<P> One of the best - known examples of convergent evolution is the camera eye of cephalopods (such as squid and octopus), vertebrates (including mammals) and cnidaria (such as jellyfish). Their last common ancestor had at most a simple photoreceptive spot, but a range of processes led to the progressive refinement of camera eyes--with one sharp difference: the cephalopod eye is "wired" in the opposite direction, with blood and nerve vessels entering from the back of the retina, rather than the front as in vertebrates . This means that cephalopods do not have a blind spot . </P> <P> Birds and bats have homologous limbs because they are both ultimately derived from terrestrial tetrapods, but their flight mechanisms are only analogous, so their wings are examples of functional convergence . The two groups have powered flight, evolved independently . Their wings differ substantially in construction . The bat wing is a membrane stretched across four extremely elongated fingers and the legs . The airfoil of the bird wing is made of feathers, strongly attached to the forearm (the ulna) and the highly fused bones of the wrist and hand (the carpometacarpus), with only tiny remnants of two fingers remaining, each anchoring a single feather . So, while the wings of bats and birds are functionally convergent, they are not anatomically convergent . Birds and bats also share a high concentration of cerebrosides in the skin of their wings . This improves skin flexibility, a trait useful for flying animals; other mammals have a far lower concentration . The extinct pterosaurs independently evolved wings from their fore - and hindlimbs, while insects have wings that evolved separately from different organs . </P> <P> Flying squirrels and sugar gliders are much alike in their body plans, with gliding wings stretched between their limbs, but flying squirrels are placental mammals while sugar gliders are marsupials, widely separated within the mammal lineage . </P> <P> Insect mouthparts show many examples of convergent evolution . The mouthparts of different insect groups consist of a set of homologous organs, specialised for the dietary intake of that insect group . Convergent evolution of many groups of insects led from original biting - chewing mouthparts to different, more specialised, derived function types . These include, for example, the proboscis of flower - visiting insects such as bees and flower beetles, or the biting - sucking mouthparts of blood - sucking insects such as fleas and mosquitos . </P>

Homologous features can be associated with divergent evolution