I am not a biologist or scientist of any sort. Sometimes I just ponder stuff - and I was wondering - for animal life that is more than single-celled, how many types of procreation strategies are there? I am not sure if “procreation strategies” is even the right term- take a look at what I list and let me know:
Queen + Hive
Massive egg laying; no nurture
Egg - Newt/larvae - Cocoon/Chrysalis - full adult (for amphibians and some insects)
Egg + care for egg; limited nurture
Higher-volume live birth; short nurture
Low Volume live birth; long nurture
A few questions:
Am I framing the issue correctly?
If “procreation strategies” is not the correct phrase, what is?
What are the official names of these strategies?
Any major strategies I have missed (I didn’t list splitting - I think that is single-cell based…)
Given that these appear to have evolved as animal complexity has evolved, what might be a next logical strategy? Could in-vitro fertilization be included?
Any other interesting insights about this topic a layperson like me might be interested in hearing about?
What you are looking for, I think, is “life-history strategies,” a major field of research in evolutionary ecology.
The major contrasting strategies are called “K-selection,” for those species with long life, long development, and low reproductive rate, vs “r-selection,” for those species with short life, rapid development, and high reproductive rate.
Here is a rather informal overview of some of the issues involved in life-history strategies.
You’ve made a good start on framing it, but have mixed together a couple different ways of dividing things.
The first way is along the line that goes from ‘many, cheap offspring’ (‘r-stategy’) to ‘few, expensive offspring’ (‘K-strategy’). This is a general concept, and there’s not necessarily a precise mathematical way to assign an organism an exact place on the line. But in general, you can tell which end of the line a given organism is closer to, and it’s a useful concept – for instance to quickly get some concept of how an oak tree (just for instance) population will grow and change in different ways than a dandelion population.
This is also a somewhat relative measure, too. Mice have a lot of cheap offspring, compared to humans, but few, expensive offspring compared to most beetles.
Eggs vs. live birth, and chrysalis versus gradual change are completely different way of organizing things. These are better termed development strategies (they’re about how an organism changes as it develops from young to adult), and don’t necessarily have anything to do with whether the organism is more r or K-like. For instance, a frog might lay huge amounts of eggs, few of which survive, while a penguin or other bird might only lay one egg, but tend it carefully.
Finally, there are methods of reproduction, such as typical bacterial division (cloning), standard male/female sexual reproduction, the queen/hive insects, some insects that reproduce both by cloning and by sexual reproduction, etc. etc. These don’t necessarily have anything to do with r vs K strategies.
So Quercus you are saying they should be arrayed in a Table, with K or r strategies as rows, say, and different “development strategies” across the column headings. From there one should be able to sort all multi-celled animal life into one cell of the table? And from there we could either make it a 3-D table to include reproduction approaches, or simply comment on those within each 2-D cell…
Hasn’t anyone done this? It feels like it should be a standard Biology chart, like a Periodical Table for Chemistry or something…
These categories would all come under “life history stratgies.” The other two items you listed are not.
This is just one type of social behavior, specifically, “eusociality,” in which some members of the society (workers) sacrifice their own reproduction in order to raise their close relatives. Eusocial organisms tend to be K-selected.
This is a developmental strategy rather than a life-history strategy. Species with larval forms can be either r- or K-selected.
You are in part mixing up life history strategies with other things.
On preview, I see that **Quercus ** has already mostly covered this, but having written it I’ll go ahead and post it.
You’re absolutely right that you could. (Though in practice, you might have to keep adding columns as another bizarre organism is discovered. Did you know that some fish change sex as they get bigger? How cool is that as a development strategy? So there’s probably something out there with a development strategy you’ve never imagined)
But ‘K-ness’ and development strategy are just two characteristics of an organism. You could also sort by color, or whether or not it photosynthesizes, or size or anything else. So there’s no particular reason for a table of ‘K-ness’ vs development strategy to be as central to biology as the periodic table is to chemistry.
Biology is a lot sloppier than Physics or Chemistry. As a said before, and as the article I linked to indicates, r-K selection is itself a continuum, without discrete breaks, and there are all kinds of exceptions and intermediate conditions. Developmental strategies are to some extent independent of life history strategies, but can be related - for example, some K-selected amphibians may breed in the larval form, while others eliminate the larval form entirely, developing into the adult form directly from eggs.
You could try to categorize this - and I imagine someone has made the attempt - but it’s really too complicated for simple summary.
Keep in mind that these “strategies” are human inventions that we impose on the natural world to aid in our own understanding. You can get too hung up on the classification scheme and miss the real nature of the beast-- that it’s a continuum.
Just like the speciec classification system. Nature “doesn’t care” what we humans call a species, and hence we have to create the term “hybrid”, which in point of fact is often just another individual in the population.
Not necessarily; there are animals that reproduce parthenogenetically - i.e. clone themselves; some of them do this exclusively, others do it as ancilliary to more conventional sexual reproduction.
There’s also the creche strategy - where nurture is performed in bulk by the colony - but is distinct from the hive strategy because the reproductive function remains distributed amongst the individual members of the colony.
Quercus and Colibri - thank you for the insights. John Mace, sounds like you are on the same page with them regarding how to think about biology.
I hear you all about development strategies being a continuum - it just strikes me that some sort of structure to sort out such elemental differences between groups would be incredibly useful - and complementary to a taxonomy breakout. But since I am not a scientist, I have no basis whatsoever to determine what is useful or not, so at this point I’ll just sit down, thank you very much.
Mangetout (O Eater of All Things) - wow, can you please present an example of an animal type that follows a creche strategy? I don’t know that I have heard of that.
I had of course heard of (relatively) simpler animals that change their gender due to internal and environmental reasons, like fish and amphibians…
Some penguin species implement a creche strategy; I think this works for them largely because they can’t produce lots of cheap offspring, because the conditions are too harsh for their survival, but they must actually leave the young for extended periods to gather food.
Aphids would be an example of animals that switch between asexual and sexual reproduction; sometimes they mate and lay eggs, sometimes the females just pop out live young that are clones of herself (and these clones are born pregnant with more clones).