Crash Course Biology - Lecture Notes
Introduction to Life
- Life started approximately 4 billion years ago.
- Acknowledged as one of the most interesting phenomena on Earth.
- Life is diverse: squishy, slippery, slimy, sticky, spiky; various shapes and sizes.
What is Biology?
- Biology: the study of life.
- Reasons to study biology:
- Development of new medicines.
- Understanding and identifying misinformation.
- Describing biological processes (e.g., breathing).
Defining Life
- Difficult to pin down a precise definition of life.
- Traditional criteria (Aristotle):
- Growth, reproduction, response to stimuli.
- Modern definitions (NASA):
- A self-sustaining chemical system capable of evolution.
Seven Characteristics of Life
- Regulation: Maintaining stable internal conditions despite external changes.
- Example: Sweating in response to heat.
- Response to Environment: Reacting to stimuli.
- Example: Cheetahs chasing gazelles; plants turning towards the sun.
- Reproduction: Passing genetic information to offspring.
- Includes both multicellular organisms (e.g., giraffes) and single-celled organisms (e.g., yeast).
- Growth and Development: Changes based on genetic instructions.
- Example: Tadpoles developing into frogs; teenagers experiencing voice changes.
- Energy Processing: Utilizing energy for life functions.
- Example: Humans consuming food to fuel bodily functions.
- Organization: Structured arrangement of cells into tissues, organs, systems.
- Example: The structured body of a platypus.
- Adaptations: Traits shaped by evolution for survival and reproduction.
- Example: Platypus adaptations including webbed feet and venomous spurs.
The Gray Areas of Life
- Some entities blur the lines of life:
- Viruses:
- Cannot reproduce or grow independently; rely on host cells.
- Debate exists whether they are classified as living.
- Viruses have been around almost as long as cells and have evolved significantly.
Life Beyond Earth
- Astrobiology: the study of potential extraterrestrial life forms.
- Current knowledge: Earth is the only known planet sustaining life.
- Understanding life could change with new discoveries.
Interconnectedness of Life
- All living organisms share a common ancestor from 4 billion years ago.
- Molecular connections: elements in our bodies originated from stars.
- Understanding life's interconnectedness aids in addressing global challenges:
- Hunger, disease, climate change.
Conclusion
- Biology is everywhere, impacting daily life and the environment.
- Philosophical and practical questions about life contribute to scientific processes.
- Future discussions will delve deeper into the scientific process and its implications.
Produced in collaboration with HHMI Biointeractive. Visit biointeractive.org for resources.