Biology Key Terms and Concepts

Biology Terms Definitions

General Biological Concepts

• Vitalism:

  • Definition: The theory that life is a product of supernatural force.

• Mechanism:

  • Definition: The theory that life is a product of chemical and physical forces.

• Hypothesis:

  • Definition: An educated guess addressing the problem in scientific inquiry.

• Scientific Theory:

  • Definition: A hypothesis that has been proven correct through extensive testing.

• Natural Law:

  • Definition: Natural limits or governing principles of the universe.

• Descent With Modification:

  • Definition: The process in evolution where offspring differ genetically from their parents.

• Natural Selection:

  • Definition: Environmental changes that favor survival of certain traits over others within a species.

Concepts of Speciation

• Speciation:

  • Definition: The process through which new species are formed through evolution.

• Allopatric Speciation:

  • Definition: New species formation where the parent species does not coexist with the new species.

• Sympatric Speciation:

  • Definition: New species formation where the parent species continues to coexist with the new species.

• Biological Species:

  • Definition: A group of organisms capable of producing fertile offspring.

• Evolutionary Species:

  • Definition: Organisms classified together based on anatomical similarities.

• Macroevolution:

  • Definition: Large-scale evolutionary changes.

• Microevolution:

  • Definition: Small changes within a species.

• Prezygotic Isolation:

  • Definition: Mechanisms that prevent the formation of a zygote between different species.

• Postzygotic Isolation:

  • Definition: Mechanisms reducing the viability or fertility of hybrid offspring after zygote formation.

Cell Structure and Function

• Cell:

  • Definition: The smallest unit exhibiting all characteristics of life.

• Cell Theory:

  • Definition: The principle that all living things are composed of cells.

• Cell Wall:

  • Function: Provides support to plant cells and is composed of cellulose.

• Vacuole:

  • Definition: An organelle for temporary storage within a cell.

• Chloroplast:

  • Function: The organelle performing photosynthesis in plant cells.

• Cytoplasm:

  • Definition: All materials within a cell, including cytosol and organelles.

• Eukaryotic Cell:

  • Definition: Cells with compartmentalized organelles, including all organisms except bacteria.

• Prokaryotic Cell:

  • Definition: Simple cells with minimal compartmentalization, only bacteria.

• Endomembrane System:

  • Function: Membrane structures that process and distribute proteins.

  • Components: Golgi apparatus, endoplasmic reticulum, nuclear membrane, cell membrane, vacuoles, lysosomes.

• Endoplasmic Reticulum:

  • Definition: Organelle that processes and distributes proteins within the cell.

• Gene:

  • Definition: A nucleotide sequence in DNA coding for specific proteins.

• Lysosome:

  • Function: Breaks down waste materials and cellular debris.

• Mitochondria:

  • Function: Converts energy from sugars into ATP.

• Nucleus:

  • Function: Houses the cell's DNA.

• Plasma Membrane:

  • Definition: The outer boundary of a cell, also known as the cell membrane.

• Ribosome:

  • Function: Synthesizes proteins.

• Rough Endoplasmic Reticulum:

  • Definition: Part of the ER with ribosomes attached; processes proteins.

• Smooth Endoplasmic Reticulum:

  • Definition: Part of the ER without ribosomes; distributes proteins.

Cell Cycle and Division

• Mitosis:

  • Definition: The process of cell division maintaining chromosome number.

• Interphase:

  • Definition: The cell cycle stage where routine activities occur; cell is not dividing.

• G0 Phase:

  • Definition: A stage where cells carry out routine functions but do not divide.

• G1 Phase:

  • Definition: Cells are active but not dividing unless stimulated.

• S Phase:

  • Definition: The phase in which chromosomes duplicate.

• G2 Phase:

  • Definition: Organelles are produced, preparing for division.

• Cytokinesis:

  • Definition: The final phase where the cell physically divides.

Stages of Mitosis

• Prophase:

  • Events: Breakdown of nuclear membrane, condensation of chromosomes, centriole duplication and positioning.

• Centriole:

  • Function: Produces spindle and polar fibers during mitosis.

• Spindle Fibers:

  • Function: Attach to chromosomes, separating them during anaphase.

• Metaphase:

  • Events: Chromosomes align at cell center, spindle fibers attach.

• Anaphase:

  • Events: Begins chromosome separation.

• Telophase:

  • Events: Chromosome separation completion, nuclear membrane reforms.

• Cleavage Furrow:

  • Definition: An indentation marking point of cell division.

• Karyokinesis:

  • Definition: Division of the nucleus occurs before cytokinesis.

• Contractile Ring:

  • Function: Pinches the cell in two during cytokinesis.

Meiosis Phases

• Prophase I:

  • Events: Chromosomes condense, nuclear membrane dissolves, centrioles move.

• Metaphase I:

  • Events: Sister chromatids align at the cell equator.

• Anaphase I:

  • Events: Begins chromosome separation.

• Telophase I:

  • Events: First meiotic division is completed.

• Interkinesis:

  • Events: G2-like stage between meiosis I and II, involving chromosome de-condensation.

• Prophase II:

  • Events: Chromosomes condense, nuclear membrane dissolves again.

• Metaphase II:

  • Events: Chromosomes align at the equator, spindle fibers form.

• Anaphase II:

  • Events: Chromosome separation occurs.

• Telophase II:

  • Events: Chromosome separation complete, nuclear membrane reforms.

• Zygote:

  • Definition: A fertilized egg cell.

• Diploid: The number of chromosomes represented as 2N and represents the number of chromosomes in non-reproductive cells of an organism. The diploid number of chromosomes for humans is 46.