Life History Theory Overview

What is life history theory?

It describes the competitive allocation of resources between physiological processes

Why does life history theory involve?

• Environmental resources are limited, forcing the organism to engage in trade-offs

• Life history theory seeks to explain these trade-offs

• Which processes are prioritised and which are scarified

What is Cody’s ‘Principle of Allocation’ in reproduction vs survival?

There is negative correlations between competing traits

What are examples of reproduction vs survival?

• Reduced winter survival of lactating Cervus elaphus (lactating is very energetically demanding)

• Decreased fecundity of lines of Drosophila melanogaster selected for longevity

What are factors that contribute to increased likelihood of fertility?

• Strong immune system

• Menstruation

• More energy available for reproduction by reducing exertion

What are the different types of species in quality vs quantity of offspring?

R-selected species and K-selected species

What are the features of R-selected species?

• Many offspring, little investment in each

• Short life-span, gestation, high levels of mortality

• Typically, small body size, rapid development, large litters

• "hit and run" strategy = little parental care

• High juvenile mortality

What are the features of K-selected species?

• Few offspring, much investment in each

• Long life-span, large body size, low mortality

• Specialised competitors for exploiting key resources

• Mortality late in life

What type of species are humans?

Humans are the ultimate k-selected species, but is this true? Early favouring of r-selection exists:

• Australopithecines (2.5mya) and homo erectus (1.8mya)

• Exposed to variable environments, increasing fragmentation

• Probing new niches and occupying new territories, with rapid population growth in new habitats

Therefore not as extreme on the spectrum as we thought so therefore somewhere in between

What is mating effort?

Everything to do with attracting a mate, including competition

What is parenting effort?

Investing all time to do with an offspring (before, during, and after birth)

How is testosterone involved in the mating vs parenting effort?

• Males with high testosterone prefer/put more effort into mating effort

• After falling in love, testosterone levels fall

• After the birth of a child, testosterone levels fall

Is there a trend regarding women in the mating vs parenting effort?

No, as there is not enough research on women to decipher a trend

What exists for parents of bi-parental species?

There are conflicts of interest for parents of bi-parental species (where one goes of to do more mating)

What is fertility?

Having kids

What is fecundity?

The ability to have kids