---
title: "Producing Our Food"
book: "Primary & Middle School Biology"
subject: biology
language: en
chapter: 43
exercises: 12
source: https://one-course.com/books/biology/1/en/chapter/43-producing-our-food
---

# Chapter 43 — Producing Our Food

Nothing on your breakfast table was found in the wild. The bread’s wheat was bred and farmed; the [milk](https://one-course.com/books/biology/1/en/chapter/8-how-animals-grow-up#def-g2-animals-grow-up-born) came from herds tended for it; the yogurt was *made* from that [milk](https://one-course.com/books/biology/1/en/chapter/8-how-animals-grow-up#def-g2-animals-grow-up-born) by billions of living workers too small to see. Humans feed themselves by managing [living things](https://one-course.com/books/biology/1/en/chapter/37-exploring-our-environment#def-g6-exploring-our-environment-components) — growing them, raising them, and putting some of the smallest to work. This chapter tours the food workshop.

## 43.1 Growing and raising

**Definition 43.1 (Crops and livestock).**

Human food production manages [living things](https://one-course.com/books/biology/1/en/chapter/37-exploring-our-environment#def-g6-exploring-our-environment-components) at two floors of the matter cycle:

- *crop growing* : managing [producers](https://one-course.com/books/biology/1/en/chapter/34-food-webs#def-g5-food-webs-roles) — wheat, potatoes, vegetables, [fruit](https://one-course.com/books/biology/1/en/chapter/16-flowers-fruits-and-seeds#prop-g3-flowers-fruits-seeds-transform) — for their [organic matter](https://one-course.com/books/biology/1/en/chapter/40-plants-are-producers#def-g6-plants-are-producers-matter) ( [Proposition 40.3](https://one-course.com/books/biology/1/en/chapter/40-plants-are-producers#prop-g6-plants-are-producers-produce) );
- *livestock raising* : managing [consumers](https://one-course.com/books/biology/1/en/chapter/34-food-webs#def-g5-food-webs-roles) — cattle, sheep, pigs, hens — for their [production of matter](https://one-course.com/books/biology/1/en/chapter/41-matter-from-food#def-g6-matter-from-food-production) ( [Definition 41.4](https://one-course.com/books/biology/1/en/chapter/41-matter-from-food#def-g6-matter-from-food-production) ): [milk](https://one-course.com/books/biology/1/en/chapter/8-how-animals-grow-up#def-g2-animals-grow-up-born) , meat, [eggs](https://one-course.com/books/biology/1/en/chapter/8-how-animals-grow-up#def-g2-animals-grow-up-born) , wool.

Farmers manage the [conditions](https://one-course.com/books/biology/1/en/chapter/37-exploring-our-environment#def-g6-exploring-our-environment-conditions) this book keeps meeting: [soil](https://one-course.com/books/biology/1/en/chapter/42-decomposers-and-the-soil#def-g6-decomposers-and-soil-soil) minerals for the crops ([Remark 22.5](https://one-course.com/books/biology/1/en/chapter/22-what-plants-need#rem-g4-what-plants-need-soil)), feed for the [animals](https://one-course.com/books/biology/1/en/chapter/2-animals-around-us#def-g1-animals-around-us-animal) — the whole ledger of [Problem 41.1](https://one-course.com/books/biology/1/en/chapter/41-matter-from-food#pb-g6-matter-from-food-1), run on purpose.

**Example 43.2 (What a wheat field is).**

A wheat field is a managed [environment](https://one-course.com/books/biology/1/en/chapter/37-exploring-our-environment#def-g6-exploring-our-environment-components) ([Proposition 35.1](https://one-course.com/books/biology/1/en/chapter/35-people-and-nature#prop-g5-people-and-nature-managed)) tuned for one [producer](https://one-course.com/books/biology/1/en/chapter/34-food-webs#def-g5-food-webs-roles): [soil](https://one-course.com/books/biology/1/en/chapter/42-decomposers-and-the-soil#def-g6-decomposers-and-soil-soil) restocked and loosened for its [roots](https://one-course.com/books/biology/1/en/chapter/3-plants-around-us#def-g1-plants-around-us-parts), sowing timed to [Proposition 9.5](https://one-course.com/books/biology/1/en/chapter/9-from-seed-to-plant#prop-g2-from-seed-to-plant-needs)’s warmth, weeds — rival colonists of [Chapter 39](https://one-course.com/books/biology/1/en/chapter/39-how-plants-spread#ch-g6-how-plants-spread) — kept out. The harvest is the [plant](https://one-course.com/books/biology/1/en/chapter/3-plants-around-us#def-g1-plants-around-us-plant)’s [seed](https://one-course.com/books/biology/1/en/chapter/9-from-seed-to-plant#def-g2-from-seed-to-plant-seed) store: grain, the packed lunches of a million never-to-be-sown wheat [plants](https://one-course.com/books/biology/1/en/chapter/3-plants-around-us#def-g1-plants-around-us-plant), diverted to bakeries.

**Remark 43.3 (Every food is a life-cycle stage).**

Read any food biologically and it is some organism’s organ or stage: grain and beans are [seed](https://one-course.com/books/biology/1/en/chapter/9-from-seed-to-plant#def-g2-from-seed-to-plant-seed) stores; potatoes, [tubers](https://one-course.com/books/biology/1/en/chapter/24-plants-without-seeds#ex-g4-plants-without-seeds-bulbtuber); apples, [fruits](https://one-course.com/books/biology/1/en/chapter/16-flowers-fruits-and-seeds#prop-g3-flowers-fruits-seeds-transform) built to be eaten ([Exercise 39.12](https://one-course.com/books/biology/1/en/chapter/39-how-plants-spread#exo-g6-how-plants-spread-12)); [milk](https://one-course.com/books/biology/1/en/chapter/8-how-animals-grow-up#def-g2-animals-grow-up-born) is mammal mother-care ([Definition 8.1](https://one-course.com/books/biology/1/en/chapter/8-how-animals-grow-up#def-g2-animals-grow-up-born)); an [egg](https://one-course.com/books/biology/1/en/chapter/8-how-animals-grow-up#def-g2-animals-grow-up-born) is a packed nursery. Food production is the art of managing [life cycles](https://one-course.com/books/biology/1/en/chapter/7-born-growing-dying#def-g2-born-grow-die-cycle) so their provisions arrive on our tables.

## 43.2 The invisible workforce: food made by microbes

**Definition 43.4 (Fermentation).**

Some foods are made by putting [living things](https://one-course.com/books/biology/1/en/chapter/37-exploring-our-environment#def-g6-exploring-our-environment-components) too small to see — *microbes* — to work on a raw material. Their feeding transforms it: the transformation is called *fermentation*, and humans have run it for thousands of years, since long before anyone knew the workers existed.

**Example 43.5 (Bread rises).**

Bread’s raw dough is flour and water — plus *yeast*, a single-celled [fungus](https://one-course.com/books/biology/1/en/chapter/42-decomposers-and-the-soil#def-g6-decomposers-and-soil-decomposers) ([Remark 29.9](https://one-course.com/books/biology/1/en/chapter/29-a-first-look-at-cells#rem-g5-first-look-at-cells-onecelled) met such lives). The [yeast](#ex-g6-producing-our-food-bread) feeds on the flour’s sugars and releases a gas; the gas’s bubbles, trapped in the stretchy dough, puff it up — the baker calls it rising. The oven’s heat then ends the workers’ shift and sets their work: the crumb’s holes are the [yeast](#ex-g6-producing-our-food-bread)’s signature.

![The workforce’s signature, baked in place: every hole in the crumb is a bubble the yeast blew.](https://one-course.com/images/onecourse/chapters/biology-1/g6-producing-our-food/img-97b7a19cee63.jpg)

*The workforce’s signature, baked in place: every hole in the crumb is a bubble the [yeast](#ex-g6-producing-our-food-bread) blew.*

**Example 43.6 (Milk becomes yogurt and cheese).**

Warm [milk](https://one-course.com/books/biology/1/en/chapter/8-how-animals-grow-up#def-g2-animals-grow-up-born) seeded with the right [microbes](#def-g6-producing-our-food-fermentation) thickens overnight into yogurt: the workers feed on the [milk](https://one-course.com/books/biology/1/en/chapter/8-how-animals-grow-up#def-g2-animals-grow-up-born)’s sugar and release an acid, and the acid sets the [milk](https://one-course.com/books/biology/1/en/chapter/8-how-animals-grow-up#def-g2-animals-grow-up-born) — the fresh tang *is* the acid. Cheese starts similarly, then goes further: curds pressed, salted and ripened for months, the [microbes](#def-g6-producing-our-food-fermentation) working on through the ripening — a cheese’s holes, rind and power of smell are their long shift’s log.

**Remark 43.7 (Helpful and harmful microbes).**

The [germs](https://one-course.com/books/biology/1/en/chapter/6-healthy-habits#def-g1-healthy-habits-germs) of [Definition 6.1](https://one-course.com/books/biology/1/en/chapter/6-healthy-habits#def-g1-healthy-habits-germs) taught caution about [microbes](#def-g6-producing-our-food-fermentation); this chapter adds the other half: *chosen* [microbes](#def-g6-producing-our-food-fermentation), working in *controlled* [conditions](https://one-course.com/books/biology/1/en/chapter/37-exploring-our-environment#def-g6-exploring-our-environment-conditions), are among our oldest employees — in bread, yogurt, cheese, and the vinegar barrel. The craft is always the same: welcome the chosen workers, and keep [conditions](https://one-course.com/books/biology/1/en/chapter/37-exploring-our-environment#def-g6-exploring-our-environment-conditions) that suit them and not the spoilers. Salting, cooling, drying and cooking are all ways of refusing [conditions](https://one-course.com/books/biology/1/en/chapter/37-exploring-our-environment#def-g6-exploring-our-environment-conditions) to unwanted [microbes](#def-g6-producing-our-food-fermentation) ([Proposition 42.8](https://one-course.com/books/biology/1/en/chapter/42-decomposers-and-the-soil#prop-g6-decomposers-and-soil-speed) works on a ham exactly as on a [leaf](https://one-course.com/books/biology/1/en/chapter/3-plants-around-us#def-g1-plants-around-us-parts) pile).

## 43.3 From field to table, honestly

**Proposition 43.8 (The costs on the table).**

Every plate is an output of managed land and [living things](https://one-course.com/books/biology/1/en/chapter/37-exploring-our-environment#def-g6-exploring-our-environment-components), and carries their arithmetic:

- [plant](https://one-course.com/books/biology/1/en/chapter/3-plants-around-us#def-g1-plants-around-us-plant) foods arrive one floor from the [light](https://one-course.com/books/biology/1/en/chapter/37-exploring-our-environment#def-g6-exploring-our-environment-conditions) ; [animal](https://one-course.com/books/biology/1/en/chapter/2-animals-around-us#def-g1-animals-around-us-animal) foods route through a [consumer](https://one-course.com/books/biology/1/en/chapter/34-food-webs#def-g5-food-webs-roles) first and pay [Proposition 41.6](https://one-course.com/books/biology/1/en/chapter/41-matter-from-food#prop-g6-matter-from-food-losses) ’s toll ( [Exercise 41.12](https://one-course.com/books/biology/1/en/chapter/41-matter-from-food#exo-g6-matter-from-food-12) );
- lasting production must keep [Proposition 35.5](https://one-course.com/books/biology/1/en/chapter/35-people-and-nature#prop-g5-people-and-nature-lasting) ’s three rules — feed the [soil](https://one-course.com/books/biology/1/en/chapter/42-decomposers-and-the-soil#def-g6-decomposers-and-soil-soil) , keep the helpers, take no faster than renewal;
- and waste undoes it all: food thrown away spent its land, water and work for no one.

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

**Method 43.9 (Reading a food’s story).**

For any food in the kitchen:

1. name the organism and the organ or stage it is ( [Remark 43.3](#rem-g6-producing-our-food-stage) );
2. place it on the cycle: [producer](https://one-course.com/books/biology/1/en/chapter/34-food-webs#def-g5-food-webs-roles) ’s matter, [consumer](https://one-course.com/books/biology/1/en/chapter/34-food-webs#def-g5-food-webs-roles) ’s product, or microbe-made?
3. if microbe-made, name the raw material and what the workers changed;
4. trace it to its [leaf](https://one-course.com/books/biology/1/en/chapter/3-plants-around-us#def-g1-plants-around-us-parts) ( [Method 40.8](https://one-course.com/books/biology/1/en/chapter/40-plants-are-producers#met-g6-plants-are-producers-trace) ) — the trail still always ends in the [light](https://one-course.com/books/biology/1/en/chapter/37-exploring-our-environment#def-g6-exploring-our-environment-conditions) .

**Example 43.10 (The method at breakfast).**

Yogurt, by the method: (1) [milk](https://one-course.com/books/biology/1/en/chapter/8-how-animals-grow-up#def-g2-animals-grow-up-born) — a cow’s mother-care product — transformed; (2) [consumer](https://one-course.com/books/biology/1/en/chapter/34-food-webs#def-g5-food-webs-roles)’s product, microbe-finished; (3) raw material [milk](https://one-course.com/books/biology/1/en/chapter/8-how-animals-grow-up#def-g2-animals-grow-up-born), workers soured and set it; (4) [milk](https://one-course.com/books/biology/1/en/chapter/8-how-animals-grow-up#def-g2-animals-grow-up-born) from the cow, cow from grass, grass from [light](https://one-course.com/books/biology/1/en/chapter/37-exploring-our-environment#def-g6-exploring-our-environment-conditions). Three organisms and a workforce of billions, in one small pot.

## 43.4 Exercises

**Exercise 43.1 ★.**

Define [crop growing](#def-g6-producing-our-food-farming) and [livestock raising](#def-g6-producing-our-food-farming), naming the floor of the matter cycle each manages.

**Solution of Exercise 43.1.**

[Crop growing](#def-g6-producing-our-food-farming) manages [producers](https://one-course.com/books/biology/1/en/chapter/34-food-webs#def-g5-food-webs-roles) — [plants](https://one-course.com/books/biology/1/en/chapter/3-plants-around-us#def-g1-plants-around-us-plant) grown for their [organic matter](https://one-course.com/books/biology/1/en/chapter/40-plants-are-producers#def-g6-plants-are-producers-matter). [Livestock raising](#def-g6-producing-our-food-farming) manages [consumers](https://one-course.com/books/biology/1/en/chapter/34-food-webs#def-g5-food-webs-roles) — [animals](https://one-course.com/books/biology/1/en/chapter/2-animals-around-us#def-g1-animals-around-us-animal) raised for their production: [milk](https://one-course.com/books/biology/1/en/chapter/8-how-animals-grow-up#def-g2-animals-grow-up-born), meat, [eggs](https://one-course.com/books/biology/1/en/chapter/8-how-animals-grow-up#def-g2-animals-grow-up-born), wool.

**Exercise 43.2 ★.**

For each food, name the organism and the organ or stage: grain, potato, apple, [milk](https://one-course.com/books/biology/1/en/chapter/8-how-animals-grow-up#def-g2-animals-grow-up-born), [egg](https://one-course.com/books/biology/1/en/chapter/8-how-animals-grow-up#def-g2-animals-grow-up-born).

**Solution of Exercise 43.2.**

Grain: the wheat [plant](https://one-course.com/books/biology/1/en/chapter/3-plants-around-us#def-g1-plants-around-us-plant)’s [seed](https://one-course.com/books/biology/1/en/chapter/9-from-seed-to-plant#def-g2-from-seed-to-plant-seed) (its packed store). Potato: the potato [plant](https://one-course.com/books/biology/1/en/chapter/3-plants-around-us#def-g1-plants-around-us-plant)’s [tuber](https://one-course.com/books/biology/1/en/chapter/24-plants-without-seeds#ex-g4-plants-without-seeds-bulbtuber). Apple: the apple tree’s [fruit](https://one-course.com/books/biology/1/en/chapter/16-flowers-fruits-and-seeds#prop-g3-flowers-fruits-seeds-transform). [Milk](https://one-course.com/books/biology/1/en/chapter/8-how-animals-grow-up#def-g2-animals-grow-up-born): the cow’s mother-care product. [Egg](https://one-course.com/books/biology/1/en/chapter/8-how-animals-grow-up#def-g2-animals-grow-up-born): the hen’s packed nursery.

**Exercise 43.3 ★.**

What is [fermentation](#def-g6-producing-our-food-fermentation)? Name two fermented foods and their raw materials.

**Solution of Exercise 43.3.**

The transformation of a raw material by feeding [microbes](#def-g6-producing-our-food-fermentation). Bread (raw material: flour dough, worker: [yeast](#ex-g6-producing-our-food-bread)) and yogurt (raw material: [milk](https://one-course.com/books/biology/1/en/chapter/8-how-animals-grow-up#def-g2-animals-grow-up-born), workers: souring [microbes](#def-g6-producing-our-food-fermentation)); cheese and vinegar serve too.

**Exercise 43.4 ★.**

Tell why bread rises: the worker, its food, what it releases, and what the oven does.

**Solution of Exercise 43.4.**

The [yeast](#ex-g6-producing-our-food-bread) — a single-celled [fungus](https://one-course.com/books/biology/1/en/chapter/42-decomposers-and-the-soil#def-g6-decomposers-and-soil-decomposers) — feeds on the flour’s sugars and releases a gas; the stretchy dough traps the gas as bubbles and puffs up. The oven’s heat ends the [yeast](#ex-g6-producing-our-food-bread)’s work and sets the risen crumb, holes and all.

**Exercise 43.5 ★.**

What sets [milk](https://one-course.com/books/biology/1/en/chapter/8-how-animals-grow-up#def-g2-animals-grow-up-born) into yogurt, and where does the tang come from?

**Solution of Exercise 43.5.**

The acid released by the [microbes](#def-g6-producing-our-food-fermentation) feeding on the [milk](https://one-course.com/books/biology/1/en/chapter/8-how-animals-grow-up#def-g2-animals-grow-up-born)’s sugar: the acid thickens and sets the [milk](https://one-course.com/books/biology/1/en/chapter/8-how-animals-grow-up#def-g2-animals-grow-up-born), and the fresh tang is the acid itself.

**Exercise 43.6 ★.**

Give three ways of refusing [conditions](https://one-course.com/books/biology/1/en/chapter/37-exploring-our-environment#def-g6-exploring-our-environment-conditions) to unwanted [microbes](#def-g6-producing-our-food-fermentation), from [Remark 43.7](#rem-g6-producing-our-food-goodbad).

**Solution of Exercise 43.6.**

Salting, cooling (fridge), drying — also cooking: each denies unwanted [microbes](#def-g6-producing-our-food-fermentation) a working condition (moisture, warmth), exactly as cold slows a compost heap.

**Exercise 43.7 ★★.**

A wheat field manages every need of [Proposition 22.3](https://one-course.com/books/biology/1/en/chapter/22-what-plants-need#prop-g4-what-plants-need-needs) on purpose. Match each need to the farmer’s action of [Example 43.2](#ex-g6-producing-our-food-wheat).

**Solution of Exercise 43.7.**

Water: the farmer relies on (and sometimes brings) rain. [Light](https://one-course.com/books/biology/1/en/chapter/37-exploring-our-environment#def-g6-exploring-our-environment-conditions): sowing in open fields, spaced so every [plant](https://one-course.com/books/biology/1/en/chapter/3-plants-around-us#def-g1-plants-around-us-plant) gets its share. Warmth: sowing timed to the warm season. Air: open ground, loosened [soil](https://one-course.com/books/biology/1/en/chapter/42-decomposers-and-the-soil#def-g6-decomposers-and-soil-soil). [Mineral salts](https://one-course.com/books/biology/1/en/chapter/22-what-plants-need#prop-g4-what-plants-need-needs): manure and restocking after harvest.

**Exercise 43.8 ★★.**

Run [Method 43.9](#met-g6-producing-our-food-read) on cheese, step by step.

**Solution of Exercise 43.8.**

(1) Organism and stage: cow’s [milk](https://one-course.com/books/biology/1/en/chapter/8-how-animals-grow-up#def-g2-animals-grow-up-born) — a [consumer](https://one-course.com/books/biology/1/en/chapter/34-food-webs#def-g5-food-webs-roles)’s product. (2) Cycle place: [consumer](https://one-course.com/books/biology/1/en/chapter/34-food-webs#def-g5-food-webs-roles)’s product, microbe-finished. (3) Raw material [milk](https://one-course.com/books/biology/1/en/chapter/8-how-animals-grow-up#def-g2-animals-grow-up-born); the workers sour and set it into curds, then ripen the pressed cheese for months — holes, rind and smell are their log. (4) Trail: [milk](https://one-course.com/books/biology/1/en/chapter/8-how-animals-grow-up#def-g2-animals-grow-up-born) from the cow, cow from grass, grass from [light](https://one-course.com/books/biology/1/en/chapter/37-exploring-our-environment#def-g6-exploring-our-environment-conditions).

**Exercise 43.9 ★★.**

Why does refrigeration keep food — and why does the same cold slow a compost heap? One principle, two kitchens: name it.

**Solution of Exercise 43.9.**

[Microbes](#def-g6-producing-our-food-fermentation) are living workers with [conditions](https://one-course.com/books/biology/1/en/chapter/37-exploring-our-environment#def-g6-exploring-our-environment-conditions): cold nearly stops their feeding. In the fridge that protects the food (the spoilers idle); in the winter heap it delays the compost (the [decomposers](https://one-course.com/books/biology/1/en/chapter/42-decomposers-and-the-soil#def-g6-decomposers-and-soil-decomposers) idle). The principle: decomposition and spoilage run at the pace [conditions](https://one-course.com/books/biology/1/en/chapter/37-exploring-our-environment#def-g6-exploring-our-environment-conditions) allow.

**Exercise 43.10 ★★.**

Reconcile [Definition 6.1](https://one-course.com/books/biology/1/en/chapter/6-healthy-habits#def-g1-healthy-habits-germs) with this chapter: how can [microbes](#def-g6-producing-our-food-fermentation) be both the hand-washing enemy and the yogurt workforce?

**Solution of Exercise 43.10.**

“Microbe” names a vast crowd of different tiny [living things](https://one-course.com/books/biology/1/en/chapter/37-exploring-our-environment#def-g6-exploring-our-environment-components). Some, in the wrong place, cause illness — those the hand-washing targets; others, chosen and managed in controlled [conditions](https://one-course.com/books/biology/1/en/chapter/37-exploring-our-environment#def-g6-exploring-our-environment-conditions), make bread rise and [milk](https://one-course.com/books/biology/1/en/chapter/8-how-animals-grow-up#def-g2-animals-grow-up-born) set. Enemy or employee is not the microbe’s nature but the match of [species](https://one-course.com/books/biology/1/en/chapter/30-biodiversity#def-g5-biodiversity-species), place and management.

**Exercise 43.11 ★★.**

Using [Proposition 43.8](#prop-g6-producing-our-food-costs), explain why a thrown-away ham sandwich wastes more than the same weight of thrown-away bread.

**Solution of Exercise 43.11.**

The ham routed through a pig: its weight cost many times its weight in feed, plus the pig’s burned share, land and water — the [consumer](https://one-course.com/books/biology/1/en/chapter/34-food-webs#def-g5-food-webs-roles) floor’s toll. The bread’s wheat came one floor from the [light](https://one-course.com/books/biology/1/en/chapter/37-exploring-our-environment#def-g6-exploring-our-environment-conditions). Wasting the sandwich wastes both ledgers; the ham’s is the longer one.

**Exercise 43.12 ★★★.**

For thousands of years, bakers and brewers ran [fermentation](#def-g6-producing-our-food-fermentation) without knowing [microbes](#def-g6-producing-our-food-fermentation) existed. What did they actually manage, in [Proposition 37.6](https://one-course.com/books/biology/1/en/chapter/37-exploring-our-environment#prop-g6-exploring-our-environment-decide)’s terms — and why did their recipes work anyway?

**Solution of Exercise 43.12.**

They managed the workers’ *[conditions](https://one-course.com/books/biology/1/en/chapter/37-exploring-our-environment#def-g6-exploring-our-environment-conditions)*: warmth for the dough’s corner, the starter kept and fed, salt and timing tuned by trial across generations. The recipes worked because keeping [conditions](https://one-course.com/books/biology/1/en/chapter/37-exploring-our-environment#def-g6-exploring-our-environment-conditions) right keeps the right [living things](https://one-course.com/books/biology/1/en/chapter/37-exploring-our-environment#def-g6-exploring-our-environment-components) thriving — whether or not anyone knows the [living things](https://one-course.com/books/biology/1/en/chapter/37-exploring-our-environment#def-g6-exploring-our-environment-components) are there. They farmed [microbes](#def-g6-producing-our-food-fermentation) blind, and well.

## 43.5 Problem: The Class Bakery

**Problem 43.1.**

Weekend problem — one batch of bread, followed from seed to slice

For the school fair, the class bakes bread from scratch — and keeps its [biology](https://one-course.com/books/biology/1/en/chapter/1-living-or-not-living#def-g1-living-or-not-living) notebook open from the wheat field visit in July to the loaves in November.

**Part I — The field (July).**

1. The farmer shows the ripe wheat: “the harvest is the [plant](https://one-course.com/books/biology/1/en/chapter/3-plants-around-us#def-g1-plants-around-us-plant) ’s packed lunches.” Unpack the phrase with [Definition 9.1](https://one-course.com/books/biology/1/en/chapter/9-from-seed-to-plant#def-g2-from-seed-to-plant-seed) — what is each grain, and for whom was it packed?
2. In whose [leaves](https://one-course.com/books/biology/1/en/chapter/3-plants-around-us#def-g1-plants-around-us-parts) , and with what inputs, was the grain’s [organic matter](https://one-course.com/books/biology/1/en/chapter/40-plants-are-producers#def-g6-plants-are-producers-matter) manufactured?
3. The farmer sows only part of the harvest next autumn and sells the rest. Name the two fates of a wheat grain, in life-cycle terms.
4. The field’s [soil](https://one-course.com/books/biology/1/en/chapter/42-decomposers-and-the-soil#def-g6-decomposers-and-soil-soil) gets manure after harvest. Which return rule is this, and which of the [plant](https://one-course.com/books/biology/1/en/chapter/3-plants-around-us#def-g1-plants-around-us-plant) ’s five needs does it serve?

**Part II — The bakery (November).**

5. The class mixes flour, water, salt and [yeast](#ex-g6-producing-our-food-bread) , and sets the dough in a warm corner. Why warm? Answer for the [yeast](#ex-g6-producing-our-food-bread) as for any living worker ( [Proposition 42.8](https://one-course.com/books/biology/1/en/chapter/42-decomposers-and-the-soil#prop-g6-decomposers-and-soil-speed) has the pattern).
6. An hour later the dough has doubled. Explain the rise: what did the [yeast](#ex-g6-producing-our-food-bread) feed on, what did it release, and what trapped it?
7. One team’s dough, forgotten by a drafty cold window, barely rises. Diagnose — and say which fair-test comparison the two teams have accidentally run.
8. In the oven the loaves stop rising and set. What has the heat done to the workforce, and what remains as its signature in the crumb?

**Part III — The accounting.**

9. Trace the finished slice to the [light](https://one-course.com/books/biology/1/en/chapter/37-exploring-our-environment#def-g6-exploring-our-environment-conditions) , link by link.
10. The fair also sells butter and ham sandwiches. Rank slice, butter and ham by the floors their matter routed through, and state which paid the biggest toll of [Proposition 41.6](https://one-course.com/books/biology/1/en/chapter/41-matter-from-food#prop-g6-matter-from-food-losses) .
11. Unsold dough is composted, not binned. Follow its [organic matter](https://one-course.com/books/biology/1/en/chapter/40-plants-are-producers#def-g6-plants-are-producers-matter) one turn further around the cycle — who takes it, and toward what?
12. Close the notebook with one sentence containing: [producer](https://one-course.com/books/biology/1/en/chapter/34-food-webs#def-g5-food-webs-roles) , [consumer](https://one-course.com/books/biology/1/en/chapter/34-food-webs#def-g5-food-webs-roles) (if any), microbe workforce, and [light](https://one-course.com/books/biology/1/en/chapter/37-exploring-our-environment#def-g6-exploring-our-environment-conditions) .

**Solution of Problem 43.1.**

**1.** Each grain is a [seed](https://one-course.com/books/biology/1/en/chapter/9-from-seed-to-plant#def-g2-from-seed-to-plant-seed): a tiny wheat [plant](https://one-course.com/books/biology/1/en/chapter/3-plants-around-us#def-g1-plants-around-us-plant) packed with a [food store](https://one-course.com/books/biology/1/en/chapter/20-animals-through-the-seasons#def-g3-animals-through-seasons-active), made by the parent for that plantlet’s first days — not for us, though we divert it.

**2.** In the wheat [plants](https://one-course.com/books/biology/1/en/chapter/3-plants-around-us#def-g1-plants-around-us-plant)’ own green [leaves](https://one-course.com/books/biology/1/en/chapter/3-plants-around-us#def-g1-plants-around-us-parts), from water and [mineral salts](https://one-course.com/books/biology/1/en/chapter/22-what-plants-need#prop-g4-what-plants-need-needs) of the [soil](https://one-course.com/books/biology/1/en/chapter/42-decomposers-and-the-soil#def-g6-decomposers-and-soil-soil) and carbon dioxide of the air, with [light](https://one-course.com/books/biology/1/en/chapter/37-exploring-our-environment#def-g6-exploring-our-environment-conditions) as the [energy](https://one-course.com/books/biology/1/en/chapter/18-a-balanced-diet#prop-g3-balanced-diet-jobs).

**3.** Sown, a grain runs its [life cycle](https://one-course.com/books/biology/1/en/chapter/7-born-growing-dying#def-g2-born-grow-die-cycle): [germination](https://one-course.com/books/biology/1/en/chapter/9-from-seed-to-plant#def-g2-from-seed-to-plant-germination) to [plant](https://one-course.com/books/biology/1/en/chapter/3-plants-around-us#def-g1-plants-around-us-plant) to new grain. Sold and milled, its [life cycle](https://one-course.com/books/biology/1/en/chapter/7-born-growing-dying#def-g2-born-grow-die-cycle) ends and its [food store](https://one-course.com/books/biology/1/en/chapter/20-animals-through-the-seasons#def-g3-animals-through-seasons-active) becomes ours — lunch packed for a plantlet, eaten by a person.

**4.** Return what you borrow: the manure’s rotting restocks the [mineral salts](https://one-course.com/books/biology/1/en/chapter/22-what-plants-need#prop-g4-what-plants-need-needs) that the harvest carried off — serving the need for [mineral salts](https://one-course.com/books/biology/1/en/chapter/22-what-plants-need#prop-g4-what-plants-need-needs).

**5.** Because [yeast](#ex-g6-producing-our-food-bread) is a living worker: warm, it feeds and works fast; cold, it idles — the compost crew’s rule, at bakery scale.

**6.** It fed on the flour’s sugars and released gas; the stretchy dough trapped the gas as bubbles, and the bubbles doubled the dough.

**7.** The cold window idled the [yeast](#ex-g6-producing-our-food-bread) — barely fed, barely any gas. The two teams ran an accidental fair test of warmth: same dough, same day, one condition different, two risings to compare.

**8.** The heat has killed the [yeast](#ex-g6-producing-our-food-bread), ending the shift; the set crumb keeps the bubbles’ holes — the workforce’s signature, baked in place.

**9.** Slice from loaf, loaf from dough, dough from flour, flour from grain, grain from the wheat [plant](https://one-course.com/books/biology/1/en/chapter/3-plants-around-us#def-g1-plants-around-us-plant)’s [leaves](https://one-course.com/books/biology/1/en/chapter/3-plants-around-us#def-g1-plants-around-us-parts) — manufactured there from mineral inputs with [light](https://one-course.com/books/biology/1/en/chapter/37-exploring-our-environment#def-g6-exploring-our-environment-conditions): the trail ends in the July field’s sunshine.

**10.** Slice: one floor ([producer](https://one-course.com/books/biology/1/en/chapter/34-food-webs#def-g5-food-webs-roles) to table, with a microbe finish). Butter: two floors (grass to cow to cream). Ham: two floors with the biggest toll — the pig burned and dropped most of its feed’s matter before any became ham. The slice is cheapest in matter; the ham dearest.

**11.** The compost’s [decomposers](https://one-course.com/books/biology/1/en/chapter/42-decomposers-and-the-soil#def-g6-decomposers-and-soil-decomposers) — worms, woodlice, [fungi](https://one-course.com/books/biology/1/en/chapter/42-decomposers-and-the-soil#def-g6-decomposers-and-soil-decomposers), unseen crews — dismantle the dough’s [organic matter](https://one-course.com/books/biology/1/en/chapter/40-plants-are-producers#def-g6-plants-are-producers-matter) to [humus](https://one-course.com/books/biology/1/en/chapter/42-decomposers-and-the-soil#def-g6-decomposers-and-soil-soil) and [mineral salts](https://one-course.com/books/biology/1/en/chapter/22-what-plants-need#prop-g4-what-plants-need-needs): one turn on from food to next year’s [soil](https://one-course.com/books/biology/1/en/chapter/42-decomposers-and-the-soil#def-g6-decomposers-and-soil-soil) fertility.

**12.** For example: “Our bread was built by a [producer](https://one-course.com/books/biology/1/en/chapter/34-food-webs#def-g5-food-webs-roles) from [mineral matter](https://one-course.com/books/biology/1/en/chapter/40-plants-are-producers#def-g6-plants-are-producers-matter) and [light](https://one-course.com/books/biology/1/en/chapter/37-exploring-our-environment#def-g6-exploring-our-environment-conditions), raised by a microbe workforce, and needed no [consumer](https://one-course.com/books/biology/1/en/chapter/34-food-webs#def-g5-food-webs-roles) floor at all — though the ham sandwiches next door needed one.”