Read the following passage and answer the questions that follow:
[CAT 2017 Slot 1]
Scientists have long recognised the incredible diversity within a species. But they thought it reflected evolutionary changes that unfolded imperceptibly, over millions of years. That divergence between populations within a species was enforced, according to Ernst Mayr, the great evolutionary biologist of the 1940s, when a population was separated from the rest of the species by a mountain range or a desert, preventing breeding across the divide over geologic scales of time. Without the separation, gene flow was relentless. But as the separation persisted, the isolated population grew apart and speciation occurred.
In the mid-1960s, the biologist Paul Ehrlich - author of The Population Bomb (1968) - and his Stanford University colleague Peter Raven challenged Mayr's ideas about speciation. They had studied checkerspot butterflies living in the Jasper Ridge Biological Preserve in California, and it soon became clear that they were not examining a single population. Through years of capturing, marking and then recapturing the butterflies, they were able to prove that within the population, spread over just 50 acres of suitable checkerspot habitat, there were three groups that rarely interacted despite their very close proximity.
Among other ideas, Ehrlich and Raven argued in a now classic paper from 1969 that gene flow was not as predictable and ubiquitous as Mayr and his cohort maintained, and thus evolutionary divergence between neighbouring groups in a population was probably common. They also asserted that isolation and gene flow were less important to evolutionary divergence than natural selection (when factors such as mate choice, weather, disease or predation cause better-adapted individuals to survive and pass on their successful genetic traits). For example, Ehrlich and Raven suggested that, without the force of natural selection, an isolated population would remain unchanged and that, in other scenarios, natural selection could be strong enough to overpower gene flow...
1) Which of the following best sums up Ehrlich and Raven's argument in their classic 1969 paper?
(1) Ernst Mayr was wrong in identifying physical separation as the cause of species diversity.
(2) Checkerspot butterflies in the 50-acre Jasper Ridge Preserve formed three groups that rarely interacted with each other.
(3) While a factor, isolation was not as important to speciation as natural selection.
(4) Gene flow is less common and more erratic than Mayr and his colleagues claimed.
2) All of the following statements are true according to the passage EXCEPT
(1) Gene flow contributes to evolutionary divergence.
(2) The Population Bomb questioned dominant ideas about species diversity.
(3) Evolutionary changes unfold imperceptibly over time.
(4) Checkerspot butterflies are known to exhibit speciation while living in close proximity.
3) The author discusses Mayr, Ehrlich and Raven to demonstrate that
(1) evolution is a sensitive and controversial topic.
(2) Ehrlich and Raven's ideas about evolutionary divergence are widely accepted by scientists.
(3) the causes of speciation are debated by scientists.
(4) checkerspot butterflies offer the best example of Ehrlich and Raven's ideas about speciation.
The passage below is accompanied by a set of questions. Choose the best answer to each question.
[CAT 2018 Slot 1]
When researchers at Emory University in Atlanta trained mice to fear the smell of almonds (by pairing it with electric shocks), they found, to their consternation, that both the children and grandchildren of these mice were spontaneously afraid of the same smell. That is not supposed to happen. Generations of schoolchildren have been taught that the inheritance of acquired characteristics is impossible. A mouse should not be born with something its parents have learned during their lifetimes, any more than a mouse that loses its tail in an accident should give birth to tailless mice....
Modern evolutionary biology dates back to a synthesis that emerged around the 1940s-60s, which married Charles Darwin’s mechanism of natural selection with Gregor Mendel’s discoveries of how genes are inherited. The traditional, and still dominant, view is that adaptations – from the human brain to the peacock’s tail – are fully and satisfactorily explained by natural selection (and subsequent inheritance). Yet [new evidence] from genomics, epigenetics and developmental biology [indicates] that evolution is more complex than we once assumed....
In his book On Human Nature (1978), the evolutionary biologist Edward O Wilson claimed that human culture is held on a genetic leash. The metaphor [needs revision].... Imagine a dog-walker (the genes) struggling to retain control of a brawny mastiff (human culture). The pair’s trajectory (the pathway of evolution) reflects the outcome of the struggle. Now imagine the same dog-walker struggling with multiple dogs, on leashes of varied lengths, with each dog tugging in different directions. All these tugs represent the influence of developmental factors, including epigenetics, antibodies and hormones passed on by parents, as well as the ecological legacies and culture they bequeath....
The received wisdom is that parental experiences can’t affect the characters of their offspring. Except they do. The way that genes are expressed to produce an organism’s phenotype – the actual characteristics it ends up with – is affected by chemicals that attach to them. Everything from diet to air pollution to parental behaviour can influence the addition or removal of these chemical marks, which switches genes on or off. Usually these so- called ‘epigenetic’ attachments are removed during the production of sperm and eggs cells, but it turns out that some escape the resetting process and are passed on to the next generation, along with the genes. This is known as ‘epigenetic inheritance’, and more and more studies are confirming that it really happens. Let’s return to the almond-fearing mice. The inheritance of an epigenetic mark transmitted in the sperm is what led the mice’s offspring to acquire an inherited fear....
Epigenetics is only part of the story. Through culture and society, [humans and other animals] inherit knowledge and skills acquired by [their] parents.... All this complexity... points to an evolutionary process in which genomes (over hundreds to thousands of generations), epigenetic modifications and inherited cultural factors (over several, perhaps tens or hundreds of generations), and parental effects (over single-generation timespans) collectively inform how organisms adapt. These extra-genetic kinds of inheritance give organisms the flexibility to make rapid adjustments to environmental challenges, dragging genetic change in their wake – much like a rowdy pack of dogs.
1) Which of the following, if found to be true, would negate the main message of the passage?
(1) A study highlighting the criticality of epigenetic inheritance to evolution.
(2) A study affirming the influence of socio-cultural markers on evolutionary processes.
(3) A study indicating the primacy of ecological impact on human adaptation.
(4) A study affirming the sole influence of natural selection and inheritance on evolution.
2) The Emory University experiment with mice points to the inheritance of:
(1) acquired parental fears
(2) psychological markers
(3) personality traits
(4) acquired characteristics
3) Which of the following options best describes the author's argument?
(1) Mendel’s theory of inheritance is unfairly underestimated in explaining evolution.
(2) Wilson’s theory of evolution is scientifically superior to either Darwin’s or Mendel’s.
(3) Darwin’s and Mendel’s theories together best explain evolution.
(4) Darwin’s theory of natural selection cannot fully explain evolution.
4) The passage uses the metaphor of a dog walker to argue that evolutionary adaptation is most comprehensively understood as being determined by:
(1) socio-cultural, genetic, epigenetic, and genomic legacies.
(2) genetic, epigenetic, developmental factors, and ecological legacies.
(3) ecological, hormonal, extra genetic and genetic legacies.
(4) extra genetic, genetic, epigenetic and genomic legacies.
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