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.
Answer:Living organisms are dependent on other living organisms to survive
Explanation:
Crossing over in germinal cells during gametogenesis is one of the primary causes of this variance. In humans, gametes are generated during meiosis, which reduces the chromosome number to 23.
One cell divides twice during meiosis to create four daughter cells. These four daughter cells are haploid, meaning they have half the amount of chromosomes as the parent cell. Meiosis generates sex cells or gametes? (eggs in females and sperm in males).
During meiosis, homologous chromosomes are paired, resulting in gene recombination.
Non-sister chromatids exchange genetic material, resulting in novel allele combinations.
Learn more about to meiosis visit here;
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Answer:
Explanation:
They are located at the armpits, anogenital regions,ear canal,eye lids, areola and nipples of the breast.
The Apocrine gland has a direct link to the hair follicle.it is made up of clusters of secretory tubules, which emptied to the hair follicles through the excretory duct. This gland secretions is not continuous, but in periodic fashion. The components of the secretion are protein,lipids, steroids. The secretion is usually odorless and Oily in nature. However this changed when mixed with bacterial or germs on exposure to the skin surface.
At the base of the hair follicles are the sebacious glands which produced sebum. Therefore as the apocrine secretion leaves the secretory ducts, they are mixed with sebum to reach the epidermal surface of the skin.
Our most distant predecessor is Australopithecine who lived about up to 3 million years ago. Then homo habilis and homo erectus evolved, but they have been living more less at the sime time - it's unsure which of them was the first one (it was about 2.5 million years ago). Homo sapiens appeared about 200 thosuand years ago.
