Week 3 Flashcards

Question

How is human health impacted by extreme heat events?

Answer 1

In 10 days in 2007, Athens experienced extreme heat events >45˚C. Physiological responses to heat stress Effectiveness of responses is limited Increase in deaths and admissions for heatstroke during heatwaves

Answer 2

Increase in the number of ehat related deaths in 2050 compared to 2005 Decrease in cold related deaths but not as many as lost due to heat

Answer 3

Sweat responses Volume /surface area Evolution in stress response genes Evolution in heat stress genes?

Answer 4

Likely too slow to counter rapid environmental change

Answer 5

IPCC reports - sea level rise Spread of uninhabitable areas Displacements predicted by climate change

Answer 6

There is only a limit to how many and where they can move to For some animals there is many areas they can migrate too or cant move quick enough

Answer 7

Describes how civilisations ended due to increased per head human impact on environment (overpopulation, deforestation and overhunting) mixing with climate change

Answer 8

Easter island population: Settles around 1000 years ago Population was around 3,000 at peak and within a hundred years was around a couple hundred

Answer 9

Ageing (or senescence) is a reduction in vital rates (age-specific survival and fertility)

Answer 10

Ageing (or senescence) is a physiological deterioration of an organism resulting in a decline in probability of survival and reproductive performance with advancing age

Answer 11

Historically, scientists thought that ageing affects humans and livestock but does not affect wild animals in natural environments

Answer 12

Whether animals can, or cannot, reveal an innate deterioration is almost literally a domestic problem; the fact is that under the exactions of natural life they do not do so. They simply do not live that long.

Answer 13

Ageing ubiquitous in nature and most animals do age

Answer 14

Wolves hunt elk Old wolves have lower killings and sucesses than in their prime compared to young inexperinced wolves

Answer 15

Reviewing studies of wild animals, we find evidence for senescence in 175 species across 340 studies

Answer 16

Ocean Quahog (clam) 507 years Three-toed box turtle 65 years Rockfish 100-200 years

Answer 17

Ergo, Hydra may be seen as a pool of three stem cell lineages rather than an organism

Answer 18

Hydra shows no signs of senescence in laboratory conditions

Answer 19

Nevertheless, within-cell repair is imperfect and cannot solely protect against damage accumulation Cellular damage drift leads to accumulation of damaged cell lineages, hence senescence

Answer 20

High prevalence and continued division of Hydra׳s three stem cell lineages act against damage drift Asymmetrical damage transmission during cell division – like bacteria Germline is not segregated from the soma

Answer 21

When starved, heat-shocked or injured, goes back to the previous developmental stage, a polyp, which then produces a new adult form (a medusa) This cycle can be repeated several times

Answer 22

Small pest beetle Trogoderna glabrum Larvae can partially reverse development in the absence of food This cycle can be repeated several times

Answer 23

However, after several cycles the ability to regrow diminishes and repeatedly reversed beetles show physiological deterioration Time to regrowth increased from 9 days to 28 days in the fourth cycle In other words, they do not escape ageing

Answer 24

Baboons and dogs have a lower natural hazard at early years but increase at a quickier rate than turtles

Answer 25

Weismann's group selection theory Medewar's mutation accumulation Williams antagonistic pleiotropy

Answer 26

Hayflick's limit Rate of living and mitochondrial theory of ageing Reactiove Oxygen Species damage Telomeres Disposable soma Developmental theory of ageing

Answer 27

Telomeres are protective caps on end of DNA Telomerase is active in germline cells but is tightly repressed in normal somatic cells Lack of telomerase causes cells to lose telomeres with cell division and senescence or cell death Telomerase is reactivated is most cancers

Answer 28

When regulating duration of life, the advantage of the species and not the individual is alone of any importance. Weismann suggested that long life after reproduction is unnecessary

Answer 29

Naive group-selectionism - Gene-level selection > group level selection Circular reasoning - Soma is perishable and vulnerable so nature made no effort to endow this part of individual with a life of unlimited length

Answer 30

Weismann abandoned his ‘group selection’ stance and focused on the segregation between the germline and the soma – his main and long-standing contribution to our understanding of ageing

Answer 31

Immortal cell lineage of germ plasm can develop into mortal cell lineage during embryo or adult life

Answer 32

Haldane, 1941 – Huntington’s disease, caused by a dominant allele with high penetrance rather common – too common? Age of onset – 35.5 years

Answer 33

Mutation accumulation (MA) Medawar 1952 Antagonistic pleiotropy (AP) Williams 1957

Answer 34

Accumulation of alleles with late-acting deleterious effects due to weakening of selection late in life

Answer 35

Trade-off between early and late life fitness

Answer 36

Selection cannot "see" deleterious mutations whose effects are confined to late ages

Answer 37

Compared two populations of wild North American opposums that lived on the main land and on the island – 1989 - 2009 Mainland – many predators Island – no predators Isolation – 4000-5000 years Opposums on island live longer, age slower and have smaller litters

Answer 38

Flight is protection against predation that will lead to evolution of longer intrinsic lifespans and slower ageing

Answer 39

“Low adult death rates should be associated with low rates of senescence, and high adult death rates with high rates of senescence." - Williams 1957

Answer 40

Birds live longer than terrestrial mammals accounting for body mass Bats live as long or longer than birds

Answer 41

de Magalhães, Costa compared mass of mammal and birds compared natural log of maximum longevity Birds were shown to have live longer compared to similar sizes mammals

Answer 42

The general trend is that the bigger the body mass the longer the lifespan

Answer 43

Arboreal mammals live longer than terrestrial mammals due to trees having fewer predators and more escape oppotunities

Answer 44

High mortality group had a higher mortality rate due to age Low mortality group had a lower mortality rate due to age

Answer 45

Mutation accumulation - neutral in early life but failure rate increases over time Positive pleiotropy - Negative throughout life but the failure rate increase with age

Answer 46

20 random mutations in Drosophila - Brengdahl 2020 16 reduce fitness overall 14 reduce fitness more in late-life 13 reduce fitness in early-life but more so in late-life

Answer 47

50 generations of selection - Drosophila Melangaster “base” lines and old lines

Answer 48

For both male and female flies form the old lines lived longer but at the cost of reduced fecundity (prodiced fewer eggs)

Answer 49

Age-1 (+)(N2 Bristol) - All dead by day 25 but on day 2 produced 120 eggs a day Age-1 (hx546)(TJ1052) - All dead by day 40 but on day 2 produced 90 eggs a day

Answer 50

They are not mutually exclusive!! Perhaps more direct evidence for AP Other key arguments for predominant role of AP are: phenotypic plasticity major effect genes

Answer 51

Resource allocation and Early life inertia

Answer 52

Disposable soma”; Reduced risk of early-life mortality Insufficient resources --> Insufficient repair

Answer 53

Developmental/programmatic theories of ageing; Hyperfunction Insufficient selection --> Insufficient regulation