Living Things Have Cells - Middle School Life Science

What is the correct conclusion if you observe many repeating, membrane-bounded units in a leaf sample?

The leaf is composed of cells. Membrane-bounded units are cells, confirming the tissue is living.
What is the best reason to make a wet mount when viewing cells under a light microscope?

To keep the specimen hydrated and improve viewing clarity. Water prevents drying and helps light pass through the specimen.
Which practice best ensures a fair test when comparing two microscope slides of different tissues?

Keep magnification and lighting the same for both slides. Controlling variables ensures differences are due to tissue type only.
Which observation best distinguishes cells from nonliving crystals under a microscope?

Cells show membrane boundaries and internal structures like nuclei. Living cells have membranes and organelles; crystals lack these features.
What cell structure forms the outer boundary of both plant and animal cells?

Cell membrane. This flexible barrier controls what enters and exits all cells.
Which tool is most appropriate for collecting evidence that cells exist in a tissue sample?

A microscope. Cells are too small to see with the naked eye, requiring magnification.
Which observation best distinguishes a plant cell from a cheek cell in microscope evidence?

A rigid cell wall forming box-like shapes. Animal cells lack walls, so they appear round or irregular.
Which step should you do first when focusing a microscope to find cells on a slide?

Start on lowest power and use the coarse focus knob. Low power gives widest field of view; coarse knob moves stage quickly.
Which focusing knob should you use at high power to avoid crashing the lens into the slide?

Fine adjustment knob. Fine adjustment makes small movements to prevent lens-slide contact.
What is the correct term for a group of similar cells working together, often sampled in investigations?

Tissue. Cells organize into tissues for specialized functions.
What is the cell theory statement that supports the claim that living things are made of cells?

All living things are composed of one or more cells. This fundamental principle states all organisms consist of cellular units.
Find the correct conclusion: You observe no cells at high power; what is the most likely investigation error?

The specimen was not centered/focused at low power first. High power has a narrow field; specimens must be centered at low power first.
What structure in plant cells provides strong evidence of cellular organization by forming box-like boundaries?

Cell wall. Plant cell walls create visible rectangular compartments showing cellular structure.
What is the best control condition when testing whether stain improves visibility of nuclei?

An unstained slide prepared the same way. Controls differ only in the tested variable, keeping all else constant.
What is the best operational definition of a cell for a microscope investigation?

The smallest unit of life visible as a bounded structure under a microscope. Cells appear as distinct compartments with clear boundaries when magnified.
Which investigation result best supports cell theory: all samples show cells or only one sample shows cells?

All living samples show cells. Universal presence of cells confirms all life is cellular.
What organelle contains green pigment and is commonly observed in plant cells during investigations?

Chloroplast. Chloroplasts contain chlorophyll for photosynthesis in plant cells.
What is one controlled variable when comparing cell observations across multiple slides?

The magnification used. Controlled variables must stay constant to ensure fair comparison.
What is the independent variable in an investigation comparing plant and animal slides?

The type of specimen (plant versus animal). Independent variables are what you deliberately change or compare.
Which stain is commonly used to increase contrast in plant tissue such as onion cells?

Iodine solution (Lugol's iodine). Iodine stains cellulose and starch, enhancing plant cell visibility.
Which observation is the strongest evidence that a sample is living tissue: crystals or cells?

Cells. Only living things have cells; crystals are non-living mineral structures.
What is total magnification if the ocular lens is $10\times$ and the objective is $4\times$ ?

$40\times$ . Multiply ocular ( $10\times$ ) by objective ( $4\times$ ) magnification.
Which cell structure is commonly visible as a darker, round region in stained animal cells?

Nucleus. The nucleus contains DNA and appears dark when stained.
What is total magnification if the ocular lens is $10\times$ and the objective is $40\times$ ?

$400\times$ . Total magnification equals ocular lens times objective lens magnification.
What is the correct order of magnification steps when focusing a light microscope?

Start low power, focus, then increase to higher power. This sequence prevents losing the specimen when switching magnifications.
What is the correct term for a single-celled living thing that can be observed as one cell under a microscope?

Unicellular organism. Examples include bacteria and amoebas that live as single cells.
Which visible feature best supports that cheek tissue is made of cells when viewed under a microscope?

Many repeated membrane-bound units (individual cells). Multiple distinct cellular units prove tissue is composed of individual cells.
What is the cell theory statement that links cells to the structure of living things?

All living things are made of one or more cells. This is the first principle of cell theory, established by Schleiden and Schwann.
What structure is present in plant cells but not in typical animal cells and supports evidence of cells?

A cell wall. Cell walls provide rigid support and protection unique to plants.
Identify the dependent variable in an investigation testing whether stain improves cell visibility.

Visibility/contrast of cell structures under the microscope. The dependent variable is what you measure in response to the treatment.
What is the correct definition of a cell in life science?

The smallest unit of life that carries out life processes. Cells perform all functions necessary for life, from metabolism to reproduction.
Which stain is commonly used to make cheek cell nuclei easier to see in a classroom investigation?

Methylene blue. This blue dye binds to nucleic acids, highlighting nuclear structures.
Which evidence most directly supports that an onion epidermis is living: cell wall, nucleus, or starch grains?

Nucleus. The nucleus controls cell activities and indicates living cellular function.
What is the correct evidence-based conclusion after observing many similar units with membranes in tissue?

The tissue is composed of cells. Repeated membrane-bound units are the defining characteristic of cellular tissue.
What is the main purpose of staining a microscope slide in a cell investigation?

To increase contrast so cell structures are easier to see. Stains bind to cell parts, making transparent structures visible.
Which microscope part should you use first to locate a specimen: low power or high power?

Low power (lowest magnification). Starting with low magnification provides a wider field of view to find specimens.
What is the correct order of microscope magnifications from lowest to highest power?

Scanning, low, high. Scanning (4x) provides overview, low (10x) locates cells, high (40x) shows details.
Identify the best evidence-based claim if onion cells and cheek cells both show boundaries and nuclei.

Both plant and animal tissues are made of cells. Observing cells in different organisms supports cell theory universality.
Identify the independent variable in an investigation comparing stained vs unstained cheek cell slides.

Presence of stain (stained vs unstained). The independent variable is what the experimenter changes (stain/no stain).

Study these flashcards