Hypophyseal portal system allows the hypothalamus to have direct communication with the anterior pituitary.
The hypophyseal portal system is a network of blood vessels that connects the anterior portion of the gland and hypothalamus at the base of the brain. Two capillary beds, one in the median eminence and the other in the anterior pituitary, make up the portal system. Its principal job is to swiftly transfer and exchange hormones between the anterior pituitary gland and the hypothalamic arcuate nucleus.
The cortisol, androgens, and aldosterone hormones interact with anterior pituitary gland cells via travelling through the hypophyseal portal system. Hormonal signaling through the hypophyseal portal system enables connection between these two structures.
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Answer:
A. the heterozygote advantage
Explanation:
Heterozygote advantage is the condition where the heterozygous individual has higher relative fitness than both homozygous dominant and homozygous recessive individual. This means that the heterozygote individual has higher chances of surviving than both the homozygous counterparts. Sickle cell anemia is a recessive inherited disorder in which oxygen carrying hemoglobin has an abnormal structure. Hence, the resultant RBCs are not spherical but have crescent sickle shape. The oxygen carrying capacity of such RBCs is drastically reduced but they are unaffected by malarial parasite due to their abnormal structure.
- A person with both the recessive genes for sickle cell would not be able to survive due to insufficient oxygen transport in body.
- A person with both the dominant genes would be free of sickle cell anemia but in case of malaria would not be able to survive as the normal RBCs would be hijacked by the parasite.
- A hetrerozygote would survive both in malaria and sickle cell condition since he has enough normal RBCs for oxygen transport but also has sickle cell RBCs which are unaffected by malarial parasite.
Answer:
Option D
Explanation:
Cyanobacteria preserve its photosynthetic pigments in the thylakoids which allows masking of green of chlorophyll a and other accessory pigment i.e phycobiliproteins (phycocyanin, allophycocyanin and phycoerythrin).
Chlorophyll a is mainly responsible for harvesting light for photosynthesis. Phycocyanin is blue in color, allophycocyanin is blue in color and phycoerythrine is red in color. These together harvest light in the green, yellow and orange part of the spectrum which cannot be used by other phytoplankton species
Hence, option D is correct
Answer: A factor that could adversely affect its success is the ice floes melting causing the polar bears to have to stay in the water longer and have to take the chance of the seals spotting them first or the chance of getting tired easily
Explanation:
