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DELETERIOUS MUTATIONS. “The effects of such a mutation accumulation process would only become manifest at the organismal level after the environment changes such that individuals experience less extrinsic mortality (e.g., due to decreased predation) and thus live to an age where they actually express the symptoms of aging.” http://www.nature.com/scitable/knowledge/library/the-evolution-of-aging-23651151 View in LinkedIn

MUTATION ACCUMULATION. "Medawar reasoned that, if the effects of a deleterious mutation were restricted to late ages, when reproduction has largely stopped and future survival is unlikely, carriers of the negative mutation would have already passed it on to the next generation before the negative late-life effects would become apparent. In such a situation, natural selection would be weak and inefficient at eliminating such a mutation, and over evolutionary time such effectively neutral mutations would accumulate in the population by genetic drift, which in turn would lead to the evolution of aging.” http://www.nature.com/scitable/knowledge/library/the-evolution-of-aging-23651151 View in LinkedIn

SNUFFING MUTATIONS. “If a beneficial or deleterious mutation occurs only after reproduction has ceased, then it will not affect fitness (reproductive success) and can therefore not be efficiently selected for or against. However, even if a mutation occurs earlier, say during the reproductive period, its effects may not be visible to selection since, if extrinsic, environmentally imposed mortality is high, individuals that could express the mutation are likely to be dead already.” http://www.nature.com/scitable/knowledge/library/the-evolution-of-aging-23651151 View in LinkedIn

RURAL REASONS. “This decline is in line with that of many other farmland species and is attributed to changes in farming practices: the switch from spring- to autumn-sown cereals; increased use of pesticides; increased use of herbicides; the switch from haymaking to cutting for silage before the grass has set seed; reduced spillage of grain and improved; storage to meet EU regulations.” https://www.britishbirds.co.uk/wp-content/uploads/article_files/V96/V96_N09/V96_N09_P439_446_A004.pdf View in LinkedIn

EARLY DEMISE. “For most organisms, the natural world is dangerous since it abounds with competitors, predators, pathogens, accidents, and other hazards. It follows from this that in natural populations most individuals die or get killed before they can grow old and suffer the symptoms of aging: thus, individuals have a very small overall probability of being alive and reproductive at an advanced age.” http://www.nature.com/scitable/knowledge/library/the-evolution-of-aging-23651151 View in LinkedIn

US SPARROW COLLAPSE. “After its introduction in the 1850s, the house sparrow quickly spread across North America, and 40 years later, it had colonized large parts of the continent. At its peak, the number could have touched half a billion. After that, the house sparrow population shrank in stages with periodic rapid decreases. In between, the numbers stabilized, before the decline continued. Lately, subpopulations, especially in the big cities, have all but collapsed.” https://lnkd.in/dGi32hq View in LinkedIn

EUROPEAN SPARROW COLLAPSE. “Dutch house sparrow (Passer domesticus) densities dropped by nearly 50% since the early 1980s, and similar collapses in population sizes have been reported across Europe.” https://lnkd.in/dyehfe7 View in LinkedIn

SPARROW MICROBIOTA. “We found urbanisation to be associated to lower microbiota species diversity, modifications in taxonomic composition and community structure, and changes in functional composition. Our results hence shed light on a hitherto little considered perspective, i.e. that the negative effects of urbanisation on city-dwelling organisms may extend to their microbiomes, causing potential dysbioses.” https://lnkd.in/dyfjm-b View in LinkedIn

HIGHLY SOCIAL BIRDS. “Reduction of colony size below some critical threshold may impair breeding behaviour to the extent that success declines, perhaps ultimately resulting in the disappearance of the colony...and increased dispersion of the colonies.” https://www.britishbirds.co.uk/wp-content/uploads/article_files/V96/V96_N09/V96_N09_P439_446_A004.pdf View in LinkedIn

COUNTRY FACTORS. “Factors proposed for the urban House Sparrow decline: predation by hawks and cats; increased bird competition for food; nesting site losses; pollution; lack of insect food; increased pesticide use; smaller colony sizes.” https://www.britishbirds.co.uk/wp-content/uploads/article_files/V96/V96_N09/V96_N09_P439_446_A004.pdf View in LinkedIn