Why do pollen grains only produce tube in flowers of their own species

Charles darwin published his theory of evolution in 1859. in what way foes modern evolutionary theory differ from the theory as proposed by darwin? a) darwin inferred that individuals can evolve, but modern generic science has shown that this is not true. b)darwin inferred that individuals do not evolve, but modern genetic science has shown that this is not true. c)modern science has disproved most of darwin's original theory of evolution, because darwin knew nothing about generations and their role in heredity. d)generic studies have shown that gene expression and other factors operate along with natural selection, but most of darwin's theory has been supported by modern science.

Select the correct answer from each drop-down menu. in an experiment, dr. travis examined the effects of calcium intake on osteoporosis, a condition that causes an increased risk of bone fractures. the amount of calcium is variable. the risk of bone fractures .

The cluster of developing cells from conception until birth is called an