Answer:
A. Expulsion of fetus before 20th-28th week of gestation
The author supports the statement by explaining the different theories about yawning, this includes theories and some that are still studied.
The author states that scientists have not yet reached any consensus regarding theories about why humans yawn and argue this claim by explaining the following theories about yawning:
- In Antiquity: Hippocrates' Yawning Theory focused on the respiratory system by hypothesizing that yawning precedes fever and is a way of removing polluted air from the lungs.
- In the seventeenth and eighteenth centuries: Most theories focused on the circulatory system. These theories posited that yawning causes an increase in blood pressure, heart rate, and oxygen in the blood.
- Today: Dr. Robert Provine, in 2005 stated that yawning is associated with changing a state of behavior.
- Gallup in 2008 proposed that yawning is related to a way of cooling the brain's temperature.
- In 2011, Dr. Andrew Gallup and Omar Tonsi Eldakar stated that yawning is related to the outside temperature, that is, when the temperature is warm, the body yawns less frequently.
According to the above, it can be inferred that scientists have not reached a consensus on yawning because all have raised different theories to explain its function.
Learn more in: brainly.com/question/8945611
There is not any nucleus and nuclear bound organelles in prokaryotes....
Answer:
Modern amphibians are characterized by the flexibility of their gaseous exchange mechanisms. Amphibian skin is moistened by mucous secretions and is well supplied with blood vessels. It is used for respiration to varying degrees. When lungs are present, carbon dioxide may pass out of the body across the skin, but in some salamanders there are no lungs and all respiratory exchanges occur via the skin. Even in such animals as frogs, it seems that oxygen can be taken up at times by the skin, under water for example. Therefore, regulation of respiration occurs within a single species, and the relative contribution of skin and lungs varies during the life of the animal.
Explanation:
Answer:
Cell differentiation.
Explanation:
This is because cell differentiation refer to the process where cell changes from one cell types to tissues or organs or even system or specialised cells during a developmental stages to perform functions. It occur in multicellular organisms where zygote changes to tissues or system.
. This occurs through a process called gene expression. Gene expression refer to the combination of genes that can either be expressed or repressed.
