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Flashcards in Populations and Sustainability Deck (53)
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what is the carrying capacity


this is the maximum population size that can be maintained over a period in a particular habitat


what is a limiting factor


the factor whose magnitude slows down the rate of a natural process, usually stop growth in the population when the habitat reaches carrying capacity


Draw population graph


draw it


what determines size of a population

  • the balance between death rate and the rate of reproduction

what is the graph made up of


the lag phase
the log phase
stationary phase


describe the lag phase


there are only a few individuals which are still acclimatising to their habitat, at this point the rate of reproduction is low and the growth in the population size is slow


describe the log phase


resources are plentiful and conditions are good, reproduction can happen quickly with the rate of reproduction exceeding morality so the population size increases rapidly


describe the stationary phase


the population size has levelled out at carrying capacity of the habitat, the habitat cannot support a larger population and in this phase the rates of reproduction and mortality rates are equal, the population size therefore stays stable or fluctuates very slightly up and down in response to small variations in environmental conditions each year


what types of limiting factors are there


density dependent

density independent


describe density dependent


when the factor infleunces the population more strongly as population size increases, for example availability of food, water, light, oxygen, shelter decrease, as population size increases level of predators increase and competition increases for both individuals of the same species and individuals of other species, the carrying capacity is the upper limit that these factors place on the population size


describe density independent


act just as strong irrespective of the environment for example low temperatures may kill the same proportion of individuals in an environment irrespective of its size


what are the two types of strategist


K- strategists

R- strategists


what is a k-stratgist

  • this is a species whose population size is determined by the carrying capacity

describe what influences a K-strategist


populations limiting factors exert a more significant effect as the population size gets closer to the carrying capacity causing the population size to gradually level out


describe the characteristics of K-strategists

  • Low reproductive rate
  • Slow development
  • Late reproductive age
  • Long lifespan
  • Large body mass

what is a R-strategist


in these species the population size increases so quickly that it can exceed the carrying capacity of the habitat before the limiting factors can start to have an effect


describe what influences an R-strategist

  • Once carrying capacity has been meet there are no longer enough resources to allow individuals to reproduce or even to survive, and an excessive build up of waste products may start to poison the species and they begin to die entering a death phase, this is known as boom and bust

what are the characterstics of an R-strategist

  • High reproductive rate
  • Quick development
  • Young reproductive age
  • Short life span
  • Small body mass

what is the most important influence on population growth

  • Most important influence on population growth is the physical rate at which individuals can reproduce, this type of growth is characerstic of species with short generation times and of pioneer species, quick population growth means pioneer r-strategist species colonise a disturbed habitat before K-strategists, dispersing to other habitats once limiting factors start to have an effect

Draw graph for population growth in r-strategist species




what is intraspecific competition


competition between individuals of the same species


what is interspecific competition


competition between individuals of different species


describe how predators can act as a limiting factor for prey which can then affect the predators population size

  1. When the predator population gets bigger more prey are eaten
  2. The prey population then gets smaller leaving less food for the predators
  3. With less food fewer predators can survive and their population size reduces
  4. With fewer predators fewer prey are eaten and their population size increases
  5. With more prey the predator population gets bigger and the cycle starts again

when does competition happen


when resources are not present in adequate amounts to satisfy the needs of all the individuals who depend on those resources, if a resource is in short supply in an ecosystem there will be competition between organisms for that resource, as the intensity of competition increases the rate of reproduction decreases whilst the death rate increases


describe intraspecific competition

  • Intraspecific competition happens between individuals of the same species as factors such as food supplies become limiting, individuals compete for food, those individuals best adapted to obtain food survive and reproduce whilst those not so well adapted fail to reproduce or die
  • May be fluctulations during the stationary phase but size remains stable
  • If population size decreases competition reduces and the population size increases
  • If population size increases competition increases and the population size drops

describe interspecific competition

  • This happens within individuals of different species and can affect both the population size of a species and the distribution of species in an ecosystem
  • If two spieces niche overlap then this results in more intense competition and if the niches are the same then one is outnumbered by the other and dies out, two species cannot occupy the same niche, this is the competitive exclusion principle and can be used to explain why particular species only grow in particular places
  • On the other hand sometimes interspecific competition simply results in one population being smaller than the other with both population sizes remaining relatively constant
  • In a lab it is easier to exclude the effects of other variables so the habitat of the two species remains stable, in the wild a wide range of variables may act as a limiting factors for the growth of different populations and may change on a daily basis or over the course of a year

what is conservation


this is the maintenance of biodiversity, including diversity between species, genetic diversity within species and maintenance of a variety of habitats and ecosystems


what is preservation


maintenance of habitats and ecosystems in their present condition minimising human impact


what are the threats to biodiversity

  • Over exploitation of wild populations for food, for sport, for commerce
  • Habitat disruption and fragmentation as a result of more intensive agricultural practises, increases pollution or widespread building
  • Species introduced to an ecosystem by human that out compete other native species leading to their extinction

what does successful conservation require


requires consideration of the social and economic costs to the local community and effective education and liaison with the community


what does conservation involve

  • establishing national parks
  • green belt land
  • sites of special scientific interest
  • legal protection to endangered species or conserving them

describe the management strategies for conservation

  • Raise carrying capacity by providing extra food
  • Move individuals to enlarge populations or to encourage natural dispersion of individuals between fragmented habitats by developing dispersal corridors of appropriate habitat
  • Restrict dispersal of individuals by fencing
  • Control predators and poachers
  • Vaccinate individuals against disease
  • Preserve habitats by preventing pollution or disruption or intervene to restrict the progress of succession by for example coppicing, mowing or grazing

describe the negatives of managing a community in conservation

  • Sometimes management is inappropriate as disruption of a community may have gone too far, understanding which species was part of the original community is not always celar and succession is likely to take a long time before it allows a community to survive again – short cutting takes large knowledge of the species involved
  • Where environment conditions have remained stable it is possible to clean up pollution, remove unwanted species or recolonise with the original species for example captive kl
  • community with a slightly different community rather than to rehabilitate the original community

why do we conserve

  • ethics

- economic and social reasons


describe ethical reasons to conserve

  • Species have value and humans have an ethical responsibility to look after them
  • Subjective arguments
  • Arguments in favour of human activities work against conservation and are driven by economics, expressing the value of conservation in economic terms is more effective in driving governments to prioritise conservation

describe economic and social reasons to conserve species

  • Many species already have direct economic value when harvested, this value is the easiest to measure, others may also have direct value that is not recognised
  • Many plant and animal are our food source and were originally domesticated from wild species
  • Genetic diversity in wild strains may be needed in the future to breed for diseases resistances and improve yield in animals and plants and drought tolerance in plants
  • Natural environments are value source of potentially beneficial organism, many of the drugs we use today were discovered in wild plant species
  • Natural predators of pests can act as biological control agents – preferable to causing pollution with artificial chemicals but few species are yet being used
  • Many species have indirect economic value, also difficult to quantify
  • Other communities are important in maintaining water quality, protecting soil and breaking down waste products
  • Ecotourism and recreation in the countryside also have significant social and financial value which derives from aesthetic value of living things
  • Reduction in diversity results in droughts or flooding and associated economic costs

how to manage timber production

  • use small scale timber production

- use large scale timber production


describe small scale timber production

  • Coppicing provides a sustainable supply of wood
  • The stem of a deciduous tree is cut close to the ground and once cut new shoots grow from the cut surface and mature into narrow stems, these can be used for fencing, firewood or furniture, after cutting them off new shoots start to grow again and the cycle continues
  • Provide a consistent supply of wood, woodland managers divide a wood into sectiosn and cut one section each year, this is rotational coppicing and by the time they want to coppice the first section again the new stems have grown and have matured
  • In each section some trees are left to grow larger without being coppiced and these trees are called standards and are harvested to supply larger pieces of timber
  • Rotational coppicing is good for biodiversity, as left unmanaged woodland goes through process of succession blocking light to the woodland floor and reducing the number of species growing there, but in rotational coppicing different areas of woodland provide different types of habitat letting more light in and increasing the number and diversity of species

describe large scale timber production

  • Large scale production of wood for timber involved clearing all the trees in one area which destroys habitats on a large scale, reduces soil mineral levels and leads soil susceptible to erosion, trees usally remove water from soil and stop soil beign washed away by rain, soil may run off into waterways polluting them, trees also maintain soil nutrient levels through their role in carbon and nitrogen cycle
  • Now have the following principles …
  • Any tree which is harvested is replaced by another tree
  • The forest as a whole must maintain its ecological function regarding biodiversity, climate and mineral and water cycles
  • Local people should benefit from the forest
  • Selective cutting involves removing only the largest and most valuble trees leaving the habitat broadly unaffected
  • Sustainability maganing forests involves balancing conservation against the need to harvest wood both to maintain biodveristy and to mae the woodland pay for itself, if each tree supplies more wood, fewer trees need to be harvested therefore foresters..
  • Control pests and pathogens
  • Only plant particular tree species where they know they will grow well
  • Position trees an optimal distance apart, if trees are too close this causes too much competition for light and they grow tall and tin producing poor quality timber

describe the principles for the management of fisheries

  • Fishing must take place at a level which allows it to continue indefinitely, over-fishing must be avoided because it can reduce fish populations to zero, reduce fishing if over fishing happens and this can increased productivity and is good for profitability, given high stock values it can support a more efficient harvest
  • Fishing may be managed to maintain the structure, productivity, function and diversity of the ecosystem, this means that there should not be permanent damage to the local habitat and any effect on dependent species is minimised
  • Fisher must adapt to changes and comply with local, national and international regulations

describe aquaculture

  • Provides sustainable fish stocks, raising stocks of fish in aquaculture restricts the impact on oceanic fish stocks and it is expanding rapidly, feed more people than traditional capture fisheries

what are the two examples of successful conservation


Terai region

Maasai Mara


describe conservation in the Terai region

  • In the south of Nepal is the Terai region made up marshy grasslands, savannah and forests
  • Densely population and home to endangered species
  • Many national parks in the region
  • For over 10 years the forests in the terai region have been under pressure from expansion of agriculture into forested resrouces and replacement of traditional agricultural crop varieties with modern ones, in response the WWF found that rural livelihoods are heavily dependent on the forests which are also home to many of the regions endangered species, forests can provide local people with a sustainable source of fuel, animal feed, food, building materials, agricultural and household tools as well as medicines
  • Local people have such a high stake in the forests the WWF with Nepalese government in the Terai arch landscape programme focused on conservation of the forest landscape as a whole, to ensrue conservation with development they introduced community forestry initiatives in which local people had rights to exploit the forest as well as look after it
  • Helped to create forest corridors between national parks which are essential to the dispersal and survival of tigers and they counteracted poachers and illegal felling
  • Forestery work also developed and diversified on and off farm activity, built entrepreneurial skills and stimulated small credit and marketing schemes
  • Other contributions to the Terai-arc project included constructing waterholes, monitoring endangered speicies and eradicating invasive species
  • Community involvement combined with governmental and non governmental leadership is successful and the tigers are using the corridors between national pars and their population size is steadily growing

describe conservation in the Maasai Mara region

  • It is a famous destination for wildlife watchers, with large populatiosn of antelope and other large mammals, because the maasaio mara combines high endemic poverty with abundant wildlife populations that attract tourism, there has been scope to develop conservation-compatible land that rewards local people financially whilst conserving habitats and species that are the basis for tourism
  • After the creation of national parks reminaing Maasia land was held in trust until 1968, this was when the lands were designated as group ranches, worried about their tenure on the land many maasai took individual title over smaller portions – triggerland use change
  • Amount of agriculture increased and this limited wildlife to increasingly small islands and constrainted the movement
  • Density of wildlife dropped 65% over the last 30 years and the density of sheep and goats increased, in 2005 several land owners to the north of the maasai mara reserve consolidated their land to form vonservancies in order to generate tourism income
  • Partnerships between conservancies and tourism have developed payment for wildlife conservation schemes
  • Conservancies are paid PWC revenue proportional to the area of land set aside for conservation, these conservancies are successful because they have positive social outcomes as well as positive conservation outcomes
  • There are some negative consequences of the conservancies, land owners must move their livestock out during the tourist season which leads to increased stocking densiites outside the reserve where no one received PWC money
  • Livestock have been seen as a problem for conservation however there is evidence that limited livestock graxing can have positive impacts of diversity, given how important livestock are in maasai culture and it would make sense to continue to intergrate conservation and livestock management more directly

what have humans used on the galapagos islands

  • habitat distrubance
  • over-exploitation of resources
  • effects of introduced species

describe habitat disturbance of the Galapagos islands

  • The population size increase has placed huge demands on water, energy and sanitation services, more waste and pollution has been produced and the demand for oil has increased
  • Oil spill had an effect on marine and coastal ecosystems
  • Building and conversion of land for agriculture has caused destruction and fragmentation of habitats
  • Forests of scalesia trees and shrubs have been almost eradicated on santa cruz and san christobal to make way from agricultural land

describe over-exploitation of resources on the Galapagos Islands

  • In the nineteenth century whaling boats and fur traders killed 200,000 tortoises in less than half a century
  • Charles Darwin research station has a captive breeding programme to supplement tortoise numbers
  • More recent boom in fishing for exotic species has depleted populations, depletion of sea cucumber populations has a drastic effect on underwater ecologoy and the international market for shark fin has led to the deaths of 150000 shark each year and around the islands including 14 endangered species

Describe the effect of introduced species on the Galapagos islands

  • As well as out competing local species, alien species can eat native species, destroy native species habitats or bring disease onto the islands, for example cats hunt a number of species including lava lizard and young iguanas
  • Goats feed on galapoagos rock purslane, a species unique to the islands and trample and feed upon giant tortoises, food supply and disrupt their nesting sites,
  • On the northern Isabela island, the goat has transformed forest into grassland leading to soil erosion
  • Red quinine is an affressively invasci species on santa cruz island, it occupies the highlands and spreads rapidly as it has wind dispered seeds,
  • The ecosystem in the highlands has changed from low scrub and grassland to being a closed forest canopy, this means that the native cacotilo shrub has been almost eradicated from santa cruz and the Galapagos petrel has lost its nesting sites
  • Red quinie also successfully out-competes native scalesia trees

how do they manage the effects of human activity in the Galapagos islands

  • Charles Darwin research station adopted two startegies, to prevent the introduction and dispersion of introduced species and to treat the problems caused by such species
  • They search arriving boats and tourists for foreign species
  • Natural preadtors have also been exploited to reduce the damage caused to the ecosystem by pest population, for example a controlled release of a ladybird wiped out a scale insect which was damaging plant communities
  • Culling has also been successful against feral goats on Isabela island and pigs on Santiago island
  • Because most residents were not born on the island, fostering a culture of conservation and educating new arrivals about the island is a challenge
  • Galapagos marine reserve provides a model of how local stakeholders can work together to sustainably manage a resource
  • Reserve is managed by the national park services, the Charles Darwin research station and representatives of local fisherman, the tourists industry and naturalist guides
  • 36% of ones have be designated no take areas where no extraction of resources is allowed and communities are left undisturbed

what are the effects on the Antarctic

  • Krill
  • protected areas
  • albatrosses and petrels

describe the effect of Krill on the Antarctic

  • Tiny shrimp like organisms which provide food for whales, seals, penguins, albatrosses and squid
  • Used to make nutritional supplements and for anima feed
  • Recent changes in technology mean a large amount of krill can be harvested quickly
  • Fishing boats go to the areas with the larger nuber of kirll
  • Natural predators of krill cannot adapt easily to find krill elsewhere for example penguins do not migrate very far when raising young
  • There is a trigger level catch size in areas,
  • Fishing must be conducted equally across all areas up to the total catch limit to avoid a catastrophic impact on predators

describe the effect of protected areas on the Antarctic

  • Protected areas have been established
  • The sourthern ocean whale sanctuary was established in 1994, covering the summer feeding grounds of 80-90% of the worlds whales, this followed the 1982 moratorium on whaling established by the international whaling commission
  • Within the sanctuary it is illegal to hunt and kill whales although monitoring of whaling activity still need to be maintained to ensure the sanctuary is effective
  • Currently there is initiative to expand a network of marine protected areas such as in the ross sea

describe the effect of albatrossess and petrels on the Antarctic

  • Threatened by human activity including pollution, hunting and poaching for eggs, habitat destruction and introduction of non-native predators
  • Biggest threat is long line fishing, this is when fisherman trail a long fishing line behind their boat, Attached to this line are hundred of baited hooks, when behind the boat the birds try to eat the prey and swallow the hooks, to reduce the number of deaths boats use bird scaring lines and streamers, weighted lines which skin more quickly and out of reach of the birds, they use lines at night to avoid albatross and petrel feeing times and avoid breeding and nesting time