Science 7A / 7B

Unit 1 Study Guide: Single-Celled Organisms & Cell Structure

Test: Friday, September 4, 2026 · Microscope skills, four organisms, organelles, reproduction.

This page is for studying, it is not the test and nothing on it is graded. Content matches exactly what was reviewed in class; the practice questions below are new, written to match, not copies of any quiz.

The Seven Basic Functions of Life

Nutrition, respiration, excretion, sensitivity, movement, growth, reproduction, plus homeostasis holding them all together.

nutrition	Getting energy/nutrients, e.g. Amoeba's phagocytosis or Euglena/Volvox's photosynthesis.
respiration	Releasing energy stored in food. Not breathing with lungs, every single cell does this.
excretion	Removing waste, e.g. the contractile vacuole pumping out excess water.
sensitivity	Detecting and responding to the environment, e.g. Euglena's eyespot responding to light.
movement	Changing position or moving a body part, e.g. Amoeba flowing forward with a pseudopod, or Paramecium beating its cilia.
growth	Increasing in size or, for a single-celled organism, building the materials needed before it divides.
reproduction	Producing offspring; can happen asexually (one parent) or sexually (two parents), see the reproduction section below.
homeostasis	Keeping internal conditions stable enough for all the other functions to keep happening.

Try it: Name the basic function of life a contractile vacuole performs.

Excretion, it removes excess water (waste) from the cell. Without it, water constantly leaking into the cell from its watery environment would build up and eventually burst it.

Try it: Euglena swims toward a patch of sunlight. Which two basic functions does that single action involve?

Sensitivity (the eyespot detects the light's direction) and movement (the flagellum propels the cell toward it). Two structures, two different functions, working together.

The Four Organisms: Amoeba, Paramecium, Euglena, Volvox

Paramecium

Cilia (many short, hair-like structures) beat together for fast, controlled movement. Contractile vacuole pumps out excess water.

Amoeba

Pseudopods (temporary false feet) for movement and phagocytosis, surrounding and engulfing food. Contractile vacuole for water balance.

Euglena

Flagellum (single long whip-like structure) for swimming. Eyespot detects light direction. Chloroplasts: photosynthesizes AND takes in food.

Volvox

A colony of hundreds of individual flagellated cells, each still carrying out the full function list on its own. Daughter colonies form inside and are released, asexual reproduction.

pseudopod	A temporary, false foot formed when a cell like Amoeba extends part of its own body to move or feed.
phagocytosis	The process by which a cell surrounds and engulfs food, the way an Amoeba flows around a smaller organism and seals it inside.
cilia	Many short, hair-like structures on a cell, such as Paramecium, that beat together for fast, controlled movement.
flagellum	A single long, whip-like structure a cell, such as Euglena, uses to swim.
eyespot	A light-sensitive structure near the front of Euglena that detects the direction light is coming from, letting the cell respond by swimming toward it.
contractile vacuole	A structure in Amoeba and Paramecium that pumps out excess water to manage the cell's water balance.

Try it: Which of the four organisms can both photosynthesize and take in food?

Euglena. Its chloroplasts let it photosynthesize like a plant when light is available, but unlike a plant it can also take in food directly, giving it two nutrition strategies the other three organisms here don't combine.

Try it: Which structure lets Paramecium move quickly and in a coordinated way?

Cilia, many short hair-like structures beating together. A single flagellum (Euglena's structure) is one long whip; cilia are many short ones acting in unison, which is what gives Paramecium its fast, controlled movement compared to Euglena's steady swimming.

Try it: An Amoeba is observed engulfing a smaller organism by flowing around it completely. Name the structure and the process.

The structure is the pseudopod (the false foot doing the flowing and surrounding); the process is phagocytosis (engulfing food this way).

Try it: Both Amoeba and Paramecium have a contractile vacuole. What job does it do in both, and why do they need it at all?

In both organisms it performs excretion, pumping out excess water. They live in pond water, which is less concentrated than the inside of the cell, so water constantly seeps in; without a way to pump it back out, the cell would keep swelling and eventually burst.

Cell Organelles & Cell Types

Organelle	Function
Cell membrane	Controls what enters and exits the cell
Cell wall	Structure and support; plant and bacterial cells only, not animal cells or any of the four protists above
Nucleus	Holds genetic information, directs the cell; absent in bacterial cells
Mitochondria	Release energy from food; absent in bacterial cells
Chloroplasts	Make food using light; among the four organisms above, only Euglena and Volvox have them
Vacuoles	Store materials and manage water; the contractile vacuole is a specific water-balance example

Plant cell

Nucleus
Cell wall
Chloroplasts
Mitochondria

Animal cell

Nucleus
Mitochondria
No wall
No chloroplasts

Bacterial cell

No nucleus
No mitochondria
Has a cell wall (different kind)

Common mistake No organism on this unit's list has every organelle: none of the four protists has a true cell wall, chloroplasts belong only to Euglena and Volvox, and bacteria have no nucleus and no mitochondria, the one thing that sets bacterial cells apart from every other cell type here.

Try it: A cell has no nucleus and no mitochondria. What type of cell is it?

Bacterial. It's the only cell type on this list missing both. Every other cell type here, plant, animal, and every one of the four protists, has both a nucleus and mitochondria.

Try it: A cell has a nucleus, mitochondria, a cell wall, and chloroplasts. Plant, animal, or bacterial?

Plant. Only plant cells have all four of those together: animal cells lack a cell wall and chloroplasts, and bacterial cells lack a nucleus and mitochondria entirely.

Try it: Does Euglena, one of this unit's four protists, have a cell wall?

No. None of the four protists studied this unit (Amoeba, Paramecium, Euglena, Volvox) has a true cell wall, even though Euglena does have chloroplasts like a plant cell. Having chloroplasts and having a cell wall are two separate traits, and Euglena only has one of them.

Microscope Skills

total magnification	Eyepiece power × objective lens power.
start on low power	Always, it's easier to find the specimen with a wider field of view before switching to higher power.
wet mount order	Specimen and a drop of water on the slide first, then lower the coverslip at an angle (not dropped flat), to avoid trapping air bubbles.
identification	Name a specific visible structure to justify an ID, not just a general impression of shape. One field of view is not enough to finalize an identification.

Asexual vs. Sexual Reproduction

asexual reproduction	One parent, offspring genetically identical to it. Example: a Volvox daughter colony.
sexual reproduction	Two parents, offspring with genetic variation, a new combination of both parents' genetic information.
mutation	A rare copying error that can produce variation even with only one parent (asexual reproduction).

Try it: A Volvox daughter colony forms inside its parent and is released, genetically identical. Asexual or sexual?

Asexual, one parent, identical offspring. There's no second parent contributing genetic information, so nothing gets combined or varied, the daughter colony is a copy.

Try it: If asexual reproduction produces identical offspring, how can two Volvox colonies ever end up genetically different from each other?

Mutation. A rare copying error during asexual reproduction can introduce a genetic difference even with only one parent involved. It's the one way variation can appear without sexual reproduction's two-parent gene combination.

Start here: videos + interactive

Video: Plant & Animal Cells (Generation Genius) · covers the organelle comparison table above Video: Reproduction of Living Things (Generation Genius) · asexual vs. sexual, straight from the section above PRISM: Inside the Cell (plant & animal anatomy) PRISM: Eukaryotic Cell Biology Study Guide

Also on the site

Video: A drop of pond water (Britannica, Paramecia)

Kris Tyte, Math & Science 7 · East Voyager Academy of Charlotte
[email protected] · (704) 574-9605