Paper Details: S0123 / S.Y.B.Sc. (Choice Base) Sem IV / S2015 Life Science: Paper III Date: 02-05-2018 Time:02:00 pm - 05:00 pm Q.P.CODE 34686 Answer Key Q. 1. A). Define/Explain: 1. Phylogram- A phylogram is a branching diagram (tree) that is assumed to be an estimate of a phylogeny. The branch lengths are proportional to the amount of inferred evolutionary change. A cladogram is a branching diagram (tree) assumed to be an estimate of a phylogeny where the branches are of equal lengths. 2. Outgroup-In cladistics or phylogenetics, an outgroup is a group of organisms that serves as a reference group when determining the evolutionaryrelationships of the ingroup, the set of organisms under study, and is distinct from sociological outgroups. The outgroup is used as a point of comparison for the ingroup and specifically allows for the phylogeny to be rooted. Because the polarity (direction) of character change can be determined only on a rooted phylogeny, the choice of outgroup is essential for understanding the evolution of traits along a phylogeny 3. ORF-In molecular genetics, an open reading frame (ORF) is the part of a reading frame that has the ability to be translated. An ORF is a continuous stretch of codons that contain a start codon (usually AUG) and a stop codon (usually UAA, UAG or UGA). 4. Nodes-The tips of the tree represent groups of descendent taxa (often species) and the nodes on the treerepresent the common ancestors of those descendants. 5. Duplicate Genes-Gene duplication (or chromosomal duplication orgene amplification) is a major mechanism through which new genetic material is generated during molecular evolution. It can be defined as any duplication of a region of DNA that contains a gene 6. Homologous sequences-Sequence homology is the biological homology between protein or DNAsequences, defined in terms of shared ancestry in the evolutionary history of life. Two segments of DNA can have shared ancestry either because of a speciation event (orthologs), or because of a duplication event (paralogs). 7.Common Ancestor-All species share a common descent. In evolutionary biology, a group of organisms share common descent if they have a common ancestor. There is strong quantitative support for the theory that all living organisms on Earth are descended from a common ancestor. Q. 1. B) Match the Column: a) - v);b) - vi);c) - i);d) - ii) ; e) - iii); f) - vii); g) – iv) Q.1.C) 1. FALSE 2. FALSE 3. FALSE 4. TRUE 5. TRUE 6. TRUE Q.2.A. 1. Concept of Allopatric and Sympatric Speciation: The key to speciation is the evolution of genetic differences between the incipient species. For a lineage to split once and for all, the two incipient species must have genetic differences that are expressed in some way that causes matings between them to either not happen or to be unsuccessful. These need not be huge genetic differences. A small change in the timing, location, or rituals of mating could be enough. But still, some difference is necessary. This change might evolve by natural selection or genetic drift. Reduced gene flow probably plays a critical role in speciation. Speciation can take place in two general ways. A single species may change over time into a new form that is different enough to be considered a new species. This process is known as anagenesis. More commonly, a species may become split into two groups that no longer share the same gene pool. This process is known as cladogenesis. There are several ways in which anagenesis and cladogenesis may take place. In all cases, reproductive isolation occurs. Sympatric Speciation Sympatric speciation occurs when populations of a species that share the same habitat become reproductively isolated from each other. This speciation phenomenon most commonly occurs through polyploidy, in which an offspring or group of offspring will be produced with twice the normal number of chromosomes. Where a normal individual has two copies of each chromosome (diploidy), these offspring may have four copies (tetraploidy). A tetraploid individual cannot mate with a diploid individual, creating reproductive isolation. Sympatric speciation is rare. It occurs more often among plants than animals, since it is so much easier for plants to self-fertilize than it is for animals. A tetraploidy plant can fertilize itself and create offspring. For a tetraploidy animal to reproduce, it must find another animal of the same species but of opposite sex that has also randomly undergone polyploidy. Allopatric Speciation Allopatric speciation, the most common form of speciation, occurs when populations of a species become geographically isolated. When populations become separated, gene flow between them ceases. Over time, the populations may become genetically different in response to the natural selection imposed by their different environments. If the populations are relatively small, they may experience a founder effect: the populations may have contained different allelic frequencies when they were separated. Selection and genetic drift will act differently on these two different genetic backgrounds, creating genetic differences between the two new species. 2. Social and Behavioral Characteristics of Hunting Societies: Hunter gatherer societies cover a wide range of characteristics, from really simple to reasonably complex ones. Hunter-gatherers are often grouped together based on kinship and band (or tribe) membership. Prehistoric hunter-gatherers lived in groups that consisted of several families resulting in a size of a few dozen people. The general opinion among anthropologists seems to be that as of some 40,000 years ago they were egalitarian. Not only did they indulge in food sharing, but they shared virtually all consumer goods, even down to some personal items such as smoking pipes. Most hunter-gatherers have a symbolically structured sexual division of labour. However, it is true that in a small minority of cases, women hunt the same kind of quarry as men, sometimes doing so alongside men. In addition to social and economic equality in hunter-gatherer societies, there is often, though not always, sexual parity as well. Egalitarianism was apparently an intentional policy enforced by leveling behavior from the bottom up. This ensured that leaders who exhibited “big man” behavior were kept in check by various means, including ridicule and even disobedience. Egalitarianism was thus a deliberate policy by the ordinary group members. Members who did not share according to the standards of the group were subjected to open criticism, gossip and eventually ostracism. The sharing behavior of such societies should not be understood as the more successful one sharing their resources with less successful ones - the haves sharing with the have-nots. The really interesting thing is that sharing is a practice whereby everybody gives and everybody receives. It is a demonstration of goodwill, solidarity and camaraderie. The social effects of sharing are apparently not, according to researchers, foremost in the minds of the sharers. But the result of the sharing practice is that of making equal that which is not equal through deliberate activity. People’s hunting and gathering skills are not naturally equal. But sharing makes the within-group results reasonably equal. These characteristics are probably the most fundamental ones of hunter gatherers, especially so during the formative millennia of the Pleistocene, when much of the human psyche was formed. Q.2.B) 1. Selective Factors that lead to altruistic behaviour: The importance of social interactions in developing behaviour and communication skills is seen throughout primate groups in panoply of calls, grimaces, gestures and activities used to indicate social positions, needs and means of survival. In evolutionary biology, an organism is said to behave altruistically when its behaviour benefits other organisms, at a cost to itself. The costs and benefits are measured in terms of reproductive fitness, or expected number of offspring. So by behaving altruistically, an organism reduces the number of offspring it is likely to produce itself, but boosts the number that other organisms are likely to produce. This biological notion of altruism is not identical to the everyday concept. In everyday parlance, an action would only be called ‘altruistic’ if it was done with the conscious intention of helping another. But in the biological sense there is no such requirement. Indeed, some of the most interesting examples of biological altruism are found among creatures that are (presumably) not capable of conscious thought at all, e.g. insects. For the biologist, it is the consequences of an action for reproductive fitness that determine whether the action counts as altruistic, not the intentions, if any, with which the action is performed. Altruistic behaviour is common throughout the animal kingdom, particularly in species with complex social structures. For example, vampire bats regularly regurgitate blood and donate it to other members of their group who have failed to feed that night, ensuring they do not starve. In numerous bird species, a breeding pair receives help in raising its young from other ‘helper’ birds, who protect the nest from predators and help to feed the fledglings. Vervet monkeys give alarm calls to warn fellow monkeys of the presence of predators, even though in doing so they attract attention to themselves, increasing their personal chance of being attacked. In social insect colonies (ants, wasps, bees and termites), sterile workers devote their whole lives to caring for the queen, constructing and protecting the nest, foraging for food, and tending the larvae. Such behaviour is maximally altruistic: sterile workers obviously do not leave any offspring of their own—so have personal fitness of zero—but their actions greatly assist the reproductive efforts of the queen. From a Darwinian viewpoint, the existence of altruism in nature is at first sight puzzling, as Darwin himself realized.