Which of the following refers to a hollow ball of cells that has undergone cleavage?
a. blastula
b. zygote
c. embryo
d. mesoderm
a. blastula
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More than ____ percent of couples decide to terminate a Down syndrome pregnancy
a. ten b. thirty c. fifty d. seventy e. ninety
Since all land-dwelling animals utilize oxygen for respiration, does that make oxygen a limiting
factor?
What will be an ideal response?Side A is __________ to side B
a. hypertonic b. hypotonic c. isotonic d. either isotonic or hypertonic e. either isotonic or hypotonic
The sex of birds, some insects, and other organisms is determined by a ZW chromosomal arrangement in which the males have like sex chromosomes (ZZ) and females are ZW (similar to XY in humans)
Assume that a recessive lethal allele on the Z chromosome causes death of an embryo in birds. What sex ratio would result in the offspring if a cross were made between a male heterozygous for the lethal allele and a normal female? A) 4:1 male to female B) 1:2 male to female C) 1:1 male to female D) 2:1 male to female E) 3:1 male to female