Which of the following is true concerning energy flow through an ecosystem’s food chain? a. primary consumers collect their energy from the sun. b. the sun is the final receiver of energy in an ecosystem. c. energy is lost at each successive energy level in the chain. d. tertiary consumers account for the largest store of energy. select the best answer from the choices provided a b c d

6. in the dna double helix, how are the two strands of dna held together? a. chemical bonds between base pairs hold the two strands of dna together. b. hydrogen bonds between the base pairs hold the two strands of dna together. c. hydrogen bonds between sugar groups and phosphate groups hold the two strands of dna together. d. chemical bonds between sugar groups and phosphate groups hold the two strands of dna together.

Which of these statements best describes the st. lawrence seaway? the st. lawrence seaway connects the st. lawrence river with the arctic ocean. the st. lawrence seaway provides an important trading route between the u.s. and mexico. the st. lawrence seaway provides an important trading route for the u.s, but has little value for canada. the st. lawrence seaway connects the great lakes, the st. lawrence river, and the atlantic ocean.

Atypical human cell is approximately 12.00 μm in diameter and enclosed by a membrane that is 5.000 nm thick. (a) what is the volume of the cell including the membrane? (b) what is the volume of the cell membrane? (c) what percent of the total volume does its membrane occupy? to simplify the calculations, model the cell as a sphere. enter your answers using four significant figures.