populations and sustainability Flashcards
define carrying capacity
the maximum population size that can be maintained over a period in a particular habitat
define limiting factor
the factor whose magnitude slows down the rate of a natural process
population growth graph
what are the names of point a, b and c
a= lag phase ,
b= log phase , c= stationary phase ,
describe lag phase
there may be a few individuals , which are still acclimatising to their habitat. at this point the rate of reproduction is low, and the growth in population size is low
describe log phase
resources are plentiful , and conditions are good. reproduction can happen quickly, with rate of reproduction exceeding mortality. the population size increases rapidly
describe stationary phase
the population has levelled out at the carrying capacity of the habitat . the habitat cannot support larger population. in this phase the rates of reproduction and mortality are equal. the populations size therefore stays stable , or fluctuates very slightly up and down in response to small variations in environmental conditions each year
what are density independent limiting factors
these act just as strongly, irrespectively of the size of the population
for example, particularly low temperatures may kill the same size proportion of individuals in a population , irrespective of its size
what are density dependent limiting factors
where the factor influences population more strongly as population size increases
for example , the availability of resources, like food , water , light, oxygen, nesting sites or shelter may decrease
what are the two types of strategies
r strategies
k strategies
r strategies and k strategies represent ….
two ends of a continuum of strategies adopted by living things
describe k strategies and give examples
species whose population is determined by the carrying capacity. for those 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
eg birds, larger mammals like humans , elephants and lions and larger plants
name k strategies characteristics
- low reproductive rate
- slow development
- late reproductive age
- long life span
- large body mass
describe r strategies and give examples
the population size increases so quickly that it can exceed carrying capacity of the habitat before the limiting factors start to have an effect . once the carrying capacity has been exceeded , there are no longer enough resources to allow individuals to reproduce or even survive . likewise an excessive build up of waste products may start to poison the species , and begin to die , entering a death phase
this type of population growth is known as boom or bust
for example , mice, insects, spiders, weds
name r strategies characteristics
- high reproductive rate
- quick development
- young reproductive age
- short life span
- small body mass
what is a predator
is an animal that hunts other animals (prey) for food
describe the predator prey graph steps
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 decreases
4-with fewer predators , fewer prey are eaten , and their population increases
5- with more prey , the predator population gets bigger and the cycle starts again
describe competition
competition happens when resources ( like food or water ) are not present in adequate amounts to satisfy the needs of all the individuals who depend on the resources . if a resource is in short reply in an ecosystem, there will be competition between organisms for that resource
- as the intensity of competition increases, the rate of reproduction decreases whilst death rates increase
what are the two types of competition
- interspecific competition
- intraspecific competition
describe intraspecific competition
competition between individuals of the same species
as factors such as food become limiting , individuals compete for food. those individuals best adapted to obtaining food survive and reproduce , or die , this slows down population growth and the population enters the stationary phase
describe interspecific competition
competition between individuals of different species
can affect both the population size of a species and the distribution of species in an ecosystem
what is competitive exclusion principle
two species cannot occupy the same niche
describe conservation
maintenance of biodiversity, including diversity between species, genetic diversity within species, and maintenance of a variety of habitats and ecosystems
more of an active management process involving human intervention.this includes maintaining not just the diversity between species but also genetic diversity within species, and also maintaining a range of habitats and ecosystems
describe preservation
maintenance of habitats and ecosystems in their present condition, minimizing human impact
keeping species and habitats as they are now. the approach known as preservation focuses on keeping things natural and eliminating any human effects on ecosystems that exist today
what are the threats to biodiversity
a steadily increasing human population can threaten biodiversity through
- over exploitation of wild populations for food and for commerce
- habitat disruption and fragmentation as a result of more intensive agricultural practices, increased pollution, or widespread building
- species introduced to an ecosystem by humans that out compete other native species, leading to their extinction
why do you conserve for ethical issues
they believe that every species has value and that humans have an ethical responsibility to look after them
why conserve for economic and social reasons
many species have direct economic value when harvested
- many plant sand animal species provide a valuable food source, and were originally domesticated from wild species. genetic diversity in wild strains may be needed in future to breed for disease resistance and improved yield in animals and plants, and drought tolerance in plants. likewise, new plant species may be domesticated for food use
- natural environments are a valuable source of potentially beneficial organisms. many of the drugs we use today were discovered in wild plant species
- natural predators of pests can act as biological control agents . this is preferable to causing pollution with artificial chemicals but few such species are yet being used.
- indirect - species are responsible for pollinating crop plants, therefore harvest increases
- ecotourism and recreation increase social and financial value
describe suitable management of ecosystems
the human population is getting larger increasingly quickly , and we have had to use more intensive methods to exploit our environment for resources . such approaches can disrupt or destroy ecosystems , reduce biodiversity , and even completely remove the resource we originally wanted to harvest, our use of natural resources is not sustainable
there is potential conflict between our need for resources and conservation
what are the two ways of managing timber production
small scale
large scale
what are the types of small scale timber production
coppicing
rotational coppicing
pollarding
describe coppicing
provides a sustainable supply of wood. the stem of a deciduous tree is cut close to the ground .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 and the cycle continues
describe pollarding
involves cutting the stem higher up to prevent deer eating the emerging shoots
describe rotational coppicing
to provide a constant supply of wood, woodland managers divide a wood into sections and cut one section each year
by the time they want to coppice the first section again the new stems have matured and are ready to be cut
what are the types of large scale timber management
clear felling
selective cutting
describe clear felling
cut down and remove every tree from (an area).
this destroys habitats on a large scale, reduce soil mineral levels and leave soil susceptible to erosion . trees usually remove water from soil and stop soil being washed away by rain. soil may run off into waterways , polluting them. trees also maintain soil nutrients levels throughout their role in the carbon and nitrogen cycles
describe selective cutting
involves removing only the largest , most vulnerable trees, leaving the habitat broadly unaffected
what are the two ways of managing fish stocks
fisheries
aquaculture
describe fisheries
has high economic value , but not just from sales of fish but in providing livelihoods for millions of people
- fishing must take place at a level which allows it to continue
- fishing must be managed to maintain the structure , productivity , function and diversity of the ecosystem
- must adapt to changes in circumstances and comply with local, national, and international regulations
describe aquaculture
can also provide sustainable fish stocks. raising stocks of fish in aquaculture restricts the impact on oceanic fish stocks. aquaculture is expanding rapidly, particularly in the developing world, and is expected to feed more people than traditional capture fisheries in the near future
balancing the conflict between conservation and human needs
describe the terai region
- made of marshy Greenland, savannah and forest
- many national parks
- endangered species
- under pressure form expansion of agriculture, grazing and over exploitation of resources
- forest can provide a sustainable source of fuel, animal feed, food, building materials , agriculture , food
- WWF focused on conservation of the forest
balancing the conflict between conservation and human needs
describe the massai mara
- attracts tourism, from conservation
- national parks
controlling the effects of human activities
describe the Galapagos islands
1-habitat disturbance, the population size increased placed huge demand on water, energy and sanitation services. more waste pollution
- oil spill ruined ecosystems
- land for agriculture
2-over exploitation for resources , killed half of tortoises
-fishing for exotic species has depleted populations
3- effects of introduced species- out competing local species and alien species can eat native species or habitats , or bring disease to the island
controlling the effects of human activities
the Antarctica
1 krill-large amounts can be harvested very quickly , natural predators of krill cannot adapt to find krill everywhere else - therefore fishing must be conducted equally across all areas
2- protected areas - protected areas have been established to protect whales , within the sanctuary it is illegal to hunt or kill whales
3- albatrosses and petrels - these birds are threatened by human activities such as pollution, hunting , poaching for eggs, habitat destruction. and on the fishing line there are hooks which can be swallowed , therefore increasing deaths , to decrease deaths they can have bird scaring lines and weighted lines so there out of sight from birds
the lake district
name some threats to biodiversity and the solutions
1- threat - spruce and pine conifer plantations support limited biodiversity
solution- recent initiatives have generated more varied planting and felling patterns , giving a mosaic of smaller stands of different aged trees
2-threat - invasive species spread into woodland , and outcompeting native species
solution- they are physically removed by conservation workers
3- threat- hay meadows secure a rich diversity of flowers and grasses , but are under threat due to a preference away from hay meadow
solution- farmers are paid to maintain hay meadows
Snowdonia national park
name some impacts by humans and the solution
impact
-farmers dig open drainage ditches to dry the land . however this causes poor water quality in rivers, and rain flows quickly through the habitat, increased flood risk
solution
-to mitigate the effect , drainage ditches can be blocked by hay bales
impact
-conifers are planted as cash crops. however this dries out the moorland as the trees absorb water, and the roads have to be built to carry the wood away, compacting the land
solution
-when the trees are cut down, branches are used to block drainage ditches to slow water flow and hence keep the land moist
impact
- the moorland was burnt to provide a varied habitat for grouse, but when sheep grazed the land, burning was stopped. old heather burns easily, so accidental fires can be a high risk. if the peat sets on fire, that can damage the habitat on a large scale
solution
-burning controlled fires before heather gets too old and dry is important to prevent such damage
describe conservation strategies
- establishing protected areas like national parks, green belts or SSSIs
- can also involve giving legal protection to endangered species or conserving them ex situ in zoos or botanical gardens
management strategies
- raise carrying capacity by providing extra food
- move individuals to enlarge populated , or 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
