Biology Basics

Biology is the scientific study of life and living organisms, encompassing their structure, function, growth, origin, evolution, and distribution.

The seven characteristics are organization (cells), metabolism, homeostasis, growth, reproduction, response to stimuli, and adaptation through evolution.

The levels are atoms, molecules, organelles, cells, tissues, organs, organ systems, organisms, populations, communities, ecosystems, and biosphere.

A cell is the basic structural and functional unit of all living organisms, often called the 'building block of life'.

The cell theory states that all living things are composed of cells, cells are the basic unit of life, and all cells come from pre-existing cells.

Prokaryotic cells lack a nucleus and membrane-bound organelles (e.g., bacteria), while eukaryotic cells have a nucleus and organelles (e.g., plants, animals).

The cell membrane, or plasma membrane, regulates what enters and exits the cell, maintains homeostasis, and facilitates communication using a phospholipid bilayer with embedded proteins.

Cytoplasm is the gel-like substance inside the cell membrane but outside organelles, where many cellular processes occur and organelles are suspended.

The nucleus houses the cell's DNA, controls cellular activities like growth and reproduction, and is the site of RNA synthesis.

Mitochondria are the 'powerhouses' of the cell, producing ATP through cellular respiration by breaking down glucose.

Ribosomes are small structures that synthesize proteins by translating mRNA into polypeptide chains; they can be free in cytoplasm or attached to the endoplasmic reticulum.

The RER is studded with ribosomes and modifies proteins destined for secretion or membranes, folding and adding carbohydrates.