Chapter 28

Knowledge/Comprehension Plastids that are surrounded by more than two membranes are evidence of (A) evolution from mitochondria. (B) fusion of plastids. (C) origin of plastids. (D) origin of the plastids from archaea. (D) secondary endosymbiosis.

Knowledge/Comprehension Biologists think that endosymbiosis gave rise to mitochondria before plastids partly because (A) the products of photosynthesis could not be metabolized without mitochondrial enzymes. (B) all eukaryotes have mitochondria (or their remnants) whereas many eukaryotes do not have plastids. (C) mitochondrial DNA is less similar to prokaryotic DNA than is plastid DNA. (D) without mitochondrial \(\mathrm{CO}_{2}\) production, photosynthesis could not occur.

Knowledge/Comprehension Which group is incorrectly paired with its description? (A) diatoms-important producers in aquatic communities (B) red algae-eukaryotes that acquired plastids by secondary endosymbiosis (C) apicomplexans-unicellular parasites with intricate life cycles (D) diplomonads-unicellular eukaryotes with modified mitochondria

Knowledge/Comprehension In a life cycle with alternation of generations, multicellular haploid forms alternate with (A) unicellular haploid forms. (B) unicellular diploid forms. (C) multicellular haploid forms. (D) multicellular diploid forms.

Application/Analysis EVOLUTION CONNECTION DRAW IT Medical researchers seek to develop drugs that can kill or restrict the growth of human pathogens yet have few harmful effects on patients. These drugs often work by disrupting the metabolism of the pathogen or by targeting its structural features. Draw and label a phylogenetic tree that includes an ancestral prokaryote and the following groups of organisms: Excavata, SAR, Archaeplastida, Unikonta, and, within Unikonta, amoebozoans, animals, choanoflagellates, fungi, and nucleariids. Based on this tree, hypothesize whether it would be most difficult to develop drugs to combat human pathogens that are prokaryotes, protists, animals, or fungi. (You do not need to consider the evolution of drug resistance by the pathogen.)

Synthesis/Evaluation WRITE ABOUT A THEME: INTERACTIONS Organisms interact with each other and the physical environment. In a short essay (100-150 words), explain how the response of diatom populations to a drop in nutrient availability can affect both other organisms and aspects of the physical environment (such as carbon dioxide concentrations).

Synthesis/Evaluation SYNTHESIZE YOUR KNOWLEDGE This micrograph shows a single-celled eukaryote, the ciliate Didinium (left), about to engulf its Paramecium prey, which is also a ciliate. Identify the eukaryotic supergroup to which ciliates belong and describe the role of endosymbiosis in the evolutionary history of that supergroup. Are these ciliates more closely related to all other protists than they are to plants, fungi, or animals? Explain.