The valve between the left atrium and left ventricle is the: MCQ with Answer and Explanation

Explanation:
The Haversian system (osteon) is the characteristic structural unit of compact (cortical) bone in mammals. It consists of a central Haversian canal (containing blood vessels and nerves) surrounded by concentric layers of calcified matrix called lamellae. Between the lamellae are small spaces called lacunae, which house osteocytes (bone cells). Canaliculi connect the lacunae. Bird bones are pneumatic (hollow), and cartilage lacks Haversian systems.

Explanation:
Microinjection uses a very fine glass micropipette to inject DNA directly into the nucleus of a target cell. Electroporation uses electrical pulses, biolistics is gene gun for plant cells, lipofection uses lipid vesicles.

Explanation:
The phylum Echinodermata (spiny-skinned animals like starfish, sea urchins, sea cucumbers) is uniquely characterized by a water vascular system used for locomotion, capture and transport of food, and respiration. The tube feet are the terminal effectors of this system. They exhibit secondary radial symmetry in adults, though their larvae are bilaterally symmetrical. Mollusks have a muscular foot, and arthropods have jointed appendages.