Introduction to Biology

Definition and Scope

Biology is the scientific study of life, focusing on the structure, function, growth, origin, evolution, and distribution of living organisms. It explores the diversity of life and the fundamental unit of life, the cell.

• Prefix 'bio-': Means "life."

• Suffix '-ology': Means "the study of."

• Primary focus of biology: The scientific study of life and living organisms.

Levels of Biological Organization

• Unicellular: Organisms consisting of a single cell (e.g., Bacteria).

• Multicellular: Organisms composed of multiple cells (e.g., Humans).

• Cell: The smallest and most basic fundamental unit of life.

• Organism: Any individual form of life.

Microscopy and Cell Numbers

• Microscopes: Required to observe unicellular organisms.

• Human body: Consists of trillions of cells.

Atoms and Subatomic Particles

Atomic Structure

Atoms are the smallest units of matter that retain the properties of an element. They are composed of subatomic particles: protons, neutrons, and electrons.

• Proton: Positive charge (+1), located in the nucleus.

• Neutron: Neutral charge (0), located in the nucleus.

• Electron: Negative charge (-1), found in electron shells around the nucleus.

Atomic Number and Mass

• Atomic number: Number of protons in the nucleus of an atom.

• Mass number: Total number of protons and neutrons in the nucleus.

• Atomic mass unit (AMU): Standard unit for measuring atomic mass; 1 proton = 1 AMU.

• Atomic mass: Average mass of all the atoms of an element.

Valence Electrons and Chemical Bonds

• Valence electrons: Electrons in the outermost shell, involved in chemical bonding.

• Octet rule: Atoms are more stable when their valence shell is fully occupied with eight electrons.

Energy Levels

• Electrons with the highest potential energy are found in the outermost energy shell.

• Electrons are held in atoms by electrostatic attraction to the positively charged protons in the nucleus.

Properties of Water

Cohesion and Adhesion

Water exhibits unique properties due to its molecular structure and hydrogen bonding.

• Cohesion: The ability of water molecules to stick to each other due to hydrogen bonding.

• Adhesion: The ability of water molecules to stick to other substances, such as glass.

• Surface tension: A measure of the difficulty in breaking the surface of a liquid, created by cohesive and adhesive properties.

Polarity and Hydrogen Bonding

• Polarity: Water is a polar molecule, allowing it to form hydrogen bonds with other polar or charged molecules.

• Hydrogen bonds: Weak bonds that form between the slightly positive hydrogen atom of one water molecule and the slightly negative oxygen atom of another.

Biological Applications

• Capillary action: Water moves up plant vessels due to cohesion and adhesion.

• Surface tension in organisms: Some organisms can move or rest on water surfaces due to surface tension.

Examples and Applications

• Paperclip floating: A paperclip can float on water due to surface tension, despite being denser than water.

• Adhesion example: Water sticking to a glass surface.

Organic Molecules and Chemical Bonds

Organic Molecules

Organic molecules are compounds containing carbon and hydrogen, often with other elements, forming diverse structures essential for life.

• Carbon: Forms the backbone of organic molecules, capable of four covalent bonds.

• Hydrogen: Essential for forming bonds with carbon.

• Oxygen: Essential for respiration and energy production.

• Nitrogen: Key element in amino acids and nucleic acids.

Chemical Bonds

• Covalent bond: Atoms share pairs of electrons to achieve a full outer shell.

• Double bond: Two atoms share two pairs of electrons, affecting molecular shape and reactivity.

Carbon Backbone Structures

• Linear form: Carbon atoms in a straight chain.

• Ring form: Carbon atoms connected in a closed loop.

Macromolecules

Carbohydrates

• Composed of carbon, hydrogen, and oxygen.

• Primary energy source and structural component in living organisms.

• Monosaccharides: Simple sugars, building blocks of carbohydrates.

• Polysaccharides: Complex carbohydrates made of long chains of monosaccharides.

Proteins

• Composed of amino acids.

• Essential for structure, function, and regulation of tissues and organs.

Nucleic Acids

• Composed of nucleotide chains.

• Store and transmit genetic information (e.g., DNA, RNA).

Lipids

• Hydrophobic molecules including fats, oils, and steroids.

• Store energy, provide insulation, and make up cell membranes.

Summary Table: Subatomic Particles

Summary Table: Major Elements in Living Organisms

Key Equations

• Atomic number:

• Mass number:

Additional info:

• Some context and definitions were inferred to clarify fragmented or unclear points from the original material.

• Scientific names and examples were added for completeness.