POPULATION GENETICS AND EVOLUTION (EVOLUTION AND THE ORIGIN OF LIFE (THE…
POPULATION GENETICS AND EVOLUTION
EVOLUTION AND THE ORIGIN OF LIFE
CONDITION ON EARTH BEFORE THE ORIGIN OF LIFE
THE PRESENCE OF LIFE
the chemosynthetic theory postulates a long series of slow gradual transitions from completely inorganic compounds to living bacteria.
CHEMICALS PRODUCED CHEMOSYNTHETICALLY
performed by S.Miller after the writing of Oparin and Haldane. with regard to the formation of monomers the chemosynthetic hypothesis represents a plausible model.
the evolution of chlorophyll a and photosynthesis that liberates oxygen had two profound consequences: it allowed the world to rust and it created the conditions that selected for the evolution of aerobic respiration. transition to terrestrial life became possible.
FORMATION OF POLYMERS
monomers present in the early ocean had to polymerize if life were to arise.
the aggregates would have been completely heterotrophs, absorbing all material from the ocean and modifying only a few molecules. as aggregates continue to consume certain nutrients , scarcity occured.
AGGREGATION AND ORGANIZATION
the next step in the possible chemical evolution of life would have been aggregation of chemical components into masses that had some organization and metabolism.
(process by which natural selection cause a new species to evolve)
The gradual transformation of one species into another without an increase in species number at any time within the lineage. Also called vertical evolution or speciation. occurs in many ways such as by pollen transfer, seed dispersal, and vegetative propagation.
the process whereby organisms not closely related (not monophyletic), independently evolve similar traits as a result of having to adapt to similar environments or ecological niches.
the accumulation of differences between closely related species populations, leading to speciation. Divergent evolution is typically exhibited when two populations become separated by a geographic barrier (such as in allopatric or peripatric speciation) and experience different selective pressures that drive adaptions to their new environment. After many generations and continual evolution, the populations become unable to interbreed with one another
RATE OF EVOLUTION
The rate of evolution is a variable of considerable interest in evolutionary biology. It concerns the limits of adaptation to natural environments as well as the limits of artificial selection.
deals with the abundance of different alleles within a population and the manner in which the abundance of the particular allele increases, decreases, or remains the same with the time.
FACTORS THAT CAUSE THE GENE POOL TO CHANGE
the most significant factor causing gene pool changes, is usually described as survival of the fittest. those who most adapt to the environment survive whereas less donot. The condition for the natural selection are the population must produce more offspring that can possibly grow and survive to maturity in that habitat and the second one is the progeny must differ from each other in their types of allele.
all genomes are subjected to mutagenic factors, mutation occurs continuously, existing alleles decrease in frequency and new alleles increase
the process in which human purposefully change the allele frequency of a gene pool. eg; selective breeding of crop plants and domestic animals. carried out by artificial mutation
accidents are events to which an organism cannot adapt, such as collision of large meteorite with earth, volcanic eruptions, infrequent droughts, hailstorms or floods. the number of alleles decrease or eliminated
MULTIPLE SELECTION PRESSURES
a mutation that produces an allele that would result in improved fitness is potentially advantageous selectively, but it may never have the opportunity to improve the fitness of the plant or species.
SITUATIONS IN WHICH NATURAL SELECTION DOESNOT OPERATE
if all the individuals of a population are identical genetically or if it is impossible to become adapted to a certain condition or if survival is universal