Crash Course Biology: What is Life?

Introduction

4 billion years ago, life emerged on Earth
Life is diverse: squishy, slippery, slimy, sticky, spiky
Shapes and sizes: moss, mosquito, manatee, and more
Biology: The study of life
Reasons to study biology:
- Medicine development
- Identifying misinformation
- Describing biological processes (e.g., breathing)

Not easy to define; subjective
Examples: Ants are alive; fire, computer viruses, robot vacuums are not
Philosophical Perspectives:
- Aristotle: Growth, reproduction, reaction to forces define life
- NASA: Self-sustaining chemical system capable of evolution
Modern Biologists use 7 characteristics:
1. Regulation: Keeping inner conditions steady despite outer changes (e.g., sweating, panting)
2. Response to environment: e.g., cheetahs chasing gazelles, plants turning towards the sun
3. Reproduction: Passing on genetic information to offspring
4. Growth and development: Based on genetic instructions
5. Processing energy: To perform biological functions
6. Organization: Cellular structure to organ systems
7. Evolution and adaptation: Traits that aid survival and reproduction

Non-living things with life-like traits: Organized snowflakes, growing fire
Viruses:
- Not alive by most biologists' standards
- Require host cells to replicate
- Cannot process energy or regulate itself

Biology is everywhere: Medicine, agriculture, daily human functions
All living things share a common ancestor
Interconnectedness:
- Molecules in our bodies come from star dust
- Highlights connections between all living things

Understanding life’s interconnectedness aids in addressing challenges:
- Hunger, disease, climate change
Scientific process: Philosophical and practical questions shape understanding