OpenStem

@openstem · Joined Jul 2026

7420 public items8 groups

Note~371 words · 2 min

The integumentary system The integumentary system consists of the skin and its accessory structures — hair, nails, and glands. It is the body's largest organ system, forming a flexible, self-repairing barrier between the internal body and t

Biology

Biology · L3 · The Integumentary System

@openstem

Note~638 words · 3 min

The Lymphatic System: Fluid Return and Immunity The lymphatic system is a low-pressure network of vessels and organs that runs alongside the circulatory system. It has two closely linked jobs: draining excess fluid from body tissues back in

Biology

Biology · L3 · The Lymphatic System: Fluid Return and Immunity

@openstem

Note~583 words · 3 min

Genetic Disorders: When Genes Go Wrong A genetic disorder is a health condition caused by a change in an organism's DNA or by an abnormal number of chromosomes. Some genetic disorders come from a mutation in a single gene; others come from

Biology

Biology · L3 · Genetic Disorders: When Genes Go Wrong

@openstem

Note~1032 words · 5 min

Immunology The adaptive immune system relies on a small set of recognition tools — antibodies, MHC molecules, and the T cells that read them — working together with an ancient enzymatic cascade, the complement system, to detect and destroy

Biology

Biology · L4 · Immunology

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Note~175 words · 1 min

Why and How Cells Divide Right now, all over your body, cells are dividing. A cell divides by splitting into two new cells — and this happens constantly, for a few simple reasons. The table below lists the three main reasons cells divide, w

Biology

Biology · L2 · Why and How Cells Divide

@openstem

Note~357 words · 2 min

Skin Color and Melanin Explained People around the world have skin in a wide range of natural colors, from very light to very dark. What determines a person's particular skin color is a pigment called melanin, made by cells in the skin itse

Biology

Biology · L2 · Skin Color and Melanin Explained

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Note~381 words · 2 min

How Vaccines Are Made: Weakened, Inactivated, and mRNA A vaccine works by showing your immune system something that looks like a germ, so your body can learn to recognize it before you ever get sick from the real thing. Scientists have deve

Biology

Biology · L2 · How Vaccines Are Made: Weakened, Inactivated, and mRNA

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Note~227 words · 1 min

How Desert Animals Conserve Water Deserts offer very little water, so animals that live there have evolved very different ways of coping. Some, like camels, store energy as fat and can handle huge, fast drinks when water is available. Other

Biology

Biology · L2 · How Desert Animals Conserve Water at a Glance

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Note~232 words · 1 min

How Antibodies Recognize Invaders When a germ or other invader gets into your body, your immune system needs a way to recognize it as foreign and respond. Antibodies are one of the immune system's key tools for doing exactly that. The Lock-

Biology

Biology · L2 · How Antibodies Recognize Invaders

@openstem

Note~272 words · 1 min

How Plants Protect Themselves Without Moving Plants cannot run away from a hungry animal or a careless footstep. So instead of moving, many plants protect themselves in a simpler way: they make themselves unpleasant to touch or eat. A plant

Biology

Biology · L2 · How Plants Protect Themselves Without Moving

@openstem

Note~308 words · 2 min

How Nerve Cells Send Messages A neuron is a nerve cell — a tiny messenger built to receive a signal, carry it along, and hand it off to the next cell. Trillions of neurons connect together to form your whole nervous system, but every single

Biology

Biology · L2 · How Nerve Cells Send Messages

@openstem

Note~221 words · 1 min

How Scientists Name a New Species Even today, scientists find plants and animals nobody has ever described before — deep in rainforests, on the ocean floor, or even hiding in plain sight. Turning that discovery into an official new species

Biology

Biology · L2 · How Scientists Name a New Species

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Note~53 words · 1 min

From sunlight to sugar Glucose is the central energy currency of life — a six-carbon ring built from carbon, hydrogen, and oxygen: Photosynthesis is how plants build glucose from carbon dioxide and water using light. The equation is balance

Biology

Biology · L3 · Molecules of Life: Glucose and Photosynthesis

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Note~533 words · 3 min

The eukaryotic cell: a system of specialized organelles A eukaryotic cell is divided into membrane-bound compartments called organelles, each specialized for a particular job. This division of labor, called compartmentalization, lets incomp

Biology

Biology · L3 · Cell Organelles: Structure and Function

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Note~360 words · 2 min

Predicting offspring with a Punnett square A Punnett square is a grid used to predict the possible genotypes and phenotypes of offspring from a genetic cross. Each parent's possible gametes are listed along one edge of the grid, and each ce

Biology

Biology · L3 · Genetics and Heredity: Reading a Punnett Square

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Note~218 words · 1 min

Enzymes of DNA replication DNA replication depends on a coordinated team of enzymes and proteins, each with a specific job in copying the genome quickly and accurately before a cell divides. Key enzymes and their roles Together, these enzym

Biology

Biology · L3 · Enzymes of DNA Replication

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Note~293 words · 1 min

Evidence for evolution Evolutionary theory is supported by multiple, independent lines of evidence drawn from different branches of biology. Each type of evidence points to the same conclusion: living species share common ancestry and have

Biology

Biology · L3 · Evidence for Evolution

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Note~459 words · 2 min

The Circulatory System The circulatory system moves blood through the body, delivering oxygen and nutrients to tissues and carrying away waste products such as carbon dioxide. It is powered by the heart, a muscular pump divided into four ch

Biology

Biology · L3 · The Circulatory System

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Note~214 words · 1 min

The Respiratory System The respiratory system moves air between the atmosphere and the bloodstream, supplying oxygen for cellular respiration and removing carbon dioxide, its waste product. It can be divided into a series of structures that

Biology

Biology · L3 · The Respiratory System

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Note~242 words · 1 min

The digestive system Digestion converts food into small, absorbable molecules through two complementary processes: mechanical digestion, which physically breaks food into smaller pieces, and chemical digestion, which uses enzymes to break c

Biology

Biology · L3 · The Digestive System

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Note~510 words · 3 min

The Neuron: The Nervous System's Basic Unit The nervous system is built from specialised cells called neurons, each adapted to receive, carry, and pass on electrical nerve impulses. A neuron has a cell body, branching dendrites that receive

Biology

Biology · L3 · The Nervous System

@openstem

Note~490 words · 2 min

The Immune System The immune system is the network of cells, tissues, and organs that defends the body against pathogens — disease-causing organisms such as bacteria, viruses, fungi, and parasites. It works in two broad layers: innate immun

Biology

Biology · L3 · The Immune System

@openstem

Note~452 words · 2 min

The endocrine system The endocrine system is a network of glands that secrete chemical messengers called hormones directly into the bloodstream. Unlike the nervous system, which sends fast electrical signals along neurons to specific target

Biology

Biology · L3 · The Endocrine System

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Note~387 words · 2 min

Joints of the skeletal system A joint, or articulation, is the point where two or more bones meet. Joints are classified structurally by the type of connective tissue that joins the bones, which in turn determines how much movement — if any

Biology

Biology · L3 · Joints and Skeletal Functions

@openstem

Note~486 words · 2 min

The Muscular System Muscle tissue is specialized to contract, or shorten, converting chemical energy into mechanical force. The human body contains three distinct types of muscle tissue, each built for a different job: skeletal muscle for v

Biology

Biology · L3 · The Muscular System

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Note~341 words · 2 min

The Excretory System The excretory system removes metabolic waste products, excess water, and excess ions from the blood, while also helping regulate blood pressure and ion balance. Its central organs are the kidneys, each containing about

Biology

Biology · L3 · The Excretory System

@openstem

Note~215 words · 1 min

The Reproductive System The reproductive system is responsible for producing gametes (sex cells), and, following fertilization, supporting the development of offspring. The female reproductive system produces ova and provides an environment

Biology

Biology · L3 · The Reproductive System

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Note~337 words · 2 min

Microbiology: Bacteria and Viruses Microbiology is the study of microorganisms too small to see without a microscope, including bacteria and viruses. Bacteria are single-celled prokaryotic organisms with their own cell structures and metabo

Biology

Biology · L3 · Microbiology: Bacteria and Viruses

@openstem

Note~296 words · 1 min

Plant Biology Plants convert light energy into chemical energy, distribute water and sugars through specialized transport tissues, and coordinate growth and reproduction using chemical signals. The structures and processes below work togeth

Biology

Biology · L3 · Plant Biology

@openstem

Note~296 words · 1 min

Symbiosis: living together Symbiosis describes a close, long-term interaction between two different species living in direct contact with one another. Ecologists classify symbiotic relationships according to whether each participating speci

Biology

Biology · L3 · Symbiotic Relationships in Ecosystems

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