Cell Theory
What are the three main ideas of cell theory?
1) All living things are made of cells. 2) Cells are the basic unit of structure and function. 3) All cells come from pre-existing cells
Who first observed cells using a microscope and gave them the name "cells"?
Robert Hooke observed cells in cork (1665).
If you see a tiny structure under a microscope with no nucleus, is it likely prokaryote or eukaryote? Explain in one short sentence.
Prokaryote — they do not have a nucleus.
What is a variation?
Variation = a difference among individuals (e.g., flower color differences).
What is the difference between prokaryotic and eukaryotic cells
Prokaryotic cells lack a nucleus; eukaryotic cells have a nucleus.
Which statement from cell theory explains where new cells come from?
"All cells come from pre-existing cells."
Which scientist concluded that all plants are made of cells?
Matthias Schleiden concluded plants are made of cells (1838).
A scientist finds that injured tissues heal by forming new cells. Which part of cell theory does this support?
It supports "cells come from pre-existing cells" because healing requires cell division.
How can a variation be an advantage for survival?
Advantage example: Dark-colored moths survive better on soot-dark trees when pollution is high.
Give one example of a unicellular organism and one example of a multicellular organism.
Unicellular: amoeba, bacteria, or yeast. Multicellular: human, tree, or frog.
Explain how cells are the basic unit of structure and function in living things. Explain your answer in one sentence.
Cells form the structures of organisms and perform life functions.
Which scientist concluded that all animals are made of cells?
Theodor Schwann concluded animals are made of cells (1839).
Explain in two sentences how knowing cells come from other cells helps scientists grow tissues in labs (tissue culture).
Cells divide and can be grown from samples because they originate from existing cells; scientists stimulate division and provide nutrients to culture tissues.
How can a variation be a disadvantage when environments change? Give one short example.
Disadvantage example: A bright-colored insect may be eaten more when predators increase.
List two features that prokaryotes and eukaryotes both share.
Both have cell membranes and genetic material (DNA); both carry out basic life processes.
Give an example of how cell theory shows the relationship between structure and function.
Example: Root hair cells have large surface area to absorb water — their shape supports function.
Name the scientist who stated that all cells come from pre-existing cells.
Rudolf Virchow stated "Omnis cellula e cellula" — cells come from cells (1855).
A disease damages cellular organelles so cells can't make energy. Which cell theory idea helps explain why the whole organism may get sick?
— Because cells are the basic unit of structure and function, damaged cells mean organs can't work properly and the organism becomes ill.
Explain in two sentences how natural selection works using variations.
Natural selection: Individuals with helpful variations are more likely to survive and reproduce, passing those traits on; over time the population shows more of that trait.
Define autotrophic and heterotrophic in one sentence each.
Autotrophic: makes its own food (like plants). Heterotrophic: eats other organisms for food (like animals).
Explain why understanding cell theory is important for medicine or biology
Understanding cell theory explains how diseases affect cells and how treatments target cell functions.
Put these contributors in order of their discoveries: Matthias Schleiden, Theodor Schwann, Robert Hooke, Rudolf Virchow. (One-sentence explanation for the order.)
Order: Robert Hooke → Schleiden → Schwann → Virchow. Hooke first observed cells; Schleiden and Schwann formulated cell theory for plants and animals; Virchow added that cells come from cells.
Given a fictional organism that is multicellular and autotrophic but its cells don't divide, explain in a short paragraph (3–4 sentences) why this would violate cell theory and what biological problems would follow.
This violates "all organisms are made of cells that come from pre-existing cells"; if cells don't divide the organism couldn't grow or replace damaged cells, causing developmental and maintenance problems.
Describe a short scenario (3–4 sentences) showing how a change in environment could cause a population to change over several generations because of variation.
Scenario example: If a region becomes colder, squirrels with thicker fur survive better and reproduce; over generations thicker fur becomes more common because of that variation.
Compare and contrast (two-sentence answer) a prokaryotic unicellular autotroph with a eukaryotic multicellular heterotroph.
Example: A prokaryotic unicellular autotroph (cyanobacterium) is one cell that makes food and lives alone; a eukaryotic multicellular heterotroph (a deer) has many specialized cells and eats plants — the structure and complexity differ.