Final answer:
Excavata is a group of protists with key morphological features such as a feeding groove, modified mitochondria, and various locomotive structures. Subgroups include diplomonads with mitosomes, parabasalids with a parabasal apparatus and hydrogenosomes, and euglenozoans with diverse mitochondria and chloroplasts.
Step-by-step explanation:
Key Morphological Characteristics of Excavata
Excavata is a supergroup of protists known for its distinctive morphological features. The common characteristics include a pronounced feeding groove or 'excavate' on one side of the cell, signifying how their nutrition acquisition mechanisms have evolved. The subgroups within Excavata exhibit further specializations.
The diplomonads, such as Giardia lamblia, are characterized by having two nuclei and multiple flagella. They typically lack fully functional mitochondria but contain mitosome remnants that assist in iron and sulfur metabolism. These organisms thrive in anaerobic environments and rely on pathways such as glycolysis for energy production.
Parabasalids feature a parabasal apparatus and an axostyle, which are associated with their cytoskeletal structure. Their mitochondria-like organelles, known as hydrogenosomes, generate hydrogen gas as a byproduct and function in anaerobic conditions. Trichomonads, falling under parabasalids, include Trichomonas vaginalis, a pathogen causing trichomoniasis.
Lastly, euglenozoans are a diverse group that includes both free-living and parasitic species. They have diverse forms of mitochondria and, in some cases, chloroplasts derived from secondary endosymbiosis. Their locomotion is facilitated by flagella and, in some species, an undulating membrane.