All plant and animal groups existing together and the physical factors with which they interact compose an ecosystem<span>.</span>
        
                    
             
        
        
        
Arthropods were the first animals to successfully invade land from the sea
        
             
        
        
        
Answer:
Explanation:
Four conditions are needed for natural selection to occur: reproduction, heredity, variation in fitness or organisms, variation in individual characters among members of the population. 
ORR 
Struggle for existence, variation and inheritance. These are said to be the necessary and sufficient conditions for natural selection to occur.
 
        
             
        
        
        
Fluorescent in situ hybridization (Fish) is a method employing a fluorescent dye covalently bonded to a specific nucleic acid probe identifying or tracking organisms in the environment. Fluorescent in situ hybridization (fish) can be used to determine; how many salmonella typhimurium cells are present in a sample of unpasteurized apple juice, the phylogenetic diversity of an environmental sample and also whether a specific piece of mRNA is being produced.