Unit 11: Classification and Diversity of Life
How millions of species get sorted into one family tree, from the three domains down to a single genus and species.
8 topics · 24 questions
Each topic is a path, not a menu: work down it in order and every question builds on the one above. Click any of them to watch the answer draw itself.
Why Scientists Classify Living Things
- How it worksHow does grouping organisms by shared evolutionary ancestry organize millions of known species?
- Common mistakeWhy isn't classification just about how organisms look at a glance?
- Going furtherWhat happens to an organism's classification when new genetic evidence reveals a different ancestry?
Your turn1 of 2
Before a standard naming system existed, one region might call a plant by one common name while another region called the exact same species something completely different. Why would every scientist calling the same organism by a different common name make research impossible to share?The Levels of Classification
- How it worksHow do domain, kingdom, phylum, class, order, family, genus, and species nest inside each other?
- Worked exampleFind how many levels of classification a human and a chimpanzee share before their paths split.
- Common mistakeWhy doesn't sharing a family or order automatically mean two organisms are the same species?
Your turn1 of 2
Two species share 5 of the eight classification levels (domain, kingdom, phylum, class, order, family, genus, species) before their classification paths diverge. How many of the eight levels do they NOT share?The Three Domains of Life
- How it worksHow do differences in cell membrane chemistry and genetics separate Bacteria, Archaea, and Eukarya?
- Common mistakeWhy aren't Archaea just another type of bacteria even though both lack a nucleus?
- Going furtherWhat happens to the tree of life's structure once molecular evidence splits prokaryotes into two domains?
Your turn1 of 2
Scientists discovered microorganisms thriving in boiling volcanic vents, conditions once thought too extreme for any life, and their DNA turned out to be surprisingly different from ordinary bacteria. Why did this discovery force scientists to add a whole new domain, Archaea, instead of just calling them extremophile bacteria?The Six Kingdoms
- How it worksHow do differences in cell structure and how organisms get energy separate the six kingdoms?
- Common mistakeWhy isn't a fungus simply a stationary plant that doesn't photosynthesize?
- Ties togetherHow do the three domains and six kingdoms fit together into one classification system?
Your turn1 of 2
A mushroom is stationary, grows from the ground, and doesn't photosynthesize, sharing some surface traits with plants. Why does a mushroom get its own kingdom, Fungi, instead of being grouped with plants?Binomial Nomenclature
- How it worksHow does a genus name combined with a species name pinpoint one exact organism worldwide?
- Worked exampleFind what the genus and species parts of the name Homo sapiens each tell you.
- Common mistakeWhy isn't a common name like daisy precise enough for scientific classification?
Your turn1 of 2
A single flowering plant might be called a daisy in English but have a completely different common name in another language, yet scientists worldwide refer to it by the same two-part Latin name. Why does every species get exactly two Latin names instead of one common name?Reading a Phylogenetic Tree
- How it worksHow does each branch point on a phylogenetic tree represent a shared common ancestor?
- Worked exampleFind which two species are more closely related when species A and B share a more recent branch point than either shares with species C.
- Common mistakeWhy doesn't a species positioned further to the right on a tree mean it's more evolved than one on the left?
Your turn1 of 2
A phylogenetic tree shows species branching apart at different points without listing a single calendar date anywhere on the diagram. Why can this branching diagram still show which species are more closely related than others?Protists
- How it worksHow do amoebas, algae, and paramecia differ so much while all being classified as protists?
- Common mistakeWhy isn't a protist simply a tiny, primitive version of a plant or animal cell?
- Going furtherWhat happens to algae populations that triggers a visible bloom in a warm, nutrient-rich lake?
Your turn1 of 2
The kingdom Protista includes amoebas, algae, paramecia, and many other organisms that don't have much in common with each other beyond not fitting cleanly into the other five kingdoms. Why does Protista end up as such a broad, mixed leftover group?Fungi
- How it worksHow do fungal hyphae release digestive enzymes outside their body before absorbing the nutrients?
- Common mistakeWhy isn't a fungus classified as a plant just because it grows in soil and doesn't move?
- Ties togetherHow do decomposer fungi recycle nutrients from dead organisms back into an ecosystem?
Your turn1 of 2
The visible mushroom you see poking up through soil or a rotting log is only a small fruiting structure, while a much larger network of thread-like hyphae spreads unseen underground or through the log. Why does a mushroom you see above ground represent only a tiny fraction of the whole fungus?