Humans 101

A natural place for us to begin our investigation of animal diversity is with our own species.  Who are we in the animal kingdom?  We like to think of ourselves as unique and of course, we are--yet we share common ancestry to a greater or lesser degree with all other animals.  What does that mean?  We will begin to find out by investigating the classification of humans. To understand better what we share in common at each level of the classification hierarchy, research the distinguishing features for each taxon in our family tree. Click here for a quick review of classification and how humans are classified. Then click here for details about each level of classification.  A description of what is due for this and all other assignments is given below and to the right (in blue).

Taxonomy is changing

From class, you should know that information about classification is changing. In fact, the last activity gave an example of that in reclassifying the great apes as Family Hominidae along with humans, instead of in Family Pongidae as previously. The original system scientists used was based primarily on data from comparative anatomy and embryology. But advances in DNA techniques have made it possible to compare species on the molecular level as well. These advances have in some cases confirmed what scientists believed about phylogenetic relationships and in other cases revealed surprising new information. In this task you will be focusing on what key characteristics separate different animal phyla under the traditional system, and to what extent new data sheds a different light on which phyla are most closely related. Click here to view a slide show on this topic. Pay particular attention to the diagrams that show relationships under the different systems, but read the text as well.

A tour of nine animal phyla

We often refer to life forms as "more primitive" or "more advanced."  Certainly across the nine phyla we will be examining more closely (listed to the right in green), we can see the evolution of new characteristics that offered particular advantages.  But we should keep in mind that each of these phyla continues in existence today, so in that sense all of these organisms exhibit characteristics which are successful for their way of life.  Rather than thinking of them as primitive or advanced, it is more accurate to think of them as simpler or more complex. As you familiarize yourself with each phylum look for the beauty in how each of these unique groups meets the challenges of survival.

Are birds reptiles?

As we know, DNA analysis is rearranging our thoughts about the relationships between different taxonomic groups.  It used to be that vertebrates were divided into five classes--fish, amphibians, reptiles, mammals, and birds.  But now scientists who study systematics are saying that birds should not be considered a separate class, but are descended from a dinosaur ancestor and thus are part of the reptile clade.  Take a look at some basic characteristics that differentiate classes of vertebrate.  For articles with different points of view about bird descent from dinosaurs, read here or here in support of that line of descent.  Read here for a counter view, and here for a summary of evidence for and against.

Should chimpanzees be part of genus Homo?

Students of evolution know that humans did not descend from apes, but that humans and apes share a common ancestor.  With DNA sequencing, we are now able to show that we share some 99% of our genes with our closest relative, the chimpanzee.  This research is an area of controversy, with some scientists arguing that chimpanzees should be considered a hominid in our own genus.  This would raise many ethical questions about how we treat them.  Other scientists have recently published an argument that challenges the primacy of molecular data and uses morphological traits to link humans and orangutans.  Clink on the links to read these fascinating articles and listen to a podcast on gene research into why humans can speak but chimps cannot.

For further exploration

Some of you may decide you want to know more about the diversity of life that inhabits our planet. It is a fascinating subject, filled with strange but interesting organisms and peculiar but effective ways of solving the many challenges of survival. Here are some web sites that will take you beyond the brief study we have been engaged in.

http://animals.nationalgeographic.com/animals/reptiles.html

http://animals.nationalgeographic.com/animals/fish.html

http://animals.nationalgeographic.com/animals/amphibians.html

http://animals.nationalgeographic.com/animals/birds.html

http://animals.nationalgeographic.com/animals/mammals.html

http://animals.nationalgeographic.com/animals/invertebrates.html

http://animals.nationalgeographic.com/animals/bugs.html

http://www.ucmp.berkeley.edu/exhibits/historyoflife.php
(we used some of the sites connected to this page but there are many more)

http://www.mnh.si.edu/explore/diversity.htm

http://tolweb.org/tree/

http://evolution.berkeley.edu/