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Earth observation means watching Earth using satellites or planes. It helps us see weather, forests, oceans, and cities from above. Scientists use it to study floods, pollution, and changes in nature.Earth observation is the way we study our planet using satellites, drones, or aircraft that look down from the sky. These tools take pictures, videos, and other data about the land, water, air, and even human activities. My Notes It helps us understand what’s happening on Earth and how to protect it better.

Detailed Explanation of Hydrophobic Molecules Hydrophobic molecules are substances that do not interact well with water. The term “hydrophobic” literally means “water-fearing”. These molecules do not dissolve in water and tend to separate from it, forming layers or droplets. 1. Why Are They "Water-Fearing"? To understand hydrophobic molecules, we need to understand a bit about water itself. Water is a polar molecule, meaning it has a partial positive charge on one end (near the hydrogen atoms) and a partial negative charge on the other (near the oxygen atom). This polarity allows water molecules to form strong hydrogen bonds with each other and with other polar molecules. Hydrophobic molecules are nonpolar. They do not have positive or negative ends. Because they lack charge, water molecules cannot form hydrogen bonds with them. As a result, water pushes these molecules away, or they group together to minimize contact with water. 2. Common Examples of Hydrophobic Molecules • Oils and fats (like cooking oil, butter, or wax) • Long hydrocarbon chains (like those found in gasoline or the lipid tails in cell membranes) • Many steroid hormones (like testosterone or estrogen) • Some gases, such as oxygen (O₂) and nitrogen (N₂), are mildly hydrophobic because they don't interact strongly with water 3. Behavior in Water When hydrophobic molecules are placed in water, they do not mix. Instead: • They form separate layers (like oil on water) • They might clump together (aggregation), reducing the surface area that touches water This behavior is not due to attraction between the hydrophobic molecules themselves but because water molecules prefer to stick to each other and push the nonpolar molecules away. 4. Biological Importance Hydrophobic interactions are crucial in biology: • Cell membranes: The core of the membrane is made of hydrophobic lipid tails. This creates a barrier that separates the inside of the cell from the outside environment. • Protein folding: Many proteins have hydrophobic parts that hide inside the folded structure, away from water. This folding is essential for the protein to work correctly. • Hormone transport: Some hydrophobic hormones can pass through cell membranes easily because they are nonpolar, unlike other molecules that need transport proteins. 5. Hydrophobic vs. Hydrophilic • Hydrophobic = hates water (nonpolar, repelled by water) • Hydrophilic = loves water (polar or charged, mixes with water) These two properties determine how substances behave in water and how they are used in biological systems. 6. Micelle Formation When soap or detergent is added to water, it can help mix hydrophobic oils with water. Soap molecules have two ends: • One end is hydrophilic (attracted to water) • The other end is hydrophobic (attracted to oil or grease) These molecules form structures called micelles, where the hydrophobic ends hide inside, trapping oil, and the hydrophilic ends face out, allowing it to dissolve in water. This is how soap cleans oil from your hands. Summary Hydrophobic molecules are nonpolar substances that do not mix with water because they cannot form hydrogen bonds. They play a major role in biological systems by helping form membranes, aiding in protein structure, and influencing molecule transport. Their interactions are governed not by attraction to each other, but by avoidance of water.

The pelvic cavity is the lowest part of the human body’s trunk region. It is a hollow space located beneath the abdominal cavity and surrounded by the bones of the pelvis. It plays a very important role because it holds and protects some of the most vital organs in the body related to urinary, reproductive, and digestive systems. 1. Boundaries of the Pelvic Cavity The pelvic cavity is like a deep bowl formed by bones, muscles, and ligaments. • Front and sides: Surrounded by the pelvic bones (ilium, ischium, and pubis). • Back: Formed by the sacrum and coccyx (the last parts of the vertebral column). • Top: The imaginary line that separates it from the abdominal cavity (called the pelvic inlet). • Bottom: Closed off by the pelvic floor, a group of strong muscles that hold everything up (like a hammock). 2. Parts of the Pelvic Cavity It is divided into two regions: • Greater (false) pelvis: This is the upper part that is technically more part of the abdominal cavity. It supports the intestines. • Lesser (true) pelvis: This is the lower, smaller part. It actually contains most of the pelvic organs. 3. Organs Found in the Pelvic Cavity The organs inside depend slightly on whether the person is male or female. In females, it includes: • Uterus – the muscular organ where a baby grows during pregnancy. • Ovaries – produce eggs and female hormones. • Fallopian tubes – carry eggs from the ovaries to the uterus. • Vagina – the muscular canal connecting the uterus to the outside of the body. • Bladder – stores urine. • Rectum – stores solid waste before it exits through the anus. In males, it includes: • Prostate gland – produces fluid for semen. • Seminal vesicles – help make semen. • Vas deferens – carries sperm from the testicles. • Bladder – stores urine. • Rectum – same function as in females. 4. Functions of the Pelvic Cavity • Protection: The bony structure around the pelvic cavity protects the organs inside it. • Support: It supports the weight of abdominal organs and transmits that weight to the legs. • Childbirth (in females): The shape of the true pelvis is specially adapted to allow passage of a baby during birth. • Excretion: It houses parts of the urinary and digestive systems involved in removing waste. • Reproduction: It holds and supports the reproductive organs and their functions. 5. Pelvic Floor The pelvic cavity has a "floor" made of strong muscles. These muscles: • Help hold all pelvic organs in place. • Control the release of urine and feces. • Play a role during sexual activity and childbirth. If these muscles weaken (for example, after childbirth), pelvic organs might shift out of place, causing problems like incontinence. Summary The pelvic cavity is a strong, compact, and vital region of the body, housing organs that manage urination, reproduction, childbirth, and waste removal. Its structure—bones, muscles, and ligaments—gives both protection and support to these delicate systems.