How are animals, insects etc, able to evolve defences against predators - which killed their ancestors?.?

Question

The later ones could not have seen what happened, so how are they able to know, that before they are even born, they need to evolve a certain defence mechanism, which can prevent this happening again?. Reincarnation perhaps?.

Answer 1

In fact, the defense mechanism already exists in the population. Remember that evolution works on a population of organisms, not just individuals, through the process of natural selection. The classic illustration is the evolution of the Peppered moth in Britain during the industrial revolution. Originally the majority of Peppered moths had a light coloration with black speckles and streaks which enabled them to remain camouflaged against the light back ground of the tree bark where they lived. Occasionally, a moth was born with dark coloration. Because these insects were easier to spot on the light tree bark than their light colored kindred, and therefore were easier for predators to see, most or all of them were eaten so they didn't reproduce more dark individuals. As the English countryside became more industrialized, the soot from factory smokestacks caused the bark of trees around the factory to become blackened. Now, light colored moths stood out against the darkened background so they got eaten more often, and dark moths survived to reproduce. Soon, the majority of the moths were the dark variety.
The secret to the moths success lay in their genes. The gene that caused an individual to be light colored was a dominant gene, while the dark colored gene was a recessive gene. This meant that when a pair of moths mated, that each had one gene for light color and one gene for dark color, there would be a one in four chance that their offspring would inherit the double recessive gene needed to make them dark in coloration. If the majority of individuals who were light colored were eaten before they reproduced, it meant that the dark colored individuals would tend to mate with other dark colored individuals so that all of their offspring would be dark colored.
Now imagine the above scenario only imagine that some how, all of the white individuals were eaten. This means that all the remaining individuals would be black and would only carry the recessive gene for dark coloration. Now imagine that the British passed some anti pollution laws and the bark of the trees began to revert to their natural light coloration. Since all of the light colored individuals are gone, the dominant gene for light color no longer exists in the population and all the moths born would be vulnerable. This could eventually lead to the extinction of all of the moths and hence the end of this species. In essence, they would no longer be able to adapt to this particular environmental change.
The bottom line is this: if a species is to survive in a changing environment, it must have the needed genes already present in its population to deal with the change or it will become extinct. I have attached a reference to a Wikipaedia article which explains the story of the Peppered moth in greater detail.

Answer 2

Later ones could not have 'seen what happened'????????

You're mistating the question. You ask how are insects able to evolve defences. If you understand evolution you will know precisely how they evolved adaptations to predation and any other challenges of their environment. I do not think this is the forum to sum up natural selection but there are plenty of good books out there you need to look up.

I hope 'reincarnation' is just a joke.

You can go old school with Origin of Species or pick up almost any of Dawkins books (except unweaving the rainbow and the god delusion)

regards

Answer 3

A man called Darwin sorted this out, of the animals that run the predators ate the slowest ones so only the faster ones got to breed, The ones that are poisonous the same deal the least poisonous got eaten leaving the more poisons and slightly chewed to bread and so on for every defence mechanism for every prey species the ones that were not at the top of their game got eaten. Thus survival and breading of the fittest.

Answer 4

Their ancestors aren't the ones that got killed... their ancestors are the ones who were slightly better adapted and survived to pass on that adaptation to their offspring.

Random mutations in the DNA are in every living person - most of them are silent, most of them are harmless. The vast majority of the ones that aren't silent are harmful - one example of this is sickle cell anaemia, where the red blood cells are deformed. Incidence of this disease if fairly low except in tropical regions affected by malaria, where a heterozygous copy of the sickle cell gene provides protection against malaria. So a heterozygous gene pattern at this point can be called a "defence mechanism".

So, how do the tropical babies "know" to be born with a copy of a normal allele and a copy of a sickle cell allele? There's a disadvantage to being born with a double copy of either. Two normal alleles means that you're more likely to die of malaria, but two sickle cell alleles means that you can't carry oxygen around your body properly. So chances are that a good proportion of adults in those areas are heterozygous -have one of each.

If you have parents with alleles Aa and Aa, then every single possible combination of these is AA, Aa, Aa and aa. So more of their children are, statistically, going to be Aa than anything else. Add the that the chances of baby AA getting malaria and aa not surviving due to its sickle cell anaemia, and you see the start of a defense mechanism to the predator (the mosquito) evolving.

Answer 5

They don't "know". There are random mutations all the time. Most are detrimental, and the organism dies. Some are beneficial, and the organism lives to pass on the genes for that mutation. So if an insect happens to be born with a gene that creates a bad-smelling chemical, and therefore the insect doesn't get eaten, it'll pass that gene on to its kids.

Answer 6

In early Earth while the Oxygen content fabric of the ambience became right into a lot larger substantial bugs did exist. they simply choose greater Oxygen interior the ambience to grow to be giants, many bugs can stay interior the water, i assume in the process the ice a while many went lower back, needless to say you already know that throughout the time of Ice a while the equator remains ice unfastened. purely as quickly as has the worldwide thoroughly frozen over, that became into while all of the land hundreds have been on the south pole and it close down the Earths temperature administration, the oceans circulate retains the earths climate basic