Topic 5 on the wild side Flashcards
succession
Is the progressive change in the composition and diversity of a species in a community in one place over a period of time
primary succession
starts in a newly formed habitat where there has never been a community before.
Climax community
stable final community
nature of species present depends on environment
have lower biodiversity when preceding stages in succession as dominant species out compete others.
pioneer species
the first species to colonise
They are the only species that can cope with the extreme conditions
secondary succession
occurs where there is habitat destruction
on bare soil where an existing community has been cleared
soil already contains seeds (seed bank)
deflected succession
community that remains stable because of human activity prevents succession
this prevents the loss or change in biodiversity in certain areas.
different methods for studying climate change
- temperature records
- studying peat bogs
- pollen grains in peat bogs
- dendrochronology
- changing rainfall patterns
- ice cores
temperature records
1650 to present only in certain places may have been collected with less accurate equipment
dendrochronology
study of tree rings
every year produce new layers of xylem vessels the diameter of these vary from season to season.
wide vessels in spring. narrow in summer and they produce none in autumn and winter
different width of rings tells us the condition of that year
can’t give precise dates
but can go back 3,000 years
ice cores
goes back 400,000 years
as water freezes bubbles of air become trapped with in the ice the ratio of the different O2 isotopes gives an estimated average air temperature when ice was formed
peat bogs
peat is the accumulation of partially decayed organic matter
anaerobic and acidic conditions prevent decay.
as absence of oxygen and low pH reduces activity of microorganisms
by studying plant and insect remains especially pollen grains tells us about air temperature.
pollen grains
goes back 20,000 years
pollen grains from peat
- plants produce vast amounts of pollen
- pollen grains have a tough outer layer resistant to decay
- each species of plant has distinct pollen
- peat forms in layers the deeper it is the older. use carbon-14 dating to work out age
- each species has a set of optimum ecological conditions. allowing us to infer what temperature conditions where like.
changing rainfall patterns
an increase in rainfall amount in winter slight decrease in spring and increase in rainfall on wet days means total rainfall increased on wet days. But less total rainfall as there are less wet days. these changes are consistent with climate model
greenhouse gas
a gas in the atmosphere that stops the infra-red radiation from escaping creating a greenhouse effect keeping the earth warm
carbon dioxide
greenhouse gas
strong correlation between temperature and CO2 concentration.
CO2 concentration has been rising since 1750 due to the industrial revolution
rise in CO2 concentration leads to a rise in temperature followed by a rise in CO2 released from the oceans leading to further warming
methane CH4
greenhouse gas
produced by anaerobic decay of organic mater in landfill. incomplete combustion of fossil fuels absorbs more IR than CO2 but has a shorter retention time could be reduced by better waste recycling and using bio fuels
when burned produces CO2 and H2O
why is global warming a controversial issue
science cannot prove theories only disprove them
in complete knowledge of climate system data sets being used to make predictions has limitations
there is not precise way to measure CO2 produced
what are the ethical arguments surrounding climate change and global warming
- well all have the right to choose whether or not we use fossil fuels to achieve good standard of living
- we have a duty to allow others to improve their standard of living
- we have a duty to preserve the environment for the next generation
what other factors affect climate change other than CO2
- other greenhouse gases
- aerosols - extremely small particles or liquid droplets
- degree of reflection on earth surface covered by ice or snow.
- the fraction of earth covered with ice and snow
- extent of cloud cover
- changes in the sun radiation
why are climate change predictions often incorrect
- limited data
- limited knowledge of how climate system works
- limitations in computing resources
- failure to include all factors affecting the climate
- changing trends in factors included e.g faster than expected loss of snow or ice or greater CO2 emissions
why do climate models predict a cooler UK
as the Artic sheet ice reduces there is an influx in fresh water into north Atlantic which freezes at 0oc expands rising to the surface rather than sinking as salt water does at that temperature
the north Atlantic drift breaks down as a result stopping bringing warm waters to Britain causing surface temperature in north west Europe to fall by 5oc
why are trees particularly vulnerable to climate change
they are unable to grow, reproduce and disperse seeds quickly enough to cope with changing conditions.
their distribution changes more slowly than the climate changes
what changes in populations and ecosystems caused by climate change
- changing distribution of species
- altered development and life cycles
increasing temperature means photosynthesis rate becomes
faster leading to faster growth
warmer conditions leads to increase in temperature crop yield
in cooler climates photosynthesis is temperature limited a rise in temperature will result in faster photosynthesis as enzyme catalysed reactions occur more quickly. Above a certain temp plants enzymes work more slowly.
temperature coefficient Q10
Q10 = rate of reaction at temperature T + 10oc / rate of reaction at temp T
the rate of collision and so the rate of reaction approximately doubles for each 10oc rise in temperature this is shown in the Q10 ratio
describes mathematically what happens to the rate of reactions as temperature increases by 10oc
what is the effect of low temperature on enzyme activity
at low temperature reaction is very slow because the enzyme and substrate molecules have low kinetic energy and so move more slowly and collide less often.
meaning there are fewer enzyme substrate complexes formed in a given time
what is the effect of high temperature on enzyme activity
as temperature increases rate increases.
as enzyme and substrate molecules have high kinetic energy and so move faster and collides more. therefore the substrate binds with the enzymes active site more frequently.
what is the Q10 for most enzyme controlled reactions
Q10 between 2 and 3
this is the factor by which the rate changes
a value of 2 means the rate of reaction doubles with a 10oc rise.
a value of 3 means it triples.
optimum temperature
the temperature at which rate of reaction is highest
if the temperature rises above this enzyme molecules vibrates and bonds break preventing substrate from fitting into active site slowing reaction eventually shape of active site is lost and enzyme is denatured.
phenology
the study of seasonal events timing of events is a useful biological indicator of global climate change
why may climate change reduce survival rates in hatching birds
if temperatures rise there may be a mismatching between hatching time and peak food available
the emergence of adults is synchronised with periods of max food availability
different evidence for evolution (4)
- DNA hybridisation
- DNA molecular clocks
- DNA profiling
- DNA and protein sequencing
DNA hybridisation
molecular evidence for evolution by separating strands of DNA of two species and then mixing 1 strand from each species so the strands will form H bonds with each other forming hybrid DNA. nor all bases will have complementary base pair and form H bond. so when heated will denature at lower temperature.
the more similar the sequences the higher the temperature to denature.
DNA molecular clocks
use of PCR and automated DNA sequencing machines to rapidly determine DNA base sequence as species evolve they accumulate random mutations at a regular rate becoming more genetically different. For a given gene, mutation rate is fairly constant molecular rate is fairly constant molecular change in DNA overtime used to make a molecular clock , which pinpoints important evolution event.
by comparing no. of differences between species possible to calculate how long ago their shared ancestor existed
DNA profiling
PCR and gel electrophoresis.
restriction enzymes cut DNA at specific sequences producing different sized fragment s which can be visualised as series of bands.
If a mutation has occurred the enzyme will not cut the DNA and size of fragment and position of band will change
differences in fragment lengths produced provide info about genetic differences.
the more closely related the more bands on the profile will match
DNA and protein sequencing
by comparing the sequence of bases in DNA or the amino acid sequence of different species it is possible to determine how closely related organisms are in evolutionary terms
if 2 species have very few differences they evolved from a common ancestor more recently than organism with more differences.
peer review
where reviewers examine paper critically checking work is valid. if it includes the proper controls, use of statistics appropriately and compare it to other research to see if conclusions are justified.
peer remain anonymous as this allows the freedom to be critical without causing offence, it prevents the author from influencing the reviewers.
conferences
- allow scientists to review new findings and question those present
- allows scientists to communicate with collages discus current ideas and spark new ideas and future projects
- enable funding bodies to assess outcomes of the research they are paying for
Darwin’s observations and conclusions
- there is a struggle for existence. competition
organisms produce more offspring than can survive and reproduce. numbers in natural populations stay same overtime. - survival of the fittest. Natural selection
there is a huge variation with species.
those species best adapted to conditions are more likely to survive and breed.
Darwin’s theory
struggle for existence
the idea of competition for survival between members of the same species.
as a population increases in size environmental factors halt the increase.
many individuals die to prediation, competition for food and other resources or due to the rapid spread of disease resulting from overcrowding. population remains constant.
Darwin’s theory
survival of the fittest and natural selection
those individuals that are best adapted to conditions in their environment are more likely to survive and breed
they have a selective advantage
individuals with these adaptive features will be more common in the next generation. the organisms that are not well adapted die and do not produce offspring over a period of time the characteristics change to adapted form
evolution
the change in allele frequency in a population of organisms overtime
allele frequency
relative frequency of a particular allele in a population
speciation
the formation of new and distinct species in the course of evolution
how does allopatric speciation occur
- geographical barrier causes 2 populations to become re-productively isolated.
- the 2 groups are exposed to different selection pressures leading to random advantageous mutations accumulating causing allele frequency in the 2 populations to change
- overtime the allele frequency changes so much that when reintroduced they are not able to interbreed to produce fertile offspring.
allopatric speciation
occurs where populations are geographically isolated from one another.
preventing the group from mating with each other and so the population becomes re-productively isolated.
sympatric speciation
this occurs where the 2 populations become reproductively isolated in the same environment without any geographical barriers, due to other isolating mechanisms
what are the isolating mechanisms that cause sympatric speciation (6)
- ecological isolation
- temporal isolation
- behavioural isolation
- physical incompatibility
- hybrid in-availability
- hybrid sterility
what is ecological isolation
sympatric speciation
the species occupy different parts of the habitat
what is temporal isolation
sympatric speciation
the species exist in the same area but reproduce at different times
what is behavioural isolation
sympatric speciation
the species exist in same area but do not respond to each other’s courtship behaviour
what is physical incompatibility
sympatric speciation
species co-exist but there are physical reasons that prevent them from copulating
what is hybrid in-availability
sympatric speciation
in some species, hybrids are produced but don’t survive long enough to reproduce
