Viewed 20/04/17
https://www.youtube.com/watch?v=0-7iXyYS0uw
This week my
blog is all about creatures who fly! This is going to be one of my personal favorites!
How are they specialised for flight and why did
this develop? How did they evolve their phenotypes and their morphology? We
know that changes in morphology are some of the most visibly noticeable and
therefore are more difficult and time consuming changes to achieve. Logically it
must have proved advantageous to make these changes throughout time. Additionally,
flight has evolved in more than one separate instance among different species
without any single common ancestor. It
is said that it has happened at least four separate times across the groups of insects,
birds, bats and as early as the pterosaurs, this reoccurring coincidence is
referred to as convergent evolution (Gleiss, 2010).
Bats are the most recent group to have evolved to
use flight (Figure 1), and are said to have had a walking/ gliding ancestor. The
bones of this ancestor would have experienced repetitive impacts closely in
line with the limb as part of locomotion, some evident changes are the
specialisation of the limbs, of which have been structurally modified and
lightened over time to accommodate for wing muscle tissue and to better handle
pressure gradients used for lift/acceleration through the much finer, longer pent
dactyl wing bones (Swartz, 1992) this evolved them from a previously walking/gliding
creature into a climbing/flying one.
Figure 1. Fruit
Bat (Pteropodidae)
Viewed 20/04/17:
http://bit.ly/2o6ANZM
Birds have an extensive history of recorded
fossils (Figure 2), with the more famously known Archaeopteryx as the most
commonly accepted transitional ancestor, because of its avian and reptilian
traits (Figure 3). While it is agreed that the earlier ancestors of birds were
reptilian dinosaur-era creatures like archaeopteryx and had feathers, it is still unclear
and debated whether the flight first developed from a “trees downward”, gliding
approach or whether it was a “ground upwards”, speed-running and leaping
combination that eventually resulted in bird like creatures taking to the air (Sereno &
Chenggang, 1992).
Figure 2. Lorikeets
(Trichoglossus moluccanus)
Viewed 20/04/17:
http://bit.ly/2oS3mr0
Figure 3. Archaeopteryx
Fossil
Viewed 20/04/17: http://bit.ly/2oRVRjN
Insects have evolved flight a great many times, the
first examples of insects in the air were most likely caused by jumping or
falling, potentially to avoid predators, or being swept up by the wind. The
origin of insect wings has been greatly speculated with two main theories, one
of a tracheal system modification and secondly a lateral outgrowth from the
paranotal lobes (Flower, 1964)
References:
Flower, J.W. 1964, On the origin of
flight in Insects, Journal of Insect Physiology, Volume 10, Issue 1, pp
81-88
Very interesting. Do you know in which group of insects flight is thought to have originated first? What evidence is there that flight evolved from a “ground upwards” approach?
ReplyDelete