1) A scientist is searching for chemical compounds involved in embryonic limb de
ID: 85937 • Letter: 1
Question
1) A scientist is searching for chemical compounds involved in embryonic limb development. She discovers a new compound that is transiently (briefly) expressed in the limb and only seems to affect cells in its immediate vicinity (up to a few cell lengths away). How should the scientist classify this chemical compound?
- as a neurotransmitter
- as a paracrine factor
- as a peptide hormone
- as a steroid hormone
2)The parathyroid gland and the thyroid gland work together to regulate calcium levels in the body. Which of the below responses is true?
- Calcitonin is released by the parathyroid gland to increase levels of calcium in the body
- When circulating levels of calcium are too high, the production of parathyroid hormone is increased
- Calcitonin is released by the thyroid gland to increase levels of calcium in the body
- When circulating levels of calcium fall too low, the parathyroid gland triggers release of parathyroid hormone
3)Why might natural selection have favored cephalization?
- It allows animals to better detect stimuli behind them, if they are moving forward
- It is advantageous for animals that have very simple nervous systems, because it allows for ganglia to be spread evenly throughout an animal's body
- It allows animals to interact with the environment equally from all sides of the body at the same time
- It allows animals to better detect and capture prey
Explanation / Answer
1) A scientist is searching for chemical compounds involved in embryonic limb development. She discovers a new compound that is transiently (briefly) expressed in the limb and only seems to affect cells in its immediate vicinity (up to a few cell lengths away). How should the scientist classify this chemical compound- as a paracrine factor, when protein synthesized by one cell can diffuse to a few cell length to its neighbour cells, this process is known as paracrine infarction and these proteins are known as paracrine factors.
2. The parathyroid gland and the thyroid gland work together to regulate calcium levels in the body. Which of the below responses is true--When circulating levels of calcium fall too low, the parathyroid gland triggers release of parathyroid hormone.
3.Why might natural selection have favored cephalization-- It allows animals to interact with the environment equally from all sides of the body at the same time
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