Levels of Organization: Cells to Organ Systems — Practice · Grade 7 Science

Chapter: Body Organization, Transport & Movement

What this practice covers

By the end of Levels of Organization: Cells to Organ Systems you should be able to:

8 questions, written answer and multiple choice, each with a worked explanation.

Vocabulary used: tissue, organ, organ system, specialization, system boundary.

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.

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