Archaea

Most archaeans don’t look that different from bacteria under the microscope. The extreme conditions under which most species of archaea live has made them difficult to culture, so their unique place among living organisms long went unrecognized. However, biochemically and genetically, they are as different from bacteria as you are. They are not Bacteria, they […]

The Tree of Life: Part 3

The tree of life, as scientists understand it, is not static – it changes. Classification systems have changed with science’s understandings of the diversity and organization of the living world, so don’t think that we know it all! Prior to the 1970s, scientists generally classified living things as Bacteria or Eucarya. The scientific community was […]

Bacteria

Bacteria are everywhere. Only a few micrometers in length and having a wide range of shapes, from spheres to rods to spiral, bacteria are the huddled masses of the microbial world, performing tasks that include everything from causing disease to fixing nitrogen in the soil. Humans need bacteria. In fact, there are approximately ten times […]

The Tree of Life: Part 2

Most of the organisms that scientists know exist fit in the second domain: Bacteria. The bacteria are a large group of unicellular microorganisms. Bacteria are ubiquitous in every habitat on Earth, growing in soil, acidic hot springs, radioactive waste, water, and deep in the Earth’s crust, as well as in organic matter and the live […]

Eucarya

A eukaryote is an organism whose cells are organized into complex structures enclosed within membranes. Many living organisms we are familiar with, including all animals, plants, and fungi, are eukaryotes. The defining membrane-bound structure that differentiates eukaryotic cells from other types of cells is the nucleus. Cells without a nucleus are called prokaryotic cells, and […]

The Tree of Life

The phylogenetic tree or evolutionary tree shows the evolutionary relationships among various biological species. In a phylogenetic tree, each node with descendants represents the most recent common ancestor of the descendants. Each node is called a taxonomic unit. Key Concept: All cells come from preexisting cells. Most broadly, scientists classify life into three domains. Humans, […]