When the comb jelly, Mnemiopsis leidyi, was introduced into the Black Sea, its population exploded to 500 comb jellies per cubic yard in 1988. The jellies devoured all the zooplankton and fish larvae, drastically reducing the numbers of the native fish populations. This situation demonstrates . a.
the difference between biotic and abiotic factors in an ecosystem.
b.
effects of local evolution or migration on an ecosystem.
c.
the impact of removing or adding organisms to an ecosystem.
d.
the types of interactions between organisms in an ecosystem.

- calcium has greater affinity to bond with electron receptors than hydrogen does and hence, it has the ability to replace hydrogen in most of its compounds.

- lithium has 2 valence electrons in the product because it can make only 1 bond with hydrogen. beryllium has 4 valence electrons in the product because it can only make 2 bonds. it has fewer electrons than neon and can react with electron donors. each hydrogen has 2 valence electrons, the same as helium.

- the covalent bond formed between carbon and hydrogen is polar because carbon is more electronegative than hydrogen and it attracts the bonded electron pair closer to itself, thus giving hydrogen a partial positive charge.

- a hydrogen bond is a relatively weak bond that hydrogen atoms make with the electronegative atoms nitrogen, oxygen or fluorine.

so the best choice is a.) 2 calcium (ca) atoms

periodic trends is an atom that gets larger as the number of electronic shells increase, the radius of atoms increases as you go down a certain group in the periodic table of elements. in general, the size of an atom will decrease as you move from left to right of a certain period.