6.3.2 Populations and sustainability Flashcards
lag phase features
reproductive rate is slow
population size is small
takes time for dispersed individuals to find each other to mate
acclimatising to habitat
exponential phase (log) phase features
reproductive rate > death rate
pop. size increases rapidly
plenty of resources e.g. food (little competition)
little disease
few predators
no overcrowding
low environmental resistance (biotic and abiotic factors which limit population growth)
stationary phase features
reproductive rare = death rate (population size remains stable)
habitat cannot support larger population
reached carrying capacity (k)
carrying capacity definition
maximum number of individuals in a population supported by a particular habitat, determined by limiting factors
(k)
factors limiting population growth and effect
food water space light oxygen predation disease competition prevents populations from exceeding carrying capacity
r-strategists features
higher reproductive rate quicker development of population earlier reprodutive age shorter life span smaller body mass
k-strategists features
lower reproductive rate slower development later reproductive age longer life span large body mass
boom and busts method
some species exceed their carrying capacity due to rapid reproductive rate
once exceeded, insufficient resources to maintain the population and some die
death also caused by build up of waste products
predator-prey relationship
prey population increases when predator numbers are low and low environmental resistance with few limiting factors
more prey = more food for predators
population of predator increases after a long time
more prey eaten by predators = prey numbers decrease
less food for predators, fewer survive and predator numbers decrease
cycle repeats
prey population reach higher than predators
intraspecific competition features
within species
as environmental pressures increase (factors become limiting), competition increases
those best adapted survive, reproduce and pass on their genes (others die)
keeps stationary phase stable
interspecific competition features
between 2 or more different species
competitive exclusion (when differenr species populations grow together but one dies out due to competition)
or
species fill out slightly different niches (both persist populations grow much slower than when grown alone)
conservation definition
using nature in a sustainable manner
active management of ecosystem
preservation definition
protection of ecosystem from interference so that it remains in its original state
how increasing human populations threatened biodiversity
over-exploitation of wild populations for food
disrupting habitats with urbanisation and pollution
introduicng non-native spcies which competitively exclude native species
dynamic conservation definition
preservation of organisms and environments that are at risk from human activity
requires management and the creation of new habitats, which may need reclamation of land
ecosystem management strategies examples
reclaim ecosystem by reversing effects of human activity
raise carrying capacity by providing more food
introduce more individuals to enlarge populations
create corridors which connect fragmented habitats (allow species to move between them)
restrict dispersion of individuals by fencing
control predators and poachers
vaccinate individuals against disease
preservatipn of habitats by protecting against pollution or disruption or restrict succession (copping, grazing, etc.)
what is clear-felling and why it’s bad
clear-felling = completely cutting down all of the trees in an area
trees take up water from soil and stops soil erosion, which pollutes rivers
trees keep nutrient levels in balance in carbon and nitrogen cycle
clear-felling leads to opposite
sustainable production definition
harvesting in amounts which leave sufficient organisms to grow and replenish what has been harvested and can be carried on indefinitely
sustainable forestry features
woodland must be able to maintain its ecological function of biodiversity, climate, mineral and water cycles
local people should benefit from forest
balance is needed between making money, supplying plenty of wood and maintaining biodiversity
how to ensure each tree yields maximum amount of wood
control pests and pathogens
only plant tree species that grow well in an area
plant trees optimal distances apart to prevent too much competition for light, water and minerals
coppicing features
cuts tree trunk close to ground to encourage new, thinner stems to grow
thin wood can be used to furniture, firewood etc. but trees don’t die and no replanting needed
rotational coppicing method
woodland divided up and different sections coppicing on different years
coppicing can be done continuously to provide continuous supply of wood
standards = trees left uncoppiced and cut to produce larger timber for planks (more value)
pollarding definition
cutting higher up the tree to prevent herbivory
aquaculture features
breeding, rearing and harvesting of plants and animals in all types of water environments
restricts impact on oceanic fish stocks
fisheries economic feature
high economic value (sales + jobs)
marine stewardship council principles for sustainable management
overfishing must be avoided to stop extinction of species (aim to maintain population at its carrying capacity and only harvest excess numbers)
no permanent damage to local habitats (maintains structure and function of ecosystems)
always comply with local, national and global regulations (be flexible with these)
