Activity 3-Cladistics (Group 1) PDF

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Summary

The word "cladistics" comes from the Greek word "branch." The branches of
the Tree of Life are the branches with which cladistics is concerned (Wilkinson, 2011).
Cladistics is a method for determining the branching pattern of the Tree of Life, and thus the
historical (phylogenet...

Description

Activity 3: Cladistics: Understanding Evolution 1

Adrias, K.J., 1Fernandez, H., 1Manangan, J.L., 1Pula, F.R. 1Salappudin, A. & 1Unaid,

M. Department of Biology and Natural Sciences, College of Science and Mathematics, Western Mindanao State University, Normal Road, Baliwasan, Zamboanga City, Zamboanga Del Sur, 7000, Region IX, Philippines

Introduction. The word "cladistics" comes from the Greek word "branch." The branches of the Tree of Life are the branches with which cladistics is concerned (Wilkinson, 2011). Cladistics is a method for determining the branching pattern of the Tree of Life, and thus the historical (phylogenetic) relationships that connect all living and extinct species (Gregory, 2010). Cladistics is a philosophy of classification for some researchers, as well as a method of inferring evolutionary relationships and common ancestry. Willi Hennig, a German entomologist, is regarded as the founder of cladistics and is credited with developing both the fundamental argumentation and the philosophy of cladistic classification (Mayr, 2010). As a result, cladistics has come to be associated with a subset of quantitative data analysis methods that can generate relationship hypotheses (trees) from complex data derived from the phenotype and/or genotype, and that allow the similarities and differences between different types of organisms to be summarized (Williams, 2020). The concept of cladistic relationships is central to cladistics. This is a relative term based on how recent common ancestors are (Wilkinson, 2011). If two or more species (e.g. humans and chimps) share a common ancestor that is not shared by the other species (e.g. gorillas), they are cladistically more closely related to each other than to some other species (e.g. gorillas) (Figure 1). This is distinct from other types of relationship concepts. In a genetic sense, for example, an individual organism is usually equally related to its parents as it is to its offspring (Farris, 2010). If the cladistic concept were applied to these same organisms, the individual and its offspring would be more closely related to each other than either is to the parent. Although this may appear strange in the context of individual organisms, the concept of cladistic relationships is particularly useful for describing relationships between species rather than individual organisms within species (Griffiths, 2012). A monophyletic group or clade is a group of species that includes all descendants of their last common ancestor in cladistics. The Tree of Life is divided into clades, each of which represents a complete branch. Cladistics is based on the idea that members of a group have a shared evolutionary history and are "closely related," more so to other members of the same group than to other organisms. Cladistics generates hypotheses about organism relationships in a way that, unlike other systems, predicts the organisms' properties. This is particularly important when searching for specific genes or biological compounds (Lipscomb, 2010). Cladistics has become the most popular method for classifying organisms. The classification system is required. That is, we need words like beetle and conifer to talk about a variety of organisms at the same time. In fact, formal classification schemes in biology have a long history, dating back to the 1700s, long before Darwin proposed his natural selection theory. Because it recognizes and employs evolutionary theory, cladistics is now the method of choice for classifying life (de Quieroz and Gauthier, 2013).

Figure 1. Cladistic relationships among three Great Apes depicted in the form of a tree or cladogram.

Objectives. After completing this exercise, students should be able to: a. Understand the topic cladistics. b. Distinguish between phenetics, phylogeny and cladistics. c. Generate a cladogram.

Construct a Cladogram: This part shows the construction of a cladogram of ten (10) microorganisms such as Escherichia coli, Volvox, Amoeba, Paramecium, Aspergillus, Euglena, Rhizopus, Saccharomyces cerevisiae, Chlamydomonas and Plasmodium vivax with interpretation. Table 1. Character and Character States Nucleus Membrane Unicellular Multicellular Sexual Asexual -bound Reproduction Reproduction Organelles Escherichia coli

Absent

Absent

Present

Absent

Absent

Present

Volvox

Present

Present

Present

Present

Absent

Present

Amoeba

Present

Present

Present

Absent

Absent

Present

Paramecium

Present

Present

Present

Absent

Present

Present

Aspergillus

Present

Present

Present

Present

Absent

Present

Euglena

Present

Present

Present

Absent

Absent

Present

Rhizopus

Present

Present

Absent

Present

Present

Present

Saccharomyces cerevisiae

Present

Present

Present

Absent

Present

Present

Chlamydomona Present s

Present

Present

Absent

Present

Present

Present

Present

Present

Absent

Present

Present

Plasmodium vivax

Table 2. Numerical Representative Character States Nucleus

1 – Present

0 – Absent

Membrane-bound Organelles

1 – Present

0 – Absent

Unicellular

1 – Present

0 – Absent

Multicellular

1 – Present

0 – Absent

Sexual Reproduction

1 – Present

0 – Absent

Asexual Reproduction

1 – Present

0 – Absent

Table 3. Character Representation for Character States in Animals Nucleus Membrane Unicellular Multicellular Sexual -bound Reproductio n Organelles

Asexual Reproduction

Escherichia coli

0

0

1

0

0

1

Volvox

1

1

1

1

0

1

Amoeba

1

1

1

0

0

1

Paramecium

1

1

1

0

1

1

Aspergillus

1

1

1

1

0

1

Euglena

1

1

1

0

0

1

Rhizopus

1

1

0

1

1

1

Saccharomyces cerevisiae

1

1

1

0

1

1

Chlamydomona 1 s

1

1

0

1

1

1

1

1

0

1

1

Plasmodium vivax

Multicellular

SR

Nucleus; Membranebound Organelles Figure 2. Cladogram of the ten (10) microorganisms

Interpretation In the cladogram above, there are six phylogenetic characteristics that are studied, which are the presence of nucleus and membrane-bound organelles, unicellular, multicellular, sexual reproduction, and asexual reproduction. It shows that Volvox, Rhizopus, Aspergillus, and Amoeba are closely related to each other. On the other hand, E. coli and Amoeba are distantly related as it moves towards the right of the diagram, which indicates that these organisms became less related to each other. The E. coli is the outgroup in the cladogram shown above.

Discussion. This part of the activity includes the graphic organizer for the presentation of the topic cladistics, it also discusses how phenetics, phylogeny and cladistics are distinguished from each and lastly the argumentative essay about the activity. Graphic Organizer:

Distinguish between phenetics, phylogeny and cladistics.

Phenetics is a method of grouping organisms based on their overall similarity, which involves plesiomorphic and apomorphic similarity. Also, this concept allows ordinary data to be designated even though the entries in a matrix are said to be shared derived characters and phenetic characters are the data and images used in phenetics which are identical and in with varying methodologies (Farris, 2012)....