-> Organisms look alike because their body designs are similar. If body designs are similar, then the blueprints for these designs should also be similar. So, when organisms reproduce, they basically make copies of these blueprint designs. -> In Class IX, we learned that chromosomes in the nucleus of a cell contain information for passing on traits from parents to the next generation through DNA molecules. -> The DNA in the cell nucleus provides instructions for making proteins. If the information in the DNA changes, different proteins will be made, ultimately resulting in different body designs.
-> In reproduction, one important step is creating a copy of the DNA. Cells use chemical reactions to make copies of their DNA. This results in two copies of the DNA in a reproducing cell, which then need to be separated from each other. -> However, simply pushing out one copy of the DNA while keeping the other in the original cell wouldn't work because the copy pushed out wouldn't have the necessary structure to sustain life processes. -> DNA copying is accompanied by the creation of an additional cellular apparatus. After that, the DNA copies separate, each with its own cellular apparatus. Essentially, one cell divides into two cells.
-> Are these two cells absolutely identical? Well, that depends on how accurately the copying reactions occur. No biochemical reaction is completely reliable, so it's only expected that the process of copying DNA will have some variations each time. -> As a result, the DNA copies generated will be similar but not identical to the original. Some of these variations might be so significant that the new DNA copy can't work with the cellular apparatus it inherits, causing the newborn cell to die. -> However, there could also be many other variations in the DNA copies that won't have such a drastic outcome. -> So, the surviving cells are similar but slightly different from one another. -> This natural tendency for variation during reproduction is what ultimately leads to evolution, which we'll discuss in the next chapter.
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-> Organisms look alike because their body designs are similar. If body designs are similar, then the blueprints for these designs should also be similar. So, when organisms reproduce, they basically make copies of these blueprint designs.
-> In Class IX, we learned that chromosomes in the nucleus of a cell contain information for passing on traits from parents to the next generation through DNA molecules.
-> The DNA in the cell nucleus provides instructions for making proteins. If the information in the DNA changes, different proteins will be made, ultimately resulting in different body designs.
-> In reproduction, one important step is creating a copy of the DNA. Cells use chemical reactions to make copies of their DNA. This results in two copies of the DNA in a reproducing cell, which then need to be separated from each other.
-> However, simply pushing out one copy of the DNA while keeping the other in the original cell wouldn't work because the copy pushed out wouldn't have the necessary structure to sustain life processes.
-> DNA copying is accompanied by the creation of an additional cellular apparatus. After that, the DNA copies separate, each with its own cellular apparatus. Essentially, one cell divides into two cells.
-> Are these two cells absolutely identical? Well, that depends on how accurately the copying reactions occur. No biochemical reaction is completely reliable, so it's only expected that the process of copying DNA will have some variations each time.
-> As a result, the DNA copies generated will be similar but not identical to the original. Some of these variations might be so significant that the new DNA copy can't work with the cellular apparatus it inherits, causing the newborn cell to die.
-> However, there could also be many other variations in the DNA copies that won't have such a drastic outcome.
-> So, the surviving cells are similar but slightly different from one another.
-> This natural tendency for variation during reproduction is what ultimately leads to evolution, which we'll discuss in the next chapter.