Life Processes in Animals - Reproduction and Nervous System

The average menstrual cycle lasts approximately 28 days, though this varies between individuals (typically 21-35 days). Option C correctly states the average. Option B (2 weeks = 14 days) is too short for a complete cycle, and option A (20 days) is below the typical range.

During menstruation, the thickened endometrial lining breaks down and sheds from the uterus, exiting through the vagina as menstrual flow. This is option D. Option C describes the proliferative phase before menstruation, when the lining builds up to potentially receive a fertilized egg.

Fallopian tube is the part of female reproductive system where fertilization takes place.

Human gestation normally lasts 280 days (40 weeks) from the last menstrual period. Option C is correct. Option A (28 months) is far too long, and option B (280 weeks = 5.4 years) is incorrect - it should be 40 weeks, not 280 weeks. Option D is obviously incorrect.

Egg and sperm fertlizes in the middle part of the fallopian tubes, also known as oviducts.

The human brain is divided into two cerebral hemispheres (left and right), connected by the corpus callosum. Option B is correct. This bilateral structure is fundamental to brain organization. Options A, C, and D are incorrect - humans have exactly two hemispheres, not one, three, or four.

Sperm cells are streamlined and propel themselves using a flagellum (tail) that whips in a coordinated manner to swim toward the egg. Option C is correct. Option A is incorrect because sperm have a single flagellum, not cilia. Option B is false - sperm are highly motile cells designed specifically to reach the egg.

Digestion is primarily controlled by the autonomic nervous system and enteric nervous system, operating involuntarily and unconsciously. In contrast, thinking, learning, and memorizing are conscious cognitive functions directly managed by the central nervous system. Option C correctly identifies digestion as not being under conscious control.

Photoreceptors in the retina (rods and cones) detect light and convert it to electrical signals that the brain interprets as vision. Option B is correct - eyes contain these photoreceptors. Ears detect sound (hearing), skin detects touch and temperature, and tongue contains taste buds for gustation.

Pituitary gland is the master gland of the body.

The meninges are three-layered protective membranes (dura mater, arachnoid mater, pia mater) that cover both the brain and spinal cord within the central nervous system. Option A correctly identifies this dual coverage. Options B and C name specific brain regions only, while option D only mentions the spinal cord.

The cerebrum is the largest part of the human brain, comprising about 85% of brain weight and responsible for higher cognitive functions like thinking, reasoning, and voluntary movement. Option A is correct. The cerebellum coordinates balance and movement, the pons regulates breathing and relays signals, and the temporal lobe is just one region within the cerebrum.

Testosterone is the primary male sex hormone (androgen) produced mainly in the testes, responsible for male sexual development and characteristics. Option B is correct. Melatonin regulates sleep-wake cycles, oxytocin is involved in bonding and childbirth, and insulin regulates blood sugar levels.

The placenta facilitates bidirectional exchange between maternal and fetal blood. Oxygen and nutrients flow from mother to fetus, while waste products (primarily carbon dioxide) flow from fetus to mother for elimination. Option C is correct - the mother's blood removes CO2 waste from fetal circulation.

The placenta is the specialized organ that transfers oxygen, nutrients, and antibodies from the mother's blood to the fetus while removing waste products. Option A is correct. Blood capillaries are tiny vessels, the uterus is the muscular organ that houses the fetus, and the oviduct (fallopian tube) is where fertilization occurs, not nutrient transfer.

Thyroxine is a thyroid hormone that regulates metabolism, growth, and development. It is produced by the thyroid gland, not the reproductive organs. Progesterone, estrogen, and testosterone are all reproductive hormones involved in sexual development, menstrual cycles, and fertility.

Spinal cord is related to the central nervous system

Olfactory receptors are specialized sensory neurons located in the nasal epithelium that detect odor molecules. The nose is the primary organ of smell, housing these receptors in the upper nasal cavity. Eyes are for vision, ears for hearing, and tongues for taste.

 Sperms are stored in the epididymis.