1. A normal cell in a laboratory forms a single layer on a dish. When the cell touches other cells, it halts dividing. Which of the following hypotheses explains this phenomenon? a. It was regulated by kinases and cyclins.

b. Cells grow and divide in response to one growth factor.

c. It happens when internal and external signals stimulate genes that help produce self-destructive enzymes.

d. Receptors on adjacent cells have bound to each other causing the cells’ cytoskeleton to form structures that may hinder the signals that activate the growth.

Many kangaroo rats live in the sonoran desert of the southwestern united states. they have a variety of adaptations for living in the desert. under which circumstance would the kangaroo rats of the sonoran desert be most likely to develop new adaptations by natural selection?

(drag each tile to the correct identify which questions can be answered by what can be answered by science or which cannot. -is it right or wrong to use genetic engineering to produce new food products? -what are the most common social settings that tend to produce accomplished artists? -if a new gene is added to the genome of a tomato species, will that species be more resistant to insects? -should humans use biotechnology to bring extinct organisms from the fossil record back to life? -do the types of organisms found in the fossil record appear in consistent sequences in different parts of the world? -are michelangelo's paintings more impressive than rembrandt's?

The intervention of extraterrestrials has been used to explain the bermuda triangle, a region of the atlantic ocean where ships and planes are frequently lost, leaving no evidence behind. how would this explanation best be characterized?