Levels of Structural Organization

Chemical Level

The simplest level of organization that includes atoms and molecules essential for life.

Cellular Level

The level where cells, the basic units of life, emerge, each with distinct functions and organelles.

Tissue Level

Groups of similar cells that work together to perform a specific function, categorized into four main types.

Epithelial Tissue

Covers body surfaces and lines cavities, involved in protection, absorption, and secretion.

Connective Tissue

Supports, binds, and protects other tissues and organs; includes bone, adipose, and blood.

Muscle Tissue

Responsible for movement, classified into skeletal (voluntary), cardiac (heart), and smooth (involuntary) types.

Nervous Tissue

Composed of neurons and glial cells, it transmits impulses and processes information.

Organ Level

A structure composed of two or more tissue types working together to perform specific functions.

Organ System Level

Groups of organs that work together to perform complex functions; includes 11 major organ systems.

Circulatory System

System that transports blood and nutrients throughout the body.

Respiratory System

Facilitates gas exchange, supplying oxygen and removing carbon dioxide.

Digestive System

Breaks down food and absorbs nutrients necessary for the body.

Nervous System

Controls body functions through nerve impulses.

Endocrine System

Regulates bodily functions through the release of hormones.

Musculoskeletal System

Provides support, stability, and movement for the body.

Immune System

Protects the body against disease and foreign invaders.

Urinary System

Removes waste and regulates fluids in the body.

Reproductive System

Involved in producing offspring.

Integumentary System

Protects the body and helps regulate body temperature.

Lymphatic System

Supports immune function and maintains fluid balance in the body.

Organism Level

The highest level of organization where all systems work together to maintain life.

Hierarchical Structure

The organization of the human body in levels, facilitating complex interactions among its parts.

Organelles

Specialized structures within cells that perform specific functions necessary for survival.

Atom

The basic unit of a chemical element, consisting of a nucleus surrounded by electrons.

Molecule

A group of two or more atoms bonded together, representing the smallest fundamental unit of a chemical compound.

Cell Membrane

A biological membrane that separates and protects the interior of a cell from its external environment.

Nucleus

The control center of a cell, containing the majority of its genetic material.

Chromosome

A structure composed of DNA and proteins that carries genetic information.

Gene

A segment of DNA that contains the instructions for building a specific protein.

Ribosome

The cellular machinery responsible for synthesizing proteins from amino acids.

Metabolism

The sum of all chemical reactions that occur within a living organism.

Homeostasis

The process by which living organisms regulate their internal environment to maintain stability.

Photosynthesis

The process by which plants convert light energy into chemical energy, using carbon dioxide and water.

Cell Division

The process by which a parent cell divides into two or more daughter cells, essential for growth and repair.

Enzyme

A biological catalyst that speeds up chemical reactions in living organisms.

Hormone

A signaling molecule produced by glands that regulate various physiological processes.

Antigen

A substance that triggers an immune response, often associated with pathogens.

Antibody

A protein produced by the immune system that recognizes and neutralizes foreign objects like bacteria and viruses.

Vaccine

A biological preparation that provides active acquired immunity to a particular infectious disease.

Pathogen

A microorganism that causes disease, such as bacteria, viruses, or fungi.

Genotype

The genetic constitution of an organism, determining specific traits.

Phenotype

The observable physical or biochemical characteristics of an organism, determined by its genotype.

Mutation

A change in the DNA sequence of an organism, which can lead to variations and evolution.

Organism Classification

The method of grouping organisms based on shared characteristics and evolutionary relationships.

Ecosystem

A biological community of interacting organisms and their physical environment.

Biodiversity

The variety of life in a particular habitat or ecosystem.

Biotic Factors

Living components of an ecosystem that affect organisms, such as plants, animals, and microbes.

Abiotic Factors

Non-living physical and chemical components of an environment, such as sunlight, temperature, and water.

Symbiosis

A close and long-term biological interaction between two different species.

Commensalism

A type of symbiotic relationship where one species benefits while the other is neither helped nor harmed.

Mutualism

A type of symbiotic relationship where both species benefit from the interaction.

Parasitism

A type of symbiotic relationship where one organism benefits at the expense of another.

Natural Selection

The process through which species adapt to their environment based on heritable traits.

Evolution

The change in the heritable traits of biological populations over successive generations.

Cloning

The process of creating genetically identical copies of an organism or cell.

Stem Cells

Undifferentiated cells that have the potential to develop into different cell types.

Neurotransmitter

A chemical messenger that transmits signals across a chemical synapse from one neuron to another.

Prokaryotic Cell

A simple, unicellular organism that lacks a nucleus and membrane-bound organelles.

Eukaryotic Cell

A more complex cell type with a nucleus and organelles, found in multicellular organisms.

Cell Theory

A fundamental theory in biology stating that all living things are composed of cells.

Chloroplast

An organelle in plant cells that conducts photosynthesis, converting sunlight into energy.

Mitochondria

Known as the powerhouse of the cell, mitochondria generate ATP through respiration.

ATP (Adenosine Triphosphate)

The primary energy carrier in cells that powers cellular processes.

Cell Cycle

The series of phases that a cell goes through to divide and create new cells.

Cytoplasm

The gel-like substance within a cell that holds organelles in place.

Cellular Respiration

The process of breaking down glucose to produce energy (ATP) in cells.

Photosynthetic Pigments

Compounds in plants that absorb light, crucial for the process of photosynthesis.

Chromatin

The form of DNA that is loosely packed in the nucleus during interphase.

Cell Signaling

The process by which cells communicate with each other through chemical signals.

Transcription

The process of copying a segment of DNA into RNA.

Translation

The process where ribosomes synthesize proteins based on mRNA sequences.

Genetic Code

The set of rules by which information encoded in genetic material is translated into proteins.

RNA (Ribonucleic Acid)

A nucleic acid involved in protein synthesis and gene regulation.

Endoplasmic Reticulum

A network of membranes involved in protein and lipid synthesis; includes rough and smooth types.

Golgi Apparatus

An organelle that modifies, sorts, and packages proteins for secretion or delivery.

Lysosome

A membrane-bound organelle containing enzymes that digest waste materials and cellular debris.

Plant Cell vs Animal Cell

Plant cells have a rigid cell wall; animal cells have centrioles and are more flexible.

Cell Differentiation

The process by which cells become specialized in structure and function.

Signal Transduction Pathway

The process by which a chemical or physical signal is transmitted through a cell.

Phagocytosis

A type of endocytosis in which cells engulf large particles or other cells.

Exocytosis

The process by which substances are expelled from a cell through vesicles.

Stem Cell Division

The process by which stem cells divide and can become any type of cell.

Apoptosis

The programmed cell death that occurs in multicellular organisms.

Oncogene

A gene that has the potential to cause cancer when mutated or expressed at high levels.

Tumor Suppressor Gene

A gene that protects a cell from one step on the path to cancer.

Genetic Drift

A mechanism of evolution that causes allele frequencies to change randomly.

Chromosomal Aberration

A deviation from the normal structure or number of chromosomes in a cell.

Phenotypic Plasticity

The ability of an organism to change its phenotype in response to environmental conditions.

Ecosystem Services

The benefits provided by ecosystems that support human life, such as clean air and pollination.

Carrying Capacity

The maximum population size that an environment can sustain indefinitely.

Invasive Species

Non-native organisms that disrupt local ecosystems and cause harm to native species.