Lab # 2 - DIVERSITY OF LIFE
Life is divided into 5 kingdoms by many systematists:
(Cell lacks nucleus)
|Monera||3500 my - Recent||Bacteria & cyanobacteria ("blue-green algae")|
(Cell has a nucleus)
|Late Precambrian - Recent||Single-celled microfossils (diatoms, foraminifera) & multicellular seaweed|
|Eukaryota||Fungi||Silurian - Recent||Toadstools, fungi. Single- or multi-celled. Plant-like but donít photosynthesize.|
|Eukaryota||Plantae||Silurian - Recent||Plants. Multicellular, photosynthetic.|
|Eukaryota||Animalia||Latest Precambrian - Recent||Animals.|
The Animalia is divided into the following phyla
(phyla in bold are in todayís lab):
The Linnaean system of classification is a hierarchical scheme, and is the way organisms have been classified since the 1700ís. Fossil species are erected on the basis of hard-part morphology, whereas the biological (living) species concept is based on soft-parts and reproductive behavior also. All the categories above the species level are to some extent arbitrary, although reflecting evolutionary relationships in some general sense. Similar species are grouped in genera, genera in families, etc.; e.g.
In addition, there may be super- or sub- classes, orders, & families (divisions in the case of plants), because Life is complicated! As you can see, the Vertebrata donít really have a taxonomic level in the Linnaean system, but they are defined cladistically as "craniates with backbones" (basically, chordates are animals with notochords, an internal supporting rod; and craniates are those chordates with skulls). In the last few years cladistics has become an important method of classifying organisms, based on their relationships with other organisms. Cladistics will be discussed in class and will be the subject of Lab 4.
Classification of the Vertebrata:
All the names in bold are classes.
Some useful definitions
In this lab we will look at examples from most of the different animal phyla that are preserved as fossils. We will not consider those that do not have fossil records.
Illustrations are included for most of the groups represented in the lab, and are very useful for identifying features.
Always sketch in pencil and include a scale.
Sketch this specimen. Label the leaf scars (attachment points for leaves).
Sketch the specimen. The groove running around the specimen is the attachment point for leaf whorls.
Sponges. Sessile aquatic (mainly marine) organisms that lack tissues and organs. They have an internal skeleton which may be siliceous, calcareous, or organic.
The example here is Raphidonema, a cup-shape sponge from the Cretaceous.
Sketch this specimen. From your knowledge of
fossil preservation, what might itís internal skeleton have been made of?
Bryozoans are aquatic, mainly marine, found in any depth water (shoreline to the "abyssal plain": - 8500 m deep). Colonial and sessile.
Bryozoans can be a variety of forms; the specimen here is a branching form, reminiscent of coral. Another common form is a net structure, literally resembling a lace network.
Sketch this specimen from the Ordovician.
Segmented worms. They have no hard parts, and because soft parts rarely fossilize annelids are typically represented in the fossil record by the trace fossils they (! - probably) made.
The example here is from the Quaternary and consists of many tubes cemented together.
What might these structures have been used
Corals & jellyfish. They are solitary or colonial, benthic, sessile organisms; the zooids live in the structures you see preserved. Corals can be divided into 3 classes. The rugose corals (e.g. Streptelasma, a Devonian horn-shaped coral) were represented by both solitary and colonial forms, & became extinct at the end of the Permian. The tabulate corals were always colonial (Favosites is a Devonian example comprised of polygonal "corallites"), ranging from the Ordovician to the Permian. The third class is the Scleractinia, ranging from the Middle Triassic through to today. All modern corals are scleractinian, either colonial or solitary. Corals are very important in the rock record, because as colonial structures they can form great reefs, which get preserved as enormous limestone units (with the form of the reef still visible). Modern colonial forms also provide environmental information - the water has to be well-oxygenated, shallow, free from clastic input, & warm (appx. 25°C). Solitary corals can tolerate cooler, deeper water.
Sketch the 2 coral specimens at this station.
What principle (lecture 2) can you apply to determine paleoenvironmental
information from fossil corals?
The arthropods include insects, spiders and crustaceans (crabs, lobsters). Today arthropods are found in all environments - terrestrial and aquatic, and are a highly successful group. Trilobites (meaning "three-lobed animal" - head, body & tail) are common benthic fossils from the Early Cambrian to the Permian.
Sketch the Ordovician trilobite (Calymene)
at this station. Label the 3 lobes.
Solitary sessile marine benthic filter-feeders. External skeleton consists of 2 unlike valves (shells). Abundant fossils in the Paleozoic, quite rare today.
The specimen provided is a spirifid brachiopod (this group lived from the Middle Ordovician - Jurassic).
Sketch it in several views, noting the orientation
of the plane of symmetry, and the margin at the front. The V-shaped
notch allowed the organism inside to open up the valves to let water (and
hence food) in, but not so wide that predators could also get in. What
might the ridges on the surfaces of the valves have been used for?
There are 3 important fossil groups of molluscs: bivalves, gastropods and cephalopods. Molluscs are usually marine, although there are some freshwater and terrestrial forms also. Plant, flesh or filter-feeders.
Class Bivalvia (Lamellibranchia, Pelecypoda in older literature)
Early Cambrian - Recent. Figure 7d-f.
The bivalves are the only molluscs in todayís lab with 2 valves. Superficially they resemble brachiopods; however the symmetry is in a different plane: bivalves are symmetrical from the side (the 2 valves are mirror images), and asymmetrical from the top, opposite to brachiopodsí symmetry. Bivalves span a wide range of habitats: benthic, epifaunal and infaunal (burrowers & borers into hard substrates), free-swimming, freshwater and marine.
Look at the 2 specimens. Note the growth lines.
Sketch the inside of one of the valves - note the 2 shiny patches which
mark the attachment sites of the muscles used to open and close the valves.
Make sure you can distinguish between brachiopods and bivalves.
Cambrian - Recent. Figure 8.
Gastropods are snails - helically-spired molluscs. The shape of their shell is a result of rotating the internal organs. Most are aquatic, mainly living in shallow seas; they also live in freshwater and on dry land.
Sketch the 2 specimens. What might the spines
on the modern example have been used for?
Late Cambrian - Recent
Cephalopods are molluscs with tentacles and well-developed eyes, many forms having shells (which may be straight, curved, or coiled). Unlike gastropods, the coiling is in a horizontal plane (i.e. like a spiral drawn on paper in 2-D, rather than a "spiral" staircase). Living examples are exclusively marine predators including the Nautilus, cuttlefish, squid, and octopus.
This subclass includes squid and cuttlefish. The shell is internal and straight.
Sketch one of the Cretaceous Belemnites
Ammonoids have coiled shells with complex suture lines (the pattern on the outside of the shell). They are very common fossils in Mesozoic strata, especially in the Jurassic. Cretaceous forms took on more bizarre and complex coiling, often being hook-shaped, for example. Some genera have strong ribs, or bosses (knobby bumps on the surface of the shell), used to strengthen the shell. Ammonites were nektonic and could reach enormous sizes (several feet in diameter!).
Sketch the Lower Jurassic ammonite, and illustrate
part of the suture pattern.
Sessile or free-living colonial forms with an organic skeleton. Graptolites (Middle Cambrian - Late Carboniferous, ?Early Permian) are abundant fossils in Paleozoic shales, resembling saw-toothed pencil streaks on the rock! Each little "tooth" (actually a cup) was home to a zooid. They were probably planktonic filter-feeders; they are useful biostratigraphic tools for the Paleozoic.
Use a handlens to help you sketch these Ordovician
graptolites, showing the form of the sawtooth pattern.
The echinoderms include starfish, sea urchins, sand dollars, brittle stars, sea cucumbers, and sea lilies. Mobile or sessile marine organisms, typically with pentameral (5-fold) symmetry. Internal skeleton composed of calcite plates. It is thought that some early echinoderms may have been the ancestors of chordates.
Middle Cambrian - Recent
Crinoids (sea-lilies) are sessile echinoderms consisting of a stem, fixed to the sea-floor by "roots", capped by a crown (cup-shaped body), with flexible arms emanating from the latter that are used for filter-feeding. Common in the fossil record.
Study and sketch the modern crinoid (in the
jar), labeling the stem, cup & arms. Next look at the fossil example
(Pentacrinus, a Jurassic form). Sketch it, identifying and labeling
what you can.
Sea urchins. Hemispherical, disc-shaped or heart-shaped test (skeleton) consisting of interlocking plates covered by skin. Outer surface covered with spines, used for both protection and locomotion. Gregarious benthic forms living in shallow coastal water, often infaunal. Common in the fossil record.
The specimen here is Micraster, a Late Cretaceous irregular echinoid (i.e. bilateral rather than 5-fold radial symmetry). The different species of Micraster are used for zoning (i.e. using the principles of biostratigraphy to subdivide strata) chalk.
Sketch this specimen, indicating the line of
This specimen is a regular echinoid - note the pentameral symmetry. Sketch this specimen, comparing with Micraster (station 14). The mouth is on the underside, the anus is on top.
Identify these, labeling them on your sketch.
sea urchin - recent. Knowing the location of the
mouth, what feeding strategy might regular echinoids employ?
Sketch the vertebra and teeth.
Clarkson, E.N.K. 1986. Invertebrate Palaeontology and Evolution, 2nd edn. Unwin Hyman, 382 pp.