6.3.2 Flashcards
Why can exponential population growth not be sustained indefinitely?
Due to limiting factors such as the availability of food which will prevent it rising above the carrying capacity
What is a limiting factor?
Environmental resource or constraint that limits population growth
If growth of a population is plotted on a graph?
Creates a population growth curve - sigmoid population curve
Phase 1 of graph?
Slow growth - Small numbers of individuals that are initially present reproduce increasing the total population ; as birth rate is higher than death rate, population increases in size
Also slow increase due to ACCLIMATISATION
Phase 2 of graph?
Rapid growth (exponential) - number of breeding individuals increases and thus the total population multiplies exponentially (no constraints act to limit the population at this point)
Phase 3
Stable Phase - further population growth is prevented by external constraints. POPULATION SIZE DOES FLUCTUATE but overall it’s size remains stable ; birth rates = death rates
What can fluctuations in phase 3 be accounted for?
Presence of predators
Exponential growth curve?
Size of the population doubles each time a fixed period elapses
How is it best to draw an exponential growth curve?
On a logarithmic scale with the y axis increasing each time by a set factor (often by *10 - on calculator) ; this gives a linear/proportional line
X-AXIS/TIME is LINEAR
When is there a period of exponential growth?
Conditions are ideal and maximum growth rate is achieved
Examples of limiting factors?
Competition between the organisms for resources, build up of the toxic by-products of metabolism or disease
What are the types of limiting factors?
Abiotic factors - non-living factors include temperature, light, pH, the availability of water or oxygen and humidity
Biotic factors - predators, disease and competition
What is carrying capacity?
Maximum population size than an environment can support ; population size remains stable as the number of births and deaths are approximately equal
What is another biotic factor that affects population size?
Migration
Types of migration
Immigration and Emigration
Immigration
Movement of individual organisms into a particular area increasing population size ; often migrate annually to reproduce, dramatically increasing
Emigration
Movement of individual organisms away from a particular area to decrease its population size ; away from areas of high population density or poor habitat
Density independent factors?
Have an effect on the whole population regardless of its size ; these can dramatically change population size such as earthquakes, fires, volcanic eruptions and storms - in some cases they may remove whole populations of a species from a region
What has led to population explosion in humans?
Development of agriculture, industrial revolution and advances in medicine
Population growth formula?
(Population change during period/initial population) * 100
+ is population has grown
- population has decreased
What affects death rate in a population?
Age profile (elderly population = higher the death rate), quality of medical care, food availability/quality and the effects of natural disaster or war
What does the future size of a population depend on?
Number of women of children bearing age
What do organisms compete for?
Food, shelter, space and light
Competition?
Biotic (interactions of living organisms)
Interspecific : competition between different species
Intraspecific : competition betwene members of the same species
What does interspecific competition less to?
Different species competing for the same resource ; reduction of the resource available to both populations. As a result of less food, organisms will have less energy for growth and reproduction resulting in smaller populations than if only one of the species had been present
What else can happen with interspecific competition?
If two species of organisms are both competing for the same food source but one is better adapted, the less well adapted one is likely to be outcompeted ; if conditions ARE THE SAME then numbers will decline until it no longer exists in the habitat alongside the better adapted species
COMPETITIVE EXCLUSION PRINCIPLE
State definition of competitive exclusion principle?
Two species are competing for limited resources, the one that uses the resources more effectively will ultimately eliminate the other
Rey and red squirrels competition
In the 1870s - the grey squirrel, native of North America was introduced into the wild in the U.K. ) population increased rapidly in numbers and red squirrels reduced
Grey squirrel can eat a wider range of food and store more fat as it is larger ; increases chances of survival and thus ability to reproduce - increasing its population
INCREASING POPULATION OF GREY FURTHER REDUCES FOOD SUPPLY for red ; reducing their ability to survive and reproduce
Infraspecific competition
Members of same species compete for the same resource ; availability of resource determines population size and thus greater availability = greater population leading to fluctuations in the number of organisms present over time
Graph of intra specific competition
Looks like a flipped quadratic joined to a normal quadratic (pg 636)
Stage 1
Resource is plentiful so enough of that resource for all organisms to survive and reproduce, increasing population size
Stage 2
More individuals sharing food/space so resources now limited and thus not available for all organisms to survive (population decreases in size)
Stage 3
Less competition exists so again more organisms survive and reproduce resulting in population growth - a lot of same resources still available
Another major biotic factor?
Predation ; an organism kills and eats another organism - predation is a type of interspecific completion operating between prey and predator species
Evolution in predator prey relationships?
Predators have evolved to become highly efficient at capturing prey (speed/stealth) and likewise prey have evolved to avoid capture through camouflage, mimicry and defence mechanisms like spines ; HAVE HAD TO EVOLE TOGETHER IF NOT THEN ONE OF THE SPECIES MAY HAVE BECOME EXTINCT
How is predator prey relationship exploited?
By farmers ; use natural predators like ladybirds to destroy pest populations and prevent them damaging crops without the need to use pesticides
Predator prey interlinked?
As population of one changes it affects the other ; there are many fluctuations and they all essentially follow the same pattern of peaks and troughs after a time delay
Stage 1 P+P
Increase in prey population provides more food for the predators ; more survival and reproduction - results in an increase in the predator population
Stage 2
Predator population eats more prey - causing a decline in the prey population ; death rate > birth rate
Stage 3
Reduced prey population can no longer support the larger predator population ; intraspecific competition for food increased, resulting in a decrease in the size of the predator population
Stage 4
Reduced predator numbers results in less prey being killed so they increase and reproduce ; cycle begins again
What other factors influence predator prey relationships?
Availability of food plants of the prey or presence of other predators ; fluctuations may also result from seasonal changes in abiotic factors
Why should we conserve the environment?
For future generations to enjoy ; preserve the beauty of the natural world while also ensuring that the biodiversity of world ecosystems is not lost
Reasons for maintaining biodiversity?
Economics, preserving genetic variety and retaining species that might be useful to people
Conservation vs preservation
Often used interchangeably but they have different meanings
Conservation
Maintenance of biodiversity through human action or management ; this includes maintaining diversity between species, maintaining genetic diversity within a species and maintenance of habitats
What does conservation involve?
Management of ecosystems so that the natural resources in them can be used without running out ; sustainable development - the forest stewardship council ensures that forests are managed so that they provide a sustainable source of timber
What kind of management of forests are they aiming for?
Socially beneficial, environmentally appropriate and economically viable
Form of conservation?
Reclamation ; process of restoring ecosystems that have been damaged/destroyed - techniques such as controlled burning of areas of a forest, which can halt succession and increase biodiversity ; conservation is dynamic and needs to adapt to constant change
Preservation
Protection of an area by restricting or banning human interference so that the ecosystem is kept in its original state ; most commonly used when preserving ecologically, archaeologically or paleontologically sensitive resources - when lands are preserved, visitation is not allowed except by those who manage and monitor such areas
Caves?
Virgin caves (newly discovered), are pristine - may contain very sensitive geological formations and walking from one cave to the next may cause irreparable damage (soil erosion/movement of dirt) ; this can be avoided by barring entrance to caves altogether thus preserving these unique habitats - THUS ONLY PRESERVATION CAN protect integrity
Downsides of preservation?
No one able to enjoy the caves and some argue that there is no point in having a resource that cannot be used
Objects and buildings - preserved
Natural environment - conserved
Preserved habitats include areas set aside in nature reserves and marine conservation zones where human interference is prohibited
Importance of conservation?
Economic
Social
Ethical
Conservation importance - economic
Provide resources that humans need to survive (provide an income) ; rainforest species provide medicinal drugs, clothes and food that can be traded and other forests are used for the production of timber and paper
Conservation importance - social
Aesthetically pleasing ; natural beauty of wild ecosystems as well as using them for activities which are beneficial to health by providing a means of relaxation and exercise (cycling etc) ; psychologically good for patients too
Conservation importance - ethical
All organisms have a right to exist? (NO)
Moral responsibility for future generations to conserve the wide variety of existing natural ecosystems
We were the ones who caused the damage so we should fix it
Why is there a thing called sustainability?
To cope with the increased human demand for resources, intensive methods have been developed to exploit environmental resources - this can destroy ecosystems, reduce biodiversity etc so it must be done sustainably to live in the manner we are accustomed
Why is sustainable management necessary?
To conserve natural resources for future generations ; a sustainable source is a renewable resource that is being economically exploited in such a way that it will not diminish
Aims of sustainability?
Preserve the environment
Ensure resources are available for future generation
Allow humans to live comfortably
Enable less economically developed countries to develop (via exploitation of natural resources)
Create a more even balance in the consumption of these resources between more economically developed countries (MEDCs) and LEDCs
What can be done in tandem with sustainable management?
Existing resources should be used more efficiently to prevent finite resources being used up so quickly ; many products can be reused and recycled
As technology improves, alternatives may be developed that could ease the strain on current finite resources - however they may be very costly and take years to develop
Sustainable management of forests
Maintenance of a forests’ biodiversity while sustaining our supply of wood to meet demands and the economic viability of timber production
Small-scale timber production?
Coppicing is often used ; tree trunk is cut close to the ground and new shoots form from the cut surface and mature - these shoots are cut and more and produced ; SHOOTS ARE USED IN FENCING
Rotational coppicing?
Woodland is divided into sections and trees are only cut in a particular section until all have been coppiced ; coppicing then begins in another area allowing time for the newly coppiced trees to grow and this continues until you reach the trees that were first coppiced (now grown to mature sized trees) and cycle begins again
Rotational coppicing (+)
Biodiversity as the trees never grow enough to block out the light ; hence succession cannot occur and so more species can survive
Pollarding?
Alternative technique to coppicing ; trunk is cut higher up so deer and other animals cannot eat the new shoots as they appear
Sustainable timber production on a large scale?
Based around the technique of felling large areas of forest ; they are destroyed and will not regrow
How is large scale felling sustainable?
- selective cutting ; only removes the largest trees
- replace trees through replanting rather than waiting for natural regeneration ; ensure that the biodiversity and mineral and water cycles are maintained
- plant trees an optimal distance apart to reduce competition ; results in higher yields as more wood is produced per tree
- manage pest and pathogens to maximise yields
- ensure that areas of forest remain for indigenous people
Disadvantage to large scale felling?
Habitats are destroyed, soil minerals are reduced and the bare soil which is left is susceptible to erosion ; trees are important for binding soil together, removing water from soil and maintaining nutrient levels through their role in the carbon and nitrogen cycles
Demand for food?
Ever-increasing due to exponential population growth ; fish provide a valuable source of protein within the human diet
What has overfishing led to?
Populations of some species of fish decreasing significantly ; they are then unable to regenerate, meaning they will no longer be able to provide us with a food source in the future
How to overcome overfishing?
International agreements are made about the number of fish that can be caught
Common Fisheries Policy in the EU - fishing quotas provide limits on the numbers of certain species of fish that are allowed to be caught in a particular area ; aim is to maintain a natural population of these species that allows the fish to reproduce sufficiently to maintain their population
Techniques that have been used to reduce overfishing?
- use of nets with different mesh sizes ; made large enough so that immature fish can escape (only mature fish are caught - allowing breeding to continue)
- commercial and recreational fishing only allowed at certain times of the year ; protects the breeding season of some fish species and allows the fish levels to increase back to a sustainable level
- fish farming to maintain the supply of protein food while preventing loss of wild species - fish that are tolerant of high stocking densities and rapid growth are best FISH IN RICE PADDY FIELDS WHERE THEY GROW TO AN EDIBLE SIZE WHEN RICE IS READY FOR HARVEST
Masai Mara
Kenya
National reserve
Balance needs of humans and needs for conservation
What type of ecosystem is Masai Mara?
Savannah ; wildebeest and zebra migrations alongside fertile regions (close to river)
In the past - region was dominated by acacia bush ; governments have reduced them ti reduce incidence of the sleeping sickness disease it carried
Masai Mara grazing
Semi nomadic farming in the past ; tribes moved allowing vegetation time to recover from animal grazing
Grazing is now limited to the edge of the reserve and local tribes are prevented from entering the park ; larger herds graze the grassland areas and vegetation is removed, increasing soil erosion
Masai Mara cultivation
Grassland converted to crop land so natural vegetation is removed and nutrients in the soil are used up ; leads to reliance on fertilisers for effective crop growth
Masai Mara economic input
Mainly relies on tourism ; thousands flock to the area to see the animals present in their natural habitat. Ecotourism is tourism directed towards natural environments to support conservation efforts and observe wildlife ; reduces impact of tourism - less invasive than wgricukture
Principles of ecotourism
Ensure that tourism does not exploit the natural environment or local communities
Consult and engage with local communities on planned developments
Ensure that infrastructure improvements benefit local people as well as visitors
Negative of ecotourism
Repeated use of hiking trails/mechanised transport can lead to soil erosion
How does nature reserve play an important role in conservation?
Black rhinos are one of the most endangered animals in Africa and appear on IUCN critically endangered list ; despite the trade being illegal, rhino horn is in huge demand (traditional medicine) and people are lured into poaching
How did they save the rhinos?
Active conservation programme - reserve rangers, communication equipment and infrastructure - deterred poachers
Research projects in Masai Mara
Behaviour and physiology of the predator spotted Hyena - Michigan State Uni
Mara Predator Project catalogues and monitors lion populations throughout the region ; identifies population trends and responses to changes in land management, human settlements etc
Balance?
Increasing wildlife density in Masai Mara also threatens pastoral and cultivation lifestyles
Example of balance between human and animal populations
Elephants threaten cultivation ; often responsible for crop trampling and damage - land May be fenced but this affects natural migration
Legal hunting is used to cull excess animals - successfully maintain population numbers and bring in a lot of money ; but this must be constantly monitored
Livestock face threats from migratory wildlife ; during migration, wildebeest > cattle for grass so diseases are introduced to the domesticated animal populations which can be passed on to wild animals
Human population increases so they require more homes and land ; wildlife density declines significantly
Terai region
Land is fertile and is the main agricultural region of the country ; people are also engaged in a range of trades, industries and services - natural resources are at risk of being overused as a result of high population density
Ecosystem
Region is hot and humid in the summer months and is composed of a fertile alluvial soil which is rich in plant nutrients ; Terai is a region of extreme biodiversity and there are thick forests (Bengal tiger etc)
Human dependency on Terai?
Many people depend on Terai for their livelihoods ; source of national income - as a result of poverty and corruption a lot of forest has been cleared for agriculture or to sell the timber
Removal of forest from Terai?
Exacerbated the effects of monsoon flooding causing severe disruptions to communities downstream - communities would be left with only small isolated pockets of forest ; devastating fir wildlife and local population who rely on forest for tourism and harvesting wood/using it as fuel
Sustainable forest management in Nepal
Provide a livelihood for local people and conserve forests and income ; local community forestry groups that set up their own operational plans and set harvesting rules # rates/prices for products and determine how surplus income is distributed/spent
Forestry Stewardship Council certification
Community forestry groups
Securing biodiversity of forested areas
Sustainable wood fuel sources
Employment and income generation through forest protection
Improved soil/water management across the region
Increase in retail price of forestry products - economic input is higher
Management strategies for sustainable land use?
Promoting production of fruits and vegetables in the hills and mountain regions
Improving irrigation facilities to enhance crop production
Multiple cropping (more than one crop grown on a piece of land)
Growth of nitrogen fixing crops (pulses/legumes)
Crop varieties resistant to various soil/climatic and biotic challenges
Fertilisation technology to enhance crop yields (manure)
What is Terai trying to do?
Secure economic welfare and biodiversity of the region
What is a peat bog?
Region of wet spongy ground that contains decomposing vegetation ; it is a carbon sink and the peat can be used as fuel if dried - it releases CO2 into the atmosphere and takes thousands of years to form (important in preventing climate change)
Why is peat important?
Used for farmers and gardeners who mix it with soil to improve soil structure and to increase acidity ; peat has very favourable moisture-retaining properties when soil is dry and prevents excess water killing roots
PEAT IS NOT FERTILE ITSELF ; commercial peat extraction is a major threat to ecosystems
How does Peat form?
Plant material is inhibited from full decaying by acidic and anaerobic conditions ; wet or boggy areas and therefore peat is mainly composed of wetland vegetation including mosses and shrubs
Peat plants?
Mosses and bog cotton etc have adapted to grow and thrive in wet conditions with few nutrients ; they support many insects and the lack of predators makes peatland ideal for birds to nest - abundance of insects, spiders etc provides food for many species
Why is it important we maintain peatland ecosystems?
Flood management, erosion control and carbon storage
This decline has occurred through afforestation (establishment of forest in an area where there was none), peat extraction and agricultural intensification, including land drainage - all contributed rot he drying out of the bogs
How to conserve areas of lowland bog?
Ensuring peat and vegetation of bog surface is undisturbed and as wet as possible ; surrounded by ditches to allow water to run off, preventing flooding of nearby land. DITCH BLOCKING MAY BE REQUIRED TO RAISE WATER TABLE TO BOG SURFACE
How does removing trees from peat bogs help?
They have a high water requirement due to transpiration ; any tree seedling that has the potential to remove water from an area of peatland should be removed to maintain water levels in that area
Controlled grazing?
Maintains biodiversity; ensures a diverse wetland surface in terms of structure/species composition - provides many habitats for rare insect species
What is happening to Peat bogs nationally?
Wildlife rrusts and natural England and RSPB all working together to strike a balance between need to exploit the land and maintain biodiversity ecosystems
Environmentally sensitive ecosystems
Ecosystems that are less resistant to change than others ; mass tourism can for example being economic vitality to the area but can also bring about changes to an environment that are not always positive (loss of biodiversity)
Management techniques in environmentally sensitive areas
Limiting the areas tourists can visit Controlling the movement of livestock Introducing anti-poaching measures Replanting of forests and native plants Limiting hunting through quotas and seasonal bans
Galápagos Islands
Archipelago of volcanic islands that rise up from the pacific ocean - never been connected to mainland so original flora and fauna ENDEMIC
Animals on Galapagos
Many are reptiles ; Galapagos rice rat is only mammal and over millions of years, animals and marine birds have arrived on the islands/adapted to their environment in isolation
Galapagos giant tortoise
Flightless cormorant (reduced wings better for fishing underwater)
Marine iguana (ability to swim effectively ; allows these ectothermic to bask in the sun and raise their body temperatures ; black/dark grey - higher their temp, the longer they can forage)
Plants on Galapagos?
Coastal zone - salt tolerant species such as mangrove and saltbush
Arid zone - drought-tolerant species like cacti and the carob tree
Humid zone - dense cloud-forest ; they support populations of mosses and liverworts
Whaling trade 1800s?
Disrupted Galapagos fragile ecosystem by allowing domestic animals to roam loose and chopping forests for fires to render down whale fat and removing many giant tortoises (goats outcompeted tortoises)
Measures taken to protect the Galápagos Islands
Introduction of park rangers across the islands
Limiting human access to particular islands
Controlling migration to and from the islands
Strict controls over movement of introduced animals (such as pigs)
Antarctica
Coldest and driest continent ; 2km thick - average temperature in Antarctica is below -30 and only has summer and winter (24 hour sunlight or darkness)
Animals in Antarctica
All endothermic animals rely on thick blubber to insulate them ; whales, seals and penguins
Emperor penguins are the only ones that remain on Antarctica during the winter /make penguins survive for up to 9 weeks on land by keeping their egg warm by balancing it on their feet and covering it with a flap of abdominal skin
Plants in Antarctica?
Only in ice free places ; lichen and moss in favourable niches (sand/soil etc) + algae are also able to grow in many sheltered areas
What has human activity done to Antarctica?
Planet-wide impacts such as global warming and ozone depletion Hunting of whales and seals and fishing of some Antarctic species Soil contamination (scientific research stations) Discharge of waste into the sea (human sewage)
Antarctic treaty of 1961 - international
Scientific cooperation between nations Protection of Antarctic environment Conservation of plants and animals Designation and management of protected areas Management of tourism
Snowdonia national park
Highest mountain range in England and Wales
2000 square kilometres
Rugged terrain of lakes and fast-flowing rivers
Animals in Snowdonia
Rich diversity of habitats provides homes for a wide range of birds
Coast and estuary : cormorants
Forest birds - flycatchers
Moorland and mountain birds like buzzards
Snowdonia plants
Snowdon lily and hardy arctic-alpine plants ; evolved to cope with extreme weather
Control of Human Activities
Millions of visitors each year
Conserve and enhance natural beauty
Promote understanding and enjoyment of special qualities of the park
Economic and social well being
How is the park Eco friendly?
Dinorwig power station pumping hydroelectric power station ; meet demands of national grid and to preserve natural beauty of Snowdonia it is located deep inside mountain - minimised impact to the environment while meeting humans demand for energy
Lake District
England’s largest national park ; scaffel pike - terrain includes regions of moorland and glacial moraines
Animals in Lake District
Water voles, roads and many species of bats - red deer etc ; native species are also under threat however
Plants present
Arctic alpine plant communities ; alpine cineuqefoil - specialised trees have evolved such as dwarf juniper and willow
Also home to sundew ; one of UK’s few carnivorous plants ; insects are trapped within its leaves by sticky mucilage (enzymes then secreted to digest the insect, releasing its nutrients for the plant)
Control of human activities in Lake District
Lake District National Park Authority ; conserve the region while enabling access for many millions of visitors each year - active management of countryside by replanting native species, this fragile ecosystem is being secured for generations to come
