Lab # 2 - DIVERSITY OF LIFE





Life is divided into 5 kingdoms by many systematists:
 

Superkingdom Kingdom Age range Examples
Prokaryota

(Cell lacks nucleus)

Monera 3500 my - Recent Bacteria & cyanobacteria ("blue-green algae")
Eukaryota

(Cell has a nucleus)

Protista 

(or Protoctista)

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):
 
 
 
Acanthocephala Mesozoa
Annelida Mollusca
Arthropoda Nematoda
Brachiopoda Nematomorpha
Chaetognatha Nemertina
Chordata Onychophora
Cycliophora Pentastoma
Cnidaria Phoronida
Ctenophora Placozoa
Echinodermata Platyhelminthes
Echiura Pogonophora
Ectoprocta Porifera
Entoprocta Priapulida
Gastrotrichia Rotifera
Gnathostomulida Sipuncula
Hemichordata Tardigrada
Kinorhyncha

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.

Kingdom Animalia
  Phylum Chordata Class Mammalia Order Primates Family Hominidae Genus Homo Species Homo sapiens
The genus (plural, genera) and species names are always either italicized or underlined.

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:

Phylum Chordata notochords Middle Cambrian - Recent Craniata skulls Vertebrata backbones Agnatha (jawless fish) L. Cambrian - Recent Gnathostomata jaws E. Devonian - Recent Acanthodia (fish w/ spiny fins) E. Silurian - E. Permian
Placodermi (armored fish) L. Silurian - E. Carboniferous
Chondrichthyes (sharks) E. Silurian - Recent
Osteichthyes (bony fish) E. Devonian - Recent Tetrapoda 4 limbs, on land L. Devonian- Recent "Amphibia" L. Devonian - Recent
Amniota amniotic egg L. Carboniferous - Recent Sauria suborbital fenestra, L. Carboniferous - Recent Dinosauria openacetabulum, L. Triassic - Recent Aves feathers L. Jurassic - Recent Synapsida synapsid-type subtemporal fenestra, L. Carboniferous - Recent Mammalia dentary-squamosal jaw joint L. Triassic - Recent


All the names in bold  are classes.
 
 

Check out the following web pages of the "Tree of Life" project:

http://phylogeny.arizona.edu/tree/phylogeny.html

http://phylogeny.arizona.edu/tree/eukaryotes/animals/animals.html The first is the introduction page - from there you can explore all the different kingdoms. The second is the animals page with links to each phyla. Click on any of the links to see color photos of examples of each group.
 
 
 
 

Some useful definitions

Where organisms live:  
Aquatic In water - freshwater or marine
Marine Oceans
Terrestrial On land (including in soil, in trees, etc.)
Colonial Many tiny individuals ("zooids") lived in the fossilized structure.
Marine terms   Pelagic Living in the water column rather than on the sea floor
Planktonic Pelagic organisms that float in the surface waters (not free-swimming)
Nektonic Pelagic organisms that are free-swimming in the water column (any depth)
Benthic On the sea-floor
Sessile Benthic organisms that do not move around (unlike mobile benthos)
Infaunal Live in sediment (i.e. under the water/sea-floor interface)
Epifaunal Live on top of sediments of the sea-floor.  
Todayís lab:

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.

For each specimen, determine (& write down!) the depositional (burial) conditions by looking at the features of the rock and the detail of preservation. Kingdom Plantae Ordovician - Recent. Figure 1, Figure 2


Station 1

Plants originated in the oceans, but spread onto land during the Devonian. Flowering plants (angiosperms) are dominant today but did not evolve until the Early Cretaceous.
  Lepidodendron Carboniferous. Trunk of a lycopsid.

Sketch this specimen. Label the leaf scars (attachment points for leaves).


Calamites

Devonian - Carboniferous. Stem of a horsetail (sphenopsid).

Sketch the specimen. The groove running around the specimen is the attachment point for leaf whorls.

Kingdom Animalia Precambrian - Recent Station 2 Phylum Porifera  
Middle Cambrian - Recent. Figure 3.

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?
 
 

Station 3 Phylum Bryozoa  
Ordovician - Recent. Figure 4.

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.
 
 
 
 

Station 4 Phylum Annelida  
Precambrian - Recent.

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 for?
 
 

Station 5 Phylum Cnidaria (or Coelenterata)  
Late Precambrian (appx. 545 Ma) - Recent. Figure 5.

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?
 
 

Station 6 Phylum Arthropoda  
Cambrian - Recent. Figure 6.

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.
 
 

Station 7 Phylum Brachiopoda  
Cambrian - Recent. Figure 7a-c.

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?
 
 

Station 8 Phylum Mollusca  
Cambrian - Recent.

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.
 
 

Station 9 Phylum Mollusca Class Gastropoda

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?
 
 

Station 10 Phylum Mollusca Class Cephalopoda

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.

Subclass Coleoidea

Early Devonian - Recent. Figure 9.

This subclass includes squid and cuttlefish. The shell is internal and straight.

Sketch one of the Cretaceous Belemnites (cigar-shaped cephalopods).
 
 

Station 11 Phylum Mollusca Class Cephalopoda

Subclass Ammonoidea

Early Devonian - end Cretaceous. Figure 10 - 11.

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.
 
 
 
 

Station 12 Phylum Hemichordata Cambrian - Recent. Figure 12.

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.
 
 

Station 13 Phylum Echinodermata Cambrian - Recent. Figure 13 a-c.

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.

Class Crinoidea

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.
 
 

Station 14 Phylum Echinodermata Class Echinoidea - Late Ordovician - Recent Figure 13 k-m.

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 symmetry.
 
 

Station 15 Phylum Echinodermata Class Echinoidea Figure 13 e-j.

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?
 
 

Station 16 Phylum Chordata Vertebrata

Sketch the vertebra and teeth.
 


Illustrations on following pages are modified from: Black, R.M. 1988. The Elements of Palaeontology, 2nd edn. Cambridge University Press, 404 pp.

Clarkson, E.N.K. 1986. Invertebrate Palaeontology and Evolution, 2nd edn. Unwin Hyman, 382 pp.