BIO1011

The Scientific Method

• . Steps in the scientific method

  • Observation: Noticing phenomena (e.g., a bird around certain flowers).

  • Hypothesis: Formulating a potential explanation (e.g., the bird feeds on nectar from those flowers).

  • Prediction: Making precise predictions based on the hypothesis (e.g., less nectar in flowers after bird visits).

  • Testing: Conducting observational studies or experiments to gather evidence.

Observational Studies

• Setting up studies to observe natural behavior:

  • Observe flowers before and after bird visits.

  • Conclusion drawn if results are consistent with hypothesis.

Experimental Studies

• Conducting controlled experiments:

  • Define Independent Variable: The factor being changed (e.g., color of flowers).

  • Define Dependent Variable: The outcome being measured (e.g., time spent feeding).

  • Example setup:

    • Use same species of flowers at the same height in different colors.

    • Measure feeding behavior of the bird.

Data Collection and Presentation

• Importance of sharing data:

  • Synthesizing data into understandable formats such as graphs.

  • X-axis: Independent variable (flower color).

  • Y-axis: Dependent variable (time spent feeding).

• Analyze results to support or refute the original hypothesis.

Development of Scientific Theories

• Difference between regular and scientific theories:

  • Scientific theories are well-tested and supported hypotheses (e.g., theory of evolution).

• Theories are subject to change with new evidence.

Key Unifying Characteristics of Living Organisms

1. Complexity

• Living organisms possess a precise spatial organization and cellular structure.

• Minimum unit of life: the cell.

  • Cells store and transfer genetic information (DNA).

  • DNA is essential for growth, development, and replication.

• All cells are enclosed within a plasma membrane, allowing selective permeability.

• They undergo metabolism: converting energy into usable forms.

2. Response to Environment

• Living organisms respond to environmental stimuli.

• Responses range from simple (bacterial reactions) to complex (multicellular plants).

3. Reproduction

• All life must reproduce to pass genetic information to future generations.

• Reproduction can be sexual or asexual (e.g., bacterial fission).

4. Evolution

• Evolution occurs over generations due to environmental pressures.

• Traits advantageous for survival can proliferate (e.g., beak size in birds).

Additional Attributes of Life

Metabolism

• Ability to absorb and convert energy is crucial for both single-celled and multicellular organisms.

Homeostasis

• Maintenance of an internal environment despite external changes (e.g., body temperature regulation).

Growth and Development

• Regulated growth is necessary, differentiating it from uncontrolled growth.

Importance of Defining Life

• Understanding what constitutes life can help in searches for extraterrestrial life.

• Discovery of organic molecules on Mars raises questions about life beyond Earth.

Ecology and Interconnectedness

• No organism exists in isolation; all interact with other organisms and their environment.

• Example of fruit trees interacting with bees (pollination) and mammals (seed dispersal).

• Human impact on ecosystems can be both positive (e.g., agriculture) and negative (e.g., extinction).

Atoms

• Definition: Atoms are the basic unit of matter, made up of three particles:

  • Protons: Positively charged particles in the nucleus.

  • Neutrons: Neutral particles in the nucleus.

  • Electrons: Negatively charged particles orbiting the nucleus.

• Element: A substance composed of a single type of atom.

Periodic Table

• Displays all known elements based on their number of protons.

• The number of protons determines the identity of the element.

• For uncharged atoms, the number of protons equals the number of electrons.

Electron Orbitals

• Electrons occupy regions called orbitals and are organized into energy levels (or shells).

  • First energy level: 1 spherical orbital (max 2 electrons).

  • Second energy level: 4 orbitals (max 8 electrons).

Covalent Bonds

• Atoms share electrons to fill their outer shells leading to stable molecules.

• An example: Hydrogen (1 bond) and Carbon (4 bonds) can form various structures.

Valence Electrons

• Electrons in the outermost shell that participate in bonding.

• Elements tend to form bonds to achieve stable configurations (full outer shell).

Polarity in Molecules

• Some molecules have regions of partial positive and negative charge due to uneven sharing of electrons (e.g., water).

• Polar molecules can form hydrogen bonds.

• Nonpolar molecules do not interact with water; they form hydrophobic interactions.

Types of Chemical Bonds

• Ionic Bonds: Occur when electrons are transferred, resulting in charged ions that attract each other (e.g., sodium and chlorine).

• Hydrogen Bonds: Weak attractions between polar molecules (e.g., water molecules).

• Van der Waals Forces: Weak attractions due to electron movement leading to temporary charge differences.

Importance of Bonds in Biology

• Bonds dictate the shape and function of biological macromolecules (proteins, carbohydrates, etc.).

• Breaking and forming of chemical bonds are integral to chemical reactions in life processes.

Water Properties

• Water's unique properties are due to its molecular structure and hydrogen bonding:

  • Cohesion: Water molecules stick together; responsible for surface tension.

  • Hydrophilic and Hydrophobic Interactions: Polar vs. nonpolar molecules respectively interact or repel.

  • Density: Ice floats on water due to less density when formed.

  • High Heat Capacity: Water absorbs significant heat without major temperature changes, protecting cellular reactions.

  • High Heat of Evaporation: Cool body through sweat evaporation, removing heat effectively.