OpenStem

@openstem · Joined Jul 2026

7420 public items8 groups

Note~178 words · 1 min

Tiny Living Things at a Glance Microorganisms are living things too small to see without a microscope. Bacteria, viruses, and fungi are three main types, and they are very different from one another — in size, in how they live, and in how t

Biology

Biology · L2 · Tiny Living Things at a Glance

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Note~261 words · 1 min

Plant Structures and Reproduction A plant's body is built from organs that each do a different job. Roots, stems, and leaves keep the plant alive and growing, while flowers handle reproduction — making the seeds that will become the next ge

Biology

Biology · L2 · Plant Structures and Reproduction Overview

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Note~339 words · 2 min

The Amazing Diversity of Invertebrates Invertebrates make up the vast majority of animal species on Earth, and they come in an astonishing range of shapes and lifestyles. Instead of one simple body plan, invertebrates are organized into man

Biology

Biology · L2 · The Amazing Diversity of Invertebrates

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Note~428 words · 2 min

Plant Defenses and Adaptations A plant cannot flee a hungry herbivore the way an animal can run from a predator, so plants have evolved a range of strategies to avoid being eaten instead: physical barriers that make biting difficult, chemic

Biology

Biology · L3 · Plant Defenses and Adaptations

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Note~610 words · 3 min

Animal Behavior: Instinct and Learning Ethology is the scientific study of animal behavior, especially behavior in an animal's natural environment. A central question in ethology is how much of a behavior is innate — built in from birth — a

Biology

Biology · L3 · Animal Behavior: Instinct and Learning

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Note~129 words · 1 min

World Biomes at a Glance A biome is a large region defined by its climate — how much rain falls and how hot or cold it gets. Each biome is home to plants and animals with adaptations suited to that climate. The table below compares five maj

Biology

Biology · L2 · World Biomes at a Glance

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Note~223 words · 1 min

Adaptations for Survival at a Glance An adaptation is any feature or behavior that helps a living thing survive in its environment. Physical adaptations are body features an animal is born with, such as fur, claws, or webbed feet. Behaviora

Biology

Biology · L2 · Adaptations for Survival at a Glance

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Note~172 words · 1 min

Human Life Stages at a Glance Every person passes through a series of general life stages as they grow. Each stage brings changes in size, skills, and independence. Growth speed also varies a great deal between species — humans take about 1

Biology

Biology · L2 · Human Life Stages at a Glance

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Note~305 words · 2 min

How Germs Spread and How Your Body Fights Back Germs are tiny living things, like bacteria and viruses, that can make you sick. They spread from person to person in a few common ways, but your body also has several layers of defense working

Biology

Biology · L2 · How Germs Spread and How Your Body Fights Back

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Note~343 words · 2 min

How Sense Organs Detect the World Sense organs are the body's link to the outside world. Each one is built to detect a specific kind of stimulus — light, sound, touch, chemicals — and turn it into a nerve signal the brain can interpret. The

Biology

Biology · L2 · How Sense Organs Detect the World

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Note~266 words · 1 min

Skin and Kidneys: Getting Rid of Waste Every day, your body's cells make waste products it doesn't need — extra water, salt, and a chemical called urea. If that waste built up, it would make you sick. The excretory system is the group of or

Biology

Biology · L2 · Skin and Kidneys: Getting Rid of Waste

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Note~205 words · 1 min

Hormones and Glands: Your Body's Messengers Your body has a way of sending messages without wires or nerves. Certain organs called glands make special chemicals called hormones and release them straight into your bloodstream. Blood then car

Biology

Biology · L2 · Hormones and Glands: Your Body's Messengers

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Note~303 words · 2 min

Growing Up: An Introduction to Human Reproduction As people grow from childhood into adulthood, their bodies go through a stage of change called puberty. Puberty is a normal, healthy part of life that every person experiences, though not al

Biology

Biology · L2 · Growing Up: An Introduction to Human Reproduction

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Note~331 words · 2 min

Why Leaves Are Green (and Why They Change Color) A leaf's color comes from tiny chemicals called pigments. Each pigment absorbs certain colors of light and reflects the rest — and the color it reflects is the color our eyes see. A leaf can

Biology

Biology · L2 · Why Leaves Are Green (and Why They Change Color)

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Note~181 words · 1 min

How Animals Talk to Each Other Animals cannot talk using words like humans do, but they still need to share information — where food is, whether danger is close, or who is ready to be a mate. To do this, animals communicate using signals: s

Biology

Biology · L2 · How Animals Talk to Each Other

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Note~248 words · 1 min

Food Groups and a Balanced Diet Every day, your body needs a mix of different nutrients to grow, repair itself, and have enough energy to move, think, and stay healthy. No single food provides everything you need, which is why eating a vari

Biology

Biology · L2 · Food Groups and a Balanced Diet

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Note~385 words · 2 min

Types of Joints: How Bones Connect and Move A joint is any place where two or more bones meet. Not all joints are the same — some let bones move a huge amount, some only let bones twist, and some barely let bones move at all. Scientists gro

Biology

Biology · L2 · Types of Joints: How Bones Connect and Move

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Note~300 words · 2 min

Discovering Cells: Microscopes and Cell Theory Before the 1600s, nobody knew that living things were made of cells — cells are simply too small to see with the naked eye. Everything changed once lens makers learned to grind curved pieces of

Biology

Biology · L2 · Discovering Cells: Microscopes and Cell Theory

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Note~377 words · 2 min

Herd Immunity: Protecting a Whole Community Getting vaccinated protects you as an individual. But it also does something bigger: when enough people in a community are immune to a disease, that disease has a much harder time spreading from p

Biology

Biology · L2 · Herd Immunity: Protecting a Whole Community

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Note~430 words · 2 min

How Water Moves Through a Plant A plant's stem already carries water upward through its xylem tubes. But what actually powers that upward movement? The answer is transpiration — water evaporating out of the leaves, which pulls a continuous

Biology

Biology · L2 · How Water Moves Through a Plant

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Note~212 words · 1 min

What Is DNA? A First Look DNA (deoxyribonucleic acid) is a long molecule found inside the cells of nearly every living thing. If you could zoom in close enough, you'd see it isn't shaped like a straight strand — it's twisted into a long spi

Biology

Biology · L2 · What Is DNA? at a Glance

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Note~273 words · 1 min

How We Keep Food From Spoiling Mold, bacteria, and other microbes are what cause food to spoil. This note isn't about the biology of spoilage — it's about the clever tricks humans have invented, long before refrigerators existed, to slow th

Biology

Biology · L2 · How We Keep Food From Spoiling

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Note~230 words · 1 min

Animal Lifespans at a Glance An animal's lifespan is the total length of time it is alive, from birth or hatching all the way to death. Lifespan is not the same thing as how long an animal takes to grow up — a mouse reaches adulthood in jus

Biology

Biology · L2 · Animal Lifespans at a Glance

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Note~267 words · 1 min

Cellular Respiration: Releasing Energy From Food Every living cell needs energy to survive — energy to grow, move, and repair itself. Cells get that energy from food through a process called cellular respiration. The simple word equation fo

Biology

Biology · L2 · Cellular Respiration: Releasing Energy From Food

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Note~189 words · 1 min

How Desert Plants Store Water Deserts get very little rain, and what does fall often disappears fast — soaked into the ground, evaporated by the sun, or run off entirely. To survive, desert plants have evolved three main water-saving adapta

Biology

Biology · L2 · How Desert Plants Store Water at a Glance

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Note~305 words · 2 min

A Gentle Introduction to Punnett Squares Every pea flower has two alleles for its color — one inherited from each parent. Purple is dominant, so scientists write it with a capital "P". White is recessive, so it gets a lowercase "p". A domin

Biology

Biology · L2 · A Gentle Introduction to Punnett Squares

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Note~346 words · 2 min

Body Systems Working Together: Circulation and Breathing On their own, the respiratory system and the circulatory system each do one job. The respiratory system moves air in and out of the lungs. The circulatory system pumps blood around th

Biology

Biology · L2 · Body Systems Working Together: Circulation and Breathing

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Note~284 words · 1 min

Two Ways to Grow Up: Complete and Incomplete Metamorphosis Many insects don't just get bigger as they grow — their whole body shape changes. This process is called metamorphosis, and insects go through it in one of two very different ways:

Biology

Biology · L2 · Two Ways to Grow Up: Complete and Incomplete Metamorphosis

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Note~147 words · 1 min

The Three Bacteria Shapes at a Glance Bacteria are far too small to see with the naked eye, but under a microscope, scientists notice they come in a few basic shapes. Shape is one of the easiest clues for identifying what kind of bacterium

Biology

Biology · L2 · The Three Bacteria Shapes at a Glance

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Note~417 words · 2 min

Three Ways Plants Grow Without Seeds Not every new plant starts life as a seed. Many plants can also reproduce asexually — growing an entirely new plant from a piece of a parent plant. Because no egg cell and sperm cell combine, there is no

Biology

Biology · L2 · Three Ways Plants Grow Without Seeds

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