Basics of Biology: Fundamental Concepts and Principles

Basics of Biology

Big Picture

Biology is the study of living things. Six characteristics differentiate living things (organisms) from nonliving things: response to the environment, growth, reproduction, homeostasis, complex chemistry, and cells. To survive, organisms interact with each other and with the environment. Biologists base their knowledge of organisms on important concepts such as the cell theory, the gene theory, homeostasis, and evolution.

Key Terms

• Biology: The study of living things.

• Evolution: Change in characteristics of living things over time.

• Natural Selection: Organisms with more favorable traits are able to produce more offspring and pass on their favorable traits.

• Adaptation: Characteristic that helps organisms survive and reproduce in a given environment.

• Population: Group of organisms of the same species living in a given area.

• Community: All organisms living in a given area.

• Ecosystem: All living things and nonliving factors in a given area.

• Biome: A group of similar ecosystems.

• Biosphere: Part of earth where all life exists.

• Symbiosis: Relationship between different organisms where at least one organism benefits from the relationship.

• Competition: Relationship between organisms needing the same resources in the same place at the same time.

Characteristics of Life

Defining Features of Living Organisms

• Response to the Environment: Detects changes in the environment and responds accordingly.

• Growth and Development: Organisms grow and develop over time.

• Reproduction: Produces offspring to ensure the continuation of the species.

• Homeostasis: Maintains internal conditions (such as body temperature) stable despite external changes.

• Complex Chemistry: Consists of complex molecules that go through chemical changes to stay alive.

• Cellular Organization: Made up of cells, which are the basic unit of structure and function in living things.

Unifying Principles of Biology

Core Biological Theories

• Cell Theory: Cells are the basic unit of life. All living things are made up of cells, and all cells come from other cells.

• Gene Theory: Genes determine the characteristics of living things. They are located on chromosomes that are found in every cell, and genes are passed on from parents to offspring.

• Homeostasis: Keeping internal conditions constant even though the external environment changes.

• Evolution: Occurs by the process of natural selection. Organisms become suited to their environment through evolution because they develop adaptations.

Interdependence of Living Things

Levels of Biological Organization

The world of living things can be organized into levels (from specific to general):

• Population → Community → Ecosystem → Biome → Biosphere

• Example: A herd of giraffes → all the plants, animals, bacteria in the area → all the living things and the water, soil, etc. in the area → all the savannas in the world → all the regions on earth occupied by living things.

Organisms depend on their environment and other organisms for survival. They interact through relationships such as symbiosis and competition.

Table: Levels of Biological Organization

Level	Description	Example
Population	Group of organisms of the same species in a given area	Herd of giraffes
Community	All organisms living in a given area	Plants, animals, bacteria in the savanna
Ecosystem	All living and nonliving factors in a given area	Living things, water, soil, etc. in the savanna
Biome	Group of similar ecosystems	All savannas in the world
Biosphere	Part of earth where all life exists	All regions on earth occupied by living things