natural selection and evolution Flashcards
why does burning wood chips not increase co2 in atmosphere in long term
co2 produced by burning wood replaces that absorbed by the trees
trees absorb co2 from atmosphere for photosynthesis
new trees are grown to replace those that are cut down
therefore no net co2 increase
explain how two species of african elephant could evolve from a common ancestor
two populations geographically isolated from each other
therefore reduced gene flow between two populations
leads to allopatric speciation
different selection pressures leading to natural selection
explain how reforestation of tropical rainforests can be used to minimise climate change
new/ growing trees result in net uptake of co2
therefore reducing co2 in atmosphere
slows the rate of global warming
explain why % of elephants without tusks may increase in future
many elephants with tusks were killed
elephants without tusks were more likely to survive and breed
therefore passing on alleles for not having tusks
increasing frequency of homozygous recessiveness int he population (no tusk phenotype)
describe how forests can be managed as a sustainable resource
replacing trees that have been cut down
cut down older trees
replace with seedlings/ rapidly growing trees
explain the impact of cutting down trees on climate change
less photosynthesis
less c fixed so more co2 in atmosphere
co2 is a greenhouse gas so more energy trapped in the atmosphere
more energy in atmospehre= increase in temperature
explain why sloth population may change in future
(found in south and central america, currently two species)
may increase due to fragmentation of habitat
different selection pressues
different allele frequencies within separate populations
evolution leading to formation of new species
may decrease to:
only one population
could be vulnerable to inbreeding depression
at risk of natural disaster, disease, predation
therefore may become extinct
