---
title: "What Is Respiration?"
book: "Primary & Middle School Biology"
subject: biology
language: en
chapter: 46
exercises: 12
source: https://one-course.com/books/biology/1/en/chapter/46-what-is-respiration
---

# Chapter 46 — What Is Respiration?

Put a woodlouse in a closed jar and, hours later, the air in the jar has changed: some of its [oxygen](#def-g7-what-is-respiration-respiration) is gone, replaced by [carbon dioxide](#def-g7-what-is-respiration-respiration). Repeat with a germinating [seed](https://one-course.com/books/biology/1/en/chapter/9-from-seed-to-plant#def-g2-from-seed-to-plant-seed), a mushroom, a goldfish, a spoonful of living [soil](https://one-course.com/books/biology/1/en/chapter/42-decomposers-and-the-soil#def-g6-decomposers-and-soil-soil) — same result, every time. [Proposition 26.5](https://one-course.com/books/biology/1/en/chapter/26-breathing#prop-g4-breathing-exchange) showed the swap in your own chest; this year opens the idea to its full width: the swap is not a human habit but a property of life itself.

## 46.1 Respiration, defined and measured

**Definition 46.1 (Respiration).**

*Respiration* is the gas exchange by which a [living thing](https://one-course.com/books/biology/1/en/chapter/37-exploring-our-environment#def-g6-exploring-our-environment-components) takes *oxygen* from its surroundings and releases *carbon dioxide*. It must not be confused with *breathing* — the visible chest movements of [Definition 26.1](https://one-course.com/books/biology/1/en/chapter/26-breathing#def-g4-breathing-movements): breathing is one way of *serving* respiration; respiration itself is the gas swap, and it goes on in every living [cell](https://one-course.com/books/biology/1/en/chapter/29-a-first-look-at-cells#def-g5-first-look-at-cells-cell), movements or none.

**Proposition 46.2 (How the swap is shown).**

Two standard bench tests reveal [respiration](#def-g7-what-is-respiration-respiration):

- an *[oxygen](#def-g7-what-is-respiration-respiration) probe* in a closed container shows the [oxygen](#def-g7-what-is-respiration-respiration) level falling while a [living thing](https://one-course.com/books/biology/1/en/chapter/37-exploring-our-environment#def-g6-exploring-our-environment-components) sits inside;
- *limewater* , a clear liquid that turns milky in [carbon dioxide](#def-g7-what-is-respiration-respiration) , clouds when the container’s air is passed through it.

Falling [oxygen](#def-g7-what-is-respiration-respiration) plus clouding [limewater](#prop-g7-what-is-respiration-shown), with a lifeless control container staying unchanged ([Method 22.1](https://one-course.com/books/biology/1/en/chapter/22-what-plants-need#met-g4-what-plants-need-fairtest) — the fair test follows us everywhere): that is [respiration](#def-g7-what-is-respiration-respiration), measured.

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

**Example 46.3 (The gallery of respirers).**

Run the two tests on a menagerie: a mouse — fast fall, quick clouding; a woodlouse — the same, smaller; a germinating pea — unmistakable (a jar of sprouting peas can exhaust its [oxygen](#def-g7-what-is-respiration-respiration) in a day); a mushroom — yes; pond snails — yes; a spoonful of living [soil](https://one-course.com/books/biology/1/en/chapter/42-decomposers-and-the-soil#def-g6-decomposers-and-soil-soil) — yes, its billions of [decomposers](https://one-course.com/books/biology/1/en/chapter/42-decomposers-and-the-soil#def-g6-decomposers-and-soil-decomposers) respiring together ([Example 42.2](https://one-course.com/books/biology/1/en/chapter/42-decomposers-and-the-soil#ex-g6-decomposers-and-soil-handful)). Only the control jar — pebbles, dry sand — changes nothing.

![The most unassuming respirer on the bench: a jar of sprouting peas can exhaust its oxygen in a day.](https://one-course.com/images/onecourse/chapters/biology-1/g7-what-is-respiration/img-8c93aea8126d.jpg)

*The most unassuming respirer on the bench: a jar of sprouting peas can exhaust its [oxygen](#def-g7-what-is-respiration-respiration) in a day.*

**Remark 46.4 (Plants respire too).**

[Remark 40.5](https://one-course.com/books/biology/1/en/chapter/40-plants-are-producers#rem-g6-plants-are-producers-gas) said it in passing; the jar proves it: a potted [plant](https://one-course.com/books/biology/1/en/chapter/3-plants-around-us#def-g1-plants-around-us-plant) *in the dark* lowers its jar’s [oxygen](#def-g7-what-is-respiration-respiration) and clouds [limewater](#prop-g7-what-is-respiration-shown) like any [animal](https://one-course.com/books/biology/1/en/chapter/2-animals-around-us#def-g1-animals-around-us-animal). In daylight the [producers](https://one-course.com/books/biology/1/en/chapter/34-food-webs#def-g5-food-webs-roles)’ manufacture masks the effect — taking in far more [carbon dioxide](#def-g7-what-is-respiration-respiration) than [respiration](#def-g7-what-is-respiration-respiration) releases — but the [respiration](#def-g7-what-is-respiration-respiration) never stops. Green does not excuse a [cell](https://one-course.com/books/biology/1/en/chapter/29-a-first-look-at-cells#def-g5-first-look-at-cells-cell) from breathing-in-the-wide-sense; nothing living is excused.

## 46.2 Why living things respire

**Proposition 46.5 (Respiration powers the cells).**

The point of the swap is *[energy](https://one-course.com/books/biology/1/en/chapter/18-a-balanced-diet#prop-g3-balanced-diet-jobs)*. In every living [cell](https://one-course.com/books/biology/1/en/chapter/29-a-first-look-at-cells#def-g5-first-look-at-cells-cell), [nutrients](https://one-course.com/books/biology/1/en/chapter/25-the-journey-of-food#def-g4-journey-of-food-digestion) ([Definition 25.3](https://one-course.com/books/biology/1/en/chapter/25-the-journey-of-food#def-g4-journey-of-food-digestion)) are slowly *burned* with the [oxygen](#def-g7-what-is-respiration-respiration) [respiration](#def-g7-what-is-respiration-respiration) brings: their [energy](https://one-course.com/books/biology/1/en/chapter/18-a-balanced-diet#prop-g3-balanced-diet-jobs) is released for the [cell](https://one-course.com/books/biology/1/en/chapter/29-a-first-look-at-cells#def-g5-first-look-at-cells-cell)’s work — contraction, building, commanding — and [carbon dioxide](#def-g7-what-is-respiration-respiration) is the burnt-out remainder, carted away. [Proposition 41.6](https://one-course.com/books/biology/1/en/chapter/41-matter-from-food#prop-g6-matter-from-food-losses)’s “burned share” was exactly this, seen from the ledger; here it is seen from the [cell](https://one-course.com/books/biology/1/en/chapter/29-a-first-look-at-cells#def-g5-first-look-at-cells-cell).

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

**Example 46.6 (The fire comparison, used honestly).**

A candle flame also consumes [oxygen](#def-g7-what-is-respiration-respiration) and releases [carbon dioxide](#def-g7-what-is-respiration-respiration) — burning and [respiration](#def-g7-what-is-respiration-respiration) are genuinely the same kind of chemistry. The differences matter as much: the [cell](https://one-course.com/books/biology/1/en/chapter/29-a-first-look-at-cells#def-g5-first-look-at-cells-cell)’s burning is slow, flameless, spread over thousands of tiny steps, and its [energy](https://one-course.com/books/biology/1/en/chapter/18-a-balanced-diet#prop-g3-balanced-diet-jobs) is captured for work rather than lost as [light](https://one-course.com/books/biology/1/en/chapter/37-exploring-our-environment#def-g6-exploring-our-environment-conditions) and scorch. [Respiration](#def-g7-what-is-respiration-respiration) is combustion domesticated — fire on a leash, in every [cell](https://one-course.com/books/biology/1/en/chapter/29-a-first-look-at-cells#def-g5-first-look-at-cells-cell) you own.

**Example 46.7 (Reading demand).**

Because the burning powers the work, demand tracks effort: the sprinting child of [Example 26.6](https://one-course.com/books/biology/1/en/chapter/26-breathing#ex-g4-breathing-running) respires far faster than the reader in the armchair; the germinating pea — building a [plant](https://one-course.com/books/biology/1/en/chapter/3-plants-around-us#def-g1-plants-around-us-plant) at full speed ([Definition 9.4](https://one-course.com/books/biology/1/en/chapter/9-from-seed-to-plant#def-g2-from-seed-to-plant-germination)) — respires far faster than the dry, waiting [seed](https://one-course.com/books/biology/1/en/chapter/9-from-seed-to-plant#def-g2-from-seed-to-plant-seed) beside it, whose [respiration](#def-g7-what-is-respiration-respiration) idles near zero for years. [Respiration](#def-g7-what-is-respiration-respiration) is the engine note of life: loud in effort and growth, a whisper in dormancy, silent only in death.

## 46.3 Respiration in every habitat

**Proposition 46.8 (One need, many surroundings).**

Every [living thing](https://one-course.com/books/biology/1/en/chapter/37-exploring-our-environment#def-g6-exploring-our-environment-components) must get its [oxygen](#def-g7-what-is-respiration-respiration) *from its surroundings* — and surroundings differ. Air is oxygen-rich; water holds far less, dissolved ([Exercise 26.11](https://one-course.com/books/biology/1/en/chapter/26-breathing#exo-g4-breathing-11) met the consequence); [soil](https://one-course.com/books/biology/1/en/chapter/42-decomposers-and-the-soil#def-g6-decomposers-and-soil-soil) and mud hold less still. Where and how a [living thing](https://one-course.com/books/biology/1/en/chapter/37-exploring-our-environment#def-g6-exploring-our-environment-components) lives is therefore shaped by how it solves its [oxygen](#def-g7-what-is-respiration-respiration) problem — the subject of the next two chapters, for [animals](https://one-course.com/books/biology/1/en/chapter/2-animals-around-us#def-g1-animals-around-us-animal)’ equipment ([Chapter 47](https://one-course.com/books/biology/1/en/chapter/47-how-animals-breathe#ch-g7-how-animals-breathe)) and for water’s economy ([Chapter 48](https://one-course.com/books/biology/1/en/chapter/48-oxygen-in-the-water#ch-g7-oxygen-in-the-water)).

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

**Method 46.9 (Testing a respiration question).**

To test any claim about [respiration](#def-g7-what-is-respiration-respiration) (“[seeds](https://one-course.com/books/biology/1/en/chapter/16-flowers-fruits-and-seeds#prop-g3-flowers-fruits-seeds-transform) respire faster warm”, “the pond mud respires”):

1. close the subject in a container, with an [oxygen](#def-g7-what-is-respiration-respiration) probe or a [limewater](#prop-g7-what-is-respiration-shown) trap;
2. build the twin control — same container, subject absent or lifeless;
3. vary one condition at a time, if the claim names one (warmth, dampness, dark);
4. read the verdict in the difference: [oxygen](#def-g7-what-is-respiration-respiration) fallen, [limewater](#prop-g7-what-is-respiration-shown) clouded — against the control’s stillness.

**Example 46.10 (The method on a cold seed).**

Claim: germinating peas respire more slowly in the cold. Two jars of sprouting peas, one at room warmth, one in the fridge; [limewater](#prop-g7-what-is-respiration-shown) traps on both; a lifeless third as control. Next day: the warm jar’s [limewater](#prop-g7-what-is-respiration-shown) is milky, the cold jar’s barely misted, the control’s clear. Verdict: [respiration](#def-g7-what-is-respiration-respiration) runs with the peas’ working pace — [Proposition 42.8](https://one-course.com/books/biology/1/en/chapter/42-decomposers-and-the-soil#prop-g6-decomposers-and-soil-speed)’s conditions-rule, measured in gas.

## 46.4 Exercises

**Exercise 46.1 ★.**

Define [respiration](#def-g7-what-is-respiration-respiration), and distinguish it from [breathing](#def-g7-what-is-respiration-respiration).

**Solution of Exercise 46.1.**

[Respiration](#def-g7-what-is-respiration-respiration) is the gas exchange by which a [living thing](https://one-course.com/books/biology/1/en/chapter/37-exploring-our-environment#def-g6-exploring-our-environment-components) takes [oxygen](#def-g7-what-is-respiration-respiration) from its surroundings and releases [carbon dioxide](#def-g7-what-is-respiration-respiration). [Breathing](https://one-course.com/books/biology/1/en/chapter/26-breathing#def-g4-breathing-movements) is only the chest’s visible pumping movements — one way of serving the exchange; the exchange itself runs in every living [cell](https://one-course.com/books/biology/1/en/chapter/29-a-first-look-at-cells#def-g5-first-look-at-cells-cell).

**Exercise 46.2 ★.**

Name the two bench tests that reveal [respiration](#def-g7-what-is-respiration-respiration), and what each shows.

**Solution of Exercise 46.2.**

An [oxygen](#def-g7-what-is-respiration-respiration) probe in a closed container — shows the [oxygen](#def-g7-what-is-respiration-respiration) level falling; and [limewater](#prop-g7-what-is-respiration-shown) — a clear liquid that turns milky when [carbon dioxide](#def-g7-what-is-respiration-respiration) passes through it.

**Exercise 46.3 ★.**

Why does every [respiration](#def-g7-what-is-respiration-respiration) experiment need a lifeless control container?

**Solution of Exercise 46.3.**

To prove the change comes from the living subject and not from the container, the day’s warmth or the [limewater](#prop-g7-what-is-respiration-shown) itself: the fair test’s twin, with life the one difference.

**Exercise 46.4 ★.**

What is the point of [respiration](#def-g7-what-is-respiration-respiration), by [Proposition 46.5](#prop-g7-what-is-respiration-power)? What is [carbon dioxide](#def-g7-what-is-respiration-respiration), in that account?

**Solution of Exercise 46.4.**

[Energy](https://one-course.com/books/biology/1/en/chapter/18-a-balanced-diet#prop-g3-balanced-diet-jobs): in every [cell](https://one-course.com/books/biology/1/en/chapter/29-a-first-look-at-cells#def-g5-first-look-at-cells-cell), [nutrients](https://one-course.com/books/biology/1/en/chapter/25-the-journey-of-food#def-g4-journey-of-food-digestion) are slowly burned with the [oxygen](#def-g7-what-is-respiration-respiration), releasing their [energy](https://one-course.com/books/biology/1/en/chapter/18-a-balanced-diet#prop-g3-balanced-diet-jobs) for the [cell](https://one-course.com/books/biology/1/en/chapter/29-a-first-look-at-cells#def-g5-first-look-at-cells-cell)’s work. [Carbon dioxide](#def-g7-what-is-respiration-respiration) is the burnt-out remainder, carted away.

**Exercise 46.5 ★.**

List five very different [living things](https://one-course.com/books/biology/1/en/chapter/37-exploring-our-environment#def-g6-exploring-our-environment-components) shown respiring in [Example 46.3](#ex-g7-what-is-respiration-gallery).

**Solution of Exercise 46.5.**

A mouse, a woodlouse, germinating peas, a mushroom, pond snails — and a spoonful of living [soil](https://one-course.com/books/biology/1/en/chapter/42-decomposers-and-the-soil#def-g6-decomposers-and-soil-soil).

**Exercise 46.6 ★.**

How can a [plant](https://one-course.com/books/biology/1/en/chapter/3-plants-around-us#def-g1-plants-around-us-plant) be shown to respire, given that daylight masks the effect?

**Solution of Exercise 46.6.**

Test it in the dark: with the light-driven manufacture stopped, the jar’s [oxygen](#def-g7-what-is-respiration-respiration) falls and [limewater](#prop-g7-what-is-respiration-shown) clouds — [respiration](#def-g7-what-is-respiration-respiration) unmasked.

**Exercise 46.7 ★★.**

Give two honest likenesses and two honest differences between a candle’s burning and 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 [respiration](#def-g7-what-is-respiration-respiration).

**Solution of Exercise 46.7.**

Likenesses: both consume [oxygen](#def-g7-what-is-respiration-respiration) and release [carbon dioxide](#def-g7-what-is-respiration-respiration); both release the fuel’s [energy](https://one-course.com/books/biology/1/en/chapter/18-a-balanced-diet#prop-g3-balanced-diet-jobs). Differences: the [cell](https://one-course.com/books/biology/1/en/chapter/29-a-first-look-at-cells#def-g5-first-look-at-cells-cell)’s burning is slow and flameless, in thousands of small steps; and its [energy](https://one-course.com/books/biology/1/en/chapter/18-a-balanced-diet#prop-g3-balanced-diet-jobs) is captured for work instead of lost as [light](https://one-course.com/books/biology/1/en/chapter/37-exploring-our-environment#def-g6-exploring-our-environment-conditions) and heat all at once.

**Exercise 46.8 ★★.**

Rank by [respiration](#def-g7-what-is-respiration-respiration) rate, with reasons: a dry pea, a germinating pea, a sprinting child, a reading child.

**Solution of Exercise 46.8.**

Sprinting child (hard muscular work) $>$ reading child (the body’s quiet standing charge) $>$ germinating pea (building fast, but small) $>$ dry pea (dormant — [respiration](#def-g7-what-is-respiration-respiration) idling near zero). Rate follows work.

**Exercise 46.9 ★★.**

A sealed jar of sprouting peas goes overnight; a candle lowered in next morning goes straight out. Explain with this chapter — and say what the [limewater](#prop-g7-what-is-respiration-shown) trap would have shown meanwhile.

**Solution of Exercise 46.9.**

All night the sprouting peas’ [respiration](#def-g7-what-is-respiration-respiration) consumed the jar’s [oxygen](#def-g7-what-is-respiration-respiration) and released [carbon dioxide](#def-g7-what-is-respiration-respiration); by morning too little [oxygen](#def-g7-what-is-respiration-respiration) remains to keep a flame alight. The [limewater](#prop-g7-what-is-respiration-shown) would have clouded steadily through the night.

**Exercise 46.10 ★★.**

Design, by [Method 46.9](#met-g7-what-is-respiration-test), the experiment for: “living [soil](https://one-course.com/books/biology/1/en/chapter/42-decomposers-and-the-soil#def-g6-decomposers-and-soil-soil) respires; baked lifeless [soil](https://one-course.com/books/biology/1/en/chapter/42-decomposers-and-the-soil#def-g6-decomposers-and-soil-soil) does not.”

**Solution of Exercise 46.10.**

Two containers with probes and [limewater](#prop-g7-what-is-respiration-shown) traps: one with fresh living [soil](https://one-course.com/books/biology/1/en/chapter/42-decomposers-and-the-soil#def-g6-decomposers-and-soil-soil), one with the same [soil](https://one-course.com/books/biology/1/en/chapter/42-decomposers-and-the-soil#def-g6-decomposers-and-soil-soil) baked lifeless — the one difference. If the living jar’s [oxygen](#def-g7-what-is-respiration-respiration) falls and its [limewater](#prop-g7-what-is-respiration-shown) clouds while the baked twin stays unchanged, the [soil](https://one-course.com/books/biology/1/en/chapter/42-decomposers-and-the-soil#def-g6-decomposers-and-soil-soil)’s life did it.

**Exercise 46.11 ★★.**

Why does a grain store’s manager fear damp grain heaps warming by themselves? Connect [Example 46.7](#ex-g7-what-is-respiration-demand) and the compost heap’s warmth ([Example 42.7](https://one-course.com/books/biology/1/en/chapter/42-decomposers-and-the-soil#ex-g6-decomposers-and-soil-compost)).

**Solution of Exercise 46.11.**

Damp grain wakes: [germination](https://one-course.com/books/biology/1/en/chapter/9-from-seed-to-plant#def-g2-from-seed-to-plant-germination) begins, and [respiration](#def-g7-what-is-respiration-respiration) rises from a whisper toward the sprouting pea’s pace — billions of grains burning their stores at once, heating the heap like the compost’s working crews. Warmth speeds the work further: a damp heap can heat itself toward spoilage. Dry grain [sleeps](https://one-course.com/books/biology/1/en/chapter/6-healthy-habits#prop-g1-healthy-habits-needs) cold; damp grain is a slow furnace.

**Exercise 46.12 ★★★.**

“[Breathing](https://one-course.com/books/biology/1/en/chapter/26-breathing#def-g4-breathing-movements) is behavior; [respiration](#def-g7-what-is-respiration-respiration) is chemistry; the first serves the second.” Defend each clause with one observation from this chapter or [Chapter 26](https://one-course.com/books/biology/1/en/chapter/26-breathing#ch-g4-breathing).

**Solution of Exercise 46.12.**

Behavior: [breathing](#def-g7-what-is-respiration-respiration) can be watched — the chest’s movements, fifteen times a minute ([Example 26.2](https://one-course.com/books/biology/1/en/chapter/26-breathing#ex-g4-breathing-watch)). Chemistry: [respiration](#def-g7-what-is-respiration-respiration) runs in things with no chest at all — peas, mushrooms, [soil](https://one-course.com/books/biology/1/en/chapter/42-decomposers-and-the-soil#def-g6-decomposers-and-soil-soil) — detected only by gas tests. Service: [breathing](#def-g7-what-is-respiration-respiration) exists to renew the [lungs](https://one-course.com/books/biology/1/en/chapter/26-breathing#def-g4-breathing-organs)’ air so the gas swap can continue — racing exactly when the [cells](https://one-course.com/books/biology/1/en/chapter/29-a-first-look-at-cells#def-g5-first-look-at-cells-cell)’ burning races ([Example 26.6](https://one-course.com/books/biology/1/en/chapter/26-breathing#ex-g4-breathing-running)).

## 46.5 Problem: The Sealed Jars

**Problem 46.1.**

Weekend problem — six jars, two mysteries, one gas swap

For the science fair, the class prepares six sealed jars, each with an [oxygen](#def-g7-what-is-respiration-respiration) probe and a [limewater](#prop-g7-what-is-respiration-shown) trap: A — pebbles; B — dry peas; C — germinating peas; D — a mouse (with food, water, and for a few hours only, under the teacher’s watch); E — a green [plant](https://one-course.com/books/biology/1/en/chapter/3-plants-around-us#def-g1-plants-around-us-plant) in the [light](https://one-course.com/books/biology/1/en/chapter/37-exploring-our-environment#def-g6-exploring-our-environment-conditions); F — the same kind of [plant](https://one-course.com/books/biology/1/en/chapter/3-plants-around-us#def-g1-plants-around-us-plant) in a dark box.

**Part I — Predictions.**

1. Predict A’s readings, and state A’s job in the experiment.
2. Predict B and C, and explain the difference although both jars hold “the same” peas.
3. Predict D, and say why the teacher limits the hours.
4. E and F hold identical [plants](https://one-course.com/books/biology/1/en/chapter/3-plants-around-us#def-g1-plants-around-us-plant) . Predict each jar’s [oxygen](#def-g7-what-is-respiration-respiration) trend, and reconcile the difference using [Remark 46.4](#rem-g7-what-is-respiration-plants) .

**Part II — Results and readings.**

5. The morning’s data match the predictions — except a classmate is amazed that F’s [plant](https://one-course.com/books/biology/1/en/chapter/3-plants-around-us#def-g1-plants-around-us-plant) “breathes like an [animal](https://one-course.com/books/biology/1/en/chapter/2-animals-around-us#def-g1-animals-around-us-animal) ”. Set out what F actually shows, and what E hides.
6. C’s [oxygen](#def-g7-what-is-respiration-respiration) fell three times faster than B’s per gram of peas. Translate the factor of three into [Example 46.7](#ex-g7-what-is-respiration-demand) ’s terms.
7. D’s [limewater](#prop-g7-what-is-respiration-shown) clouded fastest of all. Give the chain — from the mouse’s warm, moving body to the milky liquid — in four steps.
8. Name the single conclusion all of B, C, D and F support, in one sentence beginning “Every [living thing](https://one-course.com/books/biology/1/en/chapter/37-exploring-our-environment#def-g6-exploring-our-environment-components) …”.

**Part III — Pressing further.**

9. A seventh jar is proposed: mushroom slices. Predict its readings, and say which kingdom-level point of [Example 46.3](#ex-g7-what-is-respiration-gallery) it would add.
10. The fair’s visitors ask why jar C matters to farmers. Answer with the granary of [Exercise 46.11](#exo-g7-what-is-respiration-11) .
11. An eighth jar: pond water with its mud. The [oxygen](#def-g7-what-is-respiration-respiration) falls overnight. Who in the jar is respiring, and why does the finding matter for [Chapter 48](https://one-course.com/books/biology/1/en/chapter/48-oxygen-in-the-water#ch-g7-oxygen-in-the-water) ’s question?
12. Close the fair’s poster with the chapter’s distinction: which jars showed *[breathing](#def-g7-what-is-respiration-respiration)* , and which showed *[respiration](#def-g7-what-is-respiration-respiration)* ? (Careful — one word covers them all.)

**Solution of Problem 46.1.**

**1.** No change: [oxygen](#def-g7-what-is-respiration-respiration) steady, [limewater](#prop-g7-what-is-respiration-shown) clear. A is the lifeless control — the stillness every other jar is read against.

**2.** B: barely measurable change — dry peas are dormant, [respiration](#def-g7-what-is-respiration-respiration) idling. C: clear [oxygen](#def-g7-what-is-respiration-respiration) fall and clouding — [germination](https://one-course.com/books/biology/1/en/chapter/9-from-seed-to-plant#def-g2-from-seed-to-plant-germination) is full-speed building, and the work is paid in [respiration](#def-g7-what-is-respiration-respiration).

**3.** D: the fastest fall and clouding of all — a warm, moving mammal burns hard. The hours are limited because the mouse is consuming its jar’s [oxygen](#def-g7-what-is-respiration-respiration); the experiment must end long before the air runs short.

**4.** E: [oxygen](#def-g7-what-is-respiration-respiration) steady or rising — the lit [plant](https://one-course.com/books/biology/1/en/chapter/3-plants-around-us#def-g1-plants-around-us-plant)’s manufacture takes in [carbon dioxide](#def-g7-what-is-respiration-respiration) and releases more [oxygen](#def-g7-what-is-respiration-respiration) than its [respiration](#def-g7-what-is-respiration-respiration) uses. F: [oxygen](#def-g7-what-is-respiration-respiration) falling, [limewater](#prop-g7-what-is-respiration-shown) clouding — in the dark the manufacture stops and [respiration](#def-g7-what-is-respiration-respiration), never stopped, shows plain.

**5.** F shows that the [plant](https://one-course.com/books/biology/1/en/chapter/3-plants-around-us#def-g1-plants-around-us-plant) respires always — [oxygen](#def-g7-what-is-respiration-respiration) in, [carbon dioxide](#def-g7-what-is-respiration-respiration) out, like the mouse. E hides the same [respiration](#def-g7-what-is-respiration-respiration) under the bigger daytime trade: the manufacture’s intake and output swamp it. Together the twins separate the two exchanges.

**6.** The germinating pea is working three times as hard per gram — building [roots](https://one-course.com/books/biology/1/en/chapter/3-plants-around-us#def-g1-plants-around-us-parts) and shoot at full pace — and [respiration](#def-g7-what-is-respiration-respiration) is the engine note of that work.

**7.** The mouse’s [muscles](https://one-course.com/books/biology/1/en/chapter/17-bones-and-muscles#def-g3-bones-and-muscles-muscle) and warm body burn [nutrients](https://one-course.com/books/biology/1/en/chapter/25-the-journey-of-food#def-g4-journey-of-food-digestion) with [oxygen](#def-g7-what-is-respiration-respiration); the burning releases [carbon dioxide](#def-g7-what-is-respiration-respiration) into the jar’s air; the trapped air passes through the [limewater](#prop-g7-what-is-respiration-shown); the [carbon dioxide](#def-g7-what-is-respiration-respiration) turns it milky.

**8.** “Every [living thing](https://one-course.com/books/biology/1/en/chapter/37-exploring-our-environment#def-g6-exploring-our-environment-components) respires — [animal](https://one-course.com/books/biology/1/en/chapter/2-animals-around-us#def-g1-animals-around-us-animal), [plant](https://one-course.com/books/biology/1/en/chapter/3-plants-around-us#def-g1-plants-around-us-plant), [seed](https://one-course.com/books/biology/1/en/chapter/9-from-seed-to-plant#def-g2-from-seed-to-plant-seed) awake or barely asleep — taking [oxygen](#def-g7-what-is-respiration-respiration) and releasing [carbon dioxide](#def-g7-what-is-respiration-respiration).”

**9.** [Oxygen](#def-g7-what-is-respiration-respiration) falling, [limewater](#prop-g7-what-is-respiration-shown) clouding — the mushroom respires. It adds that the rule covers [fungi](https://one-course.com/books/biology/1/en/chapter/42-decomposers-and-the-soil#def-g6-decomposers-and-soil-decomposers) too: neither [plant](https://one-course.com/books/biology/1/en/chapter/3-plants-around-us#def-g1-plants-around-us-plant) nor [animal](https://one-course.com/books/biology/1/en/chapter/2-animals-around-us#def-g1-animals-around-us-animal), and no exception.

**10.** Because a granary is jar C at warehouse scale: grain kept damp begins germinating and respiring hard, heating and spoiling the store — the manager’s dryness rules are [respiration](#def-g7-what-is-respiration-respiration) control.

**11.** Everything in it: the pond snails and small [animals](https://one-course.com/books/biology/1/en/chapter/2-animals-around-us#def-g1-animals-around-us-animal), the mud’s [decomposers](https://one-course.com/books/biology/1/en/chapter/42-decomposers-and-the-soil#def-g6-decomposers-and-soil-decomposers), the [plants](https://one-course.com/books/biology/1/en/chapter/3-plants-around-us#def-g1-plants-around-us-plant) and green single [cells](https://one-course.com/books/biology/1/en/chapter/29-a-first-look-at-cells#def-g5-first-look-at-cells-cell) in their dark hours. It matters because the pond’s inhabitants all draw on one small dissolved [oxygen](#def-g7-what-is-respiration-respiration) stock — the economy the next chapters open.

**12.** Only D — the mouse — showed [breathing](#def-g7-what-is-respiration-respiration): visible chest movements serving its gas swap. Every jar with life in it showed [respiration](#def-g7-what-is-respiration-respiration): B faintly, C, D, F plainly, E masked by daylight manufacture but respiring all the same.