STANDARD 16_Heredity and Reproduction
THE CELL CYCLE
SC.912.L.16.14 Describe the cell cycle, including the process of mitosis . Explain the role of mitosis in the formation of new cells, and its importance in maintaining chromosomes number during asexual reproduction.
- The Cell Cycle is divided in two main stages: INTERPHASE 90% of the time (blue, green, and yellow areas) and M-Phase 10% of the time (Cell Division: Mitosis and Cytokinesis)(the red area)
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Why must cells divide? Go here to find out more
Cells normally grow by increasing their size, but this growth may cause some problems, triggering cell division after a certain point. There are two basic reason why they have to eventually divide.
By the process of cell division (mitosis and cytokinesis), a larger cell becomes two small cells, resolving the issues listed above.
- Traffic problems: This means that a bigger cell has serious problems moving stuff around. A smaller cell has a better ability to transport oxygen and food inside and move waste products out of the cell compared to a larger cell.
- Information overload: While a cell can grow more organelles and have a larger cytoplasm, it does not grow its DNA. DNA is the "instruction manual" for all processes in the cell, ribosomes make proteins needed everywhere and having only "one manual" causes much stress.
By the process of cell division (mitosis and cytokinesis), a larger cell becomes two small cells, resolving the issues listed above.
Functions of Mitosis:
- Growth of the multi cellular organism.
- Repair of tissues.
- Asexual reproduction: Type of reproduction that produces identical organisms. From one, two are made!
What must happen before cells divide?
How do cells divide?
Eukaryotic Cell Division (M-Phase): Mitosis: The division of the nucleus + Cytokinesis: The Division of the Cytoplasm
(Go here to find out more)
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Cytokinesis in Animal Cells vs. Plant cells
Asexual Reproduction (Mitosis) in Eukaryotic Organisms
All the examples below have many things in common:
But there are also disadvantages:
- they are all examples of asexual reproduction
- they were all conceived through mitosis.
- all offspring produced are identical to their parents.
- it is a faster process
- it increses the size of population really fast
- requires less energy
- no courtship behaviors needed
But there are also disadvantages:
- There is no genetic diversity: so if the environment is suitable, then well no problem, everyone survives. But if the environment changes and it is no longer suitable, like it normally happens in nature, then everyone will die!!
- Limited adaptations to a changing environment, can retard evolution. When there is genetic diversity in a population, evolution advances faster, because the organisms with better adaptations may survive certain environmental changes. However organisms that reproduce asexually lack this ability.
Prokaryotic Cell Division: Binary Fission
Bacterial binary fission is the process that bacteria use to carry out cell division.
- Binary fission is similar in concept to the mitosis that happens in eukaryotic organisms however its only function is asexual reproduction, increasing the bacterial population size.