Double covalent bond is formed in

 O2
 CO2
 C2H2

How many trophic levels are there in the following food chain? phytoplankton - shrimp - perch - pike - osprey

Factors that can increase mutation rates a. high temps b. low temps c. food additives d. uv rays

Which statement best describes the relationship between an allele and a gene? question 1 a. an allele is a variation of a gene that can be expressed as a phenotype. b. an allele is the part of a gene that attaches to messenger rna molecules. c. an allele is a segment of a dna molecule that controls replication of a gene.