<h3><u>Answer and Explanation;</u></h3>
- <u>Endosymbiotic theory</u> explains the origin of chloroplasts and mitochondria and their double membrane. Mitochondria of eukaryotes evolved from aerobic bacteria living within their host cell and the chloroplasts of eukaryotes evolved from endosymbiotic cyanobacteria.
- On the other hand according to the <u>autogenous hypothesis, </u>mitochondria and chloroplasts have evolved within the protoeukaryote cell by compartmentalizing plasmids or vesicles of DNA within a pinched off invagination of the cell membrane.
- <u>Endosymbiont theory </u>is the theory that suggests that simple prokaryotic cells were engulfed by larger prokaryotes 1.5 billion years ago.
- <u>Autogenous theory</u> is a theory that was proposed as an alternative to endosymbiont theory. proposes that eukaryotic organelles formed by infolding of the plasma membrane.
- <u>Horizontal gene transfer theory</u> is an alternative to endosymbiont and autogenous theories for the origin of complex organelles in eukaryotes.
In order to produce an effective immune response within the body, the person must be injected with a dosage of a virus or bacteria, and for it to be allowed to grow in the person, which replicates just enough to stimulate a response from the immune system.
Answer:
Over 95% of incoming ultraviolet radiation is absorbed in :
A. The Stratosphere.
Explanation:
- Stratosphere is the second layer of the earth's atmosphere that lies next to the troposphere.
- This layer experiences very little turbulence of air and is very significant because of the presence of Ozone layer in it.
- The UV rays entering the Earth's atmosphere, photo dissociates ozone into O₂ and O. But these molecules quickly recombine to form ozone.Thus, stabilizing the concentration of ozone in the atmosphere.
- During this photo dissociation UV radiations loses much of its energy. Thus, 95% of incoming Ultraviolet radiation gets absorbed in the Stratosphere.
- Absorption of ozone UV radiation increases exponentially with the thickness of ozone layer.