Comprehensive Biology Key Concepts: Cells, Evolution, Taxonomy, and Genetics

Biology

Study of living things and life processes.

Organism

Any individual living thing.

Cell

The smallest unit of life; all living things are made of cells.

Reproduction

Process of producing new organisms (asexual or sexual).

DNA

Genetic material carrying hereditary information.

Growth & Development

Increase in size and changes during an organism's life cycle.

Energy

Needed to carry out all life processes.

Respond to Stimuli

Reacting to environmental changes such as light, sound, or temperature.

Homeostasis

Maintaining a stable internal environment.

Evolution

Gradual change in species over generations.

Unicellular

Made of one cell.

Multicellular

Made of many cells with specialized functions.

Autotroph

Makes its own food, such as plants through photosynthesis.

Heterotroph

Obtains food from other organisms.

Herbivore

Eats plants.

Carnivore

Eats animals.

Omnivore

Eats both plants and animals.

Metabolism

All chemical reactions that maintain life.

Regulation

Control and coordination of life processes.

Hormones

Chemical messengers controlling processes like growth and metabolism.

Abiotic Factors

Nonliving parts of an environment such as sunlight, water, air, and temperature.

Biotic Factors

Living or once-living components of an environment such as plants, animals, fungi, and bacteria.

Characteristics of Life

Traits all living things share including cells, organization, growth, reproduction, response to stimuli, energy, homeostasis, and evolution.

Cell Organization

Structures in living things organized from cells → tissues → organs → systems.

Levels of Organization

Cell → Tissue → Organ → Organ System → Organism.

Negative Feedback

Returns body conditions to normal, e.g., sweating to cool down.

Positive Feedback

Increases response until event is finished, e.g., childbirth contractions.

Nutrition

Taking in and using materials for energy and growth.

Transport

Movement of materials within an organism.

Respiration

Releasing energy from food.

Excretion

Removing waste products.

Synthesis

Building larger molecules from smaller ones.

Growth

Increase in cell size or number.

Classification

Organizing and identifying organisms based on shared characteristics.

Taxonomic Categories

Domain → Kingdom → Phylum → Class → Order → Family → Genus → Species.

Three Domains of Life

Bacteria, Archaea, and Eukarya.

Bacteria

Unicellular prokaryotes found everywhere, e.g., E. coli.

Archaea

Unicellular prokaryotes living in extreme environments, e.g., halophiles.

Eukarya

Organisms with a nucleus and complex cells, including plants, animals, fungi, and protists.

Six Kingdoms of Life

Archaebacteria, Eubacteria, Protista, Fungi, Plantae, and Animalia.

Archaebacteria

Prokaryotic, unicellular, living in harsh conditions.

Eubacteria

Prokaryotic, unicellular, common bacteria.

Protista

Mostly unicellular eukaryotes; some autotrophic, some heterotrophic.

Fungi

Eukaryotic, mostly multicellular, heterotrophic decomposers.

Plantae

Eukaryotic, multicellular, autotrophic through photosynthesis.

Animalia

Eukaryotic, multicellular, heterotrophic consumers.

Fossil Record

Shows changes in organisms over time.

DNA and Genetic Similarities

Indicate common ancestry.

Homologous Structures

Similar body parts with different functions, e.g., bat wing and human arm.

Embryology

Similar early development patterns across species.

Cladogram

Diagram showing evolutionary relationships among species; nodes represent common ancestors.

Dichotomous Key

Step-by-step tool used to identify organisms using observable traits.