Sponges are similar to other animals in that they are multicellular, heterotrophic, lack cell walls and produce sperm cells. Unlike other animals, they lack true tissues and organs, and have no body symmetry.
The shapes of their bodies are adapted for maximal efficiency of water
flow through the central cavity, where it deposits nutrients, and leaves
through a hole called the osculum. Many sponges have internal skeletons of spongin and/or spicules of calcium carbonate or silicon dioxide. All sponges are sessile
aquatic animals. Although there are freshwater species, the great
majority are marine (salt water) species, ranging from tidal zones to
depths exceeding 8,800 m (5.5 mi).
Answer:
Option E, C tactile (CT) afferent
Explanation:
Whenever a slow moving gentle touch experienced, the response is due to the nerve fibers called C-Tactile afferents (CTs).
C-Tactile afferents (CTs) are unmyelinated mechanoreceptors of low threshold and low conduction velocities.
In humans, CT neurons are found in hairy skin.
The pleasant feeling observed during a slow gentle touch is due to the interaction of
CT neurons project to the insular cortex in the brain
Hence, option E is correct
Answer:
Mammals first appeared
Explanation:
The dinosaurs became extinct one million years after the Cenozoic era started. The mammals first appeared as the modern culture first appeared in that era.
<span>(According to Reference)
Whereas an onion epidermal cell has a cell wall, a human cheek cell does not. Instead, a semi-permeable membrane surrounds the cytoplasm of the cheek cell. While there are chloroplasts present in onion cells, they are absent in cheek cells. </span>
