Biology Chapter on Cladistics and Classification

Systematics and Phylogeny

• Systematics is the branch of biology that deals with the classification of organisms.
• Biologists group organisms based on shared characteristics like morphology, DNA, ecology, and behavior.

Basic Class Protocol

• No chatting during lectures to be considerate to your neighbors and the instructor.
• No lunch during lectures.
• Cell phones and laptops are not allowed during class. No texting, social media, or surfing webpages. Leave the classroom if you need to leave earlier or please inform the instructor at the beginning of the semester or class.
• Minimize noise and disturbances to other students when entering late. Enter the class through the designated doors.
• Class attendance is mandatory.

Students Learning in an In-Person Setting

• Ask questions during the lecture, not after.
• This is a large class with 250 students. Address questions to the instructor through Zoom or before class, and not in emails.
• The instructor will try to be in the room around 10:30 AM.
• Follow a clear policy structure that is the same for all students, to ensure comfortable teaching and learning.

Needed General Biology Foundations

• Meiosis and Mitosis are needed to understand the general biology foundation.
• Haploid and Polyploid cells
• DNA → mRNA → Ribosomes → Proteins
• Oxidation of sugars (electron-rich compounds) through respiration produces energy (ATP) and carbon dioxide (CO₂) as a by-product.
• Oxidation involves the loss of electrons.
• Aerobic respiration (38 ATP) versus anaerobic respiration (2 ATP): alcoholic fermentation and lactic acid fermentation.

Systematics and Classification of Organisms

• Systematics deals with organizing and classifying organisms based on shared characteristics.
• Different types of groups in classification– Monophyletic group, Paraphyletic group, Polyphyletic group

Monophyletic group

• Includes the most recent common ancestor of all its members, along with all its descendants.

Paraphyletic group

• Includes the most recent common ancestor of all its members but not all its descendants.

Polyphyletic group

• Does not include the most recent common ancestor of all its members.

Homoplasy

• A shared character state that was not inherited from a common ancestor.
• Convergent evolution and Evolutionary reversion are two kinds of homoplasy.
• Convergent evolution happens when independent species develop similar characteristics.
• Evolutionary reversal occurs when a species reverts to an ancestral character state.

Cladogram

• A branching diagram depicting a hypothesis about evolutionary relationships among organisms

Phylogenetic & Comparative Biology

• Homologous structures: structures are similar in origin and share a common ancestor, even though they may have different functions. e.g. arm of human and a bat wing
• Analogous structures: similar structures with different origins. e.g. wing of a bird and wing of an insect

Origin of Life

• Geologic time is divided into four eons: Hadean, Archean, Proterozoic, and Phanerozoic.
• Earth formed as a hot mass of molten rock about 4.5 billion years ago.
• Life originated approximately 3.5 billion years ago in the Archean.

Arthropods and Invertebrates

• Arthropods are invertebrates that possess an exoskeleton.
• Land colonization occurred around the same time, about 400,000,000 years ago.

Atmospheric Oxygen Levels

• Oxygenic photosynthesis produced atmospheric O2.
• 2 atmospheric O₂ was not present in the early atmosphere.
• There was a lag of 200 million years between the origin of photosynthesis and substantial atmospheric O₂ levels.

Origin of Mitochondria and Chloroplasts

• Mitochondria and chloroplasts likely evolved from engulfed prokaryotes that lived independently.
• Mitochondria developed from an aerobic prokaryote that formed an endosymbiotic relationship with the host eukaryote.
• Chloroplasts developed from a photosynthetic prokaryote that was engulfed by the eukaryote.

Ever-Changing Life on Earth

• Life evolved into three domains: Eubacteria, Archaea, and Eukaryotes.
• Six supergroups are identified within the Eukaryotes.

Concepts from the Video: Discovering the Great Tree of Life

• There are many possible evolutionary trees.
• The number of possible trees increases exponentially with the addition of more species.
• There are three main paradigms for constructing a tree of life : Ancestral origin of species through modification from a common ancestor; One ancestral species is the ancestor to one or more species at a particular time; and multiple ancestral species within a given tree.

Class Discussion Question

• A class discussion question to answer about a topic can aid in comprehension and the identification of gaps in knowledge.

Systematics and Classification of Organisms: Summary of Topics

• Classification is how species and larger groupings are organized into a hierarchical system, such as Genus, Family, Class, and others.
• Monophyletic group—a group that contains a common ancestor and all of its descendants
• Paraphyletic group—a group that contains the common ancestor but not all of its descendants.
• Polyphyletic group—a group that does NOT contain the most recent common ancestor of all its members.