> It's pretty easy to find examples outside of the animal kingdom where an organism's lifecycle depends on it being eaten at some point. So far as I know, there are no animals with this property.

There are parasites for which being eaten is a part of their life cycle.

https://en.wikipedia.org/wiki/Leucochloridium_paradoxum

Black widow spiders are so named because the females eat their mates. Some spider mothers become food for their own children.

Not to mention that (while not exactly what you asked for, but I think it's important to recognize) carnivores kill other species as a means of survival, and even their own species at times. Wild wolves cannot feed their pups without killing other animals. Death is common in nature.

I thought of the parasite angle later, touche. But the parasite survives the transition between hosts, so it doesn't really count from an "end a life" perspective.

The spider thing is interesting though. It would seem that being eaten by her children is an adaptation, not just an unfortunate consequence of harsh reality. The strategy appears to be: give my nutrients to my offspring, for they carry a part of me, and the survival of that part is more important than the rest.

Given that most of the cells in a human body are passengers, and not cells with human DNA in their nucleus (if they have nuclei at all), it seems pretty likely that something, somewhere, is making the same kind of sacrifice, and using a hungry human as the vehicle. And I think that ending a life on those terms falls in a different domain--both from an ethics perspective, and from a "how adversarial of an environment do you want to create for yourself"-perspective, than mere predation.

Strategies of that sort are more popular outside of the animal kingdom than in it (I think), which I think justifies a "different rules for different things" approach.

> So far as I know, there are no animals with this property.

Ultimately, many grazing animals have their property. If their numbers grow too large from lack of predators, they'll consume all available food and then starve en-masse.

Yeah, but starving en-masse isn't some kind of adaptation that they've developed in order to survive. I was thinking more about plants whose seeds germinate in the digestive tract of an animal.

Fruit is generally evolved to be eaten as a seed-dispersal and -fertilization technique. Not sure about other parts of the plant.

I disagree. What organism are you talking about exactly? Any plant I can think of doesn't require being eaten to live.

Anything that bears fruit is relying on an animal to come by and eat that fruit so that the seeds will be spread (either because the pit is hard to eat and the animal drops it, or because the seeds survive the animal's digestive tract).

There are also several fungi and protozoans who migrate between the digestive tracts of animals that eat each other (https://en.wikipedia.org/wiki/Toxoplasma_gondii for instance).

I'm not enough of a biologist to defend the point especially well, but doesn't it make sense that one would use different types of reasoning to manage relationships with different types of life?

> Anything that bears fruit is relying on an animal to come by and eat that fruit so that the seeds will be spread (either because the pit is hard to eat and the animal drops it, or because the seeds survive the animal's digestive tract).

Right, but that's not the plant, that's the fruit. If you eat the plant itself, it's dead. Same as a cow.

The example that I had in mind with the original comment was https://en.wikipedia.org/wiki/Toxoplasma_gondii#Lifecycle

I'll grant that no plants come to mind that have a niche that requires them to be wholly eaten, but I still think that deciding whether to eat a plant requires totally different logic than deciding whether to eat an animal.

So what's your position? Are you here to suggest that "we shouldn't eat animals" is absurd by equating it to "we shouldn't eat plants?"

Or are you a vegan looking to take it a step further by not eating plants that have to die in order for you to eat them? Because I'd like to hear more about somebody who sincerely held that belief.

You mean Fruitarians? They certainly exist. I do enjoy how you seem to think that it's inconceivable. HN Favourite Steve Jobs was once a Fruitarian.

https://en.wikipedia.org/wiki/Fruitarianism

I just don't understand how you can have a moral outrage to killing one thing but not another. People seem to do a little dance about plants being not as alive as animals to justify it, but it doesn't make sense to me.

The lifecycle of an organism includes reproduction and propagation.

Many plants have evolved specifically around being eaten by other animals.

>The lifecycle of an organism includes reproduction and propagation.

No, that would be different organisms.