Levels of Organization: From Molecules to Ecosystems

0:00Life is organized in levels, from tiny molecules up to whole ecosystems.

0:06We will climb them like a ladder, with one example: a salmon in a stream.

0:12At the bottom is a molecule, a group of atoms bonded together. DNA stores instructions, but it is not alive.

0:21A cell is the smallest unit of life. This heart muscle cell is alive and can contract.

0:28That is the key idea: each level has properties that the level below does not have.

0:34Similar cells working together form a tissue. Heart muscle tissue, called cardiac muscle, contracts as one.

0:43Different tissues working together form an organ, the heart. Only the whole heart can pump blood.

0:50Organs working together form an organ system. The circulatory system is the heart, blood vessels and blood.

0:58It carries oxygen and nutrients to cells all through the body.

1:03Organ systems together make an organism, one living thing: a salmon. It can swim, feed and grow.

1:11All the salmon of one species in one area form a population, with a size and a birth rate.

1:18The salmon share their stream with algae, insects and birds. Together, these populations form a community.

1:26In a community, species interact: insects eat algae, salmon eat insects, and birds eat salmon.

1:35Add the non-living parts, the water, the gravel and the light, and you have an ecosystem.

1:41Energy flows in as sunlight, while nutrients cycle and are used again and again.

1:48From molecule to ecosystem, each level has properties that the level below does not have.