Transcription
Hello seniors. I'm glad you're still here, listening to an exciting lesson related to life science. I'm Mom De La Soyna, and I'll be presenting to you today's amazing lesson. Are you excited? So do I. So let's make the most out of our class time, learn while having fun.
In the previous lesson, you've learned about how organisms change over time. This new lesson will guide you about the classification of organisms based on evolutionary relationships. How do we classify organisms based on evolutionary relationships? In the present time, scientists can build trees to show the evolutionary relationships of species as a representation of classifying organisms based on evolutionary relationships, just like you can build a family tree to show the relationships of your ancestors and their descendants.
My dear students, our lesson for today is Lesson 8: Evolutionary Relationships. At the end of this lesson, you should be able to:
1. Describe how the present system of classification of organisms is based on evolutionary relationships.
2. Interpret and explain the phylogenetic tree.
3. Explain the importance of the phylogenetic tree to evolutionary relationships of organisms.
How do we know which organisms in a tree are most closely related to one another? It's tempting to focus on the order of the branch tips on a tree, in which line goes to the right and which goes to the left. But in fact, this ordering is not meaningful at all. Instead, the common ancestry is the key to understanding evolutionary relationships, as shown in the figure. Common ancestry refers to the fact that distinct descendant lineages have the same ancestral lineage in common with one another.
One evidence for evolution is the presence of structures in organisms that share the same basic form. For example, the bones in the appendages of a human, horse, cat, porpoise, and bat all share the same overall construction, as shown in the figure, resulting from their origin in the appendages of a common ancestor. Nevertheless, they have somewhat different forms and functions. They are called homologous structures. However, analogous structures mean unrelated animals have organs with similar functions, yet are very different in structure and form.
The study of the relationships of organisms, including collection, preservation, study of specimens, and analysis of data provided by various areas of science, is called taxonomy. Moreover, in scientific terms, the evolutionary history and the relationship of an organism or group of organisms are called biology. Phylogeny describes the relationships of an organism, such as from which species it is most closely related and which organisms it is thought to have evolved. It also provides information on shared ancestry but not necessarily on how organisms are similar or different. Therefore, phylogeny is the study of determining evolutionary relationships or patterns of the descent of organisms through evolution, or simply change over time.
All the species of organisms that are alive today have descended from ancestral species. The evolutionary relationships of ancestral species and their descendants can be diagrammed using branching evolutionary trees. An evolutionary tree indicates which ancestors gave rise to which descendants, just like making a family tree.
How do scientists construct phylogenetic trees? After the analogous and homologous traits are sorted, scientists often organize homologous traits using a system called cladistics. Cladistics sorts organisms into clades, which is a group of organisms that descended from a single ancestor. Modern classification is based on evolutionary relationships called systematics or cladistics. Cladistics is a classification based on common ancestry. Phylogeny is the evolutionary history for a group of species. Evidence from species, the fossil record, and molecular data are shown with branching tree diagrams.
What is a cladogram? A cladogram is a diagram that describes evolutionary relationships among groups. It is based on phylogeny, which is the study of evolutionary relationships. Sometimes, a phylogenetic tree is also called a cladogram, though there are minor differences between the two. Biologists should group organisms based on their physical appearance. This strategy is called evolutionary classification. Cladistics, through the advances in genetics and biochemistry, this form of analysis which newer features that serve some kind of purpose and features organisms that are considered innovation.
Key aspects of a cladogram are the root, clades, and nodes. The root is the central trunk of the cladogram that indicates the ancestor common to all groups branching from it. A cladogram uses branching lines that end in a clade, which is a group of organisms sharing a common hypothetical ancestor. The points where the lines intersect are the common ancestors and are called nodes. The important factor is that the organisms in the clade or monophyletic groups stem from a single point on the tree. This is through varying the size of a clade depending on which branch point is being referenced. The term monophyletic breaks down into mono meaning one, and phyletic meaning evolutionary relationship.
That was an amazing lesson, isn't it? I hope you learned a lot in today's topic. Thank you for listening, and don't forget to take care of yourself by staying at home. See you again next time. Bye-bye.