Answer:
Clam.
Explanation:
Arthrophoda is largest phylum of the non-chordata. They are the segmented animals with jointed appendages. Their body is covered by exoskeleton and contains spiracles and body surface for respiration.
Insect, spider, crab and scorpion all are included in the phylum arthropoda. Clam is a bivalve shell that is included in the phylum mollusc. The body of clam is covered with an outer shell and their shells are connected by the abductor muscle. Hence, they are involved in phylum arthropoda.
Thus, the correct answer is option (b).
Answer:
d . different population of the same species physically separated from each other forming new species.
Answer:
d. Fluoride becomes incorporated into the crystalline structure of teeth, making them less susceptible to decay
Explanation:
Dental caries results when cariogenic (caries-causing) bacteria metabolize carbohydrates or sugars present in the mouth for their energy needs, producing organic acids as byproducts, thus lowering the pH of the plaque biofilm.
The hydroxyapatite of tooth enamel is composed mainly of phosphate ions (PO₄³⁻) and calcium ions (Ca⁺). Under normal conditions, there is a stable equilibrium between the calcium and phosphate ions in saliva and the crystalline hydroxyapatite. At low pH (acidic conditions), there is a shift in equilibrium resulting in the dissolution of hydroxyapatite from tooth enamel, a process known as demineralization. A reverse process called remineralization (the process of incorporation of minerals in tooth enamel) occurs when the saliva, acting as a buffer elevates pH. When equilibrium is shifted to favor continued demineralization, dental caries results.
However, when fluoride is present in saliva, fluorapatite, rather than hydroxyapatite, forms during the remineralization process as fluoride ions replace hydroxyl groups in the formation of the apatite crystal lattice.
Fluorapatite is less soluble than hydroxyapatite making it more resistant to demineralization, even under conditions of low pH. Thus, fluoride acts as an effective anticaries agent.
A.
The glycemic index indicates the affect of a food on a person's blood sugar level. Glucose has a glycemic index of 100.
This solar energy conversion process is known as photosynthesis. ... At this time, the oxygen level was approximately 10% of its present atmospheric concentration. ... The presence of ozone enabled organisms to develop and live on the land.
