post 3 - Sexual selection An evolutionary process whereby...

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Sexual selection: An evolutionary process whereby individual organisms select mates from the opposite sex by perceiving signals of robustness or other signs of potential reproductive fitness. Sexual selection might result in some individuals having characteristics that are individually costly to maintain or that even reduce the prospects of individual survival. The classic example is the big tail feathers of male peacocks, which render the animal more vulnerable to predation. But because females pick males with the biggest, most impressive tail feathers, these males leave behind more offspring than those less well endowed. Their reproductive fitness is superior even though they lead shorter lives, and they pass on the genetic propensity for big tail feathers to their offspring. Genotype : The genetic blueprint of an organism, largely inherited from its parents in complex, sexually-reproducing organisms. Inherited parental genotypes constitute the genotype of offspring. Phenotype: The physical manifestation of the organism (bones, tissues, organs, etc.). Phenotype is largely inherited through the genes contributed by parents. Natural selection, sexual selection, etc. work at the level of the phenotypes of individuals, because these are the interfaces with the larger world. The Red Queen Principle: This evolutionary principle states that in many cases evolutionary changes do not confer an absolute advantage, but simply allow organisms to metaphorically “stay in the same place by running faster”. As an example, a population of predators might evolve better senses of smell, the capacity to run faster, etc. Such changes put new selective pressures on the prey species, which might in response themselves adapt with greater speed, better camouflage, etc. Even though both predators and prey species adapt, their relative fitness does not change (as it would, say, if only the predators adapted). An example of this principle is the arms race of the late 20 th century, in which two sets of political competitors evolved new technological and organizational features in response to one another, but neither gained a decisive advantage.
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EARLY HOMININS THE EARLIEST HOMININS APPEARED IN AFRICA SOMETIME ABOUT 5-7 MILLION YEARS AGO, AND EVENTUALLY EVOLVED INTO SEVERAL SPECIES COLLECTIVELY CLASSIFIED AS AUSTRALOPITHECINES (DIFFERENT GENUS FROM MODERN HUMANS). THEY WERE BIOLOGICALLY QUITE UNLIKE US IN MANY WAYS--E.G. SMALLER BRAINS, LESS CLEVER HANDS, AND LESS EFFICIENT BIPEDAL POSTURE AND LOCOMOTION. THEY MAY OR MAY NOT HAVE BEEN EFFECTIVE TOOL-MAKERS. THE FIRST STONE TOOLS (OLDUWAN) APPEAR ABOUT 2.6 MILLION YEARS AGO, BUT IT IS UNKNOWN WHICH HOMININ MADE THEM.
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