Lab 5 ≠ Fossils and Species

Introduction

There are many different ways to define species, but in general they fall into two types: typological and biological. Typological definitions (based on the notion of an ideal or ≥type≤ specimen) are based on descriptive morphology of populations of organisms. Biological species definitions are based on the notion of breeding continuity, for example Ernst Mayrπs, ≥Species are populations of individuals capable of interbreeding in nature.≤ But in the paleo world, biological and genetic definitions are impractical to apply, and so we resort to what , in practice, the biologists use as well, ≥species are sets of organisms that are morphologically similar and can be distinguished from other such groups≤

An assemblage of fossils from any one deposit constitute a paleocommunity. In practice, fossil assemblages are usually a mixture of different species. One of the basic tasks of the paleontologist is sort through the variation seen in fossil assemblages and make decisions about what different kinds of species comprise an assemblage ≠ that is, to examine for interspecific variation.. A second problem is the assesment of intraspecific variation ≠ how much slop (variation) is there in the morphology of individuals of a population. The decision to divide up populations of individuals into recognizable species may seem trivial, ultimately, it can lead to some very fundamenrtal issues in evolution and biology.

Exercises

In this laboratory exercise we will look at two aspects of species in fossil populations. In the first, you will examine one of several sets of sorted fossils on display and attempt a simple method to describe the morphology of the fossils in your population. A typical method in this case would be to measure the height and width of a shell for example, and then plot your values on a graph to see what patterns emerge. A fundamental question to be addressed here is, ≥Are these population originally from one, or more species?≤ Could their variation be do to growth, or are they all adult individuals?

In the second haf of this exercise, your task is sort out a set of mixed species from collections of fossils from a Miocene deposit (Calvert Cliffs, Maryland). This deposit contains as may as 37 different species. Your task is to sort through these mixed assemblages and see if you can divide them up into separate species.