Glossary: N-P

Natural Selection

Definition: The process whereby organisms better adapted to their environment tend to survive and produce more offspring. Natural selection is the driving force of evolution.

Examples:

• The peppered moth: The peppered moth is a classic example of natural selection. In the 19th century, the peppered moth population in England was mostly light-colored. However, after the Industrial Revolution, the trees in England became covered in soot, and the light-colored moths were no longer well-camouflaged. As a result, the dark-colored moths were more likely to survive and reproduce, and the population of peppered moths became mostly dark-colored.
• Antibiotic resistance: Bacteria that are resistant to antibiotics are more likely to survive and reproduce than bacteria that are not resistant. As a result, antibiotic resistance has become a major public health problem.

Context/Function: Natural selection is the process by which evolution occurs. It is responsible for the diversity of life on Earth and the adaptation of organisms to their environment.

Nucleus

Definition: A dense organelle present in most eukaryotic cells, typically a single rounded structure bounded by a double membrane, containing the genetic material. The nucleus is the control center of the cell.

Examples:

• The nucleus of a plant cell: The nucleus of a plant cell is typically located in the center of the cell.
• The nucleus of an animal cell: The nucleus of an animal cell is typically located in the center of the cell.

Context/Function: The nucleus is responsible for controlling the cell's growth, metabolism, and reproduction. It also contains the cell's genetic material, which is passed on to daughter cells during cell division.

Organism

Definition: An individual animal, plant, or single-celled life form. Organisms are the basic units of life.

Examples:

• Animals: Dogs, cats, fish, birds, and insects are all examples of organisms.
• Plants: Trees, flowers, and grasses are all examples of organisms.
• Single-celled life forms: Bacteria, archaea, and protists are all examples of organisms.

Context/Function: Organisms are the living components of ecosystems. They interact with each other and with their environment to create a complex and dynamic system.

Phenotype

Definition: The set of observable characteristics of an individual resulting from the interaction of its genotype with the environment. The phenotype of an individual is determined by its genes and by the environment in which it lives.

Examples:

• Eye color: The phenotype for eye color is determined by the genes for eye color and by the environment.
• Hair color: The phenotype for hair color is determined by the genes for hair color and by the environment.
• Height: The phenotype for height is determined by the genes for height and by the environment.

Context/Function: The phenotype of an individual is what we see when we look at an organism. It is the physical expression of the organism's genes.

Photosynthesis

Definition: The process by which green plants and some other organisms use sunlight to synthesize foods with the help of chlorophyll pigment. Photosynthesis is a two-step process that involves the light-dependent reactions and the light-independent reactions.

Examples:

• The light-dependent reactions: The light-dependent reactions take place in the thylakoid membranes of the chloroplasts. In these reactions, light energy is used to convert water into oxygen and to produce ATP and NADPH.
• The light-independent reactions: The light-independent reactions take place in the stroma of the chloroplasts. In these reactions, ATP and NADPH are used to convert carbon dioxide into glucose.

Context/Function: Photosynthesis is the process by which most of the energy in the Earth's ecosystems is produced. It is also the process by which oxygen is produced, which is essential for the survival of most living organisms.

Prokaryote

Definition: A microscopic single-celled organism that has neither a distinct nucleus with a membrane nor other specialized organelles. Prokaryotes are the most abundant and diverse group of organisms on Earth.

Examples:

• Bacteria: Bacteria are a large group of prokaryotes that are found in a wide variety of environments.
• Archaea: Archaea are a group of prokaryotes that are found in extreme environments, such as hot springs and salt lakes.

Context/Function: Prokaryotes play an important role in many ecosystems. They are responsible for decomposing organic matter, fixing nitrogen, and producing oxygen.

Protein

Definition: Any of a class of nitrogenous organic compounds that consist of large molecules composed of one or more long chains of amino acids. Proteins are the most abundant and diverse group of macromolecules in living organisms.

Examples:

• Enzymes: Enzymes are proteins that catalyze biochemical reactions.
• Hormones: Hormones are proteins that act as chemical messengers.
• Antibodies: Antibodies are proteins that help to protect the body from infection.

Context/Function: Proteins play a vital role in all living organisms. They are involved in a wide variety of cellular processes, including metabolism, signaling, and transport.