Biology and the Tree of Life: Study Notes for BLG143 Biology I

Course Introduction

Overview

This course, BLG143: Biology I, introduces students to foundational concepts in general biology, focusing on the unity and diversity of life, the scientific method, and the evolutionary relationships among organisms. The course is offered by the Faculty of Science, Department of Chemistry & Biology at Toronto Metropolitan University.

• Course Instructor: Tarushika Vasanthan

• Lab Coordinator: Karen Puddephton

Course Structure and Assessment

Assessment Weighting

• Lecture Component: 70% of total course mark

  • Quizzes (top 8 of 10): 13%

  • Midterm Test: 27%

  • Final Exam: 30%

• Laboratory Component: 30% of total course mark

  • Lab Assignments

  • Lab Writing Assignment

  • Lab Practices

• Minimum requirements: At least 50% overall, 50% in laboratory, and 50% in lecture components.

Course Schedule and Topics

Main Topics

• Introduction, Importance of Water

• Biological Molecules

• The Cell: Components and Interactions

• Respiration and Fermentation

• Photosynthesis

• Mitosis

• Meiosis

• Genetics

• DNA Synthesis, Gene Structure, and Repair

• Genetic Code, Transcription, and Translation

• Gene Control in Prokaryotes & Eukaryotes

• Development

Chapter 1: Biology and the Tree of Life

What is Science?

Science is the systematic study of the natural, observable world. The goal is not only to obtain new facts but to discover new ways of thinking about them.

• Scientific Method: Involves asking questions, developing hypotheses, conducting experiments, and drawing conclusions based on evidence.

• Theory vs. Hypothesis:

  • Theory: A broad explanation for a general class of phenomena or observations.

  • Hypothesis: A testable statement that explains something observed.

Characteristics of Living Organisms

All living organisms share five fundamental characteristics:

• Cells: All organisms are made of cells.

• Replication: Ability to reproduce.

• Evolution: Populations evolve over time.

• Information: Genetic information is stored and transmitted.

• Energy: Ability to acquire and use energy.

Cell Theory

The cell theory states:

• All organisms are made of cells.

• All cells come from preexisting cells.

Historically, spontaneous generation was proposed, but experiments (e.g., Pasteur's flask experiment) disproved it, supporting the 'all-cells-from-cells' hypothesis.

Evolution and Natural Selection

Charles Darwin and Alfred Russel Wallace proposed that:

• All species are related by common ancestry.

• Species can change over time (descent with modification).

Natural Selection: The mechanism of evolution. For natural selection to occur:

• Individuals must vary in heritable characteristics.

• Certain traits must confer higher reproductive success in a particular environment.

Natural selection acts on individuals, but evolutionary change occurs in populations.

Genetic Information and Inheritance

Genetic information is encoded in genes, which are segments of DNA located on chromosomes. The chromosome theory of inheritance (Sutton and Boveri, 1902) established that genes are the units of heredity.

• DNA Structure: Double helix composed of four nucleotides (A, T, C, G).

• Central Dogma: Information flows from DNA to RNA to protein.

Equation (Central Dogma):

$\text{DNA} \rightarrow \text{RNA} \rightarrow \text{Protein}$

Energy and Metabolism

Cells require energy for chemical reactions and building cellular components. The two fundamental nutritional needs are:

• Chemical energy (e.g., ATP)

• Molecules for biosynthesis (e.g., DNA, proteins)

Equation (ATP hydrolysis):

$\text{ATP} + \text{H}_2\text{O} \rightarrow \text{ADP} + \text{P}_i + \text{energy}$

The Tree of Life and Phylogenetics

The tree of life describes the genealogical relationships among all living organisms. Phylogenetic trees are constructed using genetic data (e.g., DNA or RNA sequences).

• Organisms with more similar genetic sequences are more closely related.

• Main node represents the common ancestor of all living organisms.

Three Domains of Life

Domain	Characteristics	Examples
Bacteria	Prokaryotic, unicellular	Escherichia coli
Archaea	Prokaryotic, unicellular, often extremophiles	Halobacterium
Eukarya	Eukaryotic, unicellular or multicellular	Homo sapiens, Arabidopsis thaliana

Naming and Classification

Linnaeus established the binomial nomenclature system:

• Each species is given a unique two-part scientific name: Genus species

• Genus names are capitalized; species names are not.

• Scientific names are always italicized (e.g., Homo sapiens).

Experimental Design: Case Study on Ant Navigation

Researchers tested the 'pedometer hypothesis' in desert ants, which posits that ants use stride number and length to navigate back to their nest.

• Three groups: Stumps (shorter stride), Stilts (longer stride), Normal (untreated).

• Control group used to check for other factors.

• Experimental conditions controlled and repeated for reliability.

Conclusion: Ants use stride length and number to calculate distance, supporting the pedometer hypothesis.

Key Learning Objectives

• Describe the five fundamental characteristics shared by all living organisms.

• Explain the two components of the cell theory.

• Clarify the theory of natural selection and the conditions necessary for evolutionary change.

• Understand the chromosome theory of inheritance and the construction of phylogenetic trees.