Some biologists urge the collection of the few remaining individuals of some of the most threate most threatened 3) amphibian species in order to preserve them if they become extinct in the wild. If such captive-breeding programs could produce thousands of individuals from just a few of the remaining survivors, the species will still be threatened because of A) directional selection B) artificial selection C) a bottleneck effect D) mutations

Match the descriptions / definitions with the term they best describe 1. three dimensional relationship of the different polypeptide chains in a multisubunit protein or protein complex 2. common folding pattern in proteins in which a linear sequence of amino acids folds into a right-handed coil stabilized by internal hydrogen-bonding between polypeptide backbone atoms. 3. the amino acid sequence of a protein 4. a region on the surface of a protein that can interact with another molecule through noncovalent bonding. 5. three-dimensional arrangement of alpha-helices and beta-sheets within a single polypeptide, typically stabilized by a variety of noncovalent bonds, including ionic and hydrogen bonds, and nonpolar interactions / hydrophobic force. 6. the chain of repeating carbon and nitrogen atoms, linked by peptide bonds, in a protein. 7. common structural motif in proteins in which different sections of the polypeptide chain run alongside each other and are joined together by hydrogen bonding between atoms of the polypeptide backbone. 8. portion of a polypeptide chain that has a discrete tertiary structure of its own and can often fold independently of the rest of the chain 9. regular local folding patterns in a protein, including alpha-helix and beta-sheet a. primary structure b. beta-sheet c. protein d. coiled-coil e. polypeptide backbone f. secondary structure g. side chain h. tertiary structure i. binding site j. alpha-helix k. quaternary structure l. protein domain

The picture represents a structure of the respiratory system. which is the function of this structure? to bring air into the body to exchange oxygen with carbon dioxide to carry air to the lungs to release oxygen from the body

Once an egg cell is fertilized by sperm, the cell then, as the embryo develops, it receives nourishment and eliminates wastes by transferring substances from its blood to its mother's blood. a. becomes a fetus immediately and exits the womb b. begins to divide and implants itself in the wall of the uterus c. remains in the uterus without dividing for several months d. travels back to the ovaries until the fetus is developed