Life and Diversity II

Transcription

1 When we left off, we were talking about how every species of living thing is assigned a binomial name. Life and Diversity II Dr. Waggoner BIOL 1400 Turdus migratorius Erithacus rubecula Linnaeus defined species by distinctive physical features. For example, the upper jaw of this fish extends past the rear edge of the eye which makes it Micropterus salmoides (largemouth bass), and not Micropterus dolomieu (smallmouth bass). The problem is that in many species, individuals vary greatly in size, shape, color, etc. For example, these Cuban snails are all considered one species, Polymita picta. Maybe you could divide these into separate species but where would you "draw the lines"? 1

2 Species Definitions Morphological species concept a species is defined by its physical features or traits As we've seen, this can be ambiguous, especially if a species is very variable. Biological species concept a species is defined by its members' potential to interbreed All members of a species are potentially able to interbreed and produce fertile offspring with each other A species is reproductively isolated from all others; members of one species can't produce fertile offspring by breeding with other species Using the biological species concept, we sometimes find species that can t be told apart by looking. The western meadowlark and eastern meadowlark are almost physically identical, but they don't interbreed (and they also have different songs). These are cryptic species. Sturnella neglecta (Western) Sturnella magna (Eastern) Lepomis gibbosus (pumpkinseed) Species that are similar go into the same genus. The bluegill and similar fish are in the genus Lepomis... Genera that are similar go in the same family. This slide shows a few members of the family called the Centrarchidae, the sunfish family... Pomoxis nigromaculatus (black crappie) Lepomis macrochirus (bluegill) Lepomis cyanellus (green sunfish) Lepomis macrochirus (bluegill) Micropterus salmoides (largemouth bass) 2

3 2/2/11 And so on: Groupings of species are themselves clustered into higher-level groupings, each of which has a rank. Here s how we do it now... Domain Eucarya Kingdom Animalia Phylum Chordata Class Actinopterygii Order Perciformes Family Centrarchidae Genus Lepomis Species macrochirus So to review all this... We classify species using Linnaeus s system Each species gets a binomial name (two-part name) in Latin. Species are grouped into genera, genera are grouped into families, and so on, in a hierarchical classification system. The most inclusive grouping in the modern system is the domain. Three Domains of Life Eucarya / Eukaryotes Cells contain nuclei, flexible sacs in which the DNA (genetic material) is stored Eukaryote cells are compartmentalized, with many specialized "compartments" (organelles) for different functions Archaea Cells have no nuclei (prokaryotes) and aren t compartmentalized Many archaea, although not all, live in extreme environments Bacteria Cells have no nuclei (prokaryotes) and aren t compartmentalized The differences between Archaea and Bacteria involve a lot of biochemistry that we don't need to get into here For our purposes, there are four kingdoms in the eukaryote domain: animals, plants, fungi, and protists. 3

4 In this week s lab, you saw (or will see) eukaryotic cells' nuclei (best seen in your cheek cells) and some organelles (best seen in the Elodea cells). However, a lot of the complexity of eukaryotic cells can't easily be seen with the light microscope. If we look at a eukaryotic cell through a different kind of microscope, a transmission electron microscope, we can see the large, prominent, grainy nucleus (with a darker spot inside it called the nucleolus; more later on what that does) and various organelles. Viewed using the same type of microscope, bacteria can be seen to lack the nucleus and organelles of a eukaryote cell. Cross section through a bunch of archaea notice that there is no nucleus, or seemingly much of anything else. Since they both lack a nucleus, Archaea and Bacteria are both said to be prokaryotes. 4

5 2/2/11 Both archaea (top) and bacteria (bottom) are very small: cells are typicaly 1-5 microns, or millionths of a meter. Both lack a nucleus, and in fact are hard to tell apart without getting into some fairly complex biochemistry. Grand Prismatic Spring, at Yellowstone National Park, gets its colors in part from the thermophilic archaea living comfortably in near-boiling water... Many archaea, though certainly not all, live in extreme environments. The pinkish color of these pools of brine (extremely salty water), at the south end of San Francisco Bay, is due to massive numbers of halophilic ( saltloving ) archaea, which can live in water too saline for anything else. The Río Tinto, in southern Spain, is naturally acidic (about as acidic as lemon juice) and rich in heavy metals. Acidophilic archaeans live quite happily in the river; not much else can. 5

6 An undersea vent, or black smoker, thousands of feet below the ocean surface the smoke is superheated, mineral-rich water. Some extreme thermophilic archaea thrive here, at temperatures over 220 F (104.5 C). 6