Ernest Everett Just and the Living Cell
A sea urchin egg is tiny, but it helped a scientist ask a big question: How does a single cell begin to develop into an animal? Ernest Everett Just spent years studying such questions. Born on August 14, 1883, he became a scientist whose careful observations helped people understand the earliest stages of life.
Just studied marine animals, including sea urchins and sand dollars. These animals produce eggs that can be observed outside the mother's body. In seawater, a sperm cell can join with an egg cell in a process called fertilization. After fertilization, the egg begins to divide, eventually forming an embryo, an animal in its earliest stage of development.
At a marine laboratory, Just examined specimens with a microscope, an instrument that makes tiny objects appear larger. He paid close attention to the surface of the egg. When a sperm reaches an egg, changes at the egg's surface help prevent other sperm from entering. This matters because an egg usually needs genetic material from only one sperm to develop normally.
- observations:
- Things noticed carefully while watching or studying something.
- specimens:
- Living things or samples collected for study.
- genetic:
- Related to information passed from parents to their offspring.
- surroundings:
- The things and conditions around a living thing or object.
- discrimination:
- Unfair treatment of people because they belong to a particular group.
- contribution:
- Something a person gives or does to help a larger effort.
- investigate:
- To study something carefully to learn more about it.
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Main Idea
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Preview questions from this passageShowHide
- 1What is the main idea of the article? Give two details that support it.
- 2Why were sea urchin and sand dollar eggs useful for Just's research?
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About this explanatory article passage for Upper Elementary
“Ernest Everett Just and the Living Cell” is a explanatory article reading passage about Cell biology, written for Upper Elementary. It takes about 3 minutes to read (524 words) and comes with an interactive quiz and a printable worksheet with comprehension questions and an answer key.