Biology 107: Human Biology - Chapter 1: The Study of Life

Overview

• Introduction to the study of life and human biology.
• Life on Earth is varied, ranging from humpback whales to single-celled organisms like bacteria and euglena.
• All life forms, including fungi and humans, share common characteristics.

Characteristics of Living Organisms

1. Organization

   • Organisms are highly organized, from tissues to organs.
   • Unicellular organisms like bacteria have organized internal structures.

2. Acquisition of Materials and Energy

   • All living beings must acquire materials and energy to grow and reproduce.
   • Energy can be ingested or absorbed.

3. Reproduction

   • Reproduction is essential for species survival.
   • All cells originate from pre-existing cells.

4. Response to Stimuli

   • Organisms respond to environmental stimuli to maintain comfort.

5. Homeostasis

   • Homeostasis involves maintaining a stable internal environment.
   • Examples include body temperature and blood pH.

6. Growth and Development

   • All life begins from a single cell and grows through cell replication.

7. Adaptation

   • Organisms adapt to changes, both short-term (daily) and long-term (evolution).

Organization of Life

• Life exists from the atmosphere to below the soil surface.
• Earth’s biodiversity includes an estimated 5-40 million species.
• Classification of life forms includes domains, kingdoms, and further subdivisions.

Levels of Biological Organization

1. Atoms and Molecules

   • Building blocks of cells.

2. Cells

   • Basic unit of life, varies between plants and animals.

3. Tissues

   • Groups of similar cells performing a function.

4. Organs and Organ Systems

   • Combination of tissues functioning together.

5. Organism

   • Complete individual living entity.

6. Species and Population

   • Species: Group of similar organisms.
   • Population: Group of same species in an area.

7. Community and Ecosystem

   • Community: All living organisms in an area.
   • Ecosystem: Community interactions including non-living components.

8. Biosphere

   • All ecosystems on Earth.

Energy and Reproduction

• Energy is crucial for cellular function and reproduction.
• DNA directs the reproduction process, ensuring species continuity.

Adaptation and Evolution

• Life adapts over millions of years; driven by natural selection.
• Natural selection favors individuals better suited for their environments.

Taxonomy and Systematics

• Classification of life using domains, kingdoms, phylums, etc.
• Taxonomy helps group organisms and understand relationships.
• Humans classified under domain Eukarya, kingdom Animalia, and species Homo sapiens.

Scientific Naming

• Latin-based naming system: Genus (capitalized) and Species (italicized).
• Allows universal communication among scientists.

Biodiversity and Ecosystems

• Biosphere encompasses all life forms, interacting in ecosystems.
• Ecosystems have chemical cycling and energy flow, primarily from the sun.
• Human activities impact biodiversity, causing species extinction.

The Scientific Method

1. Hypothesis

   • Educated guess or statement to be tested.

2. Observation and Experimentation

   • Initial observations lead to hypothesis formulation.
   • Experiments test the hypothesis through controlled variables.

3. Data Collection and Conclusion

   • Data must be objective and quantifiable.
   • Conclusions drawn from data support or refute the hypothesis.

4. Theory Formation

   • Supported hypotheses can lead to theories after extensive testing.

Example: Agricultural Experiment

• Comparing use of nitrogen fertilizers vs. legumes for crop yield.
• Results indicated legumes increased yield over time without chemical fertilizers.

Conclusion

• Understanding biology requires observation, experimentation, and adaptation.
• The scientific method is central to biological discoveries and advancements.