Study sheet: The Logic of Life

📋 Course Outline

1. Molecular Foundations of Life
2. Cellular Organization
3. Levels of Biological Organization
4. Functions of Living Systems
5. Genetic Information and Reproduction
6. Ecological Organization
7. Evolution and Scientific Reasoning

📖 1. Molecular Foundations of Life

🔑 Key Concepts & Definitions

• Atom : An elementary chemical body consisting of a nucleus made of protons and neutrons, surrounded by an electron cloud.
• Molecule : A unit of matter made of at least two atoms joined by covalent bonds and electrically neutral overall.
• ADN : A polymer of deoxyribonucleotides that supports genetic information and normally consists of two polynucleotide strands associated by hydrogen bonds into a double helix.
• ATP : A nucleotide composed of adenine, ribose, and three phosphoryl groups whose hydrolysis supplies energy for many metabolic reactions.
• Supramolecular assembly : An assemblage of numerous macromolecules maintained by weak bonds.

💡 Memory Hook

Atom → molecule → macromolecule → supramolecular assembly

📖 2. Cellular Organization

🔑 Key Concepts & Definitions

• Cell : A closed structure bounded by a plasma membrane, containing cytoplasm and genetic material in the form of DNA, and constituting the structural, functional, and reproductive unit of life.
• Organelle : A membrane-bounded structure in the cytoplasm of a eukaryotic cell, specialized in one or more precise functions.
• Gene : A unit of genetic information made of DNA whose nucleotide sequence determines one or more characteristics, alone or with other genes.
• Information : A message made of signals whose nature, quantity, or succession forms a code that can be perceived, interpreted, and trigger a receptor response.

📝 Essential Points

📌 Microscopic structures are invisible to the naked eye, whereas macroscopic structures are visible to the naked eye and larger than 1 mm.

💡 Memory Hook

The cell is the living unit; the organelle is a specialized part of it.

📖 3. Levels of Biological Organization

🔑 Key Concepts & Definitions

• Tissue : A coherent group of cells with similar or identical structure and the same embryonic origin that jointly perform a precise function.
• Organ : An anatomically distinct structure in a multicellular organism, made of tissues and specialized in one or sometimes several relatively precise functions.
• Organism : A living system clearly bounded in space that may consist of a single cell or of numerous organs.
• Biological system : An ensemble of structures enabling the performance of the same function, generally involving organs but possibly structures at another scale.
• Plan of organization : The arrangement of organs and systems relative to one another and to the organism’s axes of polarity.

💡 Memory Hook

Cell → tissue → organ → apparatus → organism

📖 4. Functions of Living Systems

🔑 Key Concepts & Definitions

• Metabolism : The set of chemical reactions and energy transformations occurring within a cell or organism, including anabolism and catabolism.
• Growth : An increase in the size of a living organism through increases in cell number, cell volume, and/or extracellular-matrix volume.
• Development : The set of phenomena that build a complete organism and includes embryonic and post-embryonic development.
• Feedback : The control of a process by the result of that same process; negative feedback inhibits the process when its result increases, whereas positive feedback stimulates it.
• Regulation : Maintaining the equilibrium state of a biological system and/or producing an adapted response to internal or external signals.

💡 Memory Hook

Metabolism provides energy and materials, enabling growth, development, regulation, and reproduction.

📖 5. Genetic Information and Reproduction

🔑 Key Concepts & Definitions

• Mitosis : A eukaryotic cell division in which each daughter cell receives one chromatid from every chromosome, making the daughter cells genetically identical to one another and to the mother cell.
• Meiosis : A eukaryotic cell division in which each daughter cell receives one chromatid from one chromosome of each homologous pair; from a diploid mother cell, the daughter cells are haploid and have one allele for each gene.
• Fertilization : The fusion of two haploid gametes during sexual reproduction into one diploid cell called a zygote.
• Living : A living structure is autonomous, has metabolism, can develop and reproduce, and interacts with its environment; the term may be restricted to structures made of cells.
• Reproduction : The set of phenomena that enables a living organism to produce descendants.

💡 Memory Hook

Mitosis preserves genetic identity, whereas meiosis halves chromosome representation.

📖 6. Ecological Organization

🔑 Key Concepts & Definitions

• Population : A set of individuals of the same species forming a spatiotemporal unit by living and interacting at a given time in a given geographic area.
• Community : An assemblage of populations of different species living at the same time and in the same space within an ecosystem.
• Ecosystem : Different groups of living organisms associated with their biological, geological, and other environments in a given geographic area.
• Biodiversity : The natural diversity of living organisms at the levels of genes, species, functional groups, and ecosystems.
• Biocenosis : The set of living organisms in a given region or ecosystem.
• Biotope : The geographic, geological, and other environment in which living organisms exist within a given region or ecosystem.

💡 Memory Hook

Population → community → ecosystem → landscape → biosphere

📖 7. Evolution and Scientific Reasoning

🔑 Key Concepts & Definitions

• Species : A basic unit of biological classification, often defined as organisms capable of reproducing naturally with one another.
• Evolution : The modification over time of heritable characteristics in a group of living organisms.
• Phylogeny : Either the presumed evolutionary succession of biological groups leading to a species or taxon, represented by a phylogenetic tree, or the study of relationships among taxa.
• Emergent property : A property resulting from more fundamental properties while being new relative to them, so that the whole is more than the sum of its parts.

📝 Essential Points

📌 A relation is a direct or indirect link between phenomena or structures, whereas an interaction is a reciprocal action or influence between two or more objects.

📌 The principle of parsimony, or Ockham’s razor, states that without scientific evidence the simplest and statistically most plausible hypothesis should be retained over less simple and less plausible hypotheses.

💡 Memory Hook

Heritable changes over time produce evolution and can be inferred through phylogeny.

📊 Synthesis Tables

Levels of biological organization

Level	Definition	Distinguishing feature
Population	Individuals of one species	Same species
Community	Populations of different species	Different species
Ecosystem	Living groups plus environment	Biotic and abiotic components
Landscape	Interacting ecosystems in a defined area	Several ecosystems
Biosphere	All terrestrial ecosystems and their interactions	Global scale