- According to the cell theory, living organisms are composed of cells.
- Organisms consisting of only one cell carry out all functions of life in that cell.
Questioning the cell theory using atypical examples, including striated muscle, giant algae and aseptate fungal hyphae.
How does “cell” being discovered?
One day, Robert Hooke placed a cork tissue under his microscope and saw a lot of little “rooms”, he named the room “cell”. That’s how the cell was discovered.
The Cell Theory
After examining plenty of organisms samples under the microscopes, the scientists come up with a theory, called The CELL THEORY which goes…..
- Cells are the smallest units of life
- Thus, all organisms are composed of one or more cells
- Cells can arise only from pre-existing cells
- Thus, all the living organisms come to exist through reproduction
- cells perform all functions on life including,
functions of life includes: metabolism; growth; response; homeostasis; nutrition; reproduction excretion
Be reminded that, Virus is Not a Cell, so Virus is Not living organisms!
Challenges to The Cell Theory
- A cell usually contains one nucleus but the building structure of fungi, hypha which is multi-nucleated.
The muscle is similar to fungi. The building structure is muscle fibre which is a large cell contains many nuclei within a cell.
- Undifferentiated cells stick together by the extracellular material, not all large organisms are built up by multiple individual cells
- Mature red blood cell in our blood does not possess a nucleus, it cannot exert all functions of life
Theory vs Hypothesis
From above, you can see theory can be challenged and revised. In science, there are plenty of theories and hypotheses. But as an IB biology student, do you know what are theory and hypothesis?
Both theory and hypothesis predict phenomenon, but they are different in some aspects,
The above table concludes the differences between theory and hypothesis. The most important thing to remember is the theory is a much general and broader statement while the hypothesis is specific.
The below example can help you understand better!
The theory "Evolutionary adaption derived from natural selection" encloses the hypotheses, describing a much more general phenomenon.
For the hypotheses, they predict the moths and cactus environmental adaptation phenomenon specifically.
Valid hypothesis supports the validation of the theory. However, if there is an exception hypothesis that challenges the theory, the theory will be revised.
That is the end of this topic! Well done!
1. The Human Protein Altas. Skeletal Muscles. Retrieved from URL https://www.proteinatlas.org/learn/dictionary/normal/skeletal+muscle
2. Armin Hallmann. (28 Nov 2017). Unicellular to multicellular: What can the green alga Volvox tell us about the evolution of multicellularity and cellular differentiation. Retrieved from URL: https://blogs.biomedcentral.com/on-biology/2017/11/28/unicellular-to-multicellular-what-can-the-green-alga-volvox-tell-us-about-the-evolution-of-multicellularity-and-cellular-differentiation/
3. Denise Granger. (4 Jun 2016). Retrieved from URL: https://socratic.org/questions/what-are-the-functions-of-human-red-blood-cells
4. Forest Floor Narrative. (24 August 2017). Hyphal Aggregates. Retrieved from URL: https://www.forestfloornarrative.com/blog/2017/8/24/hyphal-aggregates