Life history is a concept in biology that describes the sequence of events in an organism’s life, from birth to death. It includes the timing and duration of various life events such as birth, growth, reproduction, and death. Life history theory is an analytical framework designed to study the diversity of life history strategies used by different organisms throughout the world, as well as the causes and results of the variation in their life cycles.
Life history strategies are the age- and stage-specific patterns and timing of events that make up an organism’s life, such as birth, weaning, maturation, death, etc. These events, notably juvenile development, age of sexual maturity, first reproduction, number of offspring and level of parental investment, senescence and death, depend on the physical and ecological environment of the organism.
Life history theory seeks to explain aspects of organisms’ anatomy and behavior by reference to the way that their life histories—including their reproductive development and behaviors, post-reproductive behaviors, and lifespan (length of time alive)—have been shaped by natural selection. The theory was developed in the 1950s and is used to answer questions about topics such as organism size, age of maturation, number of offspring, life span, and many others.
Life history patterns evolve by natural selection, and they represent an “optimization” of tradeoffs between growth, survival, and reproduction. Organisms have evolved a great variety of life histories, from Pacific salmon, which produce thousands of eggs at one time and then die, to human beings, who produce a few offspring over the course of decades.
In order to study these topics, life history strategies must be identified, and then models are constructed to study their effects. Finally, predictions about the importance and role of the strategies are made, and these predictions are used to understand how evolution affects the ordering and length of life history events in an organism’s life, particularly the lifespan and period of reproduction.
Life history theory draws on an evolutionary foundation, and studies the effects of natural selection on organisms, both throughout their lifetime and across generations. It also uses measures of evolutionary fitness to determine if organisms are able to maximize or optimize this fitness, by allocating resources to a range of different demands throughout the organism’s life.
In conclusion, life history is a fundamental concept in biology that describes the sequence of events in an organism’s life, from birth to death. Life history theory is an analytical framework designed to study the diversity of life history strategies used by different organisms throughout the world, as well as the causes and results of the variation in their life cycles. Life history patterns evolve by natural selection, and they represent an “optimization” of tradeoffs between growth, survival, and reproduction. Life history theory draws on an evolutionary foundation, and studies the effects of natural selection on organisms, both throughout their lifetime and across generations.