Following statements are regarding to establishing the three separate cell lineages in the mouse blastocyst.

A. The first two cell types to be specified are the inner cell mass and the trophectoderm. This involves progressive restriction of expression of the genes that code for transcription factors Oct4 and Cdx2.

B. At the eight-cell stage, all the cells express both genes at low levels, but by the late morula/early blastocyst stage, Cdx2 expression has increased in, and eventually becomes restricted to, the cells on the outside of the embryo, and these will form trophectoderm. Oct4

expression becomes restricted to the inner cell mass cells at early blastula stage.

C. Within the inner cell mass, two separate cell types arise: the epiblast cells, from which the embryo will develop; and the primitive endoderm, which will form extra-embryonic structures. This involves a progressive restriction of expression of the genes for the transcription factors Nanog and Gata6.

D. At the early blastula stage, some of the inner cell mass cells apparently at random start to express higher levels of Nanog, whereas the other cells express higher levels of Gata6.

E. By the late blastula, the cells expressing the two different transcription factors have sorted out within the inner cell mass so that cells expressing high levels of Nanog form an outer epithelial layer of primitive endoderm enclosing the epiblast cells expressing high levels of Gata6.

Which of the following statements are correct?

#Question id: 3479

#Unit 11. Evolution and Behavior

Which of the following could be classified as habituation?

A) You enter a room and hear a fan motor. After a period of time, you are no longer aware of the motorʹs noise.

B) You hear a horn while driving your car. You step on the brakes but notice the sound came from a side street. You resume your previous speed.

C) One morning you awake to a beep-beep-beep from a garbage truck working on a new early morning schedule. The next week the garbage truck arrives at the same time and makes the same noise, but does not wake you up.

#Question id: 3480

#Unit 11. Evolution and Behavior

Which of the following statements about learning and behavior is correct?

A) Operant conditioning involves associating a behavior with a reward or punishment.

B) Associative learning involves linking one stimulus with another.

C) Behavior can be modified by learning, but some apparent learning is due to maturation.

D) Imprinting is a learned behavior with an innate component acquired during a sensitive period.

#Question id: 3481

#Unit 11. Evolution and Behavior

Classical conditioning and operant conditioning differ in that

A) classical conditioning takes longer.

B) operant conditioning usually involves more intelligence.

C) operant conditioning involves consequences for the animalʹs behavior.

D) classical conditioning is restricted to mammals and birds.

#Question id: 3482

#Unit 11. Evolution and Behavior

Which statement below about mating behavior is correct?

A) Some aspects of courtship behavior may have evolved from agonistic interactions.

B) The degree to which evolution affects mating relationships depends on the degree of prenatal and postnatal input the parents are required to make.

C) The mating relationship in most mammals is monogamous, to ensure the reproductive success of the pair.

D) Polygamous relationships most often involve a single male and many females, but in some species this is reversed

#Question id: 3483

#Unit 11. Evolution and Behavior

Which of the following statements about evolution of behavior is correct?

A) Natural selection will favor behavior that enhances survival and reproduction.

B) An animal may show behavior that maximizes reproductive fitness.

C) If a behavior is less than optimal, it is not completely evolved but will eventually,become optimal.

#Question id: 3484

#Unit 11. Evolution and Behavior

Modern behavioral concepts relate the cost of a behavior to its benefit. Under which relationship might a behavior be performed?

A) cost is greater than the benefit

B) cost is less than the benefit

C) cost is equal to the benefit