In adult animals, are a source of undifferentiated cells that can divide to produce cells that can specialize.

Which of the following statements is true?

The products of Hox genes __________.

What is apoptosis?a. an experimental technique used to kill specific cellsb. programmed cell death that is required for normal developmentc. a pathological condition observed only in damaged or diseased organismsd. a developmental mechanism unique to the roundworm C. elegans

Which of the following occurs when a covalent bond forms?a. Electrons in valence shells are transferred from one atom to another.b. Electrons in valence shells are shared between atoms.c. Partial charges on polar molecules interact.d. Nonpolar molecules are pushed together.by surrounding water molecules.

What does it mean to say that a characteristic is heritable?a. The characteristic evolves.b. The characteristic can be passed on to offspring.c. The characteristic is advantageous to the organism.d. The characteristic does not vary in the population.

Could both the food competition hypothesis and the sexual competition hypothesis explain why giraffes have long necks? Why or why not?

Cell differentiation always involvesa. transcription of the myoD gene.b. the movement of cells.c. the production of tissue-specific proteins.d. the selective loss of certain genes from the genome.

Which of the following is a valid difference between embryonic stem cells and the stem cells found in adult tissues?a. In laboratory culture, only adult stem cells are immortal.b. In nature, only embryonic stem cells give rise to all the different types of cells in the organism.c. Only adult stem cells can differentiate in culture.d. Embryonic stem cells are generally more difficult to grow in culture than adult stem cells.