Chapter Summary:

Feature Investigation:

     Scientists had been studying the relationships between living organisms for quite some time. They then  discovered that it was possible to retrieve the DNA from extinct organisms in rare situations. This opened up more opportunities for the scientists to compare extinct species of organisms with similar species that still exist today. 

     Six scientists, Alan Cooper,  Cécile Mourer-Chauviré, Geoffrey Chambers, Arndt von Haeseler, Allan Wilson, and Svante Pääbo decided to run this experiment on flightless birds that existed long ago and today. They wanted to see what their DNA would show of their evolutionary relationships and how similar their DNA would be to other flightless birds'. The main birds they chose to compare were both from New Zealand, the moa and the kiwi. Moas died out long ago, but some species of kiwis still exist today. The scientists also chose to compare the DNA to flightless birds from other countries, including the emu, cassowary, rhea, and ostrich. They subjected all of the birds' DNA to PCR to amplify it, and then all of the DNA was compared. 

     The DNA between all the flightless birds showed many similarities. However, there were some differences between the sequences. In fact, there were more similarities between the kiwi and the ostrich than the kiwi and moa, even though the kiwi and moa both were found in New Zealand and ostriches are found in Africa. With these results, the scientists were able to create a new phylogenetic tree to revise these relationships.

Chapter/Case Study:

     Horizontal gene transfer is the title of any process in which an organism takes in genetic material from another organism without being an offspring of that organism. The discovery of horizontal gene transfer has forced scientists rethink the way they view the evolutionary process. 

     As the Genomes and Proteomes Connection clearly states, horizontal gene transfer has created a major role in evolution. This process is much more common in bacteria and other prokaryotic cells, and can be done via conjugation, transformation, and transduction. These transfers can give the recipient a new protein or trait that better enables their chance of survival in their environment. However, this process is not as common in multicellular eukaryotes. 

     Scientists have proposed that in early evolution, when most horizontal gene transfer was much more common, and many of the cells shared their genetic material with each other. That way, instead of an organism having only one direct ancestor, they share traits with ancestors that aren't related to their common ancestor at all. Then, the tree of life would actually be a web of life, in which the vertical branches are connected horizontally.

     Horizontal gene transfer is not as prevalent in eukaryotic cells due to multicellularity and sexual reproduction being the main form of producing offspring. If a gene were to be transfered horizontally in a eukaryotic cell, it would need to transfer into a gamete, or a cell that gives rise to a gamete.

Virtual Lecture:

Feature investigation:

Chapter 26.5

Useful Materials:

This is an image of the different ways that horizontal gene transfer can export its DNA into a recipient cell. These three types are transformation, transduction, and conjugation. These were discussed in past chapters, but are used for horizontal gene transfer. Because of the fact that these types of transfer are the most common, it makes sense that bacteria would be able to take part in horizontal gene transfer, and that it's rarer in eukaryotes, due to the fact that they are multicellular.

This video explains how to make a phylogenetic tree for animals. The feature investigation explained how the scientists created the phylogenetic tree for the flightless birds. This is only a preview of the lesson, which needs to be paid for. However, if one is interested, the link for this video is http://mindbites.com/lesson/4138-biology-construct-a-phylogenetic-tree-of-animals.

http://www.scivee.tv/node/6624

This video discusses how the tree of life is being made, and what the scientists are doing to determine how the species are related to one another and what it all means. The video even explains a lot about natural selection.

http://tolweb.org/tree/

The above link is to a website all about the Tree of Life and how scientists are pooling together all of their discoveries about the DNA they found and the relationships between organisms. This is a good website to go to if one wants to spend time learning more about the process in which the tree of life was made, and is still undergoing. 

Presentation:

Feature Investigation

Chapter 26.5