Many individuals of the platyfish, Xiphophorus maculatus, have spots on their dorsal fins. A closely related species, the swordtail, X. helleri, lacks spots. In some backcross hybrids of these species, enlarged spots develop into malignant tumors, which reduce the organisms' life spans. This could be an example of .a. the Dobzhansky-Muller model of speciation.
b. beneficial hybridization.
c. the morphological species concept.
d. gene flow.
e. genetic compatibility.

water is a polar molecule. a chemical bond is a force of attraction between atoms or ions. bonds form when atoms share or transfer valence electrons. atoms form chemical bonds to achieve a full outer energy level, which is the most stable arrangement of electrons. so, false

explanation:

in h2o molecule, two water molecules are bonded by a hydrogen bond but the bond between two h - o bonds within a water molecule are covalent. the greater the electronegativity difference, the more ionic the bond is. bonds that are partly ionic are called polar covalent bonds. nonpolar covalent bonds, with equal sharing of the bond electrons, arise when the electronegativities of the two atoms are equal.

igneous rocks which formed by the crystallization of magma at the surface of the earth called extrusive rocks. they are characterized by fine-grained textures because the rapid cooling at or near the surface did not provide enough time for large crystals to grow.

wegner's theory did not explain how the continents could move

explanation: