IGCSE Biology Paper-3: Specimen Questions with Answers 271 - 272 of 358

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Passage

shows a diagram of the human female reproductive system.

Reproductive System

Question 271 (4 of 4 Based on Passage)

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Short Answer▾

Using letters P – U, identify the parts of the human female reproductive system in Fig. 11.1.

where eggs are made …

where fertilization occurs …

where implantation of the zygote occurs …

Explanation

where eggs are made … T …

where fertilization occurs … S …

where implantation of the zygote occurs … P …

Ovary

  • The ovary is the primary female sex organ.
  • Ovary produces ova and secretes female sex hormones viz. , estrogens and progesterone

Fertilization

Fusion of a haploid male gamete and a female gamete to form a diploid cell, the zygote, is called fertilization. Fusion of gametes in the fertilization is called as syngamy. Fusion of cytoplasm is plasmogamy and fusion of nucleus is karyogamy.

Implantation

In humans, implantation is the stage of pregnancy at which the embryo adheres to the wall of the uterus. At this stage of prenatal development, the conceptus is called a blastocyst. It is by this adhesion that the embryo receives oxygen and nutrients from the mother to be able to grow.

Passage

The boxes on the left contain the names of parts of the body that produce hormones.

The boxes in the center contain the names of hormones.

The boxes on the right contain functions of these hormones.

Rate of Breathing

Question 272 (1 of 4 Based on Passage)

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Short Answer▾

Where does thyroid gland located in our body and what is the function of it?

Explanation

Thyroid Gland

  • It is single and bilobed gland present on either side of trachea below larynx the 2-lobes remain connected by a non-glandular tissue called Isthmus.
  • It is endodermal in origin
  • It is the largest endocrine gland in the body (weighing ~35 gm) .

Calcitonin (Or Thyrocalcitonin)

  • It is proteinaceous and non-iodinized hormone (Iodine absent) .
  • It is secreted from C (clear) – cells or Parafollicular cells (outside thyroid follicles)
  • It is hypocalcimic factor and decreases the amount of Ca2 + in the blood.
  • It is angonistic to PTH (Para-thyroid hormone) .

Thyroxine (T4)

  • It is Tetra-ido-thyronine and is secreted from the cells of thyroid follicles. T4 with T3 are stored as a colloidal material in the follicles.
  • Thyroxine regulates basic metabolic rate (BMR) - stimulating heartbeat, breathing rate etc.
  • It causes demineralization of bones in adults (by stimulating osteoclasts - the bone eating cells) .
  • It causes hyperglycemia by stimulating glycogenolysis and Gluconeogenesis.
  • It causes nervous excitation also.
Stimulating Heartbeat

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