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A2 biology 5.3.2

OCR biology - populations and sustainability

Define carrying capacity The maximum population size that an environment can support for a period of time
Why do populations in nature tend to fluctuate around carrying capacity? Limiting factors present at the lowest/ least favourable amount limit rate of growth and reproduction, provide environmental resistance, prevent population size exceeding carrying capacity signficnatly, not all offspring reach reproductive age
Give examples of resource and non-resource limiting factors Resources: food, water, shelter, nesting sites, space. Non-resources: pathogens, predators, degree of competition
Organisms in a climax community. Lag phase, log phase (high reproduction rate), stationary phase at carrying capacity, population size fluctuates around carrying capacity (strength of environmental resistance/ limiting factors), death phase if environment
Describe the population growth of a R-strategist and give 2 examples Pioneer species, bacteria in closed system. Lag phase, boom phase (very high reproduction rate, short generation time, population exceeds carrying capacity before limiting factors), bust (shortage of resources, intense competition, accumulating waste)
How are predator and prey population sizes linked? Limiting factors for each other. Predator population size follows prey in cycles, out of phase. Small predator population= prey reproduce . More prey available= predators reproduce . More prey eaten = limiting factor. Less food available = limiting factor
Why is it difficult to model predator-prey relationships? There are other limiting factors. Prey are eaten by more that 1 type of predator, any could be responsible for a decrease in prey population size . Predators eat more than 1 type of prey - if 1 species is unavailable it will eat more of another one.
What is an example of a predator-prey relationship that IS easy to model with a simple controlled experiment and why? Snowshoe hare and lynx (Canada). Snowshoe hare is main food source for lynx and isn't eaten by much else, almost a 1:1 relationship
What is competition? Exists between individuals when a resource is not present in sufficient amoutns to satisfy all the individuals that depend on it
What is intraspecific competition and why does it prevent population size from exceeding carrying capacity? Competition between individuals of same species, causes natural selection. If population size exceeds carrying capacity, more intraspecific competition for resources, environment cant support, death rate> reproduction rate, population size falls again.
What is interspecific competition and the competitive exclusion principle? Between individuals of different species. There is more intense competition between SPECIES with similar niches, can't coexist, 1 will be outcompeted +population size falls until new carrying capacity/ extinct in habitat. Tribolium castaneum > T. cofusum
What factors affect interspecific competition + e.g.? Changes in environmental conditions (one species may be better adapted to different conditions), limiting factors e.g. T< 29 degrees, T. cofusum survived instead
Define allelopathy Where plants release chemicals into their environment that disrupt the growth of neighbouring plants to prevent them from using resources, eliminating competition
Define sustainable forestry Regulating forests to ALLOW SIMILAR amounts of timber to be extracted each year for humans/ industry, while conserving biodiversity and protecting ecosystem, to ENSURE A CONTINUED supply of resources for future generations
How can sustainable management be achieved at a small scale in a temperate country (list techniques) Coppicing, coppicing with standards, pollarding, rotational coppicing, energy forestry
What is coppicing + advantages/ disadvantages? Cut trunks of deciduous trees close to ground, promotes growth of new branches from coppice stool, harvested. Sustainable way of harvesting wood/keeping trees alive, prevents succession, continuous supply, branches=fences. Time-consuming, labour intensive
Why might pollarding be used? Cut trunks of trees higher up to prevent deer eating emerging shoots from coppice stool
What is rotational coppicing + advantages? Divide woodland into sections, coppice different part each year. Increases biodiversity: creates a range of habitats for organisms. Freshly coppiced woodland is open +bright (suitable for grasses), mature coppice has dense canopy so less light penetrates
What is energy forestry + advantages/ disadvantages? Coppice fast growing willow/eucalyptus on a short cycle, use food as biofuel. Carbon neutral (young plants take in more CO2 by photosynthesis than they release by respiration). Less biodiveristy: close planting, monoculture
List the sustainable management techniques at a large scale in a temperate country? Selective felling, rotational felling with long rotation times, good husbandry
What is clear felling + advantages/ disadvantages? Removing all trees in a habitat. more timber, farmland. destroys habitat, soil is susceptible to erosion, runs into lakes/ rivers + pollutes them
What is selective felling + advantages/ disadvantages? Removing only the largest + most commercially valuable trees from a habitat. Habitat is largely unaffected, vegetation grows quickly in the gaps between the trees, prevents soil erosion, maintains biodiversity. But, machinery disturbs ecosystem
What are advantages/ disadvantages of rotational felling with long rotation times? Biodiversity accumulates, limits disturbance by machinery. Such a long time scale is not commercially viable
What is good husbandry? Control pests and pathogens (less trees need to be harvested if the yield of ach tree is greater), only grow tress that grow well in the environment (suited to soil, temperature), maximise the distances between trees to reduce competition
Define conservation Protecting and maintaining SPECIES, ECOSSYTEMS + BIODIVERSITY (within + between) in a sustainable way for the future, balancing human and environmental needs, dynamic process
What methods of conservation are there? Species protection:ex situ, legal status poachers, vaccinate. Land management:SSSIs/national parks, prevent succession, create new habitats, dispersal corridors. Land reclamation:recolonise, clear pollution coal spoils = liming, pioneer species. Conflicts
Why is the need for conservation increasing? Human population growth: increased waste, pollution, conversion of land for agriculture/ infrastructure, overexploitation of populations for food/ trade. Development of technology that allows more intensive resource exploitation e.g. trawlers
What are the economic reasons for conservation? Sustainable resource extraction for trade now will enable long-term use of the resource e.g. timber. Benefits to agriculture: crop pollination, natural predators, nutrient recycling
What are the social reasons for conservation? Ecotourism, recreation, resources (food, drugs, timber(, services (carbon sink, prevent flooding, crop pollination, nutrient recycling), large gene pool = potential medicines
What are the ethical reasons for conservation? Conservation is a human obligation, every species has a right to be alive.
Define preservation + eg Maintaining an ecosystem in its PRISTINE, VIRGIN, UNDISTURBED state - minimal activity is allowed that impacts the environment = NO mining + insert, RESITRCTED scientific research + tourism. E.g. Antarctica - mineral-rich, protected by from exploitation
Why are the Galapagos islands special + why are they threatened (list)? Endemic species. Number of tourists + residents has increased, now >100,000 toursits/year. Habitat disturbance, overexploitation of populations, introduction of non-native speices
How have humans disturbed the Galapagos habitats? Increased waste + pollution e.g. expansion of airport. More demand for oil = spills in 2001. More conversion of land for agriculture/ infrastructure = fragmentation, speciation, decreases size of gene pools E.G. Scalesia trees replaced by farmland on SC
How have humans over-exploited populations? Tortoises for food - no Pinta left. Sea cucumbers - Asian market. Sharks - shark fin trade
What are the effects of introducing non-native species, both accidentally and deliberately? Outcompete local species (goats for grazing, invasive red quinine tree, petrel), kill local species (cats, pigs), damage the habitat (goats, red quinine tree), bring diseases (avian malaria, bird flu). NOW 700 foreign/ 500 native plant species.
What are the management strategies adopted? Cull all goats on Isabela island. Check all tourists/ boats for non-native species. 1998 Galapagos marine reserve: coastal no-take zones. Fishing quotas. Captive breeding programme for tortoises. Educate tourists + residents. Control pests + pathogens
What is coppicing with standards and why is it commercially valuable? Coppice some trees to provide narrow branches for fencing, a continuous supply of timber. Leave some trees to grow to full size - increase biodiversity, produce large planks of wood
What are the advantages/ disadvantages of natural predators? Advantages: increase biodiversity, no need for insecticides (pollute rivers, enter food chain, harm humans, bioamplification). Disadvantages: may migrate/ eat plants
What is a wildlife corridor? Plant a strip of native trees around farmland as a corridor for native animals that are of benefit to the farmer e.g. crop pollinators, natural predators
Created by: 11043



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