• When a magnet is dipped in iron filings, we can observe that the iron filings cling to the end of the magnet as the attraction is maximum at the ends of the magnet. These ends are known as poles of the magnets.
• Magnetic poles always exist in pairs.
• Like poles repel while unlike poles attract.

Soils are complex mixtures of minerals, water, air, organic matter, and countless organisms that are the decaying remains of once-living things. It forms at the surface of land – it is the “skin of the earth.” Soil is capable of supporting plant life and is vital to life on earth.

Soils are complex mixtures of minerals, water, air, organic matter, and countless organisms that are the decaying remains of once-living things. It forms at the surface of land – it is the “skin of the earth.” Soil is capable of supporting plant life and is vital to life on earth. Soil is the thin layer of material covering the earth's surface and is formed from the weathering of rocks. It is made up mainly of mineral particles, organic materials, air, water and living organisms—all of which interact slowly yet constantly.

Cavities are permanently damaged areas in the hard surface of the teeth that develop into tiny openings or holes. Cavities are also called tooth decay or caries, which are caused by a combination of factors, including bacteria in your mouth, frequent snacking, sipping sugary drinks and not cleaning your teeth well.

The lungs deliver oxygen and remove carbon dioxide from your blood in a process called gas exchange. Gas exchange happens in the capillaries surrounding the alveoli, where the oxygen that is breathed in enters the circulatory system and carbon dioxide in the blood is released to the lungs and then breathed out.

The leaf is a collection of tissues which include: The epidermis which covers the upper and lower surfaces. The mesophyll inside the leaf which is rich in chloroplasts. The veins contains the vascular tissue (where xylem and phloem are present). A leaf is made of many layers that are sandwiched between two layers of tough skin cells (called the epidermis). The epidermis also secretes a waxy substance called the cuticle. These layers protect the leaf from insects, bacteria, and other pests.

The leaf is the primary photosynthetic organ of the plant. It consists of a flattened portion, called the blade, that is attached to the plant by a structure called the petiole. ... The vascular tissue, xylem and phloem are found within the veins of the leaf. Leaves provide food and air to help a plant stay healthy and grow. Through photosynthesis, leaves turn light energy into food. Through pore, or stomata, leaves “breathe” in carbon dioxide and “breathe” out oxygen. ... In this experiment, kids will test what happens to a leaf when covered with different materials.

A leaf is made of many layers that are sandwiched between two layers of tough skin cells (called the epidermis). The epidermis also secretes a waxy substance called the cuticle. These layers protect the leaf from insects, bacteria, and other pests. The leaf is the primary photosynthetic organ of the plant. It consists of a flattened portion, called the blade, that is attached to the plant by a structure called the petiole. The vascular tissue, xylem and phloem are found within the veins of the leaf.

Active absorption refers to the absorption of water by roots with the help of adenosine triphosphate, generated by the root respiration: as the root cells actively take part in the process, it is called active absorption. Plants absorb water from the soil by osmosis. They absorb mineral ions by active transport, against the concentration gradient. Root hair cells are adapted for taking up water and mineral ions by having a large surface area to increase the rate of absorption.

Moulting (or molting) is the manner in which an animal routinely casts off part of its body (usually the outer layer or covering) at particular times of year, or at specific points in its life cycle. ... Moulting can involve the epidermis (skin), and hair, fur, wool, or other external layer. Moulting is the process when silkworms seized feeding, becomes immobile and prepare themselves for shedding their old skin to accommodate the fast growth. Four moults takes place during the entire larval period.

A concept in ecology that describes natural systems as being in a state of equilibrium, in which disturbing one element disturbs the entire system. The inference is usually drawn that the natural state of any system is the preferred state and that it is best to leave it undisturbed. 

Ecological balance is a term used to describe the equilibrium between living organisms such as human being, plants, and animals as well as their environment. Photosynthesis that takes place in ecosystem contributes to building a good environment that stabilizes the coexistence of all organisms. Harmonious relationships reflect healthy and desirable ecological balance. Human being plays a key role to maintain ecological balance because they have the highest thinking capacity as compared to other living organisms. Sufficient food availability to all living organisms and their stability reflect the existence of ecological balance. Therefore, this balance is very important because it ensures survival, existence and stability of the environment.

Survival of all organisms is actualized due to ecological balance. Various species survive because favourable ecosystems were created. Favourable ecosystem ensures that each organism thrives and multiply as expected. They get enough food to keep them alive. Ecological balance is also important because it leads to the continued existence of the organisms. It ensures that no particular species is exploited or overused. For example, human activities such as farming and resources exploitation are checked to prevent excessive destruction of the forests. Deforestation leads to drought. Drought reduces food production resulting in insufficient food. Insufficient food leads to starvation and later death occurs, hence reducing the existence of some species.

In addition, ecological balance ensures the stability of the organisms and the environment. It creates a conducive environment for organisms multiplication and thriving. It enhances a stable environment that is free from ecological imbalances such as flood, hunger caused by drought, a windstorm that may wipe out everything and over hunting of the predators. 

Iron from sand – using a magnet or by hand. A magnet will attract all the iron pins and thus will get separated from the sand. But since iron pins and sand can be easily differentiated, they can be separated by hand picking as well.

Minerals are substances that are formed naturally in the Earth. Minerals are usually solid, inorganic, have a crystal structure, and form naturally by geological processes. The study of minerals is called mineralogy. A mineral can be made of a single chemical element or more usually a compound. A mineral is an element or chemical compound that is normally crystalline and that has been formed as a result of geological processes. Examples include quartz, feldspar minerals, calcite, sulfur and the clay minerals such as kaolinite and smectite.

Vitamins help the body function effectively. There are two types: water-soluble and fat-soluble vitamins. The water-soluble vitamins are vitamins B and C. Most vitamins come from food, but sunshine contributes to vitamin D. There are two types of vitamins: fat-soluble and water soluble. When you eat foods that contain fat-soluble vitamins, the vitamins are stored in the fat tissues in your body and in your liver. They wait around in your body fat until your body needs them.