Biological Organization and Cell Types

Unicellular and Multicellular Organisms

Living organisms can be classified based on the number of cells they possess, which influences their complexity and function.

• Unicellular: Organisms consisting of a single cell that performs all vital functions, including metabolism, excretion, and reproduction. Example: Amoeba, Paramecium

• Multicellular: Organisms composed of more than one cell, often with specialized cell types. Example: Homo sapiens (humans), Arabidopsis thaliana (a plant)

Cell Structure and Organization

Cells contain various structures that perform specific functions necessary for life.

• Organelle: A small, specialized structure within the cytoplasm of eukaryotic cells, often surrounded by membranes, that performs a specific function. Example: Mitochondria, nucleus

• Hierarchical Organization: Describes how biological systems are organized into levels or ranks, such as genes and species.

Energy and Metabolism

Energy in Biological Systems

Energy is essential for maintaining organization and enabling biological processes.

• Energy: The capacity to do work; needed to maintain organization in a system and to perform biological functions.

• Metabolism: The set of all chemical reactions that occur within living organisms to keep them alive.

• Catabolic Pathways: Metabolic pathways that break down molecules and release energy.

• Photosynthesis: The conversion of light energy to chemical energy, stored in sugars and other organic compounds. Occurs in plants, algae, and certain prokaryotes.

• Cell Respiration: The catabolic pathways of metabolism that break down organic molecules and use electron transport chains for the production of ATP.

• Homeostasis: Maintenance of internal conditions within narrow limits (relies on feedback mechanisms).

Genetics and Heredity

Genes and DNA

Genetic information is stored in DNA and determines the traits of organisms.

• Gene: A segment of DNA that contains instructions for making a particular protein.

• DNA: A nucleic acid molecule, usually double-stranded, in which each polynucleotide strand consists of nucleotide monomers with a deoxyribose sugar and nitrogenous bases.

• Mutation: A change in the nucleotide sequence of an organism's DNA or in the DNA or RNA of a virus.

Adaptation

Adaptations are inherited characteristics that enhance an organism's ability to survive and reproduce in a specific environment.

• Adaptation: Inherited characteristics of an organism that enhance its survival and reproduction in specific environments.

Classification and Taxonomy

Taxonomy and Binomial Nomenclature

Taxonomy is the science of naming and classifying organisms. Binomial nomenclature is the two-part scientific naming system for species.

• Taxonomy: The science of naming and classifying organisms.

• Binomial Nomenclature: The two-part, Latinized format for naming species, consisting of the genus and specific epithet. Example: Homo sapiens

• Genus: Taxonomic category above the species level; groups species that are structurally similar or closely related.

• Domain: The broadest taxonomic category; includes Archaea, Bacteria, and Eukarya.

• Kingdom: Taxonomic category below domain; includes groups such as Plantae, Animalia, Fungi, Protista.

Scientific Inquiry

Scientific Method and Reasoning

The scientific method is a systematic, repeatable process used to investigate phenomena and answer questions.

• Scientific Method: Systematic, repeatable process that scientists use to investigate observations, gather data, and test hypotheses.

• Hypothesis: A testable explanation for a set of observations, based on available data and guided by inductive reasoning.

• Scientific Theory: Well-supported explanation of phenomena, explaining a broad range of observations.

• Scientific Law: Describes consistent relationships in nature; rarely challenged.

• Formal Thought Process: Used to make observations and investigate them; essential for scientific inquiry.

Review Questions

• Ability to maintain constant internal environment? Homeostasis

• Genus species name of an organism? Scientific name

• Chemical reactions within a cell that use energy or produce energy? Metabolism

• Small structure within the cytoplasm that has a specific structure and function? Organelle