What makes things move, grow, warm up, or change. The total amount never increases or decreases — it only changes from one form to another.

The total mass of living or once-living material in an area, which stores the energy captured by producers.

A liquid indicator that turns yellow when more carbon dioxide is dissolved in it, and stays blue-green when less is present.

The green pigment in plant cells that absorbs sunlight for photosynthesis.

The cell structures where photosynthesis happens, using chlorophyll to convert light energy into sugar.

Pairs of cells that open and close small pores in a leaf, controlling how gases like carbon dioxide and oxygen move in and out.

A substance that changes in a visible way — often color — to signal that a specific chemical change is happening.

Cell structures that break down sugar to release usable energy — often called the cell's power plant.

The process plants use to convert sunlight, water, and carbon dioxide into sugar and oxygen.

The process cells use to break down sugar and release the energy stored inside it, using oxygen and producing carbon dioxide.

Using resources in a way that meets today’s needs without using them up for the future.

Small pores on a leaf's surface that open and close to let gases move in and out.

A single-celled fungus that breaks down sugar and releases carbon dioxide gas as a byproduct.

The nonliving parts of an environment, like sunlight, water, temperature, and soil.

Living in or related to water, such as a lake, river, or ocean environment.

A large region defined by its climate and the type of plants and animals that live there, such as a desert, rainforest, or tundra.

The living parts of an environment, including plants, animals, and other organisms.

The largest population an environment can support long-term, based on its available food, water, and space.

The typical weather pattern of a region, measured over many years.

A community of living things interacting with each other and with the nonliving parts of their environment.

The natural environment where a specific organism normally lives, providing the food, water, shelter, and space it needs.

A resource or condition — like food, water, space, or temperature — that restricts how large a population can grow.

Any individual living thing, from a single bacterium to a whale.

Water that falls from clouds to the ground as rain, snow, sleet, or hail.

Energy that travels through space as waves or particles — sunlight is a familiar example, but many other objects give it off too.

Anything an organism needs and uses from its environment, such as food, water, or shelter.

A cold forest biome dominated by evergreen trees, found in far northern regions with long winters.

A forest biome with four distinct seasons and moderate rainfall, often full of trees that lose their leaves in fall.

A cold, treeless biome with a short growing season and permanently frozen ground beneath the surface.

The shape and features of the land's surface, including its hills, valleys, and elevation.

A warm, wet forest biome near the equator that supports an especially large variety of plants and animals.