Chapter 18:Population Genetic and Evolution
Population genetics
Deals with the abundance of different allels within an population and the manner in which the abundance of particular allel increase, decrease or remain same within time
Gene pool: total number of allesa in all the sex cells of all individual constitutes.
Factors that cause the gene pool to change
Mutation
Existing allels decrease in frequency and new allels increase
Accidents
may eliminated all organism along with their allels
A
Artificial Selection
Human purposefully change the allele frequency of a gene pool
Natural selection
most significant factor causing gene pool cahnges is described as the survival of fittest.
Situation in which natural selection does not operate
If indiciduals of population are identical genetically.
If it is impossible to become adopted to a certain condition
Multiple selection pressures
Loss of individual or reduced reproduction are also caused by environmental pressures such as cold, drought, insect attack etc
Rate of Evolution
Evolution concerns the change in gross structures such as flowers, leaves, fruits, shoots and trichomes
products of developemental interaction of many genes.
If the effect of new allels fit, mutation result in adaptative structure.
Speciation
Natural selection that cause a new species to evolve
fundamental ways
Phyletic Speciation
One species gradually becomes so changed that it must be considered a new species
Ways of phyletic speciation
Divergent speciation
Pollen transfer
Seed dispersal
Vegetative propagation
All alleles of plants are present in its pollen grains
can be carried by wind, floods and sream flow. As seed germinate, grow into new plants and reproduces, the new allels can be spread throughout the new site.
If a species produces small, mobile pieces that reproduce vegetatively, can contribute to gene flow
Sone species of population evolve into new while other population either either continue relatively unchanged as original, parental species.
Abiological Reproductive Barriers:
Any physical, nonliving feature that prevents two populations from exchanging gene.
Biological reproduction barrier:
Any biological phenomenon that prevents successful gene flow
Sympatric speciation: when two groups becomereproductively isolated even though they grow together.
Prezygotic isolation mechanism: Act even before a zygote can be formed.
Postzygotic internal isolation barrier: two sub population must be considered separate species
Adaptative radiation
A species rapidly diverge intos into many new species over an extremely short time, just a million years
Convergent Evolution
If two unrelated species evolve to the point that they resemble each other strongly
EXample: Convergence of cati and euphorbias.
Evolution and origin of life 
Chemically produced chemosynthesis
Formation of polymers
Condition of Earth before the origin of life
Aggregation and organization
Early metabolism
Oxygen
The presence of life
Chemosynthesis: the most seriously considered hypothesis about the origin of life on earth
Energy sources
Time available for origin of life
Chemical present in atmosphere
The original atmosphere was repleased by second atmosphere produced by release of gasses from the rock matrix composing earth and from the heavy bombardment by meteorites.
The early second atmosphere was reducing atmosphere due to the lack of molecular oxygen and the presence of powerful reducing agent.
UV and gamma radiation from sun and heat.
Has no limit because of lack of molecular oxygen
First experimental test was performed by S. Miller
Construct a container which has boiling water at bottoma nd reducing atmosphere at top
Whwn pond and seaside poole froze,monomers became concentrated which might produce a class of polymers
Next step is organization of chemical components into masses that has some organization and metabolism.
First aggregated would have formed at random, controlled only by realtive solubility
The aggregated and first cell may have absorbed some ATP and generated more by fermentation with glycolysis for millions years.
The evolution of chlorophyll a and photosynthesis librates oxygen
allowed world to rust
Create conditions that selected for the evolution of aerobic respiration
The chemosynthetic theory postulates a long series of slow, gradual transtitions from completely inorganic compounds to living bacteria