Life-History Variables – The Elements of Evolution (51)

Life-History Variables

“You have these two lineages, plants and animals, that are very different and yet they arrive at the same conclusion. That is what’s called convergent evolution, and the stunning result is that it’s being driven by the underlying physics.” ~ Italian physicist Amos Maritan

From an evolutionary perspective, all organisms face strategic survival trade-offs. Viruses typically carry only the genes essential to their needs. In contrast, bacteria must take into account their social environment, both among their own kind and others. Horizontal gene transfer facilitates adaptability, though this is employed selectively, and so is itself a life-history variable.

“Evolution constantly faces trade-offs between objectives.” ~ Israeli biologists Elad Noor & Ron Milo

Numerous life-history variables correlate to each other. Following constructal law, energy flows – from the origination of life onwards – favor certain sets of traits. Internal and envirotypic flows interact to produce scale-invariance. Interactively, life works at every scale toward an optimality.

Whereas size factors into selected sets of life-history variables, the relationships between some life-history variables remain constant irrespective of size. Several observations suggest that relative size distribution adheres to a universal power law: a quantitative ratio that is scale-invariant. The size of an organism matters for its metabolism, growth, survival risks, and advantages within its habitat.

How quickly an organism can evolve is size-dependent. The current global warming is having the greatest impact on large animals. Small animals can more easily adapt.

Both smaller plants and animals are capable of faster rates of molecular evolution. As such, rapid climate change provokes diminution as a hedge against risk.

Certain life-history variable sets are strongly influenced by the habitat in which an organism lives. Environment and ecology drive evolution adaptively.

“Specialization between animal and plant species tend to be a consequence of the available resources.” ~ German evolutionary ecologist Matthias Schleuning

The intensity of competition and the vibrancy of interspecies interactivity makes a decisive difference in life-history variables. Darwin and later evolutionary biologists long assumed that species-rich tropical communities inclined plants and animals toward specialization as compared to their temperate counterparts. Instead, competition amid tropical diversity tends toward less dietary specialization.

“High tropical plant diversity provides many different resources to animals in a low density. Whoever is not especially choosy is at an advantage, because then the next food source is not very far away, making foraging more efficient.” ~ German ecologist Jochen Fründ

Less-persnickety animals are advantageous to plants when it comes to pollination and seed dispersal, as a plant is less likely to suffer extirpation if a certain helpful animal agent goes extinct.

“Due to the generalised relationships and the greater diversity, more species can replace the functions of individual declining species.” ~ German ecologist Nico Blüthgen

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In many instances, the trade-offs that constitute life-history variables can be inscrutable. Zebrafish bred to be bold or shy exhibit changes in body shape and locomotion.

“Complex behaviors, like the behaviors we call ‘personality’ or ‘temperament,’ can be associated – genetically correlated – with other traits that one might think are independent of such behaviors, like body shape and swimming abilities. Traits that seem unrelated may not be unrelated.” ~ American zoologist Brian Langerhans