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

artifically selection 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 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 oo

chemosynthetic-theory-8-728 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