Honours / Core Course (CC)
Unit 1 : Origin of Life (Chemical basis), RNA world hypothesis
Unit 2 : Historical review of Evolutionary concepts: Lamarkism, Darwinism and Neo Darwinism
Q.What do you mean by “Directed Mutation” theory?
This theory suggests that the offspring, for some unspecified reason to do with the hereditary mechanism, consistently tend to differ from their parents in a certain direction. In the case of wings, the explanation by the directed variation with proto wings, even though there was no advantage to it.
Unit 3 : Geological time scale, Fossil: types and age determination by Carbon dating, Evolution of horse
Q.Give example of one fossil form from Miocene with some important features.
Fossil from Miocene:
i)Exhibited the beginning of adaptation for living on the plain, ii)Middle digits on both limbs were much longer and it was probable that lateral ones only touched the ground to maintain balance, iii)All digits carried hoofs, iv)Legs were becoming of elongation and deposition of cement on the crowns, v)For the first time the valleys between the crests of teeth begin to fill up with cement formed as a deposit of ‘tartar’ on the merging portion of the crown. The amount of cement becomes progressively greater with the successive species etc.
Unit 4 : Natural Selection: Modes with Example
Q. What was the genetic basis of the melanin-related character of Biston betularia?
i)The difference in colour was controlled by one main locus, ii)The originals, peppered form was one homozygote (cc) and the melanic form was another homozygote (CC), and the C allele is dominant, iii)However, in other cases the melanin allele was less dominant and the heterozygotes were intermediate, there seem to be a number of different melanic alleles, iv)Selection may initially favoured a melanic allele with no or weak dominance and sub-sequently some other melanic alleles with stronger dominance (For further information follow our contact section).
Unit 5 : Species concept, Isolating mechanisms, modes of speciation; Speciation by chromosome rearrangement in Drosophila. Adaptive radiation/macroevolution (exemplified by Galapagos finches).
Q.Climatic changes have driven the evolution of beak size in one of Darwin’s finches”-Justify the statement.
Peter and Rosemary (1973) evidenced influence of beak size on feeding efficiency in large beaked Geospiza magnirostris and smaller G. fortis (feeding on the same kind of hard fruit).
(a)Beak size influences feeding efficiency on different food types:
Natural selection would favour larger finches when large fruits and seeds are abundant.
(b)Inherited property on beak size :
Parents with larger than average beaks produce offspring with larger than average beaks in G. fortis on Daphne major, showing that beak size is inherited. Results are shown here for 2 years in the 1970s. Grant & Grant (2000) show that the result persisted in future years.
Quantitative genetic is concerned with characters influenced by many genes. Called polygenic characters. The value of a character, like beak size, will usually also be influenced by the environment in which the individual grows up. Beak size is probably related to general body size and all characters to do with bodily stature will be influenced by the amount of food an organism happens to find during its life.
(c) Influence of food supply:
At the beginning of drought, the various types of seeds were present in their normal proportions. G. fortis of all sizes take small seeds and as the drought persisted, these smaller seeds are relatively reduced in numbers. The average available seed size became larger with time. Now the larger finches were favoured, because they eat the larger, harder seeds more efficiently. The average finch size increased as the smaller birds die off.
(d)Selection fluctuates over time:
The fluctuations in the direction of selection on beak shape-with beaks evolving up in some years, down in other years and Staying constant in yet other years-probably results in a kind of 'stabilizing selection over long period of time such that the average size of beak in the population is the size favoured by long-term average weather.
Unit 6 : Origin and Evolution of Man, Unique Hominid characteristics contrasted with primate Characteristic
Q.What are the major evolutionary trends in man?
i)Increased cranial capacity, ii)Upright posture with bipedalism, iii)Dental arch- a smoothly rounded parabola, Vertebral column with a lumber curve, iv)Canine teeth-not projecting beyond the level of the other teeth, v)High forehead without projecting eyebrow ridges, vi)Lower jaw with a projecting chin etc.
Q. How did selective pressures enhance bipedalism?
Three arenas in which selective pressures might have enhanced bipedalism are-
(1)Improved food acquisition—Early hominids lived in a patchy environment of mixed woodland and savannah(relatively dry grass land and bush land with occasional trees)that provided seasonal food supplies.
In a sense bipedalism may have arisen as a by-product of adaptations that reduced forelimb involvement in quadrupedal support and movement. As hands became increasingly specialized for grasping, selection occurred for an upright stance and for transferring locomotion to hind limbs.
(2)Improved predator avoidance—The curved hand and foot bones and relatively long arms of early Australopithecines and early Homo (H.habilis) point to persistent tree-climbing abilities.
(3)Improved reproductive success—
i.A relatively stable home base that provided more constant social relationships and perhaps closer mother-infant relationships that improved infant survival.
ii.Reduced infant injuries because infants no longer were attached to a continuously mobile mother.
iii.A reduction in the spacing between births by allowing parents to care for more offspring successfully.
Unit 7 : Population genetics: Hardy-Weinberg Law; factors disrupting H-W equilibrium (Genetic Drift, Migration and Mutation and Selection in changing allele frequencies (only derivations required). Simple problems related to estimation of allelic and gene frequencies.
Q.Calculate selection coefficient and Darwinian fitness from the dark and light Biston bitularia population.
*W-Reproductive success of individual genotype, s- selection coefficient, b/a-average progeny per individual
In the above table it is clear that the Dorset moths fitness (W) is 0.343 and therefore s=0.657 r in another way W=1-0.657=1-s=0.343
In other words the fitness of Dd or dd moth is reduced by 1-s. In the same way the fitness of the dd in the Birmingham population has been reduced by 1-0.74= 0.26.
It comes up therefore that fitness of a deleterious allele is reduced by 1-s. Therefore after one generation of selection q2 would result to q2 (1-s).
Unit 8 : Extinction, back ground and mass extinctions, detailed example of K-T extinction
Q. What are the names of mass extinctions?
Permian extinction, Ordovician-Silurian extinction, Cretaceous-Tertiary (K-T) extinction, End-Triassic extinction, Devonian extinction.
Q.What are the major causes of extinctions?
Loss of food source, loss of habitat, ecosystem imbalance, catastrophe, climate or atmospheric change, extermination, disease etc.
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Unit 9 : Phylogenetic trees, construction and interpretation of Phylogenetic tree using parsimony, convergent and divergent evolution.
Q. What do you mean by Phyletic gradualism?
This hypothesis states that evolution has a fairly constant rate, that new species arise by the gradual transformation on ancestral species and that the rate of evolution during the origin of new species is much like that at any other time. Gradualism refers to the evolutions of adaptations. Relationship with Darwinism—Darwin’s theory and subsequent versions of Darwinism are strongly gradualist about the evolution of adaptation, but they are not gradualist about the rate of evolution.
The extinct arthropod group of trilobites is classified by external morphological features such as the number of pygidial ribs. These trilobites look like a good illustration of gradual evolution.
Sheldon (1987), measured the number of pygidial ribs (the pygidium is the tail region of a trilobite’s body) in 3,458 specimens from eight generic lineages. The total time period spanned by the sections is about 3 million years. In all eight genera, the average number of pygidial ribs increased through time and in all eight the evolution was gradual; a population at any one time was usually intermediate between the samples before and after it.
Q.What are proteinoids?
[A polypeptide or mixture of polypeptides obtained by heating a mixture of amino acids]
In the 1950s, Fox and coworkers developed a technique in which heat could also be used to produce peptides from dry mixtures of amino acids. Depending on the kinds of amino acids in the mixture, they found that temperatures of 150°C to 180°C could produce as much as 40 percent yield of peptide like products with molecular weights between 4k and 10k daltons. Fox called these polymers proteinoids (also thermal proteins), and he and his group proposed that these compounds bear protein like features.
i)According to their analyses, the proteinoids possess nonrandom proportions of amino acids; that is, their compositions are not simply based on the frequency of the different amino acids in the initial mixture ii)They also suggest that the positions of the amino acids in the polymer are not based on their overall frequencies in the chain, since some amino acids preferentially occupy the N- and C-terminals of the proteinoids.
iii)The nonrandomness of proteinoid structure also seems supported by the finding that these polymers all show similar properties as tested by sedimentation rates, electrophoretic techniques, column fractionation, and other measurements. 'Thus, some preferential interaction between amino acids in proteinoid formation seems to dictate their position and frequency and lead to some degree of uniformity in the kinds of molecules produced.
iv)Although not all the amino acid bonds formed in such proteinoids are of the usual peptide variety, nor do the Shapes of these molecules follow the familiar α-helix of protein structure, there still seem to be enough peptide linkages to characterize them as proteins in many tests.
v)Thus, proteinoids give positive colour tests with the same reagents that proteins do; their solubilities resemble proteins; they are perceptible with similar reagents; and Fox and Dose propose they have other protein like traits listed in Table 1. They therefore suggest that some proteinoid reactions, combined into a particular sequence, may have served as the beginnings of later metabolic systems. Thus, decarboxylation of oxaloacetic acid can be followed by decarboxylation of its product, pyruvic acid, leading to acetic acid and carbon dioxide; or amination of pyruvic acid can lead to alanine.
Furthermore, some proteinoids even show relatively sophisticated hormonal activity and can stimulate the production of melanin-producing cells.
Although researchers have debated whether the thermal synthesis of proteins could occur extensively in present natural surroundings, the exact conditions encountered on the primitive Earth are certainly not known. Surfaces near some volcanic regions, or upwelling’s from shallow marine hydrothermal plumes, may have maintained appropriate temperatures for the condensation of amino acids.