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- DictionaryLife his·to·ry/ˈlīf ˌhist(ə)rē/
noun
- 1. the series of changes undergone by an organism during its lifetime.
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What is life history?
What are life history characteristics?
What is life history theory?
What is the life history of a species?
Feb 23, 2024 · Life history characteristics are traits that affect the life table of an organism, and can be imagined as various investments in growth, reproduction, and survivorship. The goal of life history theory is to understand the variation in such life history strategies.
- Overview
- Summary
- What is a "life history"?
- Life history strategies and natural selection
- Parental care and fecundity
- Example: Many offspring, low investment/parental care
- Example: Few offspring, high investment/parental care
- Fecundity and investment tradeoffs in plants
- Timing of first reproduction (early vs. late)
- Single vs. multiple reproductive events
How organisms allocate energy to maximize the number of offspring they leave behind.
•The life history of a species is the pattern of survival and reproduction events typical for a member of the species (essentially, its lifecycle).
•Life history patterns evolve by natural selection, and they represent an "optimization" of tradeoffs between growth, survival, and reproduction.
•One tradeoff is between number of offspring produced and the amount of energy (both physical resources and parental care) put into each offspring.
•Timing of first reproduction is another tradeoff. Early reproduction lowers the chance of dying without offspring, but later reproduction may allow organisms to have more or healthier offspring or to provide better care.
•Members of some species reproduce only once (semelparity), while members of other species can reproduce multiple times (iteroparity).
•The life history of a species is the pattern of survival and reproduction events typical for a member of the species (essentially, its lifecycle).
•Life history patterns evolve by natural selection, and they represent an "optimization" of tradeoffs between growth, survival, and reproduction.
•One tradeoff is between number of offspring produced and the amount of energy (both physical resources and parental care) put into each offspring.
•Timing of first reproduction is another tradeoff. Early reproduction lowers the chance of dying without offspring, but later reproduction may allow organisms to have more or healthier offspring or to provide better care.
What does your life history look like? In the world of ecology, that question doesn't refer to the many challenges and successes you've experienced, or to the friendships you've made along the way. (Not that those aren't good too!)
Instead, when we're talking about life history in ecology, we're thinking about basic demographic features of a population or species – the kind of things that would appear in a life table. That includes when organisms first reproduce, how many offspring they have in each round of reproduction, and how many times reproduction occurs. For humans, life history involves a late start to reproduction, few offspring, and the ability to reproduce multiple times.
All living things need energy and nutrients to grow, maintain their bodies, and reproduce. In nature, these resources are in limited supply, and there is often competition for access to them (e.g., to sunlight and minerals for plants or food sources for animals). Thus, each organism will have non-infinite resources to divide among activities like growth, body maintenance, and reproduction.
What does it mean for an organism to allocate its limited resources "well" in this context? From an evolutionary standpoint, it means that the resources are distributed among the potential activities (growth, maintenance, reproduction) in a way that maximizes fitness, or the number of offspring the organism leaves in the next generation. Organisms with inherited traits that cause them to distribute their resources in a more effective way will tend to leave more offspring than organisms lacking these traits, causing the traits to increase in the population over generations by natural selection2,3 .
Over very long periods of time, this process results in species with life history strategies, or collections of life history traits (number of offspring, timing of reproduction, amount of parental care, etc.), that are well-adapted for their role and environment. The optimal life history strategy may be different for each species, depending on its traits, environment, and other constraints2 .
In this article, we'll examine some tradeoffs in life history strategies and see examples of plants and animals that use strategies of different types.
One major tradeoff in life history strategies is between number of offspring and a parent's investment in the individual offspring. Basically, this is a "quantity versus quality" question: an organism can have many offspring that each represent a relatively small energy investment, or few offspring that each represent a relatively large energy investment.
To put this more formally, we can say that fecundity tends to be inversely related to the amount of energy invested per offspring. Fecundity is an organism's reproductive capacity (the number of offspring it's capable of producing). The higher the fecundity of an organism, the less energy it's likely to invest in each offspring, both in terms of direct resources – such as fuel reserves placed in an egg or seed – and in terms of parental care.
•Organisms that produce large numbers of offspring tend to make a relatively small energy investment in each, and don't usually provide much parental care. The offspring are "on their own," and the idea is that enough are produced that some will survive (even if the odds for any one are low).
•Organisms that make few offspring usually make a large energy investment in each offspring and often provide lots of parental care. These organisms are effectively "putting their eggs in one basket" (literally, in some cases!) and are heavily invested in the survival of each offspring.
A typical sea snail (whelk) produces hundreds of eggs at a pop, and these eggs hatch to yield baby snails that are pretty self-sufficient from the get-go. In fact, the baby snails in the first 10% of eggs that hatch will enthusiastically eat their slower-hatching siblings for breakfast4 !
Cannibalism aside, this example is a good illustration of one common type of parental investment strategy. Sea snails and many other marine invertebrates provide little (if any) care to their offspring. Instead, they use most of their energy budget to make lots of offspring, each of which is relatively small. The sea snail isn't even that impressive when it comes to numbers—a female sea urchin might release 100, 000, 000 eggs in a single spawning5 !
To see a strategy at the opposite end of the spectrum, let's consider the giant panda. Panda females typically have just one cub each time they reproduce, and the young cub is far from self-sufficient6 . That pink thing in the picture below isn't a mouse or a kitten...it's actually a newborn panda!
Animal species like the panda, which have few offspring during each reproductive event, often give extensive parental care. They may also produce larger, more energetically "expensive" offspring. The newborn panda above may look tiny, but compared to a hatching sea snail, it's massive! Species with this type of high-investment strategy use much of their energy budget to care for their offspring, sometimes at the expense of their own health.
The same broad patterns seen in animals also apply to plants. Of course, plants aren't going to provide parental care in the same way that animals do. However, they can still produce either large numbers of energetically "cheap" seeds or small numbers of energetically "expensive" seeds.
For example, plants with low fecundity, such as coconuts and chestnuts, produce small numbers of energy-rich seeds, each of which has a good chance of germinating into a new organism. Plants with high fecundity, such as orchids, take the opposite approach: they usually make many small, energy-poor seeds, each of which has a relatively low chance of surviving.
When a species starts reproducing is another important part of its life history—and another place where we see trade-offs and lots of variation among species. Some types of plants and animals start reproducing early, while others delay much longer. What are the pros and cons of these strategies?
Organisms that reproduce early have less risk of leaving no offspring at all, but this may be at the expense of their growth or health. For example, small fish like guppies use their energy to reproduce early in life, but since they throw all their energy to reproduction, they don't reach the size that would give them defense against predators. (An intimidating guppy is kind of hard to picture!)
Organisms that reproduce at a later age often have greater fecundity or are better able to provide parental care. On the flip side, they run a greater risk of not surviving to reproductive age. For example, larger fish, like the bluegill or shark, use their energy to grow to a size that gives them more protection. As a consequence, they delay reproduction, so there's more chance that they will die before reproducing (or before they've reproduced to their maximum).
In general, age at first reproduction is linked to the lifespan of a species7 . Short-lived species often start reproducing early, while long-lived species are more likely to delay reproduction. This is a good reminder that a life history strategy is an integrated "solution" to the problem of leaving as many offspring as possible, and that any one part (e.g., age of first reproduction) only makes sense in light of others (e.g., lifespan).
Another important characteristic of life history relates to how many times an organism reproduces over its lifetime. For some species, reproduction is a one-time, all-out event, and the organism doesn't survive much beyond that one event. In other species, opportunities for reproduction come around multiple times, or even many times, throughout the organism's lifetime.
To apply a little ecology vocab, we can split species into two groups:
•Those that can reproduce only once (semelparity)
•Those that can reproduce multiple times over their lifetime (iteroparity)
Life history theory (LHT) 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.
Together, the age-, size-, or stage-specific patterns of development, growth, maturation, reproduction, survival, and lifespan define an organism's life cycle, its life...
LIFE HISTORY | English meaning - Cambridge Dictionary. Meaning of life history in English. life history. noun [ C ] uk / ˌlaɪf ˈhɪs.t ə r.i / us / ˌlaɪf ˈhɪs.t̬ɚ.i / Add to word list. all the things that happen during the life of a living thing. Synonyms. biography. life story. SMART Vocabulary: related words and phrases. Life and living. alive.
life history. Traits that make up the life cycle of an organism. An organism’s life history includes characteristics related to reproduction, development, and growth (e.g., fecundity, types of larval stages passed through, size at adulthood, and habitats used at different points in the life cycle).
life history noun. plural life histories. Britannica Dictionary definition of LIFE HISTORY. [count] biology. : the full range of changes, habits, and behaviors of a living thing over the course of its life. studying the life history of bears.
