom become a cherry and left one question open: *what actually happens* when a grain of [pollen](https://one-course.com/books/biology/1/en/chapter/16-flowers-fruits-and-seeds#def-g3-flowers-fruits-seeds-parts) lands on the [pistil](https://one-course.com/books/biology/1/en/chapter/16-flowers-fruits-and-seeds#def-g3-flowers-fruits-seeds-parts)? This year, armed with [Chapter 23](https://one-course.com/books/biology/1/en/chapter/23-how-animals-reproduce#ch-g4-animal-reproduction)’s idea of [fertilization](#def-g5-flower-to-fruit-steps) and [Chapter 29](https://one-course.com/books/biology/1/en/chapter/29-a-first-look-at-cells#ch-g5-first-look-at-cells)’s [cells](https://one-course.com/books/biology/1/en/chapter/29-a-first-look-at-cells#def-g5-first-look-at-cells-cell), we can open the [flower](https://one-course.com/books/biology/1/en/chapter/16-flowers-fruits-and-seeds#def-g3-flowers-fruits-seeds-parts)’s machinery properly.

## 31.1 Flowers have male and female parts

**Proposition 31.1 (The flower’s two roles in one).**

Reproduction in flowering [plants](https://one-course.com/books/biology/1/en/chapter/3-plants-around-us#def-g1-plants-around-us-plant) is *sexual* reproduction, exactly in [Definition 23.1](https://one-course.com/books/biology/1/en/chapter/23-how-animals-reproduce#def-g4-animal-reproduction-sexual)’s sense — and most [flowers](https://one-course.com/books/biology/1/en/chapter/16-flowers-fruits-and-seeds#def-g3-flowers-fruits-seeds-parts) carry both roles at once:

- the *[stamens](https://one-course.com/books/biology/1/en/chapter/16-flowers-fruits-and-seeds#def-g3-flowers-fruits-seeds-parts)* are the [male](https://one-course.com/books/biology/1/en/chapter/23-how-animals-reproduce#def-g4-animal-reproduction-sexual) part: each grain of *[pollen](https://one-course.com/books/biology/1/en/chapter/16-flowers-fruits-and-seeds#def-g3-flowers-fruits-seeds-parts)* carries the [plant](https://one-course.com/books/biology/1/en/chapter/3-plants-around-us#def-g1-plants-around-us-plant) ’s [male](https://one-course.com/books/biology/1/en/chapter/23-how-animals-reproduce#def-g4-animal-reproduction-sexual) reproductive [cells](https://one-course.com/books/biology/1/en/chapter/29-a-first-look-at-cells#def-g5-first-look-at-cells-cell) ;
- the *[pistil](https://one-course.com/books/biology/1/en/chapter/16-flowers-fruits-and-seeds#def-g3-flowers-fruits-seeds-parts)* is the [female](https://one-course.com/books/biology/1/en/chapter/23-how-animals-reproduce#def-g4-animal-reproduction-sexual) part: deep inside it lie the *ovules* , each holding an [egg cell](https://one-course.com/books/biology/1/en/chapter/23-how-animals-reproduce#def-g4-animal-reproduction-sexual) .

The “future [seeds](https://one-course.com/books/biology/1/en/chapter/16-flowers-fruits-and-seeds#prop-g3-flowers-fruits-seeds-transform)” of [Definition 16.1](https://one-course.com/books/biology/1/en/chapter/16-flowers-fruits-and-seeds#def-g3-flowers-fruits-seeds-parts) now have their real name: [ovules](#prop-g5-flower-to-fruit-roles), waiting to be fertilized.

**Proof.** *Admitted at this level.* ∎

**Remark 31.2 (Same plan as the animals).**

[Male](https://one-course.com/books/biology/1/en/chapter/23-how-animals-reproduce#def-g4-animal-reproduction-sexual) [cells](https://one-course.com/books/biology/1/en/chapter/29-a-first-look-at-cells#def-g5-first-look-at-cells-cell), [egg cells](https://one-course.com/books/biology/1/en/chapter/23-how-animals-reproduce#def-g4-animal-reproduction-sexual), [fertilization](#def-g5-flower-to-fruit-steps): the vocabulary of [Chapter 23](https://one-course.com/books/biology/1/en/chapter/23-how-animals-reproduce#ch-g4-animal-reproduction) translates word for word. The [unity of life](https://one-course.com/books/biology/1/en/chapter/29-a-first-look-at-cells#prop-g5-first-look-at-cells-principle) again ([Proposition 29.2](https://one-course.com/books/biology/1/en/chapter/29-a-first-look-at-cells#prop-g5-first-look-at-cells-principle)) — daisies and dolphins reproduce on one underlying plan, however different the machinery looks.

## 31.2 Pollination, then fertilization

**Definition 31.3 (The two steps).**

Making a [seed](https://one-course.com/books/biology/1/en/chapter/9-from-seed-to-plant#def-g2-from-seed-to-plant-seed) takes two distinct steps:

1. *pollination* : a [pollen](https://one-course.com/books/biology/1/en/chapter/16-flowers-fruits-and-seeds#def-g3-flowers-fruits-seeds-parts) grain travels from a [stamen](https://one-course.com/books/biology/1/en/chapter/16-flowers-fruits-and-seeds#def-g3-flowers-fruits-seeds-parts) to the top of a [pistil](https://one-course.com/books/biology/1/en/chapter/16-flowers-fruits-and-seeds#def-g3-flowers-fruits-seeds-parts) — carried by an insect ( [Proposition 16.3](https://one-course.com/books/biology/1/en/chapter/16-flowers-fruits-and-seeds#prop-g3-flowers-fruits-seeds-transform) ) or by the wind;
2. *fertilization* : the landed grain grows a fine tube *down through the [pistil](https://one-course.com/books/biology/1/en/chapter/16-flowers-fruits-and-seeds#def-g3-flowers-fruits-seeds-parts)* ; through it, the [male](https://one-course.com/books/biology/1/en/chapter/23-how-animals-reproduce#def-g4-animal-reproduction-sexual) [cell](https://one-course.com/books/biology/1/en/chapter/29-a-first-look-at-cells#def-g5-first-look-at-cells-cell) reaches an ovule and joins its [egg cell](https://one-course.com/books/biology/1/en/chapter/23-how-animals-reproduce#def-g4-animal-reproduction-sexual) .

Pollination is the journey; fertilization is the meeting.

![Inside the pistil: a landed pollen grain grows its tube down to an ovule, and fertilization happens at the bottom.](https://one-course.com/images/onecourse/chapters/biology-1/g5-flower-to-fruit/fig-d43f9e6e76f9.svg)

*Inside the [pistil](https://one-course.com/books/biology/1/en/chapter/16-flowers-fruits-and-seeds#def-g3-flowers-fruits-seeds-parts): a landed [pollen](https://one-course.com/books/biology/1/en/chapter/16-flowers-fruits-and-seeds#def-g3-flowers-fruits-seeds-parts) grain grows its tube down to an ovule, and [fertilization](#def-g5-flower-to-fruit-steps) happens at the bottom.*

**Example 31.4 (Why unvisited flowers fall).**

[Remark 16.5](https://one-course.com/books/biology/1/en/chapter/16-flowers-fruits-and-seeds#rem-g3-flowers-fruits-seeds-bees)’s orchard rule now has its mechanism: no visit, no [pollen](https://one-course.com/books/biology/1/en/chapter/16-flowers-fruits-and-seeds#def-g3-flowers-fruits-seeds-parts) on the [pistil](https://one-course.com/books/biology/1/en/chapter/16-flowers-fruits-and-seeds#def-g3-flowers-fruits-seeds-parts); no [pollen](https://one-course.com/books/biology/1/en/chapter/16-flowers-fruits-and-seeds#def-g3-flowers-fruits-seeds-parts), no tube, no [fertilization](#def-g5-flower-to-fruit-steps); and an unfertilized [flower](https://one-course.com/books/biology/1/en/chapter/16-flowers-fruits-and-seeds#def-g3-flowers-fruits-seeds-parts) withers whole — no swelling [pistil](https://one-course.com/books/biology/1/en/chapter/16-flowers-fruits-and-seeds#def-g3-flowers-fruits-seeds-parts), no cherry. The missing step was invisible, a [cell](https://one-course.com/books/biology/1/en/chapter/29-a-first-look-at-cells#def-g5-first-look-at-cells-cell)’s journey down a tube — but the empty [branch](https://one-course.com/books/biology/1/en/chapter/3-plants-around-us#def-g1-plants-around-us-tree) in July is visible enough.

## 31.3 After the meeting: seed and fruit

**Proposition 31.5 (What each part becomes).**

After [fertilization](#def-g5-flower-to-fruit-steps), the transformation of [Proposition 16.3](https://one-course.com/books/biology/1/en/chapter/16-flowers-fruits-and-seeds#prop-g3-flowers-fruits-seeds-transform) runs with new precision:

- each *fertilized ovule* becomes a *[seed](https://one-course.com/books/biology/1/en/chapter/9-from-seed-to-plant#def-g2-from-seed-to-plant-seed)* — the tiny [plant](https://one-course.com/books/biology/1/en/chapter/3-plants-around-us#def-g1-plants-around-us-plant) inside it ( [Definition 9.1](https://one-course.com/books/biology/1/en/chapter/9-from-seed-to-plant#def-g2-from-seed-to-plant-seed) ) grows from the fertilized [egg cell](https://one-course.com/books/biology/1/en/chapter/23-how-animals-reproduce#def-g4-animal-reproduction-sexual) , exactly as an [animal](https://one-course.com/books/biology/1/en/chapter/2-animals-around-us#def-g1-animals-around-us-animal) grows from its own ( [Example 29.8](https://one-course.com/books/biology/1/en/chapter/29-a-first-look-at-cells#ex-g5-first-look-at-cells-one) );
- the *[pistil](https://one-course.com/books/biology/1/en/chapter/16-flowers-fruits-and-seeds#def-g3-flowers-fruits-seeds-parts)* around them swells into the *[fruit](https://one-course.com/books/biology/1/en/chapter/16-flowers-fruits-and-seeds#prop-g3-flowers-fruits-seeds-transform)* ;
- [petals](https://one-course.com/books/biology/1/en/chapter/16-flowers-fruits-and-seeds#def-g3-flowers-fruits-seeds-parts) and [stamens](https://one-course.com/books/biology/1/en/chapter/16-flowers-fruits-and-seeds#def-g3-flowers-fruits-seeds-parts) , their work done, wither and fall.

**Proof.** *Admitted at this level.* ∎

**Example 31.6 (Counting pips).**

Cut an apple across: five little chambers, a few pips in each. Every pip is one ovule that was reached by one [pollen](https://one-course.com/books/biology/1/en/chapter/16-flowers-fruits-and-seeds#def-g3-flowers-fruits-seeds-parts) tube. A lopsided apple with empty chambers on one side tells of a poorly pollinated [flower](https://one-course.com/books/biology/1/en/chapter/16-flowers-fruits-and-seeds#def-g3-flowers-fruits-seeds-parts) — too few grains landed to fertilize all the [ovules](#prop-g5-flower-to-fruit-roles), and the [fruit](https://one-course.com/books/biology/1/en/chapter/16-flowers-fruits-and-seeds#prop-g3-flowers-fruits-seeds-transform) swelled unevenly.

![The apple cut across: five chambers in a star, and in them the pips — one seed for every ovule a pollen tube reached.](https://one-course.com/images/onecourse/chapters/biology-1/g5-flower-to-fruit/img-7a9827b532b4.jpg)

*The apple cut across: five chambers in a star, and in them the pips — one [seed](https://one-course.com/books/biology/1/en/chapter/9-from-seed-to-plant#def-g2-from-seed-to-plant-seed) for every ovule a [pollen](https://one-course.com/books/biology/1/en/chapter/16-flowers-fruits-and-seeds#def-g3-flowers-fruits-seeds-parts) tube reached.*

**Example 31.7 (Wind-borne pollen).**

Grasses, wheat and hazel trees have no [petals](https://one-course.com/books/biology/1/en/chapter/16-flowers-fruits-and-seeds#def-g3-flowers-fruits-seeds-parts), no scent, no nectar — nothing to offer visitors. Their [pollen](https://one-course.com/books/biology/1/en/chapter/16-flowers-fruits-and-seeds#def-g3-flowers-fruits-seeds-parts) rides the *wind*: made in enormous quantities, dust-fine, thrown into the air to land where luck takes it. The strategy trades precision for quantity — the spore-cloud logic of [Remark 24.4](https://one-course.com/books/biology/1/en/chapter/24-plants-without-seeds#rem-g4-plants-without-seeds-sporeseed), played with [pollen](https://one-course.com/books/biology/1/en/chapter/16-flowers-fruits-and-seeds#def-g3-flowers-fruits-seeds-parts). (It is that airborne [pollen](https://one-course.com/books/biology/1/en/chapter/16-flowers-fruits-and-seeds#def-g3-flowers-fruits-seeds-parts), in passing, that tickles hay-fever noses in June.)

**Method 31.8 (Diagnosing a fruitless plant).**

A [plant](https://one-course.com/books/biology/1/en/chapter/3-plants-around-us#def-g1-plants-around-us-plant) flowered well but bears no [fruit](https://one-course.com/books/biology/1/en/chapter/16-flowers-fruits-and-seeds#prop-g3-flowers-fruits-seeds-transform). Ask in order:

1. Did pollinators reach it? (Indoors, netted, no [insects](https://one-course.com/books/biology/1/en/chapter/14-sorting-living-things#prop-g3-sorting-living-things-groups) about, cold rainy flowering weeks?)
2. If not, pollinate by hand: touch a soft brush to the [stamens](https://one-course.com/books/biology/1/en/chapter/16-flowers-fruits-and-seeds#def-g3-flowers-fruits-seeds-parts) of one [flower](https://one-course.com/books/biology/1/en/chapter/16-flowers-fruits-and-seeds#def-g3-flowers-fruits-seeds-parts) , then to the [pistil](https://one-course.com/books/biology/1/en/chapter/16-flowers-fruits-and-seeds#def-g3-flowers-fruits-seeds-parts) of another;
3. did frost or damage kill the [flowers](https://one-course.com/books/biology/1/en/chapter/16-flowers-fruits-and-seeds#def-g3-flowers-fruits-seeds-parts) before the [ovules](#prop-g5-flower-to-fruit-roles) could be fertilized ( [Exercise 16.9](https://one-course.com/books/biology/1/en/chapter/16-flowers-fruits-and-seeds#exo-g3-flowers-fruits-seeds-9) )?
4. If [fruit](https://one-course.com/books/biology/1/en/chapter/16-flowers-fruits-and-seeds#prop-g3-flowers-fruits-seeds-transform) now sets, the [plant](https://one-course.com/books/biology/1/en/chapter/3-plants-around-us#def-g1-plants-around-us-plant) ’s machinery was sound — only the journey of step 1 had failed.

## 31.4 Exercises

**Exercise 31.1 ★.**

Which part of the [flower](https://one-course.com/books/biology/1/en/chapter/16-flowers-fruits-and-seeds#def-g3-flowers-fruits-seeds-parts) is [male](https://one-course.com/books/biology/1/en/chapter/23-how-animals-reproduce#def-g4-animal-reproduction-sexual), and what does it make? Which is [female](https://one-course.com/books/biology/1/en/chapter/23-how-animals-reproduce#def-g4-animal-reproduction-sexual), and what lies inside it?

**Solution of Exercise 31.1.**

The [stamens](https://one-course.com/books/biology/1/en/chapter/16-flowers-fruits-and-seeds#def-g3-flowers-fruits-seeds-parts) are [male](https://one-course.com/books/biology/1/en/chapter/23-how-animals-reproduce#def-g4-animal-reproduction-sexual): their [pollen](https://one-course.com/books/biology/1/en/chapter/16-flowers-fruits-and-seeds#def-g3-flowers-fruits-seeds-parts) grains carry the [male](https://one-course.com/books/biology/1/en/chapter/23-how-animals-reproduce#def-g4-animal-reproduction-sexual) reproductive [cells](https://one-course.com/books/biology/1/en/chapter/29-a-first-look-at-cells#def-g5-first-look-at-cells-cell). The [pistil](https://one-course.com/books/biology/1/en/chapter/16-flowers-fruits-and-seeds#def-g3-flowers-fruits-seeds-parts) is [female](https://one-course.com/books/biology/1/en/chapter/23-how-animals-reproduce#def-g4-animal-reproduction-sexual): inside it lie the [ovules](#prop-g5-flower-to-fruit-roles), each holding an [egg cell](https://one-course.com/books/biology/1/en/chapter/23-how-animals-reproduce#def-g4-animal-reproduction-sexual).

**Exercise 31.2 ★.**

Define [pollination](#def-g5-flower-to-fruit-steps) and [fertilization](#def-g5-flower-to-fruit-steps), and say which comes first.

**Solution of Exercise 31.2.**

[Pollination](#def-g5-flower-to-fruit-steps): a [pollen](https://one-course.com/books/biology/1/en/chapter/16-flowers-fruits-and-seeds#def-g3-flowers-fruits-seeds-parts) grain travels from a [stamen](https://one-course.com/books/biology/1/en/chapter/16-flowers-fruits-and-seeds#def-g3-flowers-fruits-seeds-parts) to the top of a [pistil](https://one-course.com/books/biology/1/en/chapter/16-flowers-fruits-and-seeds#def-g3-flowers-fruits-seeds-parts). [Fertilization](#def-g5-flower-to-fruit-steps): the grain’s tube carries the [male](https://one-course.com/books/biology/1/en/chapter/23-how-animals-reproduce#def-g4-animal-reproduction-sexual) [cell](https://one-course.com/books/biology/1/en/chapter/29-a-first-look-at-cells#def-g5-first-look-at-cells-cell) down to an ovule, where it joins the [egg cell](https://one-course.com/books/biology/1/en/chapter/23-how-animals-reproduce#def-g4-animal-reproduction-sexual). [Pollination](#def-g5-flower-to-fruit-steps) comes first — the journey before the meeting.

**Exercise 31.3 ★.**

Tell the journey of one [pollen](https://one-course.com/books/biology/1/en/chapter/16-flowers-fruits-and-seeds#def-g3-flowers-fruits-seeds-parts) grain, from [stamen](https://one-course.com/books/biology/1/en/chapter/16-flowers-fruits-and-seeds#def-g3-flowers-fruits-seeds-parts) to [egg cell](https://one-course.com/books/biology/1/en/chapter/23-how-animals-reproduce#def-g4-animal-reproduction-sexual), in four steps.

**Solution of Exercise 31.3.**

Made in a [stamen](https://one-course.com/books/biology/1/en/chapter/16-flowers-fruits-and-seeds#def-g3-flowers-fruits-seeds-parts); carried (by insect or wind) to the top of a [pistil](https://one-course.com/books/biology/1/en/chapter/16-flowers-fruits-and-seeds#def-g3-flowers-fruits-seeds-parts) — [pollination](#def-g5-flower-to-fruit-steps); grows a fine tube down through the [pistil](https://one-course.com/books/biology/1/en/chapter/16-flowers-fruits-and-seeds#def-g3-flowers-fruits-seeds-parts); its [male](https://one-course.com/books/biology/1/en/chapter/23-how-animals-reproduce#def-g4-animal-reproduction-sexual) [cell](https://one-course.com/books/biology/1/en/chapter/29-a-first-look-at-cells#def-g5-first-look-at-cells-cell) reaches an ovule and joins the [egg cell](https://one-course.com/books/biology/1/en/chapter/23-how-animals-reproduce#def-g4-animal-reproduction-sexual) — [fertilization](#def-g5-flower-to-fruit-steps).

**Exercise 31.4 ★.**

After [fertilization](#def-g5-flower-to-fruit-steps): what does each fertilized ovule become? What does the [pistil](https://one-course.com/books/biology/1/en/chapter/16-flowers-fruits-and-seeds#def-g3-flowers-fruits-seeds-parts) become? What happens to the [petals](https://one-course.com/books/biology/1/en/chapter/16-flowers-fruits-and-seeds#def-g3-flowers-fruits-seeds-parts)?

**Solution of Exercise 31.4.**

Each fertilized ovule becomes a [seed](https://one-course.com/books/biology/1/en/chapter/9-from-seed-to-plant#def-g2-from-seed-to-plant-seed); the [pistil](https://one-course.com/books/biology/1/en/chapter/16-flowers-fruits-and-seeds#def-g3-flowers-fruits-seeds-parts) swells into the [fruit](https://one-course.com/books/biology/1/en/chapter/16-flowers-fruits-and-seeds#prop-g3-flowers-fruits-seeds-transform); the [petals](https://one-course.com/books/biology/1/en/chapter/16-flowers-fruits-and-seeds#def-g3-flowers-fruits-seeds-parts) (and [stamens](https://one-course.com/books/biology/1/en/chapter/16-flowers-fruits-and-seeds#def-g3-flowers-fruits-seeds-parts)) wither and fall.

**Exercise 31.5 ★.**

What is each apple pip, in this chapter’s vocabulary? What does a lopsided apple with empty chambers tell?

**Solution of Exercise 31.5.**

Each pip is a fertilized ovule become a [seed](https://one-course.com/books/biology/1/en/chapter/9-from-seed-to-plant#def-g2-from-seed-to-plant-seed). Empty chambers mean unfertilized [ovules](#prop-g5-flower-to-fruit-roles) — too little [pollen](https://one-course.com/books/biology/1/en/chapter/16-flowers-fruits-and-seeds#def-g3-flowers-fruits-seeds-parts) landed, and the [fruit](https://one-course.com/books/biology/1/en/chapter/16-flowers-fruits-and-seeds#prop-g3-flowers-fruits-seeds-transform) swelled unevenly around the shortfall.

**Exercise 31.6 ★.**

How do grasses and hazels pollinate without [petals](https://one-course.com/books/biology/1/en/chapter/16-flowers-fruits-and-seeds#def-g3-flowers-fruits-seeds-parts), scent or nectar? What is the cost of their method?

**Solution of Exercise 31.6.**

Their [pollen](https://one-course.com/books/biology/1/en/chapter/16-flowers-fruits-and-seeds#def-g3-flowers-fruits-seeds-parts) rides the wind: dust-fine, made in enormous quantities, thrown into the air. The cost is waste — almost every grain lands nowhere useful, so quantity must replace precision.

**Exercise 31.7 ★.**

Why does a [flower](https://one-course.com/books/biology/1/en/chapter/16-flowers-fruits-and-seeds#def-g3-flowers-fruits-seeds-parts) that no insect visited usually make no [fruit](https://one-course.com/books/biology/1/en/chapter/16-flowers-fruits-and-seeds#prop-g3-flowers-fruits-seeds-transform)? Name the missing step.

**Solution of Exercise 31.7.**

No visit, no [pollen](https://one-course.com/books/biology/1/en/chapter/16-flowers-fruits-and-seeds#def-g3-flowers-fruits-seeds-parts) on the [pistil](https://one-course.com/books/biology/1/en/chapter/16-flowers-fruits-and-seeds#def-g3-flowers-fruits-seeds-parts) — [pollination](#def-g5-flower-to-fruit-steps), the first step, never happened, so no tube grew and no ovule was fertilized; the [flower](https://one-course.com/books/biology/1/en/chapter/16-flowers-fruits-and-seeds#def-g3-flowers-fruits-seeds-parts) withers whole.

**Exercise 31.8 ★.**

Try it (with a flowering balcony or windowsill [plant](https://one-course.com/books/biology/1/en/chapter/3-plants-around-us#def-g1-plants-around-us-plant)): pollinate two [flowers](https://one-course.com/books/biology/1/en/chapter/16-flowers-fruits-and-seeds#def-g3-flowers-fruits-seeds-parts) by hand with a soft brush, as in [Method 31.8](#met-g5-flower-to-fruit-diagnose), and mark them with thread. Do the marked [flowers](https://one-course.com/books/biology/1/en/chapter/16-flowers-fruits-and-seeds#def-g3-flowers-fruits-seeds-parts) set [fruit](https://one-course.com/books/biology/1/en/chapter/16-flowers-fruits-and-seeds#prop-g3-flowers-fruits-seeds-transform) more often than the others?

**Solution of Exercise 31.8.**

Open answer. Expected: hand-pollinated, thread-marked [flowers](https://one-course.com/books/biology/1/en/chapter/16-flowers-fruits-and-seeds#def-g3-flowers-fruits-seeds-parts) set [fruit](https://one-course.com/books/biology/1/en/chapter/16-flowers-fruits-and-seeds#prop-g3-flowers-fruits-seeds-transform) clearly more often — the brush did the bee’s job.

**Exercise 31.9 ★★.**

List the parallels between [plant](https://one-course.com/books/biology/1/en/chapter/3-plants-around-us#def-g1-plants-around-us-plant) and [animal](https://one-course.com/books/biology/1/en/chapter/2-animals-around-us#def-g1-animals-around-us-animal) reproduction: [male](https://one-course.com/books/biology/1/en/chapter/23-how-animals-reproduce#def-g4-animal-reproduction-sexual) [cells](https://one-course.com/books/biology/1/en/chapter/29-a-first-look-at-cells#def-g5-first-look-at-cells-cell), [egg cells](https://one-course.com/books/biology/1/en/chapter/23-how-animals-reproduce#def-g4-animal-reproduction-sexual), [fertilization](#def-g5-flower-to-fruit-steps), the new individual’s first [cell](https://one-course.com/books/biology/1/en/chapter/29-a-first-look-at-cells#def-g5-first-look-at-cells-cell). Where does each item live, in the [flower](https://one-course.com/books/biology/1/en/chapter/16-flowers-fruits-and-seeds#def-g3-flowers-fruits-seeds-parts)’s case?

**Solution of Exercise 31.9.**

[Male](https://one-course.com/books/biology/1/en/chapter/23-how-animals-reproduce#def-g4-animal-reproduction-sexual) [cells](https://one-course.com/books/biology/1/en/chapter/29-a-first-look-at-cells#def-g5-first-look-at-cells-cell): in the [pollen](https://one-course.com/books/biology/1/en/chapter/16-flowers-fruits-and-seeds#def-g3-flowers-fruits-seeds-parts) grains of the [stamens](https://one-course.com/books/biology/1/en/chapter/16-flowers-fruits-and-seeds#def-g3-flowers-fruits-seeds-parts). [Egg cells](https://one-course.com/books/biology/1/en/chapter/23-how-animals-reproduce#def-g4-animal-reproduction-sexual): in the [ovules](#prop-g5-flower-to-fruit-roles) inside the [pistil](https://one-course.com/books/biology/1/en/chapter/16-flowers-fruits-and-seeds#def-g3-flowers-fruits-seeds-parts). [Fertilization](#def-g5-flower-to-fruit-steps): at the bottom of the [pollen](https://one-course.com/books/biology/1/en/chapter/16-flowers-fruits-and-seeds#def-g3-flowers-fruits-seeds-parts) tube, in the ovule. First [cell](https://one-course.com/books/biology/1/en/chapter/29-a-first-look-at-cells#def-g5-first-look-at-cells-cell) of the new individual: the fertilized [egg cell](https://one-course.com/books/biology/1/en/chapter/23-how-animals-reproduce#def-g4-animal-reproduction-sexual) in the ovule — which grows into the tiny [plant](https://one-course.com/books/biology/1/en/chapter/3-plants-around-us#def-g1-plants-around-us-plant) of the [seed](https://one-course.com/books/biology/1/en/chapter/9-from-seed-to-plant#def-g2-from-seed-to-plant-seed), as an [animal](https://one-course.com/books/biology/1/en/chapter/2-animals-around-us#def-g1-animals-around-us-animal) grows from its own first [cell](https://one-course.com/books/biology/1/en/chapter/29-a-first-look-at-cells#def-g5-first-look-at-cells-cell).

**Exercise 31.10 ★★.**

A cherry grower’s spring was cold and rainy: bees barely flew for two weeks, though no frost came and the trees blossomed magnificently. Predict July’s harvest and explain it with [Definition 31.3](#def-g5-flower-to-fruit-steps).

**Solution of Exercise 31.10.**

A poor harvest — most blossoms fell fruitless. The machinery was sound and the [flowers](https://one-course.com/books/biology/1/en/chapter/16-flowers-fruits-and-seeds#def-g3-flowers-fruits-seeds-parts) unhurt; what failed was step 1, [pollination](#def-g5-flower-to-fruit-steps): for two crucial weeks the couriers stayed home, so most [pistils](https://one-course.com/books/biology/1/en/chapter/16-flowers-fruits-and-seeds#def-g3-flowers-fruits-seeds-parts) never received [pollen](https://one-course.com/books/biology/1/en/chapter/16-flowers-fruits-and-seeds#def-g3-flowers-fruits-seeds-parts) and most [ovules](#prop-g5-flower-to-fruit-roles) were never fertilized.

**Exercise 31.11 ★★★.**

A greenhouse tomato grower installs a hive of bumblebees indoors, though no [flower](https://one-course.com/books/biology/1/en/chapter/16-flowers-fruits-and-seeds#def-g3-flowers-fruits-seeds-parts) outside can be reached from the sealed greenhouse. Using this chapter, explain exactly what service the bumblebees sell — and why fans blowing air across the [plants](https://one-course.com/books/biology/1/en/chapter/3-plants-around-us#def-g1-plants-around-us-plant) can partly replace them for tomatoes (whose [pollen](https://one-course.com/books/biology/1/en/chapter/16-flowers-fruits-and-seeds#def-g3-flowers-fruits-seeds-parts) shakes loose), while for cherry trees they could not.

**Solution of Exercise 31.11.**

The bumblebees sell [pollination](#def-g5-flower-to-fruit-steps) — the transport step: carrying [pollen](https://one-course.com/books/biology/1/en/chapter/16-flowers-fruits-and-seeds#def-g3-flowers-fruits-seeds-parts) from [stamens](https://one-course.com/books/biology/1/en/chapter/16-flowers-fruits-and-seeds#def-g3-flowers-fruits-seeds-parts) to [pistils](https://one-course.com/books/biology/1/en/chapter/16-flowers-fruits-and-seeds#def-g3-flowers-fruits-seeds-parts) inside a building no outdoor pollinator can enter. Tomato [pollen](https://one-course.com/books/biology/1/en/chapter/16-flowers-fruits-and-seeds#def-g3-flowers-fruits-seeds-parts) shakes loose easily, so a fan’s vibration and moving air can do crude transport within each [flower](https://one-course.com/books/biology/1/en/chapter/16-flowers-fruits-and-seeds#def-g3-flowers-fruits-seeds-parts) — a mechanical courier. Cherry [pollen](https://one-course.com/books/biology/1/en/chapter/16-flowers-fruits-and-seeds#def-g3-flowers-fruits-seeds-parts) must travel from tree to tree, [flower](https://one-course.com/books/biology/1/en/chapter/16-flowers-fruits-and-seeds#def-g3-flowers-fruits-seeds-parts) to [flower](https://one-course.com/books/biology/1/en/chapter/16-flowers-fruits-and-seeds#def-g3-flowers-fruits-seeds-parts), with a precision only a body that visits blossoms in turn provides; wind in a hall cannot aim, so for cherries the living courier has no cheap substitute.