- "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."
The study of how organisms allocate limited resources to various life activities such as growth, reproduction, and survival.
Life history theory: A framework that explains how organisms allocate their limited resources among growth, reproduction, and survival.
Reproductive strategies: Different reproductive strategies and the tradeoffs between quantity and quality of offspring.
Parental investment theory: The amount of resources parents invest in their offspring and how it affects offspring fitness.
Mating systems: Different forms of mating systems in animals and their evolutionary implications.
Sexual selection: The processes by which individuals compete for or are chosen as mates.
Life cycle stages: Understanding the different stages in an organism's life cycle and the different survival and reproductive pressures at each stage.
Life history trade-offs: Examining the allocation of resources among growth, reproduction, and survival and the trade-offs that arise.
Senescence: Aging and the decline in reproductive output and survivorship observed across an organism's lifespan.
Environmental variability: How changes in the environment can affect life history traits and evolution.
Life history plasticity: The ability of an organism to adjust its life history traits in response to changes in the environment.
Life history evolution: The study of how life history traits evolve over time and how these traits are shaped by natural selection.
Life history diversity: Examining the wide range of life history strategies that have evolved in different organisms.
Human life history: Understanding the unique life history traits that have evolved in humans and how they have changed over time.
r-K selection theory: Proposed by Pianka, it suggests that organisms can be classified as r-selected or K-selected based on their reproductive strategies. R-selected organisms have short lifespans, produce large numbers of offspring, and exhibit minimal parental care. K-selected organisms have longer lifespans, produce fewer offspring, and invest more in parental care.
Life history continuum: This theory highlights how organisms are positioned along a continuum between r-selected and K-selected types. There are shades of gray between the two extremes representing different life history strategies.
Life history trade-offs: This theory suggests that organisms face trade-offs in allocating their resources, such as energy, to different aspects of their life, such as growth, reproduction, and survival.
Pace-of-life theory: This theory proposed by Roff suggests that organisms can be distinguished by their pace-of-life, which is determined by the rate at which they allocate resources over time. Organisms with fast-paced lifecycles have short lifespans, reproduce early, and exhibit high rates of growth and metabolism. In contrast, organisms with slow-paced lifecycles have longer lifespans, reproduce later, and exhibit lower rates of growth and metabolism.
Optimal foraging theory: This theory postulates that organisms optimize their resources by balancing the costs and benefits of different foraging strategies.
Parent-offspring conflict: This theory focuses on the conflict between parents and their offspring over resource allocation. It predicts that offspring will demand more resources than parents are willing to provide, leading to conflict.
Life history in a changing environment: This theory suggests that organisms adjust their life histories in response to environmental factors, such as food availability and predation.
Life history plasticity: This theory acknowledges that organisms can adjust their life histories in response to specific conditions, such as higher or lower competition.
Senescence theory: This theory focuses on the decline in organism's biological functioning with age, and the trade-offs between allocating resources to reproduction or longevity.
Maternal effects theory: This theory highlights how maternal factors, such as diet and social environment, could shape the offspring's life histories beyond genetic inheritance.
- "It is a theory of biological evolution that 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."
- "A life history strategy is 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."
- "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."
- "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."
- "It serves as a method to investigate further the 'many layers of complexity of organisms and their worlds'."
- "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."
- "The theory depends on principles of evolutionary biology and ecology and is widely used in other areas of science."