Fitness
How many offspring an individual leaves that survive to reproduce, compared with others. Fitness is about reproductive success, not strength. An adaptation is a trait that raises fitness in a given environment.
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Analogy
Score in a game where points are surviving grandchildren.
In practice
A beetle that is hard for birds to see leaves more offspring in a green forest than a bright one.
Practice
Flashcards
- What does fitness measure?The number of offspring that survive to reproduce.
Interview questions
- Explain how natural selection can cause antibiotic resistance to spread in a bacterial population.
- Variation: some bacteria carry a resistance mutation
- Antibiotic kills susceptible bacteria
- Resistant survive and reproduce
- Allele frequency rises over generations
Questions people ask
Is biological fitness the same as being strong?
In biology, fitness means reproductive success, how many offspring survive to breed, and not strength or health. A strong animal that leaves no offspring has zero fitness. A small, quiet animal that raises many young has high fitness. It always refers to an environment.
What is sexual selection?
Sexual selection is a form of natural selection in which traits help an individual win mates. Examples are the peacock's tail and the antlers of stags. These traits may even lower survival, but the extra mating success makes up for it, so they spread through the population.