Following cleavage of the zygote, which of the following is the first to occur?
a. blastula
b. gastrula
c. neural crest
d. morula
e. primitive streak
D
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An example of a pathogen that undergoes rapid changes resulting in antigenic variation is _____
A) the influenza virus, which expresses alternative envelope proteins B) the strep bacteria, which can be transmitted from patient to patient with high efficiency C) human papilloma virus, which can remain latent for several years D) the causative agent of the autoimmune disease known as rheumatoid arthritis E) multiple sclerosis, which attacks the myelinated cells of the nervous system
Peter and Rosemary Grant study natural selection in finches on the Galápagos Islands. They have hypothesized that dry condition produce larger seeds and may result in larger beaks in succeeding generations of finches. The figure below shows their data from 1976 and 1987. The y-axis is the number of birds measured and the x-axis is the beak depth. Does their data support their hypothesis and why?
A. yes; because there were more birds measured in 1978 after the drought, therefore they must have been able to get food and reproduce.
B. yes; because the average beak depth of birds in the population increased from 8.8mm in 1976 to 9.8mm in 1978.
C. no; because even though more birds were measured in 1978, the beak size of the upper range was smaller.
D. no; because in 1976, before the drought, the largest beak depth was still 11.3mm.
E. no; more data would be necessary to show a support of their hypothesis.
Natural selection is random
a. True b. False Indicate whether the statement is true or false
The peripheral proteins may also function in
What will be an ideal response?