What prevents speciation from occurring in sympatric populations?

Sympatric population occupies one habitat, where organisms interbreed. Thus there is no physical barrier working to separate sub-populations. As long as random interbreeding between all members continue, sympatric speciation will not occur.

Speciation in sympatric population is rare and may occur by different means: e.g.

•Habitat selection- This includes separation and mate choice preference, ultimately leading to establishment of separate sub-populations (=demes). When gene flow between these demes completely stop, speciation is achieved. This is seen in many marine fauna.

(NEXT TO THE PHOTO)Instantaneous genetic isolation- This is very common in plants due to appearance of polyploidy, etc. due to abnormal meiosis. Chromosome doubling in accidentally generated flora immediately establishes a new species in same habitat.

answer:

the water molecules are transferred from the roots to the stem or top parts of the tall tree because of important properties of water which are adhesion, cohesion and capillary action. cohesion is the property of water molecules keeps water molecules in a combined state by sharing of bonds between them at the atomic level. adhesion allows the interaction of water molecules with other substances or substrate. adhesion will cause the attachment of water molecules to the wall of the vessel (xylem) of the plant. capillary action occurs when the adhesive force to the vessel wall is stronger than the cohesive force between water molecules. capillary action mimics the transfer of water from a tube or pipe. in this way water utilizes its property to transfer water from down to top level of the plant.