Building a Phylogenetic Tree: There are some groups that have no subset of another group... Help!! Please!!

Question

anonymous · Answer

Group	Derived Traits

	        PBL     4-CH     MG     P     PL     CT
Wolf	         +	    +	         +	  -	+	  +
Iguana	 +	    -	         -	  -	-	   -
Human	 +	   +	         +	  -	+	   -
Wombat	 +	   +	         +	  +	-	   -
Tiger        	 +	   +	         +	  -	+	   +
Ostrich	 +	   +	         -	  -	-	   -
Fish	          -	   -	         -	  -	-	   -

PBL: Paired bony limbs
4-CH: Four-chambered heart
MG: Mammary glands
P: Pouch
PL: Placenta
CT: Carnassial teeth

anonymous · Answer

Wolf, Iguana, Human, Wombat, Tiger, Ostrich all have PBL.
Human, Wombat, Tiger, Ostrich all have 4-CH.
Human, Wombat, Tiger all have MG.
and then I am stuck...

anonymous · Answer

The 4 chambered heart in the ostrich is convergent. The others are mammals.

anonymous · Answer

convergent? What do you mean? So what does that mean? D:

anonymous · Answer

A 4 chambers heart evolved independently in the lineage leading to ostriches and the lineage leading to the other three. Homoplasy is another word for the same process.

anonymous · Answer

how did it evolve independently in the lineage and how did you recognize it?

anonymous · Answer

How did it evolve is a long and complicated answer. How do you recognize it is more straightforward. Look at the character states for MG, P, PL, and CT. All of those agree for Iguana and Ostrich. So that tells you that Iguanas and Ostriches should be closely related. Wolf, human, and tiger all have a placenta, so you know those are closely related. Those 3 share mammary gland with wombat, so those 4 should be a group. 

Now you have 2 choices. Either the ostrich goes with the wolf, human, and tiger group and the placenta is lost in ostrich. Or the heart is convergent. Based on all the shared characteristics between iguana and ostrich, it's more likely that the ostrich goes with iguana, and thus the 4 chambered heart evolved separately.

anonymous · Answer

I think I'm getting it.. is it possible for you to make the tree? ahh, I hope it's nto too much to ask D;

anonymous · Answer

Give it a try. I know the tree, so me making it for you won't help you in the long run.

anonymous · Answer

can I show it to you? when I finish?

anonymous · Answer

Sure

anonymous · Answer

Ahh, omg. My unit guide says I should read this website: http://evolution.berkeley.edu/evolibrary/article/0_0_0/phylogenetics_07, and I did and the Phylogenetic tree looks simple... and I tried the question I have above: |dw:1327367282756:dw|