What is the critical difference between gemmulation and fragmentation?
a. Gemmulation is sexual and fragmentation is asexual
b. Gemmulation is haploid and fragmentation is diploid If sponges fragment, it is called gemmulation
c. Fragmentation involves providing a resistant layer of cells for a capsule; gemmulation is merely breaking off chunks of tissue to grow a new organism
d. Gemmulation involves providing a resistant layer of cells for a capsule; fragmentation is merely breaking off chunks of tissue to grow a new organism

d. Gemmulation involves providing a resistant layer of cells for a capsule; fragmentation is merely breaking off chunks of tissue to grow a new organism

Explanation:

Gemmulation and fragmentation are both a type of asexual reproduction. Gemmulation starts when mass of cell which is produced asexually that are capable of producing a new organism.  

These mass of cells gets surrounded by a protective covering which provide a resistant layer of cell and the structure is called gemmule.

In fragmentation, the parent body part breaks from the whole body and gives rise to a new organism. For example in planaria. So the correct answer is d.

in 1859, charles darwin set out his theory of evolution by natural selection as an explanation for adaptation and speciation. he defined natural selection as the "principle by which each slight variation [of a trait], if useful, is preserved".