Chordate’s organ systems include digestive, circulatory, respiratory, nervous, excretory, reproductive, and skeletal systems. Vertebrate chordates have relatively complex organs compared to invertebrates. Invertebrates have simple and less specialized organ system, but it does not necessarily mean that they are inferior– since these simple organs are still able to perform life functions in these organisms.

Frog’s lungs are filled with little sacs. Gorilla’s lungs are filled with alveoli and they are extensively branched. Sparrow’s lungs are filled with tubes and sacs. These are their main differences.

The fertilization of chordate species can be classified as oviparous, ovoviviparous, and viviparous.

1. Oviparous – species that lay eggs that will be developed outside the mother’s womb/body. Example: fishes

2. Ovoviparous – species that develop eggs inside the mother’s womb, and these eggs are nourished through the yolk. Young ovoviviparous are being born alive instead. Example: Sharks

3. Viviparous – species that born their young ones alive. The young organism develops in the mother’s womb as an embryo, fetus, and finally a baby. Its nourishment comes directly from their mother.

When compared to a two-chambered heart, a three-chambered heart is more advantageous since it is able to direct more pressure within the blood vessels to ensure that the oxygenated blood goes into the body, while the deoxygenated blood is directed into the lungs.