THIS PROMPT IS WRITTEN BY GRACE KAPOV!!!!!!!
On pages 39-47, Coyne talks about how birds evolved from reptiles. He explains reptiles began to have asymmetrical feathers to aid in flight and opposable big toes for perching. Why would these changes be beneficial for the reptiles' survival? From this evolutionary break, birds have evolved into a variety of different species due to the demands of their respective environments. According to www.birdlist.org, there are at lease 10,031 species of birds on the planet! Choose a specie of bird and explain in detail how it has evolved from its distant ancestor to fit its environment. Are there any ways in which this specie of bird does not fit its environment? Explain.
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As Coyne explains later in that same chapter on pages 46 and 47 the “ground up” theory is the more likely theory as to how birds evolved and why it makes evolutionary steps by improving individual fitness every step of the way. In this theory dinosaurs that were covered in feathers would use this as an aid in catching prey by either startling it with bright colors or making short hops to chase it down, as is proposed how Albertonykus caught its insect prey with the aid of its feathered tail; or some yet smaller dinosaurs may have developed thin membranes between limbs as means for gliding and catching prey from an unexpected approach. And as is apparent if anyone has seen how the Velociraptors hunt in “Jurrasic Park” that the talon-claw of some reptiles was a very efficient maiming and killing tool. All of these proposed adaptations would increase the fitness of the organism and are therefore justified within the context of evolution. Now let us take a look at the modern hummingbird, (generalizing the variety of species of hummingbird into one) it would have developed likely from birds that progressively became smaller to fit the niche of a pollinator for flowers and the hummingbird is well suited for this. The hummingbird’s wings are unique in that they allow the bird to hover in place near a flower so that it can continuously ingest nectar and at the same time pick up pollen from that flower. While this is great for its job as a pollinator there had to be a sacrifice in the potential defense of the hummingbird. The greatest threat for hummingbirds is from their fellow kin; hawks, blue jays, and crows. If the hummingbird had not become so small over the course of evolution then it would be more substantial in a fight but would not be able to pollinate and drink from flowers as easily. In this way there is a trade-off in the survival of the species but the hummingbird is obviously favored because they still exist today in consequential numbers.
ReplyDeleteSources:
http://dinosaurs.about.com/od/carnivorousdinosaurs/p/albertonykus.htm
http://www.hummingbirdsociety.org/hottopics/predators.asp
Great Question. Good Comment Johnathan, you and I were working on this at the same time, but you finished before me! I'll put mine up anyways :-)
ReplyDeleteOn page 46 Coyne talks about when feathers were first seen in the fossil record by examining the basic skeletal plan of birds. It is very interesting and important to notice that these essential feathers “evolved before birds could fly” (46). Therefore, feathers did NOT arise as adaptations for flying, but then what were they for? Coyne hypothesizes that they were used for display “perhaps to attract mates” (46). On the other hand, and the hand that is perhaps most likely, is that the feathers were used for insulation; unlike modern reptiles, theropods could have been warm blooded. Another debate over the evolution of feathers is what they evolved from. Coyne says that although no one knows, the best guess is that they come from the same cells that gave rise to reptilian scales, but this is not proven to be fact.
The next part of the questions asks to research a certain type of bird and explain its evolutionary history. For this I am going to choose one of my favorite birds, the penguin. The oldest known fossil of the penguin species is the Waimanu manneringi. This bird lived in New Zealand at around 62 million years ago (http://en.wikipedia.org/wiki/Penguin#Evolution). The Waimanu were generally “loon-like” birds who were already flightless; however, they contained short wings adapted for deep diving, but were not as well-adapted to aquatic life as modern penguins are today. Currently the penguins use their wings as flippers or propellers in order to use their wings to “fly” through the water (http://www.ehow.com/how-does_4567568_penguins-swim.html). The same source also describes how penguins engage the small muscles connected to their feathers to create a tight, waterproof layer. At the same time the feathers are coated with a special oil to keep the water out, as oil and water do not mix.
Other ancestors of the penguins are called “Giant Penguins” informally as they were often 5 to 6 feet tall. Currently the average size of penguins is about 24-28 inches tall, slightly over 2 feet tall (http://answers.yahoo.com/question/index?qid=20090217080859AAWzfNG). One example of these Giant penguins, called the Icadyptes salasi stood 5 feet tall, lived about 36 million years ago and lived in Peru (http://agutie.homestead.com/files/world_news_map/peru_giant_penguin.htm). The “Giant Penguin” size was found to be at a disadvantage, perhaps as it was more difficult to maneuver in the water at such a great size and to sneak up on prey, that the penguin species adapted to a smaller size.
Penguins evolved from the same common ancestor of all birds populating the planet. This common ancestor is the missing link between reptiles and birds. Much like other birds, through natural selection and evolution, feathers and wings began to form which have been proven to be extremely useful in the navigating of the water for penguins.
One way that the penguin does not fit its environment is that the penguins cannot breathe underwater (http://www.ehow.com/how-does_4566655_penguins-breathe-underwater.html). Although the average dive lasts a remarkable 6 minutes, it would be more efficient and waste less energy if the penguins were able to breathe underwater. Then they would be able to be underwater for longer periods of time, and go deeper into the ocean, which would lead to them being able to catch more prey. Eating more food gives the penguins more energy allowing them to live for a longer period of time; thus it would be a selective advantage for penguins to form gill-type mechanisms in order to breathe under water.