In the Sonoran desert, a species of cactus pollinated by hawkmoths closes its flowers at dawn (and reopens them at dusk). Propose a possible proximate and ultimate explanation for this.
What will be an ideal response?
Proximate: As the temperature cools in the desert at the end of the day, the cacti are pressured to open their flowers. As the sun rises at dawn, the increased temperatures cause the flowers to close.
Ultimate: Since flowering in the heat of the sun would not be energy efficient, the cacti could have evolved to open their flowers during a cooler time of night. Different kinds of animals are active at night as well, which could have been another factor - in order for their flowers to be pollinated, and to avoid competition with daytime pollinators, the cacti would have to flower at night.
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The fact that birds have feathers and it is thought that some dinosaurs also had feathers is an example of _____
1.exaptation 2.stasis 3.coevolution 4.adaptive radiation
A non-polar receptor will bind to a chaperone.
a. true b. false
In trisomy 21, while all genetic information is intact, a(n) abnormal copy of this chromosome creates a genetic
imbalance which causes abnormal physical and mental development. _________________ Indicate whether the statement is true or false.
It is estimated that humans can produce over 1.5 million different types of antibodies. Which of the following statements regarding this extraordinary variation is INCORRECT?
A. We inherit over 1.5 million different and distinct immunoglobulin genes from our parents at fertilization. B. V and J domains of antibody light chains are randomly joined. C. Random segments of DNA can be removed from antibody genes. D. Cytosines in the variable regions of antibody genes can be converted to uracils via hypermutation. E. V and J domains of antibody heavy chains are randomly joined.