They will best know the preferred format. When you reach out to them, you will need the page title, URL, and the date you accessed the resource. If a media asset is downloadable, a download button appears in the corner of the media viewer. If no button appears, you cannot download or save the media.
Text on this page is printable and can be used according to our Terms of Service. Any interactives on this page can only be played while you are visiting our website. You cannot download interactives. A cell is the smallest unit that is typically considered alive and is a fundamental unit of life. All living organisms are composed of cells, from just one unicellular to many trillions multicellular.
Cell biology is the study of cells, their physiology, structure, and life cycle. Teach your students about cell biology using these classroom resources. Cells function differently in unicellular and multicellular organisms. A unicellular organism depends upon just one cell for all of its functions while a multicellular organism has cells specialized to perform different functions that collectively support the organism.
Join our community of educators and receive the latest information on National Geographic's resources for you and your students.
Skip to content. Twitter Facebook Pinterest Google Classroom. Encyclopedic Entry Vocabulary. Although this knowledge is foundational today, scientists did not always know about cells. The discovery of the cell would not have been possible if not for advancements to the microscope. Interested in learning more about the microscopic world, scientist Robert Hooke improved the design of the existing compound microscope in His microscope used three lenses and a stage light, which illuminated and enlarged the specimens.
These advancements allowed Hooke to see something wondrous when he placed a piece of cork under the microscope. Hooke detailed his observations of this tiny and previously unseen world in his book, Micrographia. It was unsurprising that van Leeuwenhoek would make such a discovery. He was a master microscope maker and perfected the design of the simple microscope which only had a single lens , enabling it to magnify an object by around two hundred to three hundred times its original size.
Van Leeuwenhoek became fascinated. He went on to be the first to observe and describe spermatozoa in He even took a look at the plaque between his teeth under the microscope. In a letter to the Royal Society, he wrote, "I then most always saw, with great wonder, that in the said matter there were many very little living animalcules, very prettily a-moving. In the nineteenth century, biologists began taking a closer look at both animal and plant tissues, perfecting cell theory.
Scientists could readily tell that plants were completely made up of cells due to their cell wall. However, this was not so obvious for animal cells, which lack a cell wall.
German scientists Theodore Schwann and Mattias Schleiden studied cells of animals and plants respectively. These scientists identified key differences between the two cell types and put forth the idea that cells were the fundamental units of both plants and animals. However, Schwann and Schleiden misunderstood how cells grow. Eventually, other scientists began to uncover the truth. Another piece of the cell theory puzzle was identified by Rudolf Virchow in , who stated that all cells are generated by existing cells.
At the turn of the century, attention began to shift toward cytogenetics, which aimed to link the study of cells to the study of genetics. In the s, Walter Sutton and Theodor Boveri were responsible for identifying the chromosome as the hub for heredity —forever linking genetics and cytology. The discovery of the cell continued to impact science one hundred years later, with the discovery of stem cells, the undifferentiated cells that have yet to develop into more specialized cells.
Scientists began deriving embryonic stem cells from mice in the s, and in , James Thomson isolated human embryonic stem cells and developed cell lines. His work was then published in an article in the journal Science. It was later discovered that adult tissues, usually skin, could be reprogrammed into stem cells and then form other cell types.
His tipping-bucket rain gauge emptied itself when filled with rain. The number of times the bucket became unbalanced and tipped was recorded to measure the cumulative volume of rainwater over a given time. Hooke's wind gauge was a reinvention of the original; as the wind speed changed, so did the position of an attached mobile panel.
To improve the thermometer, Hooke added further measurements, including the freezing point of water, according to Royal Society Publishing. Hooke's most famous work was his discovery of the living cell.
Though scientists had invented the microscope decades earlier, Hooke's innovation dramatically improved the technology. He placed three mirrors in sequence to magnify the images and added a light for better viewing. The intricate internal structure of living things emerged in incredible detail under his more powerful compound microscope, according to National Geographic. Hooke detailed many of his observations in his book "Micrographia," which was filled with intricate sketches of the tiny world he saw — everything from six-sided "snowflakes" floating atop frozen urine to mold spores, which, up close, looked like tulips waving in the wind.
Hooke was also the first to examine different fossil types with a microscope, proposing in "Micrographia" that fossils form when "the Shells of certain Shel-fishes, which, either by some Deluge, Inundation, earthquake, or some such other means, came to be thrown to that place, and there to be fill'd with some kind of Mud or Clay, or petrifying Water, or some other substance.
His microscope observations also revealed how mosquitoes and lice suck blood. In , after the Great Fire of London destroyed much of the city, Hooke was given the opportunity to try his hand at architecture, according to Royal Museums Greenwich. Hooke and Sir Christopher Wren, who was also a scientist, designed a monument to commemorate the fire. The two scientist-architects decided to add scientific elements to the foot-tall 61 meters monument, which was erected between and For instance, Hooke included an underground laboratory where he could conduct many of his science experiments, while the central passage was built to house a large telescope, according to the BBC.
This laboratory remains below the monument today, although it is usually inaccessible to the public and its entrance stays covered. Scientists continue to be inspired by, and benefit from, Hooke's findings as they delve further into the microscopic world he revealed. As Hooke wrote in "Micrographia," "By the means of telescopes, there is nothing so far distant but may be represented to our view; and by the help of microscopes, there is nothing so small as to escape our inquiry.
To learn more about the wonders of the natural world, subscribe to How It Works magazine. Ailsa is a staff writer for How It Works magazine, where she focuses on writing features on science, technology, history and the environment.
0コメント