Principles of Biology: Exploring Life and the Chemical Basis of Life

Chapter 1: Exploring Life

1.0 Adaptations in Red Pandas Reflect Evolutionary History

Adaptations are inherited characteristics that enhance an organism's ability to survive and reproduce in specific environments. The red panda provides an example of how evolutionary history shapes adaptations.

• Red panda adaptations: Red and white coat for camouflage among red mosses and white lichens; dark underbelly to avoid detection from below; long bushy tail for balance and warmth; bony part in wrist for grasping bamboo.

• Evolutionary significance: These adaptations reflect the red panda's evolutionary lineage and ecological niche.

• Example: Despite similarities to giant pandas, red pandas are a distinct family group, not closely related to either bears or raccoons.

1.2 Biologists Arrange Diversity of Life into Three Domains

Biologists classify the diversity of life into three major domains based on cellular organization and genetic relationships.

• Three domains of life:

  • Domain Bacteria: Microscopic organisms with simple cells, found in many environments.

  • Domain Archaea: Also microscopic and simple, often found in extreme environments (e.g., hot springs, salt lakes).

  • Domain Eukarya: More complex cells, includes protists, fungi, plants, and animals.

• Kingdoms: Eukaryotes are further divided into kingdoms based on characteristics such as cell structure and mode of nutrition.

• Example: Protists are mostly single-celled, while animals and plants are multicellular.

1.3 Visualizing the Concept: Organizational Hierarchy

Biological organization is structured in a hierarchy from the largest to the smallest scale.

• Biosphere: All life on Earth

• Ecosystem: Environment and species

• Community: All species in an ecosystem, different species

• Population: Individuals of the same species

• Organism: Individual living being

• Organ and organ systems

• Tissue

• Cell

• Organelle

• Molecule

• Atom

1.5 Hypotheses Can Be Tested Using Controlled Experiments

Scientific hypotheses are tested through controlled experiments, which allow researchers to isolate the effects of a single variable.

• Controlled experiment: An experiment where an experimental group is compared with a control group; only one variable is changed at a time.

• Example: Mice populations of the same species placed in different environments (beach vs. inland) to test camouflage and predation rates.

• Native color control group: Mice with coloration matching their environment had lower predation rates.

• Non-native coloration experimental group: Mice with non-matching coloration had higher predation rates, supporting the hypothesis that camouflage reduces predation.

• Testing in humans: Clinical trials use random assignment and placebos to test treatments. Retrospective studies use existing records to find correlations.

• Important note: Correlation does not imply causation.

Chapter 2: The Chemical Basis of Life

2.1 Organisms Are Composed of Elements, Combined into Compounds

All living things are made up of elements, which combine to form compounds essential for life.

• Major elements in living organisms: Carbon, hydrogen, oxygen, nitrogen (make up most of the body mass).

• Proteins: Composed of carbon, hydrogen, oxygen, nitrogen, and sometimes sulfur.

• Example: Humans require 25 elements; plants require fewer. Oxygen, carbon, hydrogen, and nitrogen are the most abundant.

2.2 Trace Elements as Additives

Trace elements are required in very small amounts but are essential for health and biological functions.

• Examples of trace elements: Iron (Fe), iodine (I), fluorine (F), zinc (Zn), copper (Cu), manganese (Mn), selenium (Se), etc.

• Iron: Essential for oxygen transport in blood (hemoglobin).

• Iodine: Required for thyroid hormone production; deficiency can cause goiter.

• Fluorine: Added to water to prevent tooth decay; too much can cause stains, too little increases cavities.

• Example: Water fluoridation has been shown to reduce dental cavities in populations.

Element	Function	Deficiency Effect
Iron (Fe)	Oxygen transport	Anemia
Iodine (I)	Thyroid hormone	Goiter
Fluorine (F)	Tooth enamel strength	Tooth decay
Zinc (Zn)	Enzyme function	Impaired immunity
Additional info: Selenium (Se)	Antioxidant defense	Heart disease risk

2.3 Atoms Consist of Protons, Neutrons, and Electrons

Atoms are the basic units of matter, composed of three types of subatomic particles.

• Protons: Positively charged particles found in the nucleus.

• Neutrons: Neutral particles (no charge) also found in the nucleus.

• Electrons: Negatively charged particles orbiting the nucleus.

• Atomic number: Number of protons in an atom, determines the element.

• Mass number: Sum of protons and neutrons.

Example: Carbon has 6 protons, 6 neutrons, and 6 electrons.

Key Equations

• Atomic number: $\text{Atomic number} = \text{Number of protons}$

• Mass number: $\text{Mass number} = \text{Number of protons} + \text{Number of neutrons}$

*Additional info: The arrangement of electrons in shells determines how atoms interact and form chemical bonds.*