Sunday, 15 June 2014

Bio Geo: An Introduction

 Whew! After 3 lengthy posts on planetary science, I ve decided to take a short break and discuss something else entirely. A quick quiz before you proceed to read the rest:

How many Brazilian orangutans does it take to change a lightbulb ? Why?
None! There are no orangutans in Brazil!

He's a man-eater, I tell you

If you got it right, congratulations! Give yourself a cookie! :3

Alfred Russell Wallace,
badass enough to formulate
the theory of natural selection
when suffering a bout of malaria
 Now lets move onto biogeography. The study of the distribution of extant species across various locales. Although it was Swedish naturalist Carolus Linnaeus who first hinted at it, it was heavy popularized by Alfred Russell Wallace (co-discoverer of Darwin's theory of evolution) as he travelled and studied fauna of the Amazon rainforest, then later Indonesia, it remains a fascinating topic to this day. Charles Darwin also developed his theory of evolution by natural selection by studying biogeographic distributions of species (such as his finches) across various South American species.

Modern biogeography integrates knowledge from various fields of scientific inquiry :  geography, evolutionary biology, geology and ecology to name a few.

Ah, enough of that, let's talk about how it supports probably the most controversial scientific theory in existence : evolution.

Lets look at island biogeography. All around, we see unique, endemic species on island populations: the Madagascar lemurs, the Galapagos finches and giant tortoise, the Hawaiian hawk to name a few. How does this support evolution? Well, it highlights the concept of peripatric speciation, which is when an isolated population possesses much fewer numbers  than the main population. Islands provide the important factor of geographical isolation which leads to speciation in two different ways:

a) Reproductive isolation: the flora and fauna that find their ways to islands often do so by accident: animals carried by driftwood or floating mats of vegetation, or birds flying over. Plant spores may arrive by seed dispersal. As you can see, animals that do are effectively cut off from the mainland. So what happens is there is little to no gene flow, and previously recessive genotypes may be expressed as phenotypes.

b) environmental conditions-may be different from the mainland, leading to different selective pressures. Mutations that may otherwise be detrimental in the main population may be beneficial adaptations to the new environment.

I ll throw in some thoughts about ID and baraminology at the end.

Nevertheless, I will list only a specific few species and name them here:

The Galapagos

Anyone familiar with the creation-evolution controversy would know of these, so I ll try to keep it short and sweet, only naming a few of the truly endemic species to this amazing place. No wonder its such a popular tourist destination.

Pictured here: the famous Galapagos tortoise of which the island got its namesake, (Galapagos is Spanish for tortoise), the marine iguana, the lava lizard and the flightless cormorant. All images are taken courtesy of Mother Nature Network.


Now, I am going to carefully compare and contrast the adaptations of the flightless cormorant and the marine iguana. Lets look at the truly unique flightless cormorant first. Leave it to CMI to faithfully report their adaptations:

The changes that the flightless cormorant underwent are similar to that of other flightless birds; the keel on the breast bone which supports the muscles used for flight is much smaller, and its legs are much stronger than those of other cormorants. Not needing to use its wings for flight, its wings have deteriorated in ways that would have been eliminated in flying birds. For example, its feathers are softer and more hair-like, much like the feathers of other flightless birds.2
And further below:

This would be similar to the case of flightless beetles on windy islands that are more likely to survive, while the beetles that can fly are more likely to be swept away.4 Or else it may simply have been a case of reduced selection pressure—with none of the mainland predators and plentiful food in the sea, loss of flight would be a less serious disadvantage, much like cave creatures that lose their sight over generations.5However, this would not be an example of evolution; the mutation that caused the flightless cormorant to lose the ability to fly is an example of a loss of genetic information. Goo-to-you evolution would require changes that result in new genetic information.
Im not going to comment on "goo-to-you" evolution, but I would like to thank CMI for some useful info. Here this is clearly an adaptation in which the cormorant lost a function (flying), in this case they have lost too much muscle mass on their wings to allow them to fly. The trade-off is that a) they have, thicker, softer, denser body feathers to insulate their body b) they have thicker, stronger legs for swimming.

 Nevertheless, let us look at our next specimen: the marine iguana. A truly unique species endemic to Galapagos, it is the only species of iguana that enters saltwater to eat marine plants. Note that no other iguana does this. 

This quote (taken from here) explains it well enough: 

Marine iguanas have many adaptations for their survival. The teeth of the marine iguana are flattened laterally and lie in single rows along the sides of the jaws immediately inside of the labial scales. Along with their short and blunt snout, the iguana is able to get its jaws into close contact with the substrate for feeding. They also have long, sharp, curved claws that allow them to keep a firm hold of the ground during rough seas or when submerged. The marine iguana also has dark colored scales to help absorb as much heat as possible because they are cold-blooded. To do this they flatten themselves against the lava rocks, exposing as much skin surface as possible to the sun. The flow of heat is regulated by vessels in the chest which close and open to regulate body temperature. The marine iguana has also developed a pair of salt glands beneath the skin between the eye and the nostril on each side of the head which periodically ejects forcibly a fine spray of highly saline secretion. It can project this spray to over a foot in distance.
What are a few adaptations, based on this? a) it has a shorter snout than mainland iguanas b) it has longer, curved claws c) most surprisingly, the have a pair of salt glands that expel salt.

The last adaptation that clearly gives a gain in function that allows our marine iguana to thrive in the predator-free environment of the Galapagos. 

Do you see now? Evolution can lead to adaptations either way: it can lead to a loss of a redundant function, or a gain in a new useful function. Natural selection takes care of the rate of phenotype expression. That's all!

Which is why I dont understand CMI's MO. They claim that mutations cannot increase information, yet they dont actually define give a specific definition what information is. It could mean anything: is it a new protein? A new function? 

One more thing: throughout the Galapagos, you will notice that: a) there are no amphibians on the island b) there are many fewer species of mammals c) flora consists of mostly desert type plants. Why?

Amphibians require warm, moist environments to survive. None would have survived the trip to Galapagos: the sun and saltwater would have baked them dry. This is in contrast to reptiles, whose dry and scaly skin would have allowed them to conserve enough water to survive. This has  ramifications for the newly established field of baraminology (a field that I actually respect), in particular for explaining the enormous diversity of amphibians in the Amazon (to be further highlighted in a future post). 

In the case of many South American islands Charles Darwin visited, he also noted a conspicuous absence of mammals, with the exception of a) bats b) rodents (often introduced by ships actually). 

As for desert plants, simple! Wind dispersal maximizes the chances of seeds arriving on the island. Animal-dispersed angiosperm seeds rarely ever reached the islands. Desert-like plants would also thrive on water-poor soils on the Galapagos. 

I realise this has went a little off-topic, (it was originally going to pontificate on the beauty of these animals) but in the next post, I am going to bring up even better examples of biogeographic island biota. Stay tuned!

P.S remember that Alfred Russell Wallace himself was a deeply spiritual man. 

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