Sponges (phylum: Porifera) are animals that possess feeding cells called collar cells. These cells have a central flagellum surrounded by a collar of microvilli. The collar filters organic matter out of the water column. Which protist shares a more recent common ancestor with the poriferans?

Question

A.  Ciliates
B.  Rhodophyta
C.  Choanoflagellates
D.  Radiolarians
E.  Myxomycota

Clarify Question
· What is the key concept addressed by the question?
· What type of thinking is required?
 
Gather Content
· What do you already know about Porifera? How does it relate to the question?
 
Choose Answer
· Given what you now know, what information and/or problem solving approach is most likely to produce the correct answer?
 
Reflect on Process
· Did your problem-solving process lead you to the correct answer? If not, where did the process break down or lead you astray? How can you revise your approach to produce a more desirable result?

Answer 1

C.  Choanoflagellates

Clarify Question
· What is the key concept addressed by the question?
The question is asking you to determine which of the options shares a most recent common ancestor with Porifera. On a family tree, you and your sister would share a more recent common ancestor than you and your cousin. Look at the Eukarya family tree. Which groups have more recent common ancestors with Porifera?
· What type of thinking is required?
This question is an “apply” question, so it is asking for you to use the knowledge you already have about reading phylogenetic trees to figure out the most recent common ancestor of Porifera.
 
Gather Content
· What do you already know about Porifera? How does it relate to the question?
        o Porifera are in Kingdom Animalia. Where is Kingdom Animalia on the Eukaryote family tree?
        o Common ancestors are populations that were originally one species, but diverged into two species. They can be seen as nodes on a phylogenetic tree.
        o More closely related groups tend to have more traits in common. In this case, close relatives to Porifera are likely to have a similar feeding collar.
 
Choose Answer
· Given what you now know, what information and/or problem solving approach is most likely to produce the correct answer?
        o Now that you know Porifera are in Kingdom Animalia, find them on the Eukaryote family tree. If you have a pencil, circle them. Now trace your finger back along the branch that becomes Animalia. When it joins another line, you have found a common ancestor. Let’s call that ancestor “Mom”. How many daughters does Mom have? Now trace the line back farther to find the next common ancestor. Let’s call that ancestor “Grandma”. How many granddaughters does Grandma have? Which of the options are a sister to Porifera? Which of the options are a cousin to Porifera? Are there second-cousins?
 
Reflect on Process
· Did your problem-solving process lead you to the correct answer? If not, where did the process break down or lead you astray? How can you revise your approach to produce a more desirable result?
        o This question asked to you figure out which group was most closely related to Porifera. To answer this question correctly, you needed to apply your knowledge about phylogenies to the Eukaryote family tree.
        o If you got the correct answer, great job! Keep using the strategy you used here on other “apply” questions.
        o If you got the incorrect answer, where did the process break down? Did you remember that the closest relatives share the most recent common ancestor? Did you have trouble reading the phylogenetic tree? Reading phylogenies is difficult, and many students struggle with it at first. You should go back to the chapter on reading phylogenies to brush up. If you are still having difficulty, go talk to your professor or TA. Once you understand phylogenies, questions like this will be a lot easier.