User:Martino3/new sections homology

Structural homologies in other animal phyla

Discussions of homology commonly limit themselves to the limbs of tetrapod vertebrates, occasionally touching on other structures, such as modified teeth as in whales and elephants. Numerous homologies exist elsewhere in the animal kingdom, although some of them may be highly counterintuitive. For example, within the arthropods, Brusca and Brusca provide the following homologies for the first 10 somites (embryonic segments) in several groups of arthropods, and adds that "...the subject of head appendage homology among the arthropods is quite unsettled and highly controversial..."

Somite	Trilobite	Spider (chelicerata)	Centipede (uniramia)	Insect (uniramia)	Shrimp (crustacea)
1	antennae	chelicerae (jaws and fangs)	antennae	antennae	first antennae
2	First legs	pedipalps	-	-	second antennae
3	2nd legs	First legs	mandibles	mandibles	mandibles (jaws)
4	3rd legs	2nd legs	1st maxillae	1st maxillae	1st maxillae
5	4th legs	3rd legs	2nd maxillae	2nd maxillae	2nd maxillae
6	5th legs	4th legs	collum (no legs)	1st legs	1st legs
7	6th legs	-	1st legs	2nd legs	2nd legs
8	7th legs	-	2nd legs	3rd legs	3rd legs
9	8th legs	-	3rd legs	-	4th legs
10	9th legs	-	4th legs	-	5th legs

Homologies across phyla

See Deep homology.

Plants

Modifications of primary leaves, stems, and roots occur in many higher plants.

Examples

Primary organs	Defensive structures	Storage structures
Leaves	Spines	swollen leaves as in succulents
Stems	Thorns	tubers such as the potato, rhizomes such as ginger, and the fleshy stems of cacti.
Roots	-	carrot, and root tubers such as sweet potatoes