Biology Test - 59

The excretory system in human consistsof a pair of kidneys, one pair of ureters, aurinary bladder and a urethra. Kidneys are reddish brown, bean shaped structures situated between the levels of last thoracic and third lumbarvertebra close to the dorsal inner wall of the abdominal cavity.

Predator and prey evolve together. The prey is part of the predator's environment, and the predator dies if it does to get food, so it evolves whatever is necessary in order to eat the prey. Likewise, the predator is part of the prey's environment, and the prey dies if it is eaten by the predator, so it evolves whatever is necessary to avoid being eaten. So, predators cannot lead to the extinction of prey species.
Nicotine is an alkaloid found in the night shade family of plants (Solanaceae) that constitutes approximately 0.6−3.0% of dry weight of tobacco, with biosynthesis taking place in the roots and accumulation occurring in the leaves. Strychnine is an alkaloid plant toxin extracted chiefly from Nux vomica; formerly used as a stimulant. These are not metabolic disorder products but are metabolic wastes.

Ribosomes are non-membrane-bound organelles and granular structure that wasdiscovered by George Palade in 1953. They are composed of ribonucleic acid (RNA) and proteins. Ribosomes are protein synthesizers of acell and they are found in both Prokaryotic and Eukaryotic cells. So,'Palade particles' is another name for ribosomes.

Zygotene → Synapsis
Pachytene → Crossing over
Diplotene → Chiasmata formation
Diakinesis → Terminalisation

Cholecystocaval line separates by right & Left liver lobe.

Functional lobes and segments of the liver

• The functional right and left lobes of the liver are separated by an imaginary plane passing along the floor of fossa for gall bladder and the groove for inferior vena cava (cholecysto-caval line).
• On the anterosuperior surface of the liver, the plane passes little right to the attachment of falciform ligament. The functional right and left lobes of the liver are more or less of equal size.

The bacterium Bacillus thuringiensis (Bt) is widely used in biology as an insecticide. It produces proteins called Cry proteins, which are toxic to certain insects when ingested. These proteins have been harnessed for use as insecticides in agriculture to control pests such as caterpillars, beetles, and flies.

Tobacco plants resistant to a nematode have been developed by the introduction of DNA that produced both sense and anti-sense RNA in the host cells. This approach utilizes RNA interference (RNAi) technology, where both sense and anti-sense RNA molecules are produced within the plant cells. These RNA molecules bind to complementary sequences in the nematode's mRNA, leading to the degradation of the target mRNA and ultimately suppressing the expression of genes essential for the nematode's survival. This mechanism confers resistance to the nematode in the transgenic tobacco plants.

Testosterone secreted by Leydig’s cells.

Leydig cells produce testosterone in the testes under the pulsatile control of pituitary luteinizing hormone (LH). CAMP is the intracellular messenger for LH action on steroidogenesis, and pharmacological evidence indicates that the response to LH can be modulated by cyclic nucleotide phosphodiesterases (PDE_S).

If the vasa deferentia of man are surgically removed, Semen will be without sperms.

Sterilization provides a permanent and sure birth control. Vasectomy is very simple surgical method involving the cutting of the vas deferens in man. The vas deferens is removed or tied up through a small cut on the scrotum so that the sperms from the testicles cannot move out and hence semen released during ejaculation is without sperms.