Bio101 - Principles of Biology

Introduction

Red pandas:
- Well adapted for life in mountainous forests of Asia.
- Cinnamon red and white coat camouflages them.
- Long bushy tail provides warmth.
- Bony projection in wrist helps them grasp bamboo.
Giant pandas:
- Live in similar regions.
- Originally thought to be closely related to red pandas, but red pandas have been reclassified into their own family.
- Both at risk of extinction.

Taxonomists name species and classify them into broader groups.
Life is organized into three domains:
- Bacteria: Simple cells.
- Archaea: Simple cells.
- Eukarya: Includes protists, Fungi, Plantae, and Animalia.

Science is a way of understanding the natural world.
Science uses an evidence-based process of inquiry.
The scientific approach involves:
- Observations
- Hypotheses
- Predictions
- Tests of hypotheses
- Analysis of data
A scientific theory is broad and supported by evidence.
Example: Flashlight doesn’t work.
- Question: Why doesn’t the flashlight work?
- Hypothesis #1: Batteries are dead.
- Hypothesis #2: Bulb is burned out.

Experimental tests manipulate one component and observe effects.
Independent variable: The factor that is manipulated.
Dependent variable: The measure used to judge the outcome.
Controlled experiment: Compares an experimental group with a control group.
The use of control and experimental groups can demonstrate the effect of a single variable.
Hypotheses can be tested in humans with clinical trials, as well as retrospective or prospective observational studies.

Scientists tested hypotheses about the evolutionary relationships of red pandas.
- Initial hypothesis: Red panda related to raccoons based on physical similarities.
- Alternative hypothesis: Red panda related to giant pandas based on diet and habitat.
- Recent studies: DNA sequences classify red pandas in their own family.

Forming and testing hypotheses is at the core of science, influenced by:
1. Exploration and discovery
2. Analysis and feedback from the scientific community
3. Societal benefits and outcomes

Life has unity and diversity.
Evolution explains this unity and diversity.
Darwin synthesized the theory of evolution by natural selection.
Natural selection:
1. Population with varied inherited traits.
2. Elimination of individuals with certain traits and reproduction of survivors.
3. Increasing frequency of traits that enhance survival and reproductive success.
Each species has a family history, representing a twig on a branching tree of life.

Evolutionary theory is useful in medicine, conservation, and agriculture.
Humans act as agents of evolution through selective breeding (artificial selection).
Crops, livestock, and pets bear little resemblance to their wild ancestors.

Life processes depend on information transmission and use.
DNA is responsible for heredity and programming cell activities.
External and internal environment provides stimuli, signals, and pathways that regulate body processes and gene expression.
Information flow:
- DNA → RNA → Protein
Example: Pancreas
1. High blood glucose level signals the pancreas.
2. Pancreatic cell releases insulin.
3. Insulin stimulates body cells to take up glucose.
4. Normal blood glucose level removes signal, insulin release stops.

Structure and function are related at every level.
Molecular level: Protein structure correlates with function (e.g., hemoglobin transports oxygen).
Cellular level: Nerve cell extensions transmit impulses.

Energy flows through an ecosystem:
- Enters as sunlight.
- Converted to chemical energy by producers.
- Passed to consumers.
- Exits as heat.
Ecosystems cycle matter:
- From atmosphere and soil.
- Through producers, consumers, and decomposers.
- Back to the environment.
Photosynthesis transforms energy and matter.

Study of life ranges from microscopic to global scales.
Emergent properties result from interactions within a system.
Systems biology models biological systems by analyzing interactions among parts.