eco 2

• greenhouse effect = natural phenomenon w/0 earth's surface temp would be -18 c
• cause o natural GE: incoming rad fr sun includes UV, visible light (short wave rad) and infrared (longer wave rad - heat) can pass through atmosph
• earths surface warmed and re-radiates long wave rad in form infrared rad back to space -> absorbed by greenhouse gases -> raise earth's temp
• some infrared lost to space as heat
• GHG: those tt absorb infrared rad + cause heat retained in earths atmo
• incl water,CO2, methane, Chlorofluorocarbons, oxides o nitrogen and sulfur dioxide
• human activities have increased prod o greenhouse gases, result = enhanced greenhouse effect => attrib global warming
• enhanced greenhouse effect correlates with rising temp on earth
• human act assoc with increasing GHG incl burning ff => increase atmospheric gases, more infra-red will be absorbed, scattered and retained as heat

• defn: when an activity raises threats o harm, measures should be taken even if cause and effect relationship not scientifically est
• if effects o human induced change would be large, perhaps catastrophic, those responsible must prove tt it will not do harm before proceeding
• reverse o norm where those who concerned with change have to prove WILL do harm to prevent such changes

• strong evidence tt human activities, inclu burning ff and destruction forests causing enhanced greenhouse effect, no proof yet
• failure to slow down rising lvl carbon dioxide has conseq incl
• rising sea lvls = meltdown ice caps glaciers, warming
• permanent flooding lowland territory: vast number people live, agricultural land
• destruction forests: global temps too high to support survival and growth o trees in many parts
• interruption ocean current syst: distri warm waters fr tropics northwards, disrupt agricultural production lvls
• economic costs will be high
• some polit and business argue no need bc no direct proof
• but precau prin dictates tt measures still considered /action taken, potential great harm future gen = high
• may be too late
• action to take: conserving ff, sparingly use, develop renewable power sources / nuclear, biofuel, well insulated homes, ending forest destruction **
• strong action: international agreement and acted on by everyone simultaneously 
• developed countries need to share industrial benefits with less developed or they would have to go through same revolution
• anyone argues for continuation need to prove not cause damaging increase first according to PP

• Increased rates o decomposition o detritus previously trapped in permafrost (will increase microbial contribution to CH4 and CO2 and thus further enhance greenhouse effect)·
• Expanded range o habitats available to temperate species (Will alter ecosystems and an expansion o boreal forest will contribute to further warming o these regions since absorb radiant energy unlike ice and snow, reflect it)·
• Loss o ice habitat (leads loss ecosystems and lowland flooding)·
• Change in distribution prey species affecting higher trophic lvls (e.g. insect eating species, esp birds, will change their ranges in response to increase number o insects; ranges o many animals and plants will change)·
• Increased success pest species, including pathogens (changing habitat will expand range and ability to survive, particularly in regions where cold temperatures limit their ranges)

Natality: offspring produced and are added to population·

Mortality: individuals die and are lost fr population·

Immigration: individuals move into area fr elsewhere and are added to population·

Emigration: individuals move out o area to live elsewhere and are lost fr population

• Overall change in population size calculated
• Population change = (natality + immigration) – (mortality + emigration)

• Regular measurement of size of population  = population graph
• Three main phases of this curve are explained by change in natality and mortality
• Exponential – population may be new to area; slow start with lag phase·
• Population increases exponentially bc natality rate exceeds mortality rate·
• Resources needed by population, such as food, are abundant·
• Diseases and predators are rare

• resources not plentiful;
• disease may start to spread·
• Natality rate starts to fall and/or mortality rate starts to rise·
• Natality rate still exceeds mortality rate, so population size still rises but less rapidly

• Natality rate and mortality rate are equal so population size is constant·
• Density-dependent factors have limited population growth such as:
• i. Shortage of resources such as food / shelter
• ii. Increase of predators
• iii. Increase disease / parasites·
• become more intense as population size rises, and work together to reduce natality or increase mortality·
• Populations tend to fluctuate around carrying capacity (k)

• unlimited resources the population would increase exponentially.
• environmental resistance limits the population growth and determines the carrying capacity of the habitat
• shortage of food or prey
• predation or parasitism
• disease
• accumulation of waste
• Shortage of space or territory

Evolution is cumulative change in heritable characteristics of a population

theory of evolution requires evidence to show that organisms change overtime, production of new species of organism and that the mechanism is natural selection

• Reliable methods of radioisotope dating = ages of rock strata and fossils within· 
• Sequence o fossils in strata matches sequence in which would be expected to evolve (bacteria and simple algae first; vertebrates much later) 3.5 BYA·
• Sequence also fits in with ecology o groups, with plant fossils appearing before animal, plants on land before animals on land, and plants suitable for insect pollinators before insect pollinators·
• Many sequences o fossils are known which link together existing species with their likely ancestors

• Similarities exist in structures btwn some groups organisms·
• E.g forelimb structure pentadactyl limb o vertebrates
• Structures may look superficially different, and perform different functions but they have structural similarities tt indicate that species tt possess homologous structures may have evolved fr common ancestor tt had same kind of structure·
• Adaptive radiation fr common ancestor resulted in species tt have homologous structures tt have diff functions, but same pattern or structure

• Humans have deliberately bred and used particular animal species for thousands o years e.g. dog, cats, chickens, cow·
• Animals breeds used for livestock are clearly related to wild species in many cases can interbreed with them·
• Domestic breeds have been developed fr wild stock by selecting indic with desirable traits and breeding fr them·
• Artificial selection: process selecting desirable traits,·
• Evidence tt species can evolve rapidly, in comparison to geological time, is provided by the diverse heritable characteristics seen in domesticated breeds
• ***Process o selection desirable traits = artificial selection

• populations tend to produce more offspring than the environment can support
• bc populations living organi. increase exponentially

• 'struggle for survival' is a consequence of over-population.
• exponential growth population
• most part numbers indiv pop remain nearly constant
• environmental resistance
• struggle for existence in which some individuals survive and some die (failure compete successf. for limited resources)
• Some individuals have characteristic (or combination ) => competitive advantage.
•  individuals are consequently 'fitter' in terms of freedom from disease, food availability
• more likely to successfully reproduce

members of a species show variation

• natural selec. selects for or against certain heritable characters which lead change in allele freq over time
• variation essential for natural selec, and evol to occur
• members of a species show variation, differ in ways
• some individ have characteristics tt make them well adapted to their environ, other vice versa
• better adapted indiv tend to survive and reprod more than less well adapted = natural selection
• much variation = heritable passed on to offspring
• advantageous alleles has increased
• results o natural select. accumulate
• one generation follows another characteristics o species gradually change / species evolve

• variation can be introduced to population in various ways incl mutation, sexual reprod, conjugation
• meiosis: huge variety o genetically different gametes can be prod b one indiv through indepedent assortment and crossing over (recombination)
• fertilization: allows alleles fr two indiv to be combined together in one new individ
• conjugation/transform: bact which reprod asexually through binary fission can also exchange pieces DNA (conjug) or uptake DNA fr surroundings (Trans)
• asex reprod organis. can acq variation through mut, conjug, or trans, but w/o sexual reprod, variation is less and capacity evol less