H2 Biology 27 - Climate change

long-term, prevailing weather conditions in a given area. four physical factors, TPSW are important components of climate

statistically observable variations in climate that persist for an extended period. climate change is the outcome of both natural & man-made processes(anthropogenic)

Burning of fossil fuels

increasing energy demand & usage of humans

Deforestation

forest cleared for other land purposes; agriculture/urban development >

net reduction in carbon storage; forests(natural carbon sinks) removed >

trees cut down & burnt emits CO₂, atmospheric CO₂ levels increases

Food choices(including increased consumption of meat)

CH4 emission increases; released by animals through belching/flatulence >

manure production increases; decomposed, releases CH4, CO2 >

deforestation increases for > pastureland for livestock to graze & to grow animal feed >

inefficient; 10x > land required for animal production than vegetable products

melting of polar ice caps

rising sea levels

stress of fresh water supplies

extreme weather conditions; heat waves, heavy rains

death of coral reefs

migration of fishes & insects

release of GHG in frozen organic matter(permafrost)

area of sea ice decreases, area of white surfaces decreases >

less solar radiation reflected into space >

ocean has higher heat absorption capacity than ice, absorbs > heat than ice, ocean's temp increases >

increased temp melts > ice, further increasing ocean temp; +ve feedback loop(ice albedo feedback) accelerates climate change

1. ice sheets melting

rate of ice sheets melting > rate of ice gained from snowfall >

ice sheets melting leads to rise in sea level

2. trapped heat absorption; thermal expansion of water

increased temp, ocean absorbs > heat >

oceans warms, water expands & increases in vol

domino effect;

increased coastal erosion- land washed away by wave, high winds

> vulnerable to flooding during cyclones, possibly submerged, leading to refugees & overcrowding

salt water intrusion decreases quality of drinking water

temp increases, animals & plants demand > water for biological processes >

ice sheets, glaciers melts, increases water supply temporarily >

higher temps, rain replaces snow, rainfall increase in freq & intensity, leads to rapid movement of water from atmosphere into oceans >

> amount of runoff decreases water quality, unsafe for human consumption >

reduced rainfall decreases availability of water in dry regions >

rising sea levels @ coastal, island regions, salt water intrusion increases salinity of fresh water supplies

heat waves

temp increases, variance of temp increases >

increase in freq, intensity of prolonged period of excessively hot weather(heat waves) >

leads to longer, drier summers, snow melts earlier, > deaths, lack of rain+drought increases wildfires

heavy rains

temp increases, rate of water evaporation, capacity of air to hold moisture increases >

moister air results in more intense heavy rains & storms >

increases surface runoff as soil cannot absorb water, flooding, increased risk of landslides, degradation of water quality, decrease in agricultural production as crops damaged

zooxanthellae provides O₂, removes waste, supplies pdts. of photosynthesis hence major source of food for corals; photosynthetic pigments protect corals from harmful sunlight >

coral provides CO₂ for photosynthesis, shelter for protection against predation & extreme conditions, physical support to absorb light, nitrogen from waste supports algal growth

temp increases, causes coral bleaching >

zooxanthellae expelled from coral tissues >

bleached corals can recover if temps stabilise but too long, zooxanthellae die >

corals die, algae take over skeletons, prevents growth of new corals >

ocean acidification from > CO₂ exacerbates bleaching

leads to loss of nurseries for fishes, habitats for marine species, coastline protection preventing coastal erosion

temp increases, geographical ranges of species change to higher latitude(tropics>northerly places)/altitude(valleys>higher elevation) to return to optimal temp range >

range expansion/contraction >

fishes migrating causes ecological disruption from > competition >

insects have narrow optimal temp range, migration leads to local extinction from poleward migration/inability to adapt >

vectors spread insect-borne diseases to sub-tropical/temperate areas

permafrost(permanently frozen ground) stores large amount of carbon(carbon sink) >

thawed, acts as carbon source; releases CH₄, CO₂- bacteria decays organic matter >

global warming thaws permafrost, releases GHGs increasing global warming, thawing more permafrost - +ve feedback loop

high temps lead to:

1. stomatal closure; high temp leads to excessive transpiration, closure reduces water loss from excessive transpiration & photosynthesis rate falls

2. < stomata per leaf; reduce water loss via transpiration, plant w/ sufficient CO2 w/ < stomata @ advantage, better conserve water with same photosynthesis rate

3. > well-developed roots; rate of water uptake > rate of water loss

4. < leaves, smaller leaf area; reduces water loss by increasing roots:shoots ratio

poleward/higher latitude shift

temp increases, species range shift poleward >

boreal forests shift range to tundra region but experience range contraction as southern populations are lost faster >

increase in temp, drought freq causes less efficient photosynthesis & displaces boreal forests w/ temperate species

higher altitude shift

mountains provide shorter migration distance for higher altitudes, affect sunlight, local temp & rainfall >

warmer, drier climates shift plants upwards >

low-altitude species greatest increase in abundance from increased microbial activity in soil, high-altitude species growing slower lose out >

increased competition among high-altitude species leads to extinction

(> extreme weather conditions, increased temp)

> temp, < crop yields, < global food supply, food shortage >

mid-latitude plants benefit from warming; longer growing seasons, > precipitation, < frost -> > crop yields >

low-latitude plants @ max temp tolerance, slight temp changes < water availability, disrupt plant growth&development -> < crop yields >

sea level rises, soil erosion submerges shorelines, causes saltwater intrusion -> < arable land -> < food crop production >

migration of weeds/fungi/insects->temperate regions causes > pests,diseases damaging crops & yield >

heat waves,droughts causes heat stress in crops, limits yields. prolonged period of low water availability disrupts germination,fruit development >

high precipitation in sub/tropical regions cause flooding -> loss+destruction of food crops, soil erosion causing poor soil quality

> temp -> > ocean temp -> fishes migrate polewards ->ecological disruption, reduced catches in tropics & > warm-water species in subtropics,temperate regions >

> temp affects timing of reproduction, migration; frequent marine disease outbreaks from parasites,algae bloom; ocean acidification kills coral reefs, disrupts marine food webs,reduce abundance of tropical fish as nursuries lost>

live stock face heat stress -> < feed intake -> < animal weight gain&growth, < milk yield & > mortality rate(cows), < livestock reproduction from < fertility, < conception rates & > mortality of embryo >

livestocks > vulnerable to parasites, diseases due to earlier onset of seasons >

drought causes lost of pasture grazing land, < feed, forage quality for cattle; < crop yield >

< livestock production potential -> < global food supply

> temp to insects' thermal optical level -> > rate of enzymatic reactions >

> metabolism of insects, insects develop more quickly under high temp not exceeding optimal levels >

> temp increase speed of insect's life cycle >

insects mature, mate & reproduce in shorter span of time than normal

female a. aegypti lay eggs above water line in areas likely to temporarily flood(holes, containers) >

mosquito larvae hatch from submerged eggs 2 days after containers filled w/ water, feed on microorganisms in water >

larvae undergo developmental stages, moult 4 times over 5 days, larval stages called first to fourth instars >

when larva fully grown fourth instar, undergoes metamorphosis to form pupa>

after 2 days, fully developed adult mosquito forms, breaks through pupal case

AFM carrying dengue feeds on host, virus enters skin tgt w/ saliva >

virus infects skin cells, infects & replicates inside skin dendritic cells >

virus enters target cells(RME), activates innate IR, infected dendritic cells produce cytokines, recruits macrophages >

macrophages infected by virus, infected dendritic cells,macrophages travel to lymph nodes, virus spreads throughout body by lymphatic system, infects > cells >

spread, increase in virus -> viraemia(high level of dengue in bloodstream) >

immune system fights infection, host experiences fever >

cells display dengue viral antigens, activates active IR; B cells produce Ab released in blood, lymph fluid, r&n dengue viral particles by preventing virus from binding to macrophages & gaining entry; cytotoxic T cells r&k infected cells

infected hosts dont show any symptoms/mild symptoms >

risk factors for development of severe dengue; serotype, virulence of infecting dengue virus, age, sex, immune status, genetic background, chronic diseases >

2^o infection increased risk of severe dengue as active IS only provide immunity to 1/4 serotypes(antibody-dependent enhancement) >

infected w/ 2nd dengue serotype, virus activates IS through similar antigens; Ab from 1o infection bind to surface proteins but cant inactivate virus >

existing+new Ab produced aids virus in infecting host cells > efficiently >

IR attracts > macrophages, virus infects since not inactivated, > [virus] in bloodstream >

cytotoxic T cells release >> cytokines, cause serious inflammation, tissue damage(blood plasma leakage from capillaries, serious bleeding) >

risk of severe dengue(DHF,DSS) increases

dengue virus transmitted via bite of infected female aedes aegypti mosquito(vector) >

when mosquito feeds on blood of infected person w/ dengue virus during viraemia, dengue virus enters mosquito's system in blood meal >

dengue virus replicates, spreads through mosquito's body to reach salivary glands >

infected mosquito transmit dengue virus through saliva to another uninfected person when feeding on their blood

DENV is RNA virus w/ high error rates of RNA-dependent RNA synthesis >

DENV drug resistant as drug resistant strains selected for if antiviral drugs used for treatment of dengue >

dengue vaccine must elicit simultaneous protection against all 4 serotypes of DENV

increase in geographical range of aedes aegypti

DENV-transmitting mosquitoes found throughout sub/tropical regions >

originally originated in Africa, extending increasingly into temperate regions during northern,southern summer months >

range expansion due to spread of vectors by transport of goods & people, increased survival in new location >

facilitates wider geographical transmission of dengue

increase in no. of mosquito vectors

> temp, population increases; increasing dengue transmission correlates w/ temp rise >

rising average annual temp+increased precipitation facilitates rich breeding grounds for mosquitoes >

> temp leads to > metabolism, accelerates development >

increases activity of female mosquitoes, reduces EIP; rate of viral replication in vector increases, shortens EIP

each species evolve to thrive in habitat made up of abiotic factors(soil,moisture, temp range, light intensity) & biotic factors(food availability, presence/absence of predators) >

climate change alters key habitat elements critical to wildlife survival, may lead to > severe consequences of habitat loss

> temp,earlier spring in temperate regions w/ milder winters, longer summers; affects phenology of plants, animals >

many species move range northward/to higher altitudes >

diff species diff ability to adapt to climate changes, asynchrony, timing mismatch of biological events >

increased vulnerability of species & ecosystem

impact of climate change on 1 species can ripple thru food chain, affects wide range of other organisms >

e.g. < duration, extent of sea ice -> < abundance of ice algae ->

< zooplankton -> < arctic cod -> < seals -> < polar bears

decline in ice algae contribute to decline of polar bear population

ecological niche takes into account place where organism lives & interactions w/ environment; every organism occupies niche as factors composing niche complex & interconnected >

due to climate change, many organisms shift climatic niches, thus geographical ranges over time for suitable climatic conditions >

rate of climate change > rate of niche shifts/species adapting to new niches >

species face > competition(no 2 organisms can occupy same niche(CIP)); may not adapt to condition changes, die/fail to reproduce & gradually extinct >

species near newly suitable niches gradually occupy areas not inhabited previously

climate change causes biodiversity loss thru increased extinction rates, distribution changes, reproduction timing changes, changes in length of growing season >

tropical ecosystems normally experience narrow changes in temp, vulnerable to climate change;

species adapted to nearly constant temp, sensitive to > temp; << population >

leads to loss of rich reservoir for biomedicines; many drugs contain substances derived from plants

loss of genetic diversity for food; CWR containing genes used to improve crop qualities not collected, conserved; habitats threatened by climate change >

extinction of CWR species lead to loss of valuable genetic diversity used to improve crop quality, improve food security >