1.2: Determining How Species Are Related pg. 17 – 23 Introduction

1.2: Determining How Species Are Related
pg. 17 – 23
- The goal of modern classification is to assign species to taxa
so that the classification reflects both morphological
similarities among organisms as well as hypotheses about
their phylogeny (evolutionary history)
- The Concept of Shared Evolutionary History, is used by
biologists, to determine if two species may share a common
- The more they share a common ancestor the more related the
two species.
Evidence of Relationships among Species
- comparing the giant panda to bears and raccoons, which is it
most related to?
- How do scientists determine how much of the evolutionary
histories of the two species are shared?
- In modern taxonomy there are three main types of evidence
that are used, anatomical, physiological, and DNA.
- Panda, based on the collected evidence is more closed related
to the bear than the raccoon, physiological and DNA.
Anatomical Evidence of Relationships:
- Anatomy is the study of the structure of an organism.
eg.: Dinosaur (Oviraptor philoceratops) and Bird (New
Guinean cassowary)
- Fossils are excellent evidence used to determine relationships
between the past and present.
- Organisms may look different from the outside, but may have
similar structures inside.
- eg.: Homologous structures: whale flipper, bat wing, horse
leg, and human arm.
- Show a shared evolutionary history.
Physiological Evidence of Relationships:
- Physiology is the study of the functioning of organisms.
Physiology includes the study of the biochemistry of an
organism. Comparing proteins among different species,
allows one to measure the degree of similarity or difference
in their genetic make up. Proteins are coded for by the
organism’s DNA.
- eg.: Compare the insulin produced in a Guinea pig and a
mouse. It is not the same, therefore they are not related.
DNA Evidence of Relationships
- Genes are sections of DNA made of long chains of molecules
of nucleotides.
- Technological advances have made it increasingly possible to
determine the sequence of nucleotides of a specific gene.
- New DNA evidence has meant that prior classifications
based on morphological, physiological, or other evidence,
must be restructured.
- eg.: Fungi are more closely related to animals then plants.
Phylogenetic Trees
- Phylogenetic Trees are used to represent a hypothesis about
the evolutionary relationships among groups of organisms.
- Like a family tree, the roots or the base of the phylogenetic
tree represents the oldest ancestral species.
- The upper ends of the branches represent the present day
- Forks in each branch represents the points in the past at
which an ancestral species split-evolved, or changed over
time, becoming two new species.
- eg.: Figure 1.12: Plant eating hooved mammals, pg. 21
The Importance of Classification to Technology, Society, and the
a) sources of pharmaceutical drugs, hormones, and other
important medical products.
b) Help scientists to study and trace the transmission of diseases
and develop and test possible treatments.
c) In agriculture to develop ways to increase crop yields and
disease resistance, utilizing the technique of cross breeding
closely related species.
d) Finding new species or reclassifying an organism as a
separate species has implications for environmental
Learning Check, questions 7 – 12, pg 19
Section 1.2 Review, questions 1 – 10, pg. 23
Family Tree Graphic Organizer
In the family tree graphic organizer below, write your name in the single box on the
bottom. The two boxes above represent your parents. The very top row represents your
great grandparents.
BLM 1-3