Answer:
The number of habitats falls below a critical level.
Explanation:
The possible reason for extinction is that the number of habitats falls below a critical level. This makes it impossible for organisms to survive. 
- A habitat is the dwelling place of living organism in an ecosystem. 
- The resources and other materials that ensures the survival of an organism are made available in the habitat. 
- When a habitat begins to thin out and can no longer support organisms, then extinction will ensue.  
 
        
             
        
        
        
<span>Reproduction (or procreation) is the biological process by which new "offspring" individual organisms are produced from their "parents". Reproduction is a fundamental feature of all known life; each individual organism exists as the result of reproduction. The known methods of reproduction are broadly grouped into two main types: sexual and asexual.
In asexual reproduction, an individual can reproduce without involvement with another individual of that species. The division of a bacterial cell into two daughter cells is an example of asexual reproduction. Asexual reproduction is not, however, limited to single-celled organisms. Most plants have the ability to reproduce asexually and the ant species Mycocepurus smithii is thought to reproduce entirely by asexual means.
Sexual reproduction typically requires the involvement of two individuals or gametes, one each from opposite type of sex. The propagation of organisms can also occur through cloning.
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The correct answer for this question is letter C. Epiglottis is the one who prevents food from entering the trachea. It moves in a back and forth manner. When a person swallows, it covers the entrance of the larynx by flattening itself backwards.
        
             
        
        
        
Answer:
Rigor mortis occurs as the sarcoplasmic reticulum deteriorates, releasing calcium ions.
Explanation:
Rigor mortis means stiffening of the body after death. It is one of the most significant signs of death, caused by a change in the chemical balance of the muscles after death. This is where the muscles become hard, making them difficult or impossible to move. 
The biochemical cause of rigor mortis begins with the cessation of the pumping of calcium ions into the sarcoplasmic reticulum (due to the absence of ATP) so that the cytosolic concentration of this ion gradually increases, it also contributes to this increase in the cytosolic calcium ion concentration the degradation of the reticulum terminal cisterns. Blood circulation ceases, as does oxygen transport and withdrawal of metabolism products. Enzyme systems continue to function after some time of death. Thus, glycolysis continues in an anaerobic manner, generating lactic acid, which produces a lowering of the pH.