Zoology MCQs for NEET — Practice Questions with Answers

The NCERT states that the placenta 'facilitate the supply of oxygen and nutrients to the embryo and also removal of carbon dioxide and excretory/waste materials'. It also 'acts as an endocrine tissue and produces several hormones like human chorionic gonadotropin (hCG), human placental lactogen (hPL), estrogens, progestogens, etc.'. Oxytocin release is triggered by the foetal ejection reflex and comes from the maternal pituitary, not the placenta.

The NCERT text says, 'The signals for parturition originate from the fully developed foetus and the placenta which induce mild uterine contractions called foetal ejection reflex. This triggers release of oxytocin from the maternal pituitary. Oxytocin acts on the uterine muscles and causes stronger uterine contractions.'

The NCERT states, 'By the end of about 24 weeks (end of second trimester), the body is covered with fine hair, eye-lids separate, and eyelashes are formed.' Other options correspond to different stages.

The NCERT states, 'As a result, the blastocyst becomes embedded in the endometrium of the uterus (Figure 2.11 step H). This is called implantation and it leads to pregnancy.'

The NCERT states, 'The morula continues to divide and transforms into blastocyst...'

The NCERT states, 'It needs to be mentioned here that the inner cell mass contains certain cells called stem cells which have the potency to give rise to all the tissues and organs.'

The NCERT mentions, 'Placenta also acts as an endocrine tissue and produces several hormones like human chorionic gonadotropin (hCG), human placental lactogen (hPL), estrogens, progestogens, etc.'

The NCERT states, 'By the end of 12 weeks (first trimester), most of the major organ systems are formed, for example, the limbs and external genital organs are well-developed.'

The NCERT text explains, 'Increased production of these hormones is essential for supporting the fetal growth, metabolic changes in the mother and maintenance of pregnancy.'

The NCERT states, 'Immediately after implantation, the inner cell mass (embryo) differentiates into an outer layer called ectoderm and an inner layer called endoderm. A mesoderm soon appears between the ectoderm and the endoderm. These three layers give rise to all tissues (organs) in adults.'