The muscles are composed inside mainly of fibers, filaments and proteins, where it is important to consider the <u>length-tension</u> relationship of the thick and thin filaments to know the tension.
<h3>What is muscle contraction?</h3>
It is an organized and natural event that takes place at the level of the muscles when the fibers and proteins inside them come together, and tension is produced in the area.
<h3>Characteristics of muscle contraction</h3>
- In a muscle contraction, a tension is generated that depends on the length-tension relationship, which causes a displacement of the muscle filaments.
- The proteins actin and myosin join together, and a force is generated so that the final movement is achieved.
- To know the tension, the muscle changes length and measurable external work is produced from the force and distance traveled.
Therefore, we can conclude that the contraction allows us to make movements to reach and carry our extremities to different places.
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Answer:
The circulatory system or vascular system is an organ system that helps in the transport of the blood from and to the heart. The blood transport also takes oxygen, nutrients, hormones, and other components from the heart to the various part of the brain with the help of the arteries and carry waste such as carbon dioxide to the heart in veins.
The oxygenated blood enters in the left atrium and moves to the left ventricle to the aorta and starts its journey to the body whereas deoxygenated blood enters in the right upper chamber or right atrium of the heart and pump to the right lower chamber and to the lungs to carry the oxygen again. This process is a continuous process.
 
        
             
        
        
        
The correct answer is option A, that is, Phylum Porifera.  
The species of Phylum Porifera are aquatic, that is, mostly marine. They exhibit cellular grade of the body, they are diploblastic animals with asymmetrical symmetry. They lack body cavity and exhibits a holozoic mode of nutrition with intracellular digestion.  
They lack circulatory and nervous system and possess the tendency to regenerate their parts of the body. The organisms in phylum Porifera exhibits both asexual and sexual mode of reproduction.  
 
        
                    
             
        
        
        
In <u>asexual </u>reproduction, genetically identical offspring are produced, while in <u>sexual </u>reproduction, offspring are genetically different from each other.
Sexual reproduction is a sort of reproduction that involves a complex existence cycle wherein a gamete (inclusive of a sperm or egg mobile) with an unmarried set of chromosomes (haploid) combines with another to provide a zygote that develops into an organism composed of cells with two sets of chromosomes (diploid).
Sexual reproduction is the maximum common existence cycle in multicellular eukaryotes, which includes animals, fungi, and plants.
Asexual reproduction is a sort of reproduction that doesn't involve the fusion of gametes or change in the number of chromosomes. The offspring that get up by asexual reproduction from both unicellular and multicellular organisms inherit the whole set of genes in their single parent. Asexual reproduction is the number one shape of reproduction for single-celled organisms including archaea and bacteria.
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Answer:
Processes that takes place with oxygen is aerobic and processes that takes without oxygen is anaerobic. 
Glycolysis and Krebs Cycle produces 2 Atp and ETC produces 34 Atp