Remember when Pluto was a planet? Scientists continually restructure their way of thinking as they obtain more data.
Remember when Pluto was a planet? Scientists continually restructure their way of thinking as they obtain more data. Taxonomy is the science of naming organisms while phylogeny groups them based on evolutionary relationships (1:16). King Phillip wasn’t always so dull, but as microscopic life was discovered, the manner of classifying and sorting organisms needed updating (2:38). Primary differences between domains and kingdoms are cell type, DNA organization, organelles, energy acquisition and cell wall composition (3:15). The episode wraps up with unit connections and exam expectations (6:44).
The Question of the Day asks (7:45) Amoebas use pseudopods for motility and ingestion. What cellular structure forms the temporary pseudopods?
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Hi and welcome to the APsolute Recap: Biology Edition. Today’s episode will recap taxonomy and the organization of living things.
Zoom out:
Unit 2, and 7, and 8
There's too many topics to count
Big idea - Evolution
Dull King Phillip came over for Grape Soda. Definitely keep pots clean or families get sick. Dont kids prefer cheese over fancy green salads? Whatever tomatoes your tomAHto - these acronyms are designed to remind you of the classification hierarchy of all living things. From broadest to most specific: Domain, Kingdom, Phylum, Class, Order, Family Genus, Species.
Let’s Zoom in:
Soooo you won’t actually find the term taxonomy in the AP Biology course exam description, or CED. Taxonomy is the science of naming, describing and classifying organisms into...you guessed it….taxons, or groups. But you’ve actually been seeing and working with organisms of these taxa throughout the curriculum. In Unit 7, the emphasis will be on phylogeny - the evolutionary relationship between organisms. These two areas of study have a lot of overlap and a key feature in common. Just as with all areas of science, the more data we have, the more we have to be open to restructuring our way of thinking. Remember when we kicked pluto out of the planetary party? More data, new decisions - #science.
Imagine what it was like for early scientists to classify a duck. It walks, swims and flies! With no knowledge of the microscopic world or cellular structure, they had to rely upon macroscopic observable phenotypes, and at times, behaviors. Greek philosopher and scientist Aristotle thought so anyways, living in the mid 300’s BC. He thought that organisms ranged from the most simple, to most complex and grouped them all into only two types - plants and animals. Carolus Linnaeus came around in the 1700s adding a group called “minerals” (a bit off the mark) but he did leave us with the binomial nomenclature Genus Species naming system, which we still use in part today.
In 1674, Anton van Leeuwenhoek, the "father of microscopy", sent the Royal Society of London a report on his first observations of microscopic single-celled organisms. And just like that, the world view expanded! The discovery of microscopic life threw a wrench in the current classification system - causing a shift to classify unicellular organisms separately from multicellular. It wasn’t until the mid 1900s that the classification systems started to distinguish between cell types within groupings, prokaryotes and eukaryotes. Yada yada yada - here’s what we have today.
There are three accepted Domains of life. Domain’s Bacteria and Archaea both contain unicellular prokaryotes that reproduce asexaully. Their DNA is mostly organized into circular chromosomes with some plasmids and they have smaller 70s ribosomes. Bacteria, sometimes called eubacteria (remember the prefix eu means true) have cell walls made of the polysaccharide peptidoglycan whereas Archaea do not. Archaea are often called as you will find them in environments with similar conditions to early earth - like hot springs, salt flats, and geysers.
Domain Eukarya contain unicellular and multicellular eukaryotes. Their DNA is organized into linear chromosomes with histones inside of a nucleus, rarely have plasmids, and have larger 80s ribosomes. A defining characteristic of this domain are membrane bound organelles, like the endoplasmic reticulum and Golgi body. There are four kingdoms. The animal kingdom contains multicellular heterotrophic organisms with no cell walls - they’ve got to move around after all. The plant kingdom are multicellular autotrophs with cell walls made of cellulose and polysaccharides. The Fungi kingdom contains unicellular and multicellular heterotrophs that obtain nutrients through absorption and have cell walls made of chitin. And lastly, the protists - our kingdom of misfit organisms. Unicellular and at times colonial eukaryotes - this group contains cells that may contain animal, plant, or fungal characteristics. Consider the euglena - a microscopic pond organism that moves around like an animal and photosynthesizes like a plant! If Aristotle struggled classifying a duck - he would have no idea what to do with a euglena.
Historically, the number of accepted classification kingdoms has grown from two to six. However, recent phylogenetic research doesn’t support any of the traditional systems. And what about viruses? They aren’t living things (not made of cells and don’t reproduce independently) YET they are classified in their own evolutionary way. After all, they have genes and do change over time. Like I said at the beginning of this episode - “the more data we have, the more we have to be open to restructuring our way of thinking.” Perhaps our definition of life will change in the near future, inviting viruses to the party.
Time for unit connections. Unit 4 with cell communication - think quorum sensing and neurotransmitters, Unit 6 with biotechnology and plasmids, Unit 7 with population variations and phylogeny, and Unit 8 with energy flow through ecosystems.
Alright - what about the exam? You may be asked to predict evolutionary relationships based on shared characteristics or lab results. Additionally, correlating autotrophic characteristics and chemosynthetic pathways to energy flow - be sure to check out some diagrams.
To recap…… King Phillip wasn’t always so dull, but as microscopic life was discovered, the manner of classifying and sorting organisms needed updating. Taxonomy is the science of naming and classifying organisms while phylogeny groups them based on evolutionary relationships. Primary differences between domains and kingdoms are cell type, DNA organization, organelles, energy acquisition and cell wall composition.
Coming up next on the Apsolute RecAP Biology Edition: The endomembrane system.
Today’s question of the day is about amoebas
Question of the day: Amoebas use pseudopods for motility and ingestion. What cellular structure forms the temporary pseudopods?