Answer:
SARS- CoV- 2 is a virus that infects human by the oral-respiratory way in which the virus enters the body and these viruses have spikes on their surface made of spike proteins that allow these viruses to bind with the infected cell.
The infected cells have ACE2 receptor that is protein present on the surface of the human cells. Binding allows the structural change in the virus to fuse and enter in the cell where viruses reproduce them selves with the cell with cell system.
Answer:
If humans were still hunting and gathering food instead of farming - taken into account that the entire population hunts and gathers food in the context of this question - the majority of people would have dark-skin complexions.
Explanation:
This is easily explained by a hunter-gatherer's way of living. Before humans learned to raise animals and grow crops, the majority of us were hunters and gatherers. Hunters and gatherers lived, and still continues to live, their lives very differently from how we are living at present. They'd spend hours hunting - as their name suggests - and catching food out in the wild, which exposes them to a higher amount of sunlight than our everyday way of living. To cope with this, evolution also played an important part in determining the survival of these people in the scorching sun - they evolved to producing high amounts of melanin. Melanin is a dark pigment that helps protect our skin cells against the harmful UV rays from the sun. Lighter skinned people have less melanin than darker skinned people, and when that extra melanin is produced, you'd see it as a tan. Hunter-gatherers produced high amounts of melanin, primarily because they had adapted to spending a large fraction of their time out in the open. The melanin acts like a built-in sunscreen for them, protecting them from getting skin cancers like melanoma.
Answer: Radiography: projectional, a single image, used for mammography
Fluoroscopy: used a contrast agent or dye, live imaging, real-time monitoring.
Explanation:
Answer:
The correct answer is - biodiversity is a good thing.
Explanation:
Biodiversity is the variety of types of life including all organisms present on earth or if related to a specific area then the ecosystem. Biodiversity helps in boosting the productivity of the ecosystem and each organism of the ecosystem plays an essential role in it.
The higher the biodiversity more chances of survival of organisms. Biodiversity provides oxygen, water and soil that helps to strengthen the ecosystem.
Answer:
Absorben o excretan agua salada para mantener la homeostasis.
Explicación:
La regulación hídrica y salina en peces de agua dulce y salada se realiza según las condiciones ambientales. Los peces pueden pasar mucha orina muy diluida en la que hay menos solutos o sales, y logran el equilibrio de electrolitos en el cuerpo mediante el transporte activo de sales a través de las branquias. En un ambiente marino hipertónico, los peces de agua salada comienzan a beber agua de mar y mantienen el equilibrio electrolítico mientras excretan el exceso de sales a través de sus branquias y su orina.
