Glossary
Antibiotic Resistance
The ability of bacteria to survive and grow in the presence of antibiotics that would normally kill or inhibit them, often due to genetic mutations.
Example:
When a patient doesn't finish their full course of antibiotics, they might leave behind the most resilient bacteria, leading to the development of antibiotic resistance in the remaining population.
Evolution
The process by which populations of organisms change over successive generations, driven by mechanisms like natural selection.
Example:
The long necks of giraffes are a classic example of evolution, as ancestral giraffes with slightly longer necks had an advantage in reaching food and passed on those traits.
Extinct
The complete disappearance of a species from Earth, meaning no living individuals of that species remain.
Example:
Dinosaurs are a famous example of a group of animals that became extinct millions of years ago, leaving only their fossilized remains.
Fossil record
The total collection of fossils that have been discovered, providing historical evidence of life on Earth and the changes species have undergone over geological time.
Example:
Discovering a series of horse fossils showing gradual changes in leg and tooth structure over millions of years provides strong evidence from the fossil record for their evolution.
Genetic drift
Random fluctuations in allele frequencies in a population from one generation to the next, especially significant in small populations.
Example:
If a small group of butterflies is blown by a storm to a new island, the genetic makeup of the new colony might be very different from the original population purely by chance, illustrating genetic drift.
Genetic variation
The differences in DNA sequences among individuals within a population, providing the raw material upon which natural selection acts.
Example:
The wide range of coat colors in domestic dogs, from golden retrievers to poodles, is a result of extensive genetic variation within the species.
Genomic changes
Alterations in the DNA sequence or structure of an organism's genome over time, which can lead to new traits or the loss of old ones.
Example:
The ability of some humans to digest lactose into adulthood is due to recent genomic changes that allowed the lactase enzyme to remain active.
Mutations
Random changes in the DNA sequence of an organism, which are the ultimate source of new genetic variation.
Example:
A sudden change in a fruit fly's DNA that causes it to have white eyes instead of red is a mutation, which could then be passed on.
Natural selection
A primary mechanism of evolution where individuals with heritable traits better suited to their environment tend to survive and reproduce more successfully, passing those advantageous traits to their offspring.
Example:
In a forest, green beetles are camouflaged better than brown beetles, so birds eat fewer green beetles. This leads to more green beetles surviving and reproducing, demonstrating natural selection.
Pathogen Evolution
The rapid genetic changes in disease-causing organisms (like viruses and bacteria) that allow them to adapt to host defenses, treatments, or new environments.
Example:
The emergence of new strains of the flu virus each year, requiring new vaccines, is a direct result of pathogen evolution.
Population
In the context of evolution, a group of individuals of the same species living in the same geographic area that can interbreed, and it is at this level that evolution occurs.
Example:
A population of finches on an isolated island might develop different beak sizes over generations due to the types of seeds available.
Recombination
The process by which genetic material is rearranged, typically during meiosis, leading to new combinations of alleles in offspring.
Example:
When you inherit a mix of traits from both your mother and father, it's partly due to recombination shuffling their genes during the formation of egg and sperm.
Resistance
The inherited ability of an organism to tolerate or overcome a harmful environmental factor, such as a pesticide, herbicide, or drug.
Example:
Some weeds have developed resistance to common herbicides, requiring farmers to use different chemicals or methods to control them.