Everyone knows the mantis, mostly because the image of the mantis bride who eats the groom in the black cat sheriff is deeply rooted in the hearts of the people, in addition to the mantis, in nature, there are some spiders and other creatures in nature.
Of course, in addition to the phenomenon of eaters, red salmon, born in rivers and growing in the sea, usually migrate only once in their lives, and slowly die after mating and spawning. Migrating red salmon bring back a large amount of nutrients from the ocean, completing the cycle of matter and energy within nature.
There is also the broad-legged bag shrew, which is a very interesting animal, it is not big, like a small mouse. Broad-footed bag shrews mate in the summer, and all male broad-footed bag shrews die after the summer is over.
"Floating day, ephemera i", this day, the ephemera mated madly, and then died. Cephalopods of the deep-sea squid float up during the breeding season, mate, exhaust energy, leave egg sacs behind and die.
Suicidal mating of animals, why do some animals still fight for themselves when they know they will die? Suicidal mating in animals is an altruistic act, an act of sacrifice within an altruistic act.
In the theory of evolution, people refer to the combined measure of an individual's ability to survive, reproduce, and survive offspring as fitness. The greater the fit, the greater the chance of an individual surviving and reproductive success. But the altruistic behavior exhibited by animals increases not their own suitability, but the suitability of other individuals.
Therefore, from the perspective of fitness, Altruistic Behavior usually refers to those behaviors that improve the suitability of other individuals at the expense of reducing their own suitability. In other words, it refers to those behaviors that sacrifice their own survival and reproduction to a certain extent, while increasing the survival chances and reproductive success rates of other individuals.
Among them, the sacrifice behavior mostly occurs in elderly organisms and ambitions, the purpose is to sacrifice a part of the sacrifice in exchange for reproductive ability and strong individuals and the survival of population cubs when encountering predators, the sacrificial individuals are generally old and weak and male, and the genes of the strong are better than the genetic quality of the old and weak, the higher the survival rate of the population cubs, the more conducive to the reproduction of the population, their genes can also be continued. This survival strategy relies on natural selection to promote the optimization of population genes, so that the population is more adaptable to the environment.
In the herd, the teaching of the old elephant to the young elephant is also an altruistic act
But are males all fearless sacrifices? Not really, in 1977 Dawkins proposed the selfish gene theory. It is believed that the basic unit of natural selection is genes, and genes are not only the basic units of natural selection, but also the basic units of self-interest protection. An organism is simply a carrier of genes, a machine that is controlled by genes.
Individual behavior, whether altruistic or selfish, is under the control of genes. A prominent feature of the success gene is ruthless selfishness, in which the individual can be altruistic in behavior, but must be genetically self-interested; superficial altruism, substantive self-interest.
In the case of red salmon, salmon colonies, in order to return to the original waters to spawn, and the genes in the body in order to allow the salmon to complete the migration, the body constantly secretes powerful hormones to fight against countercurrent, so after spawning. Red salmon is also exhausted, all the hormonal systems in the body are out of balance, the immune mechanism is stagnant, unable to resist any infection, the stomach, kidneys and other organs have also developed lesions and ulceration, and eventually died of infection and internal organ collapse. The hormone that dominates the entire spawning history is cortisol, known as the "stress hormone," so salmon die after fulfilling their purpose of reproducing offspring.
Why does the gene do this, the purpose of the gene is to complete its own continuation, although the salmon sacrificed, but it has been continued, ostensibly altruistic, substantively self-interested.
Because from the genetic point of view, the so-called evolution refers to the process of some genes in the gene pool becoming more and other genes becoming less, that is, the process of changing the frequency of genes, and the altruistic and even self-sacrificing behavior exhibited by biological organisms in some cases seems to reduce their suitability on the surface. In fact, the generalized fitness is added, that is, the ability of the individual to successfully transmit or the same genes as himself in the offspring (not necessarily the offspring of his own reproduction).
As we can see, the same is true of the possum, female possums in order to improve the survival rate of offspring, they will choose multiple male mates, and in order to adapt to the changes in the female, a single male brown tasmodium has to work to get more offspring, and then in the reproductive period, the male possum will have extremely high levels of testosterone and cortisol (also known as "stress hormones") in the blood.
Testosterone allows Marsupials to mobilize all the energy in their bodies to power reproductive behavior, and the increase in cortisol gives them a stronger ability to tolerate exhaustion and pain. But the consequences can be imagined, after the end of breeding, due to excessive consumption, the ensuing side effects make the male possum die tragically.
Therefore, why some animals still struggle to survive knowing that they will die, this is because the purpose of biological survival is for the continuation of genes, even for humans.