Amino acids, sugars, and ions move<span> across </span><span>the cell membrane</span>
Answer:
c. it leads to a redistribution of alleles
Explanation:
The gene flow can be defined as the movement of genetic material from one population to another within the same species. This movement may be associated 1-with the migration of individuals and subsequent reproduction of these organisms in the new population or 2-with the movement of gametes (eg., pollen dispersal) among populations. In both cases, gene flow is known to alter the frequency of particular alleles between populations and consequently also modify the evolutionary patterns of these populations.
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:
The correct answer is option B, The gametophytes grow directly from the sporophyte
Explanation:
Conifers are gymnosperm which reproduce through the exposed seeds (seeds not included in fruits) found in the cones. The trees or plant on which these conifers grow are called sporophytes. In the sporophyte, the male and female gametes fuse together to form zygote which further develops into a seed. At the right time, these seeds get dispersed into wind and they grow into new plants known as sporophytes.
