A cell can only respond to signals from other cells, not from the physical environment. receptor activation. The ability of a specific tissue or organ to respond to the presence of a hormone is dependent on: the presence of the appropriate receptors on the cells of the target tissue or organ.
C. Because they contain water ammonia, and methane
The neritic zone is permanently covered with generally well-oxygenated water, receives plenty of sunlight and has low water pressure; moreover, it has relatively stable temperature, pressure, light and salinity levels, making it suitable for photosynthetic life.
The horsehoe crab because it was one of the first animals to ever live on earth
Answer:
<u>Light microscope</u>:
- use a beam of light to produce magnified images
- can be used to examine living cells and tissues
<u>Scanning electron microscope</u>:
- use a beam of electrons to produce magnified images
- can be used to examine DNA
- can be used to examine cells
<u>Transmission electron microscope</u>:
- use a beam of electrons to produce magnified images
- can be used to examine DNA
- can be used to examine cells
Explanation:
Light microscope: is a commonly used microscope also known as compound microscope. Magnifies images from 40X upto 1000X. It uses ray of visible light to produce a magnified image. The light microscope can be used to view specimen of both living and dead cells or tissues. However, it doesn't give a detailed view of a specimen like electron microscope.
Scanning electron microscope: It uses electron beam as an illuminating source. It has a much higher resolving power than light microscope because it uses electrons instead of light. It magnifies object upto 500000 times the actual size. Internal structures can also be viewed. However, only dead specimen can be used because the beam of electrons can kill the cells. They are of two types:
- <u>Scanning electron microscope(SEM): </u>an electron beam passes over the specimen's surface and displaces electrons which are then focused on a screen to form an image. Images appear in 3-D
- <u>Transmission electron microscope: </u>electromagnets magnify the image by passing beam of electrons through a thin specimen. Images appear in 2-D
