Answer: The literal reason would be because our ancestors did. The ancestors of all modern mammals had five digits on each limb up to 360 million years ago.
Explanation:
Mitosis creates two identical daughter cells that each contain the same number of chromosomes as their parent cell. Apart from this reduction in chromosome number, meiosis differs from mitosis in yet another way. Specifically, meiosis creates new combinations of genetic material in each of the four daughter cells.
Answer:
A. engulfing of small photosynthetic prokaryotes by larger cell
Explanation:
The endosymbiotic theory states that some of the organelles in today's eukaryotic cells were once prokaryotic microbes. In this theory, the first eukaryotic cell was probably an amoeba-like cell that got nutrients by phagocytosis and contained a nucleus that formed when a piece of the cytoplasmic membrane pinched off around the chromosomes. Some of these amoeba-like organisms ingested prokaryotic cells that then survived within the organism and developed a symbiotic relationship.
Some Evidence for this is based on the following:
1. Chloroplasts are the same size as prokaryotic cells, divide by binary fission, and, like bacteria, have Fts proteins at their division plane.
2. The mitochondria are the same size as prokaryotic cells, divide by binary fission, and the mitochondria of some protists have Fts homologs at their division plane.
3. Mitochondria and chloroplasts have their own DNA that is circular, not linear.
4. Mitochondria and chloroplasts have their own ribosomes that have 30S and 50S subunits, not 40S and 60S.
5. Several more primitive eukaryotic microbes, such as Giardia and Trichomonas have a nuclear membrane but no mitochondria.
En las arqueas, generalmente se encuentra en la forma L-isomérica, mientras que las bacterias y eucariotas tienen la forma D-isomérica. Una segunda diferencia es la presencia de un enlace éter en oposición a los lípidos enlazados a éster que se encuentran en eubacterias y eucariotas.
