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' flat animals ') [3] is a phylum of free-living (non-parasitic) marine invertebrates. [4] [5] They are blob-like animals composed of aggregations of cells. Moving in water by ciliary motion, eating food by engulfment, reproducing by fission or budding, placozoans are described as "the simplest animals on Earth."
When the concentrations of algae are high the animals are more likely to engage in social feeding behavior. [19] Not all bacteria in the interior of Placozoa are digested as food: in the endoplasmic reticulum, an organelle of the fibre syncytium, bacteria are frequently found that appear to live in symbiosis with Trichoplax adhaerens. [20]
Appearance of baleen hair in a whale's open mouth Cross-section of jaw showing bone a, gum b, rigid plate c and frayed baleen hairs d and e. Baleen is a filter-feeding system inside the mouths of baleen whales. To use baleen, the whale first opens its mouth underwater to take in water.
Usually, the food is embedded in a string of mucus produced in the mouth, creating a coiled conical mass in the style sac. This action, rather than muscular peristalsis, is responsible for the movement of food through the gastropod digestive tract. [1] Two diverticular glands open into the stomach, and secrete enzymes that help to break down ...
They typically feed by drawing in water through pores, filtering out small particles of food. [127] The Ctenophora and Cnidaria are radially symmetric and have digestive chambers with a single opening, which serves as both mouth and anus. [128] Animals in both phyla have distinct tissues, but these are not organised into discrete organs. [129]
Subsequent adaptations appear to have favored forward filtering appendages. Filtering appendages generate water currents that bring food items into reach for collection by setae. Other setae may be used to brush the filtering setae clean, and yet other setae may transport food items to the mouth.
The Cestida ("belt animals") are ribbon-shaped planktonic animals, with the mouth and aboral organ aligned in the middle of opposite edges of the ribbon. There is a pair of comb-rows along each aboral edge, and tentilla emerging from a groove all along the oral edge, which stream back across most of the wing-like body surface.
The food is masticated in the mouth of the parent into a bolus and then transferred to the infant for consumption [3] (some other animals also premasticate). Cattle and some other animals, called ruminants, chew food more than once to extract more nutrients. After the first round of chewing, this food is called cud.