Answer:
endosymbiosis.
Explanation:
By the beginning of the 20th century, researchers thought that plastids and mitochondria could come from bacteria. These would have been ingested by primitive cells and live within them in symbiosis.
Answer;
-Chitin is a structural carbohydrate that forms their exoskeleton
Explanation;
-Chitin is the main component in the exoskeletons of arthropods and crustaceans and is also in the cell walls of fungi.
-It is a linear long chain polymer consisting of repeated units of N-acetyl-glucosamine.
-The main function of the chitin-containing exoskeleton is to keep the inner soft tissue safe from any sort of injury and also prevents the delicate tissues from drying (acts as a water tight barrier against dehydration).
Answer:
a. resolve the branching patterns (evolutionary history) of the Lophotrochozoa
b. (the same, it is repeated)
Explanation:
Nemertios (ribbon worms) and foronids (horseshoe worms) are closely related groups of lofotrocozoa. Lofotrocozoans, or simply trocozoans (= tribomastic celomados with trocophoric larva) are a group of animals that includes annelids, molluscs, endoprocts, brachiopods and other invertebrates. They represent a crucial superphylum for our understanding of the evolution of bilateral symmetry animals. However, given the inconsistency between molecular and morphological data for these groups, their origins were not entirely clear. In the work linked above, the first records of genomes of the Nemertine worm Notospermus geniculatus and the foronid Phoronis australis are presented, along with transcriptomes along the adult bodies. Our phylogenetic analyzes based on the genome place Nemertinos as the sister group of the taxon that contains Phoronidea and Brachiopoda. It is shown that lofotrocozoans share many families of genes with deuterotomes, suggesting that these two groups retain a common genetic repertoire of bilaterals that do not possess ecdisozoans (arthropods, nematodes) or platizoos (platelets, sydermats). Comparative transcriptomics demonstrates that foronid and brachiopod lofophores are similar not only morphologically, but also at the molecular level. Although the lofophore and vertebrates show very different cephalic structures, the lofophorees express the vertebrate head genes and neuronal marker genes. This finding suggests a common origin of the bilaterial pattern of the head, although different types of head will evolve independently in each lineage. In addition, we recorded innate immunity expansions of lineage-specific and toxin-related genes in both lofotrocozoa and deuterostomes. Together, this study reveals a dual nature of lofotrocozoans, in which the conserved and specific characteristics of the lineage shape their evolution.
