Evolution of Behaviour

13/01/2011 § 1 Comment

After a break full of finishing up extra credit, we started on our new unit, Behaviour. Behaviour in an animal is the way it acts or responds to a stimulus (which is some kind of factor from the environment or from another animal that evokes the reaction out of the individual.

The first example we looked at in class was with lions. In a pack of lions, called a pride, the majority of the lions are females, so: lionesses, who are all sisters and related to one another. There are many cubs in the pride and all of those cubs are fathered by the single male in the group: the alpha lion. He is in charge of taking care of his pride, defending the other lions from stray male lions that look to invade the pride. When an invading male lion wants to try and take over the pride, he can try. But the resident male lion will definitely fight back. After the battle ensues the start of a new pride if the invading male lion wins. (If not, then the resident lion can stay in his pride, having successfully defended it).

But say the invading lion did win. The pride then has a new leader. The new alpha lion has two options: 1) be nice to the cubs that are already there, or 2) take them all out. The lion probably doesn’t know why he does it, only that it is beneficial for him if his own cubs are running around in the pack, not the previous lion’s cubs.

[The females, however, don’t just let the new lion kill their cubs. They have their own ways that might decrease the new lion’s chances of killing the cubs or completely avoiding the cubs’ deaths. These include simply avoiding the stray male lions, fighting the male lion, or if he hasn’t killed her cubs yet, to mate with him and make him think that the current cubs are his.]

The new lion then brutally kills off all of the cubs so that he might be able to mate with the females, to produce his own cubs, carrying his genes. (That is why killing the previous cubs would be beneficial; so that the next genes in the next generation of lions would have his genes). This is selfishness on the male lion’s part because he’s only focused on his own genetic interests, killing off numerous cubs to give his own genes a chance in the next generation.

(Another example of an animal that kills other offspring is the jacana – except the females do the killing, in this case.)

We learned about the dog genome project that proved that genes can control behaviour. In the project, results showed that after interbreeding certain dogs, 9/16 would have both dominant traits out of two traits. 3/16 would have only one dominant trait out of two, and another 3/16 would possess the other dominant trait. then, 1/16 would be completely recessive and not have any dominant trait. This proves that with interbreeding, and with the mix of genes, the new allele combinations in the next dogs can control their behaviours.

Finally, any behaviour that is beneficial for relatives is selected for and this is seen especially in bees. The one queen produces the eggs, all the males are never fertilized and are all haploid, and the females are all workers. Males do mitosis, making the exact same cells and keeping them haploid, while the females do normal meiosis. Daughter bees are more related to one another than male bees (son bees) are.

The essay question for this short unit is Why are humans nice? because apparently, humans are nice. No, ha, they are nice. But there could be genetic reasons behind that and after reading Eros and Evolution over the break and drowning myself in the words ‘genes’, ‘sex’, ‘evolution’ and more words like ‘why’, ‘how’, and ‘reason’, I’m pretty sure that humans’ behaviours and the reasons that they are nice do come from genes. Maybe not completely, but a large part can come from their genes.

§ One Response to Evolution of Behaviour

  • Dave Ferguson says:

    Kari,

    Excellent job of discussing the evolution of kin selection in the context of your extra credit reading of Eros and Evolution. You took excellent notes. I’d love to hear your reflection on the book sometime!

    Mr. F.

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