How do the body's systems work together? - The digestive system: It digests food and converts it into simple nutrients (glucose, amino acids, fatty acids) that reach the blood to nourish the cells. - The respiratory system: Oxygen enters the body and carbon dioxide exits, ensuring the continuation of cellular respiration within the cells. - The circulatory system (heart and blood vessels): It transports food and oxygen to all parts of the body, and removes waste products such as carbon dioxide and urea. - The excretory system (kidneys and skin): gets rid of waste products resulting from vital processes such as urine and sweat, in order to maintain the body's internal balance. - The nervous system: It regulates the functioning of different organs and sends signals to control movement and respond to external stimuli. - Muscular and skeletal system: Provides movement and support for the body, and helps protect internal organs. - The immune system: It defends the body against microbes and foreign substances, thus maintaining health. Summary Each system has a specific function, but the integration of these systems is what ensures human survival. Digestion provides food, respiration provides oxygen, blood circulation delivers both to the cells, excretion removes waste, and the nervous system coordinates all of this.

What are microbes? Microbes are microscopic organisms that cannot be seen with the naked eye; some are beneficial and some are harmful. - They are found in the air, water, soil, and on the bodies of living organisms. 🔬 Types of microbes Viruses: The smallest living organisms, they cause diseases such as influenza and AIDS. - Bacteria: Some are beneficial (such as yogurt bacteria), and some are harmful (such as typhoid bacteria). - Fungi: such as yeast used in bread making, including harmful ones like a fungus that causes skin diseases. - Protozoa: such as amoebas that cause dysentery. 🌍 Where it is found - In the soil, water, and air. - Inside the bodies of living organisms and on their surface. ✅ Benefits of microbes - Production of some medicines, such as penicillin, from fungi. - Manufacturing foods such as yogurt and cheese using beneficial bacteria. - Analysis of organic matter and restoration of elements to the soil. ⚠️ The dangers of microbes - It causes serious diseases such as: typhoid, dysentery, influenza. Food spoils when it grows on it. 🛡️ Ways to prevent microbes - Wash your hands thoroughly before and after eating. - Keep food in the refrigerator. - Boil or sterilize the water before drinking. - Getting vaccinated against diseases

First: Mitosis ✳️ Definition: It is a cell division that occurs in somatic cells (such as skin and muscle cells), and its purpose is growth and replacement of damaged cells. 🔁 Result: This results in two perfectly identical cells, each with the same number of chromosomes (46 in humans). 📘 Its importance: Growth - Tissue regeneration Wound healing 🧠 Stages of mitosis: 1. Prophase: Chromosomes begin to appear 2. Metaphase: The chromosomes are aligned in the middle of the cell. 3. Anaphase: The chromosomes separate and move to the ends. 4. Final: Two new nuclei are formed --- 🧪 Second: Meiosis ✳️ Definition: It is a division that occurs in reproductive cells (eggs and sperm), and its purpose is to reduce the number of chromosomes by half in preparation for reproduction. 🔁 Result: This results in four asymmetrical cells, each containing half the number of chromosomes (23 in humans). 📘 Its importance: - Production of reproductive cells Maintaining a constant number of chromosomes in living organisms - Increase genetic diversity among individuals 🧠 Stages of meiosis: It consists of two successive divisions: First division: Reduction in the number of chromosomes - Second division: Similar to mitosis, to form 4 cells

First: Regular speed It is the speed that does not change with time, meaning the body moves at the same rate all the time. ✳️ Its characteristics: - The distance traveled is constant in each unit of time. - The graph between distance and time is a slanted straight line. Example: A car traveling at a speed of 60 km/h without changing. Second: Variable speed It is the speed that changes with time, meaning the body can speed up or slow down while moving. ✳️ Types: - Positive acceleration: when speed increases with time. Negative acceleration (deceleration): when the speed decreases over time.

What is a cell? The cell is the smallest living unit in the body of a living organism, and it is responsible for all vital processes such as growth, reproduction, and respiration. There are two types of cells: - Plant cell 🌿 - Animal cell 🐾 Basic cell components: A cell is made up of a group of parts, and each part has an important function: - The plasma membrane: It surrounds the cell and controls the entry and exit of substances from it. - Cytoplasm: A gel-like substance that fills the cell and contains the rest of the components. - The nucleus: the control center of the cell, containing the genetic material that determines the characteristics of the organism. - Mitochondria: They produce the energy that the cell needs to function. - Vacuole: It stores water and nutrients, and is large in plant cells and small or indistinct in animal cells. - The cell wall: It is found only in plant cells, and it helps to give the cell shape and rigidity. - Chloroplasts: found in plant cells, they perform photosynthesis to make food using sunlight. The difference between a plant cell and an animal cell: Plant cells contain additional components not found in animal cells. For example, the cell wall, which gives it a stable shape and rigidity, and chloroplasts, which enable it to produce its own food through photosynthesis. Also, the vacuole in plants is large and prominent, while in animals it is small or absent. As for the animal cell, it depends on ready-made food, and it does not contain chloroplasts or a cell wall, and this makes its shape more flexible.