Answer:
The correct option is A. Steroid hormones exert their action by entering the nucleus of a cell and initiating or altering the expression of a gene.
Explanation:
Steroid hormones are derived from cholesterol and regulate multiple biological processes. All steroid hormones exert their action by crossing the plasma membrane and by binding with their respective intracellular receptors. They stimulate cell growth in a very different way, their lipophilic nature gives them the ability to cross lipid barriers, so, without the need for extracellular signals, these hormones can easily enter the cell, cross the cytoplasm and reach the nucleus. There they bind to specific receptors that are associated with DNA promoter regions, modifying their structure and promoting the expression of the genes under their control.
Answer:
B
Explanation:
Some mutations can be harmful or helpful depending on the environment.
The DNA is found in the nucleus of the cell
Answer:
The water is transported to the top most leaves (and rest of its parts) of a tall tree by three actions:
1) root pressure (osmosis)
2) capillary action (adhesion)
3) evapotranspiration (cohesion)
Explanation:
The trees contain a series of interconnected tissues (xylem and phloem) that act as network for transport of water and nutrients throughout the tree. The root pressure and capillary action push the water, while the transpiration from the leaves pull the water. The root pressure is generated by osmotic movement of water from soil to the root tissues. The capillary action is caused due to adhesion of water molecules. However, root pressure and capillarity is thought to support only few meters of water column. The rest of the water transport (esp. in tall trees) is attributed to negative pressure generated by evaporation of water from leaves. This negative pressure creates a vacuum and pulls the water from the roots.
Hope this helps.
