Introduction to Biology and the Scientific Method: Study Notes

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Introduction to Biology

What is Biology?

Biology is the scientific study of life and living organisms. It encompasses the structure, function, growth, origin, evolution, and distribution of living things.

Biology is the study of organisms (living things).
All living things share a common ancestor from billions of years ago.
Despite the diversity of life, organisms share many common features.

Life on Earth: Biomass Distribution

Biomass refers to the total mass of living organisms in a given area, measured in tonnes of carbon.

Global biomass: 546 billion tonnes of carbon.
Animal biomass: 2 billion tonnes of carbon (0.4% of total biomass).
Biomass is distributed among various groups of organisms.

History of Life on Earth

The Earth is approximately 4.5 billion years old.
First true cells appeared about 3.9 billion years ago.
Life has existed for most of Earth's history.

Early Earth Conditions

Initially, Earth was a ball of molten rock and had to cool before life could exist.
Water, essential for life, likely arrived via icy comets that melted upon impact.

Cell Fossils

Oldest known cell fossils found in Australia (1990s), similar to cyanobacteria.
These fossils are about 3.5 billion years old and represent the first organisms to perform photosynthesis.

Evolution of Larger Organisms

First plants and animals appeared about 500 million years ago.
Humanoid species have existed for about 2.5 million years; anatomically modern humans for about 200,000 years.

Dinosaurs and Birds

Dinosaurs (reptiles) first appeared around 240 million years ago.
All except flying dinosaurs went extinct 66 million years ago.
Birds are direct descendants of flying dinosaurs.

Characteristics of Life

Common Properties of Living Organisms

Made of cells: All life forms consist of one or more cells.
Respond to stimuli: Organisms sense and respond to their environment.
Reproduction: Ability to produce offspring and pass on genetic material.
Homeostasis: Maintaining a stable internal environment.
Adaptation (Evolution): Ability to evolve and adapt to the environment.
Obtain and process energy: Acquire energy from the environment for metabolism.
Genetic material (DNA): Contains instructions for growth, development, and traits.

Cells: The Basic Unit of Life

All organisms are composed of one or more cells.
Cells vary in type and function.
Viruses are not considered alive because they are not made of cells.

Response to Stimuli

Organisms detect and respond to changes in their environment (stimuli).
Stimulus: Any detectable change (e.g., light, temperature, moisture, food, chemical signals, touch).

Reproduction

Single-celled organisms reproduce by cell division (binary fission), producing identical offspring.
Multicellular organisms reproduce sexually or asexually, passing DNA to offspring who are similar but not identical to parents.

Adaptation and Evolution

Organisms adapt to their environment through evolution by natural selection.
Adaptations include camouflage, speed, armor, use of habitat, food sources, and climate survival strategies.

Homeostasis

Homeostasis is the maintenance of a steady internal state.
Examples: Regulation of temperature, pH, nutrient and waste concentrations.
Organisms have evolved mechanisms to maintain homeostasis in their environments.

Energy and Metabolism

All organisms require energy for metabolic processes (chemical reactions in cells).
Main energy sources: food (other organisms) and sunlight (photosynthesis).

Adaptations to Food Sources

Organisms have evolved digestive systems, behaviors, anatomical structures, and metabolic pathways to utilize available energy sources.

Genetic Material (DNA)

Growth and development are directed by genes (segments of DNA coding for proteins).
Genes determine unique traits of each species.
Individuals within a species share most traits but have some variation.

The Process of Science

The Scientific Method

Scientists use a systematic approach to investigate natural phenomena and answer questions.

Ask a question (often based on observation).
Conduct background research.
Develop a hypothesis (a testable explanation).
Test the hypothesis through experimentation.
Analyze the results (data).
Draw conclusions from the results.
Report findings to the scientific community.

Experiments in Biology

Experiments often involve two or more similar groups.
Only one factor (variable) is changed between groups.
Independent variable: The factor that is manipulated.
Dependent variable: The outcome measured.
Control group: Not manipulated; used for comparison with the experimental group.

Statistical Methods

Used after data collection to determine if observed differences are due to chance.
Larger sample sizes improve statistical reliability.

Model Systems

Biologists use model organisms (e.g., mice) to study processes relevant to other species (e.g., humans).

What is Science?

Science is an evidence-based approach to understanding the world.
Relies on testable hypotheses and reproducible results.
A hypothesis that withstands repeated testing may become a scientific theory.

Science vs. Non-Science

Disciplines like art, music, literature, and religion are not science because they are not evidence-based or testable.
Science does not address moral or ethical questions directly.
Some scientific discoveries may raise ethical or societal issues.

Importance of Biology

Agriculture: Improving crops and livestock.
Energy: Understanding biological energy sources and cycles.
Medicine: Advancing health and disease treatment.
Public Policy: Informing decisions on health, environment, and technology.
Conservation: Preserving ecosystems and biodiversity for the future.

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