Answer:
the electron microscope
Explanation:
The first strands of DNA were observed through the electron microscope.
Answer:
Porifera or Sponges
Explanation:
Porifera is the phylum of the simplest multicellular marine animals. Their body is composed of two cell layers (something like tissues) and mesophyl between them. The body is in direct contact with surrounding water through the large number of pores and channels. What makes Sponges so simple is that their cells are unspecialized and that they don't have nervous, digestive or circulatory systems.
Answer: B
Explanation: Most mammals have only one pair of sex chromosomes in each cell. Males have only one Y chromosome and one X chromosome, while females have two X chromosomes. In Mammals, the Y chromosome contains a gene, SRY, which triggers embryonic development in a male.
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<h2>Answer:</h2>
<u>Typical rates of sea-floor spreading are approximately </u><u>5 cm per year</u>
<h2>Explanation:</h2>
Sea-floor spreading is a process that happens at the mid-oceanic ridge where a divergent boundary is causing two plates moving away from one another resulting in spreading of the sea floor. To calculate the spreading rate of one side of a mid-ocean ridge by dividing distance by time (Distance/Time = Rate) The typical rates of sea -floor spreading are approximately is 5 centimeter per year.
Answer:
Stem cells provide new cells for the body as it grows, and replace specialised cells that are damaged or lost. They have two unique properties that enable them to do this: They can divide over and over again to produce new cells. As they divide, they can change into the other types of cell that make up the body.
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