Body Organization, Transport & Movement — Chapter Practice, Grade 7

Five focused units, a three-session investigation, chapter review, and chapter quiz.

Problem 1

Why is the heart an organ rather than only one tissue?
Answer and explanation

It combines several tissue types that contribute different roles to pumping and maintaining its structure.

Problem 2

What should a body-system arrow label identify?
Answer and explanation

The material, information, or interaction represented, such as oxygen transport, rather than an unexplained connection.

Problem 3

Why can cells with similar genetic information have different roles?
Answer and explanation

They use that information differently and develop specialized structures and activities suited to different functions.

Problem 4

Does lacking organs make a bacterium nonliving?
Answer and explanation

No. A single cell can function as a living organism without organs.

Problem 5

Illustrative model: digestion makes small food molecules available; an intestinal surface absorbs them; circulation transports them; muscle cells use materials and energy during contraction. Identify relevant levels of organization and explain why no listed system independently completes the entire process.
Answer and explanation

The digestive system processes and absorbs food molecules, the circulatory system transports them, and muscle cells use them in cellular work. Organs contain interacting tissues, and tissues contain specialized cells. The pathway connects levels and systems; neither an intestine nor a muscle cell independently performs every step. The diagram is a selected model, not a complete anatomical description.

Identify digestive and circulatory organ-system roles.

Locate exchange surfaces within organs and tissues.

Connect transport to cellular use.

Response criteria

  • Explain the relevant biological process accurately.
  • Use the supplied evidence and show calculation steps with units where needed.
  • Connect a labeled model or mechanism with the claim.
  • State an assumption, evidence limitation, or useful next observation.

Problem 6

A diagram includes the heart but no vessels. What important relationship is missing?
Answer and explanation

The transport network connecting the heart with tissues is missing. Pumping must be connected to pathways and exchanges to explain delivery and return.

Response criteria

  • Explain the relevant biological process accurately.
  • Use the supplied evidence and show calculation steps with units where needed.
  • Connect a labeled model or mechanism with the claim.
  • State an assumption, evidence limitation, or useful next observation.

Problem 7

Which order moves from a smaller organizational level to a larger one?
  1. Organ→cell→tissue
  2. Cell→tissue→organ
  3. System→cell→organ
  4. Tissue→organism→cell
Answer and explanation

Cell→tissue→organ

Cells contribute to tissues, and multiple tissue types contribute to organs.

Problem 8

Why should a transport diagram include both delivery and exchange?
Answer and explanation

Materials must move to tissues and cross appropriate surfaces. Naming a pump without routes and exchanges leaves the mechanism incomplete.

Problem 9

Why is grinding alone not complete chemical digestion?
Answer and explanation

It changes piece size and surface area but does not necessarily break the relevant chemical bonds into absorbable components.

Problem 10

Why is the stomach-only model incomplete?
Answer and explanation

Processing, transport, digestive contributions, and much absorption occur through several organs, especially the small intestine.

Problem 11

How does more exchange area help the absorption model?
Answer and explanation

It provides more surface across which materials can move under suitable conditions, rather than making food molecules appear from nothing.

Problem 12

Does absorbing sugar mean all its energy has already been used?
Answer and explanation

No. Absorption makes material available for transport; later cellular processes transfer its stored energy or use its matter.

Problem 13

Illustrative comparison: Sample A remains in one large piece; equal-mass Sample B is divided into small pieces. Both experience the same stated enzyme conditions; B breaks down faster. Explain a surface-area mechanism, distinguish observation from inference, and connect digestion with absorption.
Answer and explanation

Faster breakdown in B is consistent with increased exposed surface for enzyme contact under the stated conditions. The result is evidence about breakdown rate, not proof that absorption or energy use has already occurred. Further measurements could check the products and their passage across an exchange surface. Other changed conditions would weaken the isolated surface-area explanation.

Identify comparable mass and conditions.

Connect smaller pieces with more exposed surface.

Separate breakdown from later boundary crossing.

Response criteria

  • Explain the relevant biological process accurately.
  • Use the supplied evidence and show calculation steps with units where needed.
  • Connect a labeled model or mechanism with the claim.
  • State an assumption, evidence limitation, or useful next observation.

Problem 14

A diagram says food energy is created in the stomach. Correct it.
Answer and explanation

Food already contains chemical energy. Digestion processes molecules and absorption makes products available; cellular processes transfer energy into usable forms rather than create it.

Response criteria

  • Explain the relevant biological process accurately.
  • Use the supplied evidence and show calculation steps with units where needed.
  • Connect a labeled model or mechanism with the claim.
  • State an assumption, evidence limitation, or useful next observation.

Problem 15

Which describes absorption?
  1. Food crosses the intestinal lining into transport
  2. Chewing reduces piece size
  3. A diagram label gets larger
  4. All energy is created
Answer and explanation

Food crosses the intestinal lining into transport

Absorption is boundary crossing; chewing is mechanical processing.

Problem 16

Why can equal masses in smaller pieces be processed faster under matched conditions?
Answer and explanation

Smaller pieces can provide more exposed surface for contact. The explanation requires comparable materials and reaction conditions.

Problem 17

Is exhaled air pure carbon dioxide?
Answer and explanation

No. It remains a mixture including nitrogen, oxygen, carbon dioxide, and water vapor in different proportions.

Problem 18

Why are thin surfaces relevant?
Answer and explanation

They shorten the distance materials must cross and support exchange under suitable conditions.

Problem 19

Why is “every artery carries oxygen-rich blood” inaccurate?
Answer and explanation

Arteries are defined by direction from the heart; the lung-circuit artery carries blood toward gas exchange before it becomes oxygen-rich.

Problem 20

Why is inhalation alone not the whole oxygen pathway?
Answer and explanation

Oxygen must cross exchange surfaces, travel in blood, and reach cells; inhalation is only one step.

Problem 21

Illustrative draft: air enters lungs; oxygen then moves directly from lungs to every muscle cell; no vessels or heart are drawn. Repair the pathway, label gas exchanges, and distinguish the pathway from cellular respiration.
Answer and explanation

Oxygen enters lung air spaces, crosses into blood, is transported through the heart and vessels, and reaches tissues by exchange. Carbon dioxide can follow a return pathway toward lung release. Cellular respiration occurs in cells and uses food and oxygen in the aerobic model; it is not simply the act of breathing. The diagram is simplified and does not show every anatomical detail.

Add lung exchange into blood.

Add heart and transport vessels.

Add tissue exchange and cellular use.

Response criteria

  • Explain the relevant biological process accurately.
  • Use the supplied evidence and show calculation steps with units where needed.
  • Connect a labeled model or mechanism with the claim.
  • State an assumption, evidence limitation, or useful next observation.

Problem 22

A vessel carries blood from the heart toward the lungs. Is it an artery or vein under the directional definition?
Answer and explanation

It is an artery because it carries blood away from the heart, regardless of its oxygen content before lung exchange.

Response criteria

  • Explain the relevant biological process accurately.
  • Use the supplied evidence and show calculation steps with units where needed.
  • Connect a labeled model or mechanism with the claim.
  • State an assumption, evidence limitation, or useful next observation.

Problem 23

Which structure supplies the pumping action in circulation?
  1. Heart
  2. Food molecule
  3. Lung air alone
  4. Microscope lens
Answer and explanation

Heart

The heart pumps blood; lungs supply gas exchange and ventilation functions.

Problem 24

Why do respiratory and circulatory systems both matter to oxygen delivery?
Answer and explanation

Respiration-related surfaces exchange gases, while circulation moves oxygen-containing blood toward tissues. Cells also require exchange at the destination.

Problem 25

Why is listing bones alone not a structure-function explanation?
Answer and explanation

It identifies parts but does not explain how their arrangement contributes to support, protection, or movement.

Problem 26

Why are opposing muscle actions useful?
Answer and explanation

They allow movement in different directions because a contracting muscle pulls rather than actively pushes along the same attachment.

Problem 27

Can a paper lever determine someone’s safe lifting limit?
Answer and explanation

No. It omits biological and individual factors and is only a selected relationship model.

Problem 28

Why does movement depend on more than muscles?
Answer and explanation

Coordination, support, exchange, and cellular energy processes interact with muscle contraction.

Problem 29

Illustrative paper hinge: String A bends a joint when pulled; String B straightens it when pulled. The hinge and attachments are unchanged. Explain the represented mechanism, connect it with muscles, and state two limits of the analogy.
Answer and explanation

The strings represent pulls that can rotate the hinge in opposite directions, analogous to coordinated muscle actions. The model does not show nerves, living tissue, energy transfers, changing forces, or exact anatomical scale. It illustrates a mechanical relationship without establishing individual performance or health.

Identify the hinge as a turning point.

Connect each pull with an opposing action.

State missing tissues and cellular processes.

Response criteria

  • Explain the relevant biological process accurately.
  • Use the supplied evidence and show calculation steps with units where needed.
  • Connect a labeled model or mechanism with the claim.
  • State an assumption, evidence limitation, or useful next observation.

Problem 30

A diagram says one muscle contracts to bend and then pushes to straighten a joint. What needs correction?
Answer and explanation

Skeletal muscle contraction produces a pull. Opposing muscle action or another force can restore the movement; relaxation is not an active push along the same attachment.

Response criteria

  • Explain the relevant biological process accurately.
  • Use the supplied evidence and show calculation steps with units where needed.
  • Connect a labeled model or mechanism with the claim.
  • State an assumption, evidence limitation, or useful next observation.

Problem 31

What does a tendon connect in this model?
  1. Muscle and bone
  2. Only two air spaces
  3. A scale bar and nucleus
  4. Food and soil
Answer and explanation

Muscle and bone

Tendons transmit muscle forces to bones in the studied arrangement.

Problem 32

Name one omitted process in a paper joint model and why it matters.
Answer and explanation

Nervous coordination is omitted; actual movement depends on signals controlling muscle actions. Cellular energy processes and living tissue properties are other valid examples.

Problem 33

Why is excretion not identical to eliminating unabsorbed food?
Answer and explanation

Excretion removes wastes produced by metabolism; unabsorbed food is material that did not enter those cellular pathways.

Problem 34

Does entering a filtrate guarantee a substance leaves in urine?
Answer and explanation

No. Some substances are returned to blood during subsequent processing.

Problem 35

Why must a model’s interval be stated?
Answer and explanation

Input and output amounts are comparable only when they refer to the same period and boundary.

Problem 36

Does regulation require an unchanging number at every instant?
Answer and explanation

No. Regulated conditions can vary within ranges while feedback and exchanges help maintain function.

Problem 37

Illustrative processing record for one model interval: 100 water units enter a filtrate; 96 return to the blood pathway; 4 leave through the urine pathway. Check the model balance, calculate the returned fraction, and explain why it is not a real intake recommendation.
Answer and explanation

The model balances its 100 input units with 100 output units, and 96% return through the stated pathway. It represents selective processing rather than all filtrate being excreted. The numbers are invented for one boundary and interval; they do not describe a person’s whole water budget or prescribe fluid intake.

Add outputs: 96+4=100.

Calculate returned share: 96/100×100%.

Identify the simplified boundary and invented units.

Response criteria

  • Explain the relevant biological process accurately.
  • Use the supplied evidence and show calculation steps with units where needed.
  • Connect a labeled model or mechanism with the claim.
  • State an assumption, evidence limitation, or useful next observation.

Problem 38

A draft calls kidney processing a digestive absorption step. Correct the system relationship.
Answer and explanation

Kidneys process materials from blood and regulate excretion and balance. Digestive absorption moves food-related materials across the intestinal lining; circulation connects the systems but the steps differ.

Response criteria

  • Explain the relevant biological process accurately.
  • Use the supplied evidence and show calculation steps with units where needed.
  • Connect a labeled model or mechanism with the claim.
  • State an assumption, evidence limitation, or useful next observation.

Problem 39

Which material can be excreted through lungs?
  1. Carbon dioxide
  2. Every chromosome
  3. Whole bone
  4. Every unabsorbed food piece
Answer and explanation

Carbon dioxide

Carbon dioxide produced in cellular metabolism can be transported to lungs and released.

Problem 40

A model returns 45 of 50 filtered units. What percent returns?
Answer and explanation

90 %

45/50×100=90%, for the invented model.

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