6.3.2 Populations and Sustainability Flashcards
Population + factors that affect it
-population= all the organisms of one species in a habitat
-population size= total no. of organisms of one species in a habitat
-affected by:
- abiotic factors= i.e light, water available, temp, pH, humidity(affects growth + success of reproduction)
- biotic factors= inter/intra specific competition + predation, predators, disease
Population growth curve
-phase 1: slow growth = small no. of individuals initially present will reproduce, increasing total population(birth rate is higher than death rate)
-phase 2: rapid growth = as no. of breeding individuals increase, the total population multiplies exponentially
-phase 3: stable state = population growth is prevented by external constraints–} population size fluctuates but overall size remains relatively stable(birth and death rates approx. equal)
What is carrying capacity?
-maximum population size that an ecosystem can support
How does migration affect population size?
-immigration= movement of individual organism into a particular area increases population size
-emigration= movement of individual organisms away from particular area decreases population size
What are density independent factors?
-factors that have an effect on the whole population regardless of its size i.e earthquakes, volcanic eruptions
-can dramatically change population size + even remove whole populations of a species
Interspecific competition
-when 2 organisms of different species occupy the same niche + compete with each other for resources
-resources available for both populations are reduced–} less energy for growth + reproduction, resulting in smaller population sizes
-one species may be better adapted to its surroundings+ outcompete other species, so only one population size decreases(competitive exclusion)
-i.e grey squirrels(invasive species) competed with red squirrels + eventually adapted to have better chance of survival)
Intraspecific competition
-occurs when members of the same species compete for the same resource
-availability of the resource determines the population size(greater availability = larger population can be supported)–} fluctuations in the no. of organisms present in a particular population over time
-max size= carrying capacity
Stages of intraspecific competition graph
- all organisms have enough of the resource to survive + reproduce= increase in population size
- more individuals to share food/space with so resources become limited= population size decreases
- less competition due to smaller population, more survival + reproduction= population growth
Predator-prey relationships
-size of of predator + prey populations are interlinked–} as one population changes it causes change in the other via negative feedback
-results in fluctuations in the size of both populations
Describe the pattern of predator-prey relationships
- increase in prey population provides more food for predators so they can survive + reproduce–} increase in predator
- increased predator population eats prey + causes decline in their population(higher death than birth rate)
- less prey cannot support high predator population–} intraspecific variation leads to decrease in predator populations
- less predators means that prey population can survive + reproduce–} increase in prey population
What other factors affect predator-prey relationships?
-availability of food for prey, presence of other predators, seasonal changes in abiotic factors
What is conservation?
-maintenance of biodiversity through human action + management
-involves managing ecosystems so that the natural resources can be used without running out + can be available for future generations
-can also involve reclamation(restoring damaged/destroyed ecosystems)
Reasons why conservation is important
-economic= provides resources that humans need to survive i.e drugs, food + make an income from(trade on local + global scale)
-social= people enjoy natural beauty of wild ecosystems, beneficial for health i.e relaxation + exercise
-ethical= organisms have a right to exist, we have a moral responsibility for future generations conserve ecosystems
-ecological= can help prevent climate change i.e not burning tress, helps maintain food chains
What is preservation?
-protection of an ecosystem/area by restricting or banning human interference
-mostly used for sensitive resources–} nothing is removed + only used for activities that don’t damage them
What is a sustainable resource?
-renewable resource that is being economically exploited in such a way that it will not diminish or run out
Small-scale timber production
-coppicing= tree trunk is cut close to the ground–}root system remains intact so shoots can grow
-rotational coppicing is often used(woodland divided into sections and cut in intervals)–} maintains biodiversity as trees never grow enough to block out the light so succession cannot occur + more species can survive
-pollarding= trunk is cut higher up to reduce consumption of shoots from herbivores
Large-scale timber production
-felling large areas of the forest:
-selective cutting(only removing largest trees)
-replace trees through replanting to maintain biodiversity + mineral/water cycles
-plant trees at optimal distance to reduce competition + produce higher yields
-manage pests + pathogens
:( destroyed habitats, soil minerals are reduced + bare soil is susceptible to erosion
Managing fishing: international agreements + fishing quotas
-countries fish in the same oceans + fish travel between international waters, so agreements must be made about no. of fish that can be caught i.e Common Fisheries Policy in the EU
-quotas provide limits on no.s of certain species that are allowed to be caught in a particular area–} must maintain natural population so they can reproduce to prevent extinction
Other techniques to manage fishing
-use nets with larger mesh sizes so young fish can escape and continue breeding
-allow fishing at only certain times a year to protect breeding season + allow fish sizes to increase back to sustainable level
-fish farming to maintain supply of protein food whilst preventing the loss of wild species
Ecosystem management: Masai Mara
-national reserve in Kenya–} savannah that is home to huge populations i.e wildebeests + zebras
-increased cultivation over the years(more cropland)
-Masai people traditionally earn a living by raising livestock BUT can lead to overgrazing
-conservationists work with them to ensure they make money via ecotourism + conservation whilst being sustainable i.e legal hunting to cull excess animals, fencing areas to prevent crops being trampled on
Ecosystem management: Terai arc
-area of forest + grasslands that have endangered species living there i.e Bengal tiger
-areas of the forest are being destroyed to make way for more houses + development–} animals more likely to destroy crop fields + humans can hunt easier
-recent intro of more conservation i.e using solar cookers + sustainable wood fuel sources, improved soil + water management across the region
Ecosystem management: Peat bogs
-store water + carbon dioxide
-farmers use it to graze sheep + deer but this causes loss of moss species + soil compaction
-more conservation i.e measures to reduce water run-off, removal of seedling trees from the area(high water requirement so would reduce water levels in peat bogs)
-controlled grazing to maintain biodiversity
State general ways to manage environmentally sensitive
-limiting the areas tourists can visit
-controlling the movement of livestock
-introducing anti-poaching measures
-replanting forests + native plants
-limiting hunting through quotas + seasonal bans
How are plants + animals affected by human activities in the Galapagos Islands?
-explorers + sailors that visited in the 19th century decreased animal populations by eating them
-non native animal species introduced to the natives (decrease in native population)
-fishing has caused a decrease in the populations of sea life
-non native plants compete with native + cause decrease in native populations
Control of human activities in the Galapagos Islands
-introduction of park rangers across the islands
-limiting human access to particular islands/specific areas
-controlling migration to and from the islands
-strict controls over movement of introduced animals
How are plants + animals affected by human activities in Antarctica?
-during the 20th century, whaling led to decrease in whale numbers + Antarctic blue whale becoming critically endangered
-seal hunting in the 19th century drove the Antarctic fur seal to the brink of extinction
-dumping sewage in the sea and oil spills have severely affected by wildlife
Control of human activities in Antarctica
-Antarctic treaty means it is a nature reserve
-ban of commercial whaling in the ocean surrounding Antarctica
-limits on fishing
-ships that use thick oil as fuel are banned
-restrictions on tourism
How are plants + animals affected by human activities in Snowdonia + Lake District?
-walking on footpaths leads to erosion + loss of soil from hillsides
-soil can disturb pH of the water
-people can trample on vegetation
-issues with water pollution due to phosphates in fertilisers, detergents used for washing + sewage water–} can contribute to algal growth that deoxygenate water + can kill fish
Control of human activities in Snowdonia + Lake District
-regular repair + maintenance work as well as regrowth of damaged vegetation to counteract erosion
-not take shortcuts as this would promote erosion
-drains to prevent paths from flooding
-improve sewage treatment
-supplying grants to local farmers to improve farming practices
