The discoverers of DNA were not
James D Watson and Francis Crick. They are the first scientist to formulate an
accurate description of the DNA’s (deoxyribonucleic acid) complex ,
double-helical structure. They discovered that base pairing nucleotides must
be; adenine and thymine; and cytosine and guanine. These base pairs are held
together by a hydrogen bond, atype of chemical reaction that s easy to break
and easy to reform. The statement is “DNA
is a double helix made of two strands linked together with hydrogen
bonds.”
Diffusion has a major part in this. It has proteins embedded in it that allow molecules to diffuse in and out of the cell up and down its concentration gradient.
The first invertebrates to show both segmentation and a complete digestive system belong to the phylum Annelida that includes earthworms, leech, sandworms, etc.
These segmented worms have complete digestive system which is also known as tube-within a tube. These can be found in freshwater, marine water or can even be terrestrial.
