The right answer is Mitochondria.
In the 20th century, scientists thought that plastids and mitochondria could come from procaryotes (bacteria). These would have been ingested by cells and live within them (in symbiosis). This endosymbiotic theory became perfectly plausible when it was discovered (in the 1950s and 1960s) that these organelles contained theori own DNA, tRNA and rRNA.
Answer:
Karl Landsteiner along with his coworkers recognized four types of blood groups in human beings, commonly called as ABO blood grouping.
Explanation:
The membrane of RBCs possess several antigens. Depending on the nature of antigens on the surface of RBCS various types of blood grouping has been done. Two such groupings are The ABO and Rh grouping and are widely used all over the world.
ABO grouping:
There are four types of blood groups in human beings. ABO grouping is based on the presence or absence of two surface antigens on the RBCs namely A and B. Similarly, the plasma of different individuals also contain two natural antibodies called anti-A and anti-B.
If an antigen is present on the surface of RBCs, the corresponding antibody must be absent from the plasma and if the antigen is absent on the RBCs, the corresponding antibody must be present in the plasma.
Blood group A has A antigen on RBCs and anti-B antibody in plasma
Blood group B has B antigen on RBCs and anti-A antibody in plasma
Blood group AB has A and B antigen on RBCs and no antibody in plasma
Blood group O has no antigen on RBCs and both anti-A and anti-B antibody in plasma
Rh grouping:
Another group of antigens found on the RBCs of most people is the Rh factor. People who have this antigens are said to be Rh+ve whereas those who do not are called Rh-ve. Rh groups should also be matched before transfusion because A Rh-ve person if exposed to Rh+ve blood , will form specific antibodies against the Rh antigen.
Frog's heart<span> has one ventricle, while humans have 2, hence deoxygenated blood from body mixes with the oxygenated blood coming from lungs.
Source: S</span><span>ocratic</span>
Answer: Sunlight entering the water may travel about 1,000 meters (3,280 feet) into the ocean under the right conditions, but there is rarely any significant light beyond 200 meters (656 feet).
The ocean is divided into three zones based on depth and light level. The upper 200 meters (656 feet) of the ocean is called the euphotic, or "sunlight," zone. This zone contains the vast majority of commercial fisheries and is home to many protected marine mammals and sea turtles.
Only a small amount of light penetrates beyond this depth.
The zone between 200 meters (656 feet) and 1,000 meters (3,280 feet) is usually referred to as the “twilight” zone, but is officially the dysphotic zone. In this zone, the intensity of light rapidly dissipates as depth increases. Such a minuscule amount of light penetrates beyond a depth of 200 meters that photosynthesis is no longer possible.
The aphotic, or “midnight,” zone exists in depths below 1,000 meters (3,280 feet). Sunlight does not penetrate to these depths and the zone is bathed in darkness.
‘Photic’ is a derivative of ‘photon,’ the word for a particle of light.
Respuesta:
B. pastoreo excesivo de animales de granja
Porque son lugares secos.
Explicación:
Las políticas e infraestructuras que promueven la agricultura en las tierras de pastoreo que no pueden mantener sistemas viables de cultivo, contribuyen a la desertificación. La mayoría de las áreas de tierras secas (el 65%) son tierras de pastoreo que son más adecuadas para el pastoreo sostenible que para el cultivo.