Concise Summary of Key Concepts in Biology

Learning Outcomes

• LO1: Major elements of life
• LO2: Diversity of life classification
• LO3: Definition of a cell
• LO4: Characteristics of life
• LO5: Differences between prokaryotes and eukaryotes
• LO6: Concept of endosymbiosis

Diversity of Life

• Approximately 1.8 million species identified
• Estimates of species exist from 10 to 100 million

Classification of Life

• Life classified into species and broader classifications
• Historically based on structures/functions; currently, nucleic acid comparisons are utilized (e.g., 16s rRNA)
• Each species has a two-part name (e.g., Staphylococcus aureus)
• Life classified into three domains: Eukaryotes, Bacteria, Archaea

Prokaryotes vs. Eukaryotes

• Prokaryotes: Generally smaller, no membrane-bound organelles, single chromosomal DNA, e.g., Bacteria and Archaea
• Eukaryotes: Larger, have organelles including a nucleus, several linear chromosomes
• Ribosomes present in both types, play a role in protein synthesis

What is a Cell?

• Smallest unit of organization performing life activities
• All organisms made of cells; cells share characteristics (e.g., membrane presence)

Characteristics of Life

• Living things: Reproduce, grow & develop, respond to environment, metabolize energy
• Viruses/Prions: Viruses not considered living as they require a host; prions are misfolded proteins and also not living

Organelles in Eukaryotes

• Mitochondria: Energy production, presence varies with metabolic activity
• Chloroplasts: In plants/algae, photosynthesis occurs here, contain chlorophyll and thylakoid membranes

Endosymbiotic Theory

• Eukaryotes originated from symbiosis of prokaryotic cells
• Chloroplasts evolved from engulfment of photosynthetic bacteria (cyanobacteria)
• Evidence supports this theory through structural and genetic similarities between organelles and bacteria.