climate change ii - impact on biodiversity, biomedicine & the global food supply Flashcards
(19 cards)
1
Q
what is biodiversity?
A
biodiversity describes the variety of life across all levels of biological organization, including the diversity of species, their genes, their populations, and their communities from organism to biome levels
- species diversity refers to the number & variety of species in a particular region. one component of species diversity is species richness, which is the number of different species represented in an ecological community, landscape or region. another component is species evenness/relative abundance, which refers to how close in numbers each species in an environment is
- genetic diversity refers to the differences/variations in DNA composition among individuals within a species
- ecosystem diversity refers to the number & variety of ecosystems, or the diversity of biotic communities/habitats within some specified areas
2
Q
impact of climate change on genetic diversity?
A
impact on genetic diversity
- climate change can decrease genetic diversity of populations due to directional selection & rapid migration, affecting ecosystem functioning & resilience
- GHG emissions cause temperatures to rise -> weather patterns are modified & frequency of extreme weather events increase -> warming temperatures force organisms to shift geographic ranges polewards and higher in altitude, and extreme weather events like droughts increase stress on populations. some members of particular species will not be bale to adapt and perish -> decreased population size -> smaller gene pool -> decreased genetic diversity
- as ranges shift, animals & plants may find themselves among new communities of prey, predators and parasites, to which they are not adapted
- mountaintop organisms cannot move further upslope to escape warmer temperatures, and may perish
3
Q
impact of climate change on species diversity?
A
phenological shifts in flowering plants & insect pollinators
- shifts in timing of seasons due to climate chnge has led to phenological shifts in flowering plants & insect pollinators -> mismatch between plant & pollinator populations -> extinctions of both the plant & pollinator, with consequences on the structure of plant-pollinator networks
- modification of interspecific relationships also modify community structure & ecosystem functions
reduction in amount & availability of habitat
- climate change reduces the amount & availability of habitat, and eliminates species essential to the species in question
- climate change is likely to have a particularly large impact on tropical ectotherms (cold-blooded) as they are temperature senstitive, and are already living very close to optimum temperatures
4
Q
impact of climate change on ecosystem diversity?
A
- climate change can induce changes in vegetation communities that are predicted large enough to affect biome integrity
- biomes refer to large regions with distinct climates & certain species adapted to them
5
Q
how does biodiversity loss affect biomedicines?
A
- nature has been providing medicines to treat diseases and relieve suffeirng for thousands of years
- despite great advances in rational drug design, most prescribed medicines are still derived from, or patterned after, natural compounds from plants, animals & microbes
- the value to society off the as yet discovered drugs from tropical rainforests is around US$150B
- with every species that goes extinct due to cliamte change, we lose one more opportunity to find cures for cancer, AIDS or other malaides
- eg the rosy periwinkle produce compounds that are anticancer alkaloids that treat hodgkin’s disease and a deadly form of leukemia. had this plant become extinct, these 2 fatal diseases would have claimed far more victims
- scientists lost opportunities for medical advances when 2 species of gastric brooding frogs went extinct. female frogs raised their young inside thier stomachs, where the young exuded substances to neutralize their mother’s stomach acids. any such substance could be of immense value for treating stomach ulcers
6
Q
LO: how does biodiversity loss affect food security?
A
- food security refers to the guarantee of an adequate, safe, nutritious and reliable food supply (availability, accessibility, utilisation & stablisation of food)
- biodiversity provides the food we eat. we get 90% of our food from just 15 crop species and 8 livestock species, and the lack of diversity leaves us vulnerable to failures of particular crops
- food security can be improved bby finding sustainable ways to harvest/farm novel or underutilized wild species and rare crop varieties (eg babassu palm of the tropical amazon produce more vegetable oil than any other plant
- plant species need to be maintained as a potential source of food. monocultures used in agriculture are susceptible to pest attack, so wild varieties - which may possess natural genetic resistance to these pests - represent a form of biological insurance
- this is because wild populations may be faced with constantly changing environmental conditions , and only the fittest plants and animals survive -> possess genes that make them resistant to these pressures. modern varieties of crops may have lost these genes as they were selected based on productivity, not for resistance to adverse conditions or disease
- crops relatives and wild ancestors of crops hold reservoirs of genetic diversity and can save monocultural crops from catastrophe when we transfer helpful genes by crossbreeding or genetic engineering
- climate change is threatening the strategic reservoir of crop & livestock genetic resources from which to breed the varieties that will be needed to adapt production systems to future challenges
7
Q
LO: what are the direct impacts of climate change on crops?
A
impact of increases in global mean temperature
- tropical regions are already at the upper end of optimal temperature ranges for many agricultural plants. even with low levels of warming, there could be crop loss due to heat and water stress -> reduced production of food crops in affected areas
- impacts on crop production in the mid to high latitudes are expected to be more mixed. high latitude regions are expected to benefit from warmer conditions & longer growing seasons
impact of gradual changes in precipitation
- increased frequency, duration & intensity of dry spells & droughts: water stress & increasing fire hazard would lead to loss of perennial crops -> puts pressure on grain reserves & increases dependency on food imports & food aid. droughts also reduce rates of soil moisture retention -> reduce suitability of land for crop production
- change in timing, location & amounts of rain & snowfall: increased temp -> more overall rainfall, BUT changes in patterns & seasonality of rainfall regionally means some areas see less rainfall, and changes in timing & intensity of rainfall also have significant local impacts. warmer winters + lower precipitation (snow) + earlier melt season + temp changes -> earlier runoff in spring -> only beneficial to agriculture if runoffcan be stored in times of surplus; if not, excess water will be lost to oceans. climate change also creates seasonal flow scarcities in dry season -> reduces rates of soil moisture retention -> reduces suitability of land for crop production
- increased frequency & intensity of storms & floods: climate change increases risk of extreme wet weather -> increased in total rain falling during heavy rainfall events -> destroys entire crops over wide areas, devstating food stores, assets & agricultural land
8
Q
LO: are the indirect impacts of climate change on crops?
A
1- attack by pests
- rising temp -> ability of pest populations to survive winter & attack susceptible crops increase -> range of agricultural pests expand
- pests like aphids respond positively to higher CO2 conc. increased temp in witner also reduces the mortality of aphids by enabling earlier & potentially larger dispersion
2- competition by weeds
- weeds compete with crops for light, water and nutrients
- many weeds thrive under higher temperatures, increased rainfall and increased CO2 levels
- ranges & distribution of weeds tend to increase with climate change :(
3- pathogens & diseases affecting crops may be affected by climate change
- eg aflatoxicoses outbreaks in kenya. increased risk of aflatoxin contamination is due to changing rainfall patterns, restricting the area over which certain crops can grow, like maize, a staple for millions of people
9
Q
LO: impacts of climate change on livestock & pastoral systems?
A
1- impact on animal productivity
- increased temp alters heat exchange between animals & the environment -> affects feed intake, growth, reproduction, maintenance, mortality & production
- hot & humid conditions can cause heat stress in livestock -> induces behavioural & metabolic changes like reduced feed intake and hence decline in productivity
2- impact on feed crops and forages, and grasslands
- increased temp & reduced precipitation has direct negative impacts on yield of feed crops for livestock
- increased temp increases lignification of plant tissues -> reduces digestibility and rates of degradation of plant species -> reduces nutrient availability for animals -> reduces livestock production -> impacts food security & income throguh reducstions in production of milk & meat
3- impact on animal health due to rising temperature increasing winter survival of vectors & pathogens
- eg bluetongue disease in europe -> used to be confined between 40N and 35S, but due to sensitivity to climatic conditions, it has been extending northward as a result of rising temp -> increased virus persistence during winter
10
Q
LO: impact of climate change on fisheries and aquaculture systems?
A
1- impact on reproductive cycles of fish
- changes in temperature can have a significant influence on the reproductive cycle of fish, including the spped at which they grow, reach sexual maturity & the timing of spawning
- eg: inland fisheries in malawi, africa: impact of climate change on freshwater systems (fishes caught in inland waters) are mainly due to increasing temp & sea level, change in precipitation and changes in variability of those quantities. riverine fishes are particularly sensitive to disturbances, as lower dry season water levels reduce the number of individuals able to spawn successfully, especially since many fish species are adapted to spawn in synchrony with the flood pulse. river ecosystems are particularly sensitive to change in the quantity & timing of water flows, which are likely to change with climate change
2- impact of reduction in oxygen levels
- reduced available oxygen levels, due to the warming of the surface of water, will decrease the maximum body weight of fish species around the globe -> lower catch potentials in the near future
- species intolerant to hypoxia (inadequate oxygen supply) will see their habitat size shrink and may be less productive in the future
- various fish species are migrating poleward
- will result in a large-scale redistribution of global marine fish catch potential, with a 30%-70% increase in high latitude regions, and a drop of up to 40% in the tropics
11
Q
key terminologies for dengue
A
- dengue (DEN): a viral infection transmitted by the bite of an infected female aedes mosquito
- dengue fever (DF), degnue haemorrhagic fever (DHF), dengue shock syndrome (DSS): 3 forms of dengue disease, where DSS is the most severe form
- disease: a disorder or illness that disrupts the normal functioning of the body or mind, leading to poor health. every disease is associated with a set of signs & symptoms
- epidemic: an often sudden increase in the number of cases of a disease, above what is normally expected in that population in that area
- outbreak: same definition as epidemic, but is often used for a more limited geographic area
- epidemiology: the study of the distribution and determinants of health related states or events in specified populations, and the application of this study to control health problems
- vector-borne disease (VBD): a disease that is transmited to humans by a living organism
- viremia: a medical conditions where there is presence of virus in the blood
- virulence: the relative capacity/degree of a pathogen to overcome body defenses
12
Q
LO: outline the life cycle of the dengue mosquito
A
- egg. female mosquitoes lay their eggs above the waterline of containers with water
- larva. larvae hatch when water inundates the eggs. in the following days, the larvae will feed on microrganisms and particulate organic matter found in water. larvae go through developmental stages in which they molt 3 times
- pupa. when the larva has acquired enough energy and size, metamorphosis is triggered, changing the larva into a pupa. pupae do not feed, they just change in form until the body of the adult, flying mosquito is formed
- adult. after 2 days, the fully developed mosquito emerges from teh water after breaking the pupal skin. the adult mosquito is able to fly and is no longer aquatic
13
Q
LO: outline host-pathogen interaction in the development of viral dengue disease in humans
A
- the 3 transmission cycles for the aedes virus are jungle, intermediate & urban (focus on urban cycle: human-to-mosquito-tohuman natural cycle of transmission)
- only female mosquitoes bite because it requires blood to produce eggs
- after the aedes aegypti female mosquito feed on the blood of someone infected with DENV, the mosquito becomes a dengue vector. the mosquito must take its blood meal during the period of viremia to become infected with DENV. the DENV is then present in the salivary glands of the mosquito
- humans are dead-end hosts; dengue cannot be spread directly from one person to another, and mosquitoes are necessary for transmission of the dengue virus
14
Q
LO: 5 factors affecting human susceptibility to DENV?
A
- host immune status: individuals may be at risk of a secondary infection by a DENV of different serotype
- viral strain: the association of each serotype & genotype to disease severity, epidemic potential and efficiency transmission could be influenced by the differences among them, but also by other conditions.
- host genetic status: genetic dengue susceptibility favours disease severity (eg white ppl higher chance of developing severe dengue disease than black ppl)
- age of host: influence outcome of disease following a secondary infection with DENV. younger age is associated with disease severity in individuals experiencing a secondary infection (but for first DENV infection, increase age increases severity)
- individual risk factors: determins the severity of didsease and include secondary infection, age, ethnicity and possibly chronic diseases
15
Q
LO: outline pathogen virulence of DENV
IDK HOW IMPORTANT THE DETAILS OF THE VIRUS GENOME ARE…
A
- genome of DENV: ssRNA that codes for 10 genes. 3 structural protein genes code for nucleocapsid, membrane-associated protein and envelope protein. 7 non-structural proteins genes code for proteins that play roles in viral replication & assembly
- structure of DENV: small enveloped spherical virus. virion consists of nucleocapsid enclosed in lipoprotein enveloepd. E & M proteins are embedded in the viral envelope
- dengue serotypes: DENV-1, DENV-2, DENV-3, DENV-4, each having different interactions with antibodies in human blood serum, but have the same disease and range of clinical symptoms, and share the same geographic & ecological niche. infection with 1 serotype confers lifelong immunity to that virus serotyep, but there is no cross-protection against the 3 other serotypes
- distribution of dengue serotypes: all 4 dengue serotypes circulate together in tropical and subtropical regions around the world
- pathogen virulence: viral genetic differences have been associated with differences in virulence. certain DENV strains are responsible for more severe disease. differences in virulence caused by asian & american genotypes correlated with structural differences in the 2 strains of DENV, and different geographical DENV serotypes may vary in their ability to infect different cell types or cause severe form of dengue disease
16
Q
LO: how is DENV transmitted to the human host
A
- once the virus enters the mosquito’s system in the blood meal, the virus spread through the mosquito’s body for 8-12 days. the mosquito will remain infected with DENV for its entire life
- the infected female mosquito injects its saliva into the human host to prevent the host’s blood from clotting and to ease feeding, infecting the host with DENV. during the feeding, DENV is inoculated into the host skin, and some virus is also injected directly into the bloodstream
- the virus infects nearby skin cells, keratinocytes, as well as macrophages, dendritic cells and langerhans cells. these infected cells can migrate from the initial site of infection to regional or local lymph nodes, presenting viral antigens to T cells -> initiates the cellular & humoral immune responses -> triggers recuritment of monocytes & macrophages that become subsequent targets of DENV infection
- number & variety of cells infected with DENV increases and the infection becomes disseminated throughout the lympathic system with the infection of cells of the mononuclear lineage. the spread and increase of virus results in viremia
17
Q
LO: outline drug resistance in DENV
A
- one of the biggest challenges in testing antivirals is that to be effective, the drug(s) should be delivered early after the onset of symptoms, but the vast majority of dengue patients present late during their illness.
- the drug should also be active against all serotypes, reduce symptoms and reduce incidence of severe disease
- serious dengue disease and adverse morbidity may be reversed by administering potent & safe small molecule compounds that target essential steps in virus replication early during the disease, lowering the viral load susbtantially
18
Q
describe the geographical spread of dengue virus
A
- dengue is mainly found in the tropics because the mosquitoes require a warm climate. but dengue epidemics are known to have occurred regularly in subtropical & temperate areas as well
- in countries in the equatorial zone that experience tropical monsoon seasons, dengue epidemics are a serious public health problems. dengue outbreaks may occur every year during the rainy season, where conditions are perfect for mosquito breeding
- most female aedes aegypti mosquitoes may spend their lifetime in or around the hosues where they emerge as adults meaning people, rather than mosquitoes, rapidly move the virus within and between communities
19
Q
LO: how does global warming affect the spread of mosquitoes?
A
impact of increased temperatures
- increased mosquito activity as time taken for the virus inside the mosquito to develop & become infective is shorter -> faster viral replication rate leading to mosquitoes becoming dangerous to humans more rapidly
- increased frequency of mosquito bites as female mosuqitoes bite more frequently in hotter temperatures -> increased feeding rate leads to greater capacity to produce offspring
- improved survival of eggs & adult mosquitoes as warmer temperatures increase feeding rate & reproduction -> increased incidences of disease. rise in water temeprature also reduces time taken for mosquito larvae to mature
- expand geographic range of mosquitoes’ survival as warmer winters allow mosquitoes to survive in areas that were formerly too cold
impact of other factors
- increased temperature, precipitation & humidity increases vector abundance & disease incidence
- global warming -> increased temperatures -> increased frequency & amount fo rainfall -> increases number of mosquito larval habitat & hence mosquito population size -> increases transmission potential
- but some rainfall conditions may not favor mosquitoes’ survival & reproduction; torrential rainfall & flooding causes runoff water & destroys the eggs and larvae of mosquitoes. conversely, lower rainfall creates habitats for mosquitoes as rivers dry into pools (dry season malaria), and lower rainfall increases container-breeding mosquitoes by forcing increased water storage
