What’s the question.....................
Answer: 1. Protostome development./2. Bilateral symmetry/4. Three embryonic germ layers
Explanation:
Over 600 million years ago some animals invaded aquatic and terrestrial environments in the pre-Cambrian period. These animals were enforced by huge evolutionary irradiation, and now they occupy every environment on planet Earth. From tiny insects and crustaceans smaller than 1mm in length to giant crabs from Japan that can reach 3m (with open legs), the arthropods are found in all size models, with an estimated number of more than one million species described. Concerning characteristics they are - Bilateral, triploblastic( Three embryonic germ layers), prostomial. Internally and externally segmented body, divided into at least two regions, head, and abdomen; typically with a cephalic shield or carapace. Opened circulatory system; the dorsal heart is a muscle pump with lateral Ostia for blood return.
A twitch is defined as a single, brief contraction period and then relaxation period of a skeletal muscle in response to a single stimulation. Contraction period involves receptive power strokes that pull the thin filaments past the thick filaments shortening sacromeres and muscle tension increases as the sacromeres shorten. Relaxation period begins with or release of cross bridges resulting from the return of Ca2+ back to sarcoplasmic reticulum. The strength of skeletal muscle contractions can be broadly separated into twitch, summation, and tetanus. A twitch is a single contraction and relaxation cycle produced by an action potential within the muscle fiber itself.
Answer:
The evidence suggests that these chloroplast organelles were also once free-living bacteria. The endosymbiotic event that generated mitochondria must have happened early in the history of eukaryotes, because all eukaryotes have them
Explanation:
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1. Elements are the building block of minerals
