Explanation:
The "fossil record" refers to the placement of fossils throughout the surface layers of the Earth. Older fossils are buried more deeply than younger ones. Scientists use the placement of fossils as a guide for determining when life forms existed, and how they evolved.
Answer:
There are many receptors for thyroxine on different target cells (tissues), so its effect can be huge
Explanation:
Target cell for a certain hormone is a cell that have hormone receptor specific for that hormone. There are two main types of receptors on target cell:
- cell membrane receptors (also called trans membrane receptors)-usually for peptide hormones, such as insulin
- intracellular receptors (also called nuclear receptors)-usually for steroid hormones, such as testosterone.
Hormone binding to the receptor leads to the signal cascade within the cell, which results in cell response.
Receptors for thyroid hormones are nuclear receptors.
