According to the figure below, which of the following statements reg.pdf
- 1. According to the figure below, which of the following statements regarding endosymbiosis is correct? D) Both red algae and dinoflagellates have three different genomes in a single cell.A) Cyanobacteria are a common ancestor of red and green algae.B) The red algae have two genomes, while the apicomplexans will have three.C) A heterotrophic protist that engulfed a green alga is the common ancestor of the euglenids and chlorarchiniophytes. D) Both red algae and dinoflagellates have three different genomes in a single cell. Part A According to the figure below, which of the following statements regarding endosymbiosis is correct? Cyanobacteria are a common ancestor of red and green algae. The red algae have two genomes, while the apicomplexans will have three. A heterotrophic protist that engulfed a green alga is the common ancestor of the euglenids and chlorarchiniophytes. Both red algae and dinoflagellates have three different genomes in a single cell Submit Hints My Answers Give Up Review Part Provide Feedback Continue Solution (A) The chloroplasts of red algae, green algae, and plants evolved from an endosymbiotic cyanobacterium living within a mitochondria-containing eukaryotic host cell. The evidence for this theory is as follows- (B) The unicellular red alga Cyanidioschyz lacks introns in all but 26 genes. There are only three copies of ribosomal DNA units that maintain the nucleolus and two dynamin genes that are involved only in the division of mitochondria and plastids. The Apicomplexa are a large phylum of parasitic alveolates. Most of them possess a unique form of organelle that comprises a type of plastid called an apicoplast, and an apical complex structure. Their nucleus is haploid. Hence B is false. (C) A protist is a eukaryotic organism that is not a fungus, plant or animal. Heterotrophic protists decompose organic material, feed on smaller organims such as bacteria or live inside the bodies of larger species. Euglenids are one of the best-known groups of flagellates, which are Excavate Eukaryotes of the phylum Euglenophyta. They are commonly found in freshwater, especially when it is rich in organic materials, with a few marine, and endosymbiotic members. Most euglenids are unicellular. They have descended from an ancestor that took up green algae by secondary endosymbiosis. Chlorarachniophytes are unicellular marine algae with green chloroplasts surrounded by four membranes,found in tropical oceans and are typically mixotrophic, ingesting bacteria and smaller protists as well as conducting photosynthesis. A mixotroph is an organism that can use a
- 2. mix of different sources of energy and carbon, instead of having a single trophic mode on the continuum from complete autotrophy at one end to heterotrophy at the other.The ancestor of chlorarachniophytes is thought to have been a chromalveolate, a eukaryote with a red algal derived chloroplast. Hence C is false. (D) Dinoflagellates are important marine primary producers.They are a large group of flagellate protists that constitute the phylum Dinoflagellata. Most are marine plankton, but they are common in freshwater habitats, as well. Their populations are distributed depending on temperature, salinity, or depth. Many dinoflagellates are known to be photosynthetic, but a large fraction of these are in fact mixotrophic, combining photosynthesis with ingestion of prey (phagotrophy). One of their most striking features is the large amount of cellular DNA that dinoflagellates contain. Most eukaryotic algae contain on average about 0.54 pg DNA/cell, whereas estimates of dinoflagellate DNA content range from 3–250 pg/cell, Polyploidy may account for this large cellular DNA content, but studies of DNA reassociation kinetics do not support this hypothesis. There is no evidence howing that they have different genomes in a single cell. The red algae (Rhodophyta) form a distinct group characterized by having eukaryotic cells without flagella and centrioles, chloroplasts that lack external endoplasmic reticulum and contain unstacked (stoma) thylakoids, and use phycobiliproteins as accessory pigments, which give them their red color. There is no evidence howing that they have different genomes in a single cell. Hence D is false.