Science - Unit B

An organism is any living thing that can grow and respond to its environment. It requires nutrients, which are substances from food needed for growth, health, and energy. The basic unit of life is the cell, and organisms obtain energy from their environment to make things move or change. A stimulus is anything that causes a response, which is how a living thing reacts to that stimulus. Living things also undergo growth and development, such as puberty, and all living things originate from other living things. Adaptations are characteristics that allow organisms to live and thrive in their environment.

Living things are characterized by being made of cells, needing energy, responding to the environment, growing and developing, reproducing, and having adaptations.

Structure refers to body parts, while function is the specific task or job carried out by a body part, like a bird's wings for flying.

Organ systems include the respiratory system, which transports oxygen from air to blood; the digestive system, which breaks down food; the nervous system, which coordinates and controls actions; the excretory system, which removes chemical wastes; the skeletal system, which provides support; the muscular system, which moves organs and tissues; and the integumentary system, which protects the body and senses pain and temperature.

A microscope magnifies small objects to make it visible, and a compound light microscope uses two or more lenses and a light source.

Cells are the smallest functional units of life. Tissues are groups of specialized cells, organs are groups of tissues performing specific functions, and organ systems are groups of organs working together.

Organelles are specialized structures inside a cell. The nucleus directs cellular activities, mitochondria convert glucose into ATP, vacuoles store nutrients and water, the cell membrane controls what enters and exits, the cytoplasm is where organelles are suspended, the endoplasmic reticulum helps make and transport proteins and fats, the Golgi apparatus packages and ships proteins, lysosomes break down and digest things, chloroplasts carry out photosynthesis, and the cell wall provides strength and support.

Diffusion is the movement of particles from high to low concentration (excluding water), and osmosis is the movement of water from high to low concentration. Specialized cells carry out specific functions.

Mechanical digestion is the physical breakdown of food, while chemical digestion is the breakdown by enzymes.

The digestive system includes the teeth, epiglottis, esophagus, stomach, small intestine, liver, pancreas, and large intestine. Teeth mechanically digest food; the epiglottis directs food into the esophagus; the esophagus uses peristalsis to move food to the stomach; the stomach churns food and mixes it with gastric juice; the small intestine continues chemical digestion and absorbs nutrients; the liver produces bile; the pancreas adds chemicals to break down food; the large intestine absorbs water, vitamins, and minerals; and undigested food forms feces. Organs involved are the mouth, esophagus, stomach, small intestine, pancreas, liver, gallbladder, and large intestine.

The respiratory system takes in oxygen and releases carbon dioxide. Air travels through the nose, mouth, trachea, bronchi, and lungs. Inhaling involves contracting rib and diaphragm muscles, while exhaling involves relaxing those muscles. Gas exchange occurs in the alveoli, where oxygen is drawn into the lungs and capillaries facilitate the exchange.

The circulatory system delivers nutrients and transports oxygen to cells. The right heart pumps blood to the lungs to receive oxygen and release carbon dioxide. The left heart receives oxygen-rich blood from the lungs and then pumps this oxygen-rich blood to the body. Blood travels through vessels (arteries) from the heart to the body, delivering nutrients to each cell. Capillaries facilitate the exchange of oxygen from the blood into the body’s cells. Veins then carry blood back to the heart.

The excretory system removes toxic substances and converts them into urea. Kidneys filter blood; renal arteries bring blood to the kidneys; renal veins return filtered blood; ureters connect the kidneys to the bladder; the bladder holds urine; and sweat glands remove excess waste. Organs involved are the kidneys, renal arteries, bladder, urethra, and skin.

The nervous system consists of neurons. It's organized into the central nervous system (brain and spinal cord) and the peripheral nervous system (cranial and spinal nerves). Neurons function with dendrites receiving messages, the cell body passing messages from dendrites to the axon, and the axon transmitting pulses. Sensory neurons carry information from the head to the central system, while motor neurons carry information