DNA recombination changes the genetic makeup of organisms
Indicate whether the statement is true or false
TRUE
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The Y chromosome can be used to trace ancestry because:
A. natural selection favors specific mutations in specific places. B. mutations in the Y chromosome occurred as people migrated around the globe. C. mutations in the Y chromosome are independent of mutations in mitochondria. D. mutations in the Y chromosome occur only in a few locations. E. nonmutant Y-chromosome genotypes are eliminated from human populations.
Why are mammalian reflexes so fast? (Check all that apply.)
_____ They use neurons with extra-wide axons. _____ They complete the sensory input-to-motor output circuit in only 2-3 neurons. _____ They do not send signals to the brain and back. _____ They activate a large number of sensory neurons, which speeds things up after the motor neuron performs spatial summation. _____ There was a selective advantage to evolve rapid responses to certain types of stimuli. Clarify Question · What is the key concept addressed by the question? o Cause of the speed of reflexes. · What type of thinking is required? o Answering this question correctly depended not only on distinguishing between the different components of a reflex arc, but also analyzing why this neural set-up promotes speed of signal transmission. Gather Content/Choose Answer · What do you already know about reflexes? What other information is related to the question? o To solve this problem, you’ll need to know that a reflex arc is composed of only 2 or 3 neurons that connect in the spinal cord. One is a sensory neuron that has its cell body in the dorsal root ganglia outside of the spinal cord. Sometimes these neurons synapse directly to a motor neuron which exits the spinal cord through the ventral roots. Often, the connections between these two types of neurons are modulated by interneurons, which are commonly inhibitory. All of these connections occur in the spinal cord and not the brain, which makes the distances that these signals travel much shorter and faster. These faster responses have evolved to help vertebrates respond rapidly to stimuli that could be dangerous. Reflect on Process · Did your problem-solving process lead you to the correct answer? If not, where did the process break down or lead you astray? How can you revise your approach to produce a more desirable result? o If you figured out the correct answer, great! If not, where did you go wrong? Did you think that neurons in reflexes are so fast because they are so large in diameter? It is true that action potentials are conducted faster down larger axons than smaller ones, but many of the axons involved in reflexes are not large (for example, simple pain receptors). Did you think that large numbers of sensory neurons would speed a reflex up? Probably not. If anything, it might slow things down. Spatial summation involves input from multiple neurons, but a reflex could only involve two neurones, so the answer beginning with 'They activate a large number of sensory neurons' cannot be correct.
Which of the following organisms exhibits
cephalization? a. snail b. sea anemone c. sea star d. sponge e. Trichoplax
A community that contains a low species diversity will often have a high species richness.
Answer the following statement true (T) or false (F)