Chapter 28

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

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.

Which group is correctly paired with its description? (A) diatoms-important consumers in aquatic communities (B) diplomonads-protists with modified mitochondria (C) apicomplexans-producers with intricate life cycles (D) red algae-acquired plastids by secondary endosymbiosis

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.

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).