Complete question: What situation might develop in a population having some plants whose flowers open at midday and other plants whose flowers open late in the day?
a. Temporal isolation
b. Geographic isolation
c. Behavioral isolation
d. Genetic drift
Answer:
a. Temporal isolation
Explanation:
Temporal isolation is one of several mechanisms of reproductive isolation. Temporal isolation occurs when some organisms of a population exhibit different timing of reproductive maturity. It also occurs when some members of a population reproduce at a different time from the others. This does not allow interbreeding between them.
When plants of a population open flower at a different time of day, cross-pollination would not occur between these plants. This represents temporal isolation.
Answer:
Facilitated diffusion
Explanation:
Facilitated diffusion is the process of diffusion in which ion or some substances are transported across the membrane by a specific carrier membrane protein. The process does not require the input of energy and is driven by a concentration gradient.
The absorption of simple sugars in small intestine occurs through facilitated diffusion. The polar sugar molecules can not cross the nonpolar inner core of the membrane. Hence, the membrane proteins transport the sugars down the concentration gradients without any input of energy.
A certain bacterial mRNA is known to represent only one gene and to contain about 800 nucleotides. If you assume that the average amino acid residue contributes 110 to the peptide molecular weight, the largest polypeptide that this mRNA could code for would have a molecular weight of about _______.
A) 800.
B) 5,000.
C) 30,000.
D) 80,000.
E) An upper limit cannot be determined from the data given
Answer:
c. 30,000
Explanation:
The gene has a total of 800 nucleotides and would be transcribed into an mRNA having about 800 nucleotides. The nucleotides of mRNA are read in the form of genetic triplets. This means that the mRNA with 800 nucleotides would have about 800/3= 266.66 or 266 genetic codes. This mRNA would be translated into a polypeptide chain having around 266 amino acids.
One amino acid contributes 110 to the molecular weight. The total molecular weight of the largest possible polypeptide that can be encoded by the said gene would b 266 x 110= 29260 (around 30,000).
