I believe it is Mechanical Energy
Answer:
presence or absence of a protective covering over the ovule
Explanation:
In angiosperms, seeds develop from ovules and are enclosed in the ovary. So, their is the presence of protective covering making the seeds enclosed.
On the other hand, gymnosperms have seeds that are borne on cones, so they are naked due to the absence of any protective covering over the ovule.
The cell membrane consists of three classes of amphipathic lipids: phospholipids, glycolipids, and sterols. The amount of each depends upon the type of cell, but in the majority of cases phospholipids are the most abundant, often contributing for over 50% of all lipids in plasma membranes.
The question is; would a drug that binds irreversibly to these receptors be an effective contraceptive in mammals?, the answer is;Yes; because if the receptors are blocked the sperms will not be able to penetrate the zonal pellucida of the egg. Contraceptives prevents pregnancy by interfering with the normal process of ovulation, fertilization, and implantation.
The breakdown of earths crust into sediment is called weathering.
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