Question

assumptions that are employeu. 2. Chapter 28 -15 pts This micrograph (Chapter review, p. 615) shows a single-celled eukaryote, the ciliate Didinium (left) about to engulf a second ciliate, Paramecium, as its prey. Historically, Didinium and Parameciumn have been classified as protozoa since they are single-celled, heterotrophic eukaryotes. Identify the eukaryotic supergroup to which ciliates belong and describe the role of secondary endosymbiosis in the evolutionary history of this supergroup. Also, as a second part of the question, indicate whether these ciliates are more closely related to all of the other protozoa than they are to the plants, fungi, or animals and explain the basis for your answer? HINT: Consider the entire eukaryotic family tree (Fig. 28.2) and the position of protozoa collectively. Are protozoa a 'grade' or a 'clade'? 3. Chapter 30 - 15 pts

Answer 1

1. Ciliates belongs to the group chromalveolata.

2. Protistic diversity has its evolution from endosymbiosis, and the mitochondria that has been evolved by endosymbiosis from aerobic prokaryote. And plastids that of photosynthetic cyanobacterium. The plastid bearing lineage evolved into the red and green algae and during the eukaryotic evolution the red and green algae went through secondary endosymbiosis and were ingested by a heterotrophic eukaryote. The proposed endosymbiont in chromoalveolates is red algae.

3. the free living red algal cell were captured and was retained by a non photosynthetic heterotrophic protist after the evolutionary split of rd and green algae wwhich is what we call secondary endosymbiosis and gave rise to the pigmented ancestor of group chromalveolata.

4. Most protists do not share common features with each other. Some of the multicellular protists like seaweed, does not possess highly specialized organs and tissues hence they are different from true plants and other eukaryotes. Fungi are more closely related to unicellular protists and they forms a paraphyletic group with some members more closely associated with fungi animals and plants. Protists and animals fall under the category of eukarya while bacteria is a seperate category.  

5. Protozoa does not form a clade but an evolutionary grade from which the members of animalia, fungi and chromista are evolved.