For each of the following questions, four choices have been provided. Select the correct alternatives. Match the following A Frog i Pituitary gland B Fish ii Metamorphosis C FSH \(\quad\) iii External fertilization \(\mathrm{D} \mathrm{LH}\) iv Testes \(\begin{array}{llll}\mathbf{A} & \mathbf{B} & \mathbf{C} & \mathbf{D}\end{array}\) (a) ii iii i iv (b) iii iv i ii (c) ii iii iv i (d) iv iii ii \(\overrightarrow{1}\)

One of the most fascinating biological processes is metamorphosis, which refers to a profound and radical change in the form of an organism from one stage of its life cycle to another. This transformation is not only visually dramatic but also involves significant changes in the organism's structure and function.

In the case of amphibians, like frogs, metamorphosis is an essential part of their development. They begin life as aquatic larvae known as tadpoles, breathing through gills and moving with the help of a tail. As they mature, they undergo a series of changes - a process called metamorphosis - that prepares them for a terrestrial adult life. Tadpoles develop legs, their tails recede, and they start to breathe air with newly formed lungs.

Stages of Frog Metamorphosis

• Egg Stage: Frog's life begins as an egg, usually laid in water.
• Larval Stage: The egg hatches into a tadpole, which is entirely aquatic.
• Metamorphosis: Gradual transformation begins; tadpole grows legs and loses its tail.
• Adult Stage: The frog becomes capable of living both in water and on land, now with lungs for breathing air.

Understanding metamorphosis gives insight into the complex life cycles of certain animals and emphasizes the intricate interaction between genetics, environment, and development.

External fertilization is a reproductive strategy where the union of male and female gametes (sperm and eggs) takes place outside the body of the parent organisms, typically in the water. It's common among aquatic animals, such as fish, amphibians, and invertebrates like corals. This method allows for the potential fertilization of a vast number of eggs, but it also comes with certain risks, like predation or unfavourable environmental conditions.

During this process, females release their eggs into the water, and males simultaneously release sperm, a process known as spawning. The sperm must then find and fertilize the eggs in the open water. Success depends on timing, proximity, and environmental factors like water temperature and pH.

Key Points in External Fertilization

• It involves releasing gametes into the water, where fertilization occurs.
• There is a high number of offspring due to the large number of eggs produced.
• The process is less controlled than internal fertilization and thus more subject to environmental challenges.

Students exploring external fertilization learn about the diversity of reproductive strategies in the animal kingdom and the important role that environmental factors play in the success of these reproductive events.

The endocrine system is a network of glands dispersed throughout the body that produce and release hormones directly into the bloodstream. These hormones act as chemical messengers, influencing many aspects of physiological function, including growth, metabolism, and reproduction.

Glands such as the pituitary, which is often referred to as the 'master gland', play a critical role. The pituitary gland releases hormones that manage the activity of other glands, for instance, FSH (follicle-stimulating hormone) and LH (luteinizing hormone). While FSH is responsible for the development of eggs in the ovaries and the production of sperm in the testes, LH triggers ovulation and stimulates the production of testosterone.

Functions of Key Endocrine Glands

• Pituitary Gland: Regulates other endocrine glands; releases FSH and LH.
• Thyroid: Influences metabolism, growth, and development.
• Pancreas: Manages blood sugar levels by producing insulin.
• Adrenal Glands: Produces hormones that help control heart rate, blood pressure, and other critical processes.

Grasping how the endocrine system functions helps students understand how hormones influence almost every cell, organ, and function of our bodies, which is paramount to maintaining homeostasis and overall health.