i have always wondered whyanimals like dogs and cats have litters at a time while humans tend to have a single children? sorry if this is a stupid question

koryos:

It is not at all a stupid question- it’s a question a lot of biologists have devoted a lot of time examining, after all, since it says a lot about an animal’s lifestyle.

The amount of offspring an animal has depends on several factors, but the main one is how many of them, on average, will survive to adulthood. For an animal like a mouse, for instance, which is basically food on four legs, it makes sense to have LOTS of babies. For an animal with tiny, tasty free-swimming larvae like a crab, it makes sense to have a HORDE of tiny babies.

For an animal like you- like a human- while it certainly isn’t the case that all human babies are bound to survive to adulthood, there’s a much higher chance of it. So instead of investing energy into having MANY babies, we invest energy into making our ONE baby be very big and strong. We can afford to do that if there’s less of a chance of it dying. If a mama mouse put all her time and effort into raising one pinky, it could very easily amount to nothing if pinky gets gobbled by a snake.

image

There is actually a name for these two strategies (and I should also mention that it is a spectrum, and those are the extreme ends)- r and K strategies. “r-selected” refers to organisms who have lots of babies, while “K-selected” refers to organisms who throw a lot of investment into only a couple at a time.

image

This graph shows what i mean. The y-axis is how many individuals of a species survive, and the x-axis is increasing age. So you can see that the amount of surviving oysters decreases sharply with age, versus the amount of humans.

r-selected organisms also have a number of other common traits, such as a short lifespan, small body size, and rapid sexual maturity. K-selected organisms are often the opposite, being large, slow-aging, and long lived. But these are not exclusive by any means; you can have very long lived animals like sea turtles, for instance, still producing great masses of eggs simply because the infant mortality is so high. Or you can have a tiny mouse-sized bat that lives 20 years to the mouse’s 2 and has one baby each season.

Basically, a lot of evolutionary factors go into an organism’s litter size.

Figures taken from these two pages, which both talk in more detail about K and r selection.

zombikki:

sacred-cows:

Omg I just went to get a latte from my regular coffee shop and I always have the same guy serving me and I must bug him so much as I would always ask for almomd milk (im lactose intolerant) but they would just have lacto free so I stuck with that and today as I drank my latte I could tell the difference in the milk and asked if they started serving almond milk and the guy just shyly said “well you always ask if we have it so i got it specially for you” thiS GUY BOUGHT THE MILK WITH HIS OWN MONEY I FEEL SO PREVILEDGED RIGHT NOW EAAAAHH

this is the start of a beautiful coffee shop AU 

smurflewis:

imguiltyofthis:

andiamburdenedwithgloriousfeels:

Do you ever start bullshitting a paper, and then look over it halfway through and think, ’…Wait a minute, I could be onto something here.’

this is the definition of college.

Literally I was writing a paper on Asian salt water crocodiles, like a simple about them paper for a college class, and I started noticing some inconsistencies in the scientific papers I was sourcing and I accidentally discovered that the crocodile has been misdiagnosed as least concerned on the endangered species list when they should be classified as endangered and now my professor is having me write a formal report to the international Red List to have them reclassified and all I wanted to do was write this paper on an animal I thought was cool and now I’m considered an expert on this species…