Populations and sustainability Flashcards
Carrying Capacity
The maximum population size that can be maintained over a period in a particular habitat
Limiting factor
The factor whose magnitude slows down the rate of a natural process
What is the first stage of a population growth chart
- describe
Lag phase
Only a few individuals acclimatising to their habitat
Rate of reproduction and population growth is slow
What is the second stage of a population growth chart
- describe
Log phase
- Resources are plentiful and conditions are good
- Reproduction happens quickly and exceeds mortality
-Population size increases rapidly
What is the third stage of a population growth chart
- describe
Carrying capacity
- Can no longer support a larger population
- Rates of reproduction and mortality equal
- Remains stable and fluctuates slightly to changes in environmental conditions throughout the year
Why can’t a habitat increase after it has reached carrying capacity
Limiting factors
Density independent: factors that act strongly irrespective of the size of population i.e. low temps
Density dependant:factors that act strongly respective of the size of population i.e. availability of food; disease
What are the two types of strategists
R strategist / K strategist - represents two ends of a continuum of strategies adopted by living things
K strategists
Species whose population size is determined by the carrying capacity
- limiting factors greater close to cc causing population size to level out
K strategists traits
bird and large mammals
- low reproductive rate
-slow development
-late reproductive age
-long lifespan
-large body mass
R strategists - graph
Population increases so quickly it exceeds cc of habitat before limiting factors have an effect
-Once cc is exceeded no longer enough resources to allow organisms to reproduce/survive or excessive build-up of waste products may start to build up and kill the species so they enter a death phase
- This is called boom and bust
R strategists traits
Mice, insects, spiders
-High reproductive rates
-Quick development
- Young reproductive age
-Short life span
-Small body mass
What is the most important influence on population growth
The rate at which individuals can reproduce
-Means r strategists colonise a habitat before a K strategist
Interspecific competition
Competition between individuals of different species
-Can affect both population size and distribution of species in an ecosystem
Intraspecific competition
Competition between individuals of the same species
-As factors such as food become limiting individuals compete for food and those best adapted to obtaining food survive and reproduce whilst those who are not will die
-This will slow down population growth and the population enters stationary phase
Relationship between a population of a predator and its prey
1) When the predator population gets bigger more prey can be 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, few prey are eaten and their population size increases
5) With more prey the predator popualtion gets bigger and the cycle starts again
What happens when competition increases
the rate of production decreases (because fewer organisms have enough resources to reproduce)
the death rate increases (because fewer organisms have enough resources to survive)
How does intraspecific competition keep the population size stable
-If population size drops competition reduces and population size increases
-If population size increases, competition increases and population size drops
Interspecific competition eg.
Gause grew two species of paramecium both separately and together
-When together there was competition for food with p.aurelia obtaining food more effectively than p.caudatum
-Over 20 days p.caudatum reduced and died out whereas p.aurelia increased and became only species remaining
What did Gause conclude
More overlap between two species’ niches results in more competition
- If two species have exactly the same niche one is out-competed by the other
-Competitive exclusion principle - why only particular species are found in particular places
What is important to note about Gause’s experiment
-Cases, where interspecific competition has not led to extinction but to population size being significant, reduced
-Lab it is easy to exclude other variables, and a change in temperature may change the outcome of the most adapted species
Allelopathy
Some plants can interfere with other plants’ physiology by releasing chemicals into their habitat and stops other plants from using resources in their habitat
Chemicals may inhibit growth, germination, nutrient uptake
Chemicals can be in roots or leaves
Conservation
Active and dynamic maintenance or improvement of biodiversity within a habitat
Preservation
Maintenance of a habitat to preserve it within its current condition
Threats to biodiversity
Steady increase in human population can affect biodiversity through:
-Over-exploitation of wild populations for food/ trade
-Habitat disruption and fragmentation as a result of more intensive agricultural practices, pollution, widespread building
-Species introduced into ecosystem by humans that out-compete native species for food and resources
What must conservation strategies take into account
-Consideration of social and economic costs to the local community
-Effective education
-Liaison with the community
Reasons organisms come extinct
H - Habitat destruction
I - Invasive species
P - Predation
P - Pollution
O - Overharvesting
What can conservation involve
National parks, Green Belt land, SSSI’s
Lega protection for endangered species, conservation ex situ in zoos/botanical gardens
Some management strategies
-Raise carrying capacity by providing extra food
-More individuals to enlarge the population/ encourage natural dispersion of individuals between fragmented habitats by developing dispersal corridors
-Restrict dispersal by fencing
-Control predators/poachers
-Vaccinate against disease
What happens if disruption of a community has gone too far
Replace a disrupted community with a slightly different community rather than rehabilitate the original community
Three reasons to conserve
Ethical
Social
Economic
Ethical reasons to conserve
-Every species has value and humans have an ethical responsibility to look after them and maintain for future generations
-All organisms have a right to survive and live in a way in which they have become adapted
Economic reasons to conserve
-Natural ecosystems provide services e.g. regulation of atmosphere/climate/ formation of fertilization in the soil/ recycling nutrients/food source/medicine
-Provide goods such as wood/fish
-eco-tourism
Social reasons to conserve
-Mental Health
-Nature walks
When might you use a preservation strategy
newly discovered caves
Sustainable
Fulfilling the needs of current generations without compromising the needs of future generations, whilst ensuring a balance between economic growth, environmental care and social well being
Sustainable small-scale timber production
Coppicing and pollarding
Copping
The stem of a deciduous tree is cut at an angle close to the ground in the winter, once cut new stems grow from the cut surface and mature into narrow stems
-repeat 7-25 years
-Wood used for fencing, firewood, furniture
Pollarding
Cutting the stem higher up to prevent deer eating the emerging roots
What is rotational coppicing
Dividing the wood into sections and cutting one section each year
-Some trees left to grow longer ‘standards’ to supply larger pieces of timber
How is rotational coppicing good for biodiversity
Woodland goes through the process of succession and blocks out light on the woodland floor - prevents a dense canopy of trees
Benefits of coppicing
-New stems grow rapidly
-The life span of the tree extended
-Provides a variety of light levels within a habitat
-Fewer larger trees means more lights for smaller plants
-Provides a variety of habitats
-Roots prevent soil erosion
Large scale timber production
Clear felling all the trees in one area
Disadvantages of clear felling
-Destroys habitats on a large scale
-Reduces soil mineral levels
-Soil susceptible to erosion
- Soil may run off into water ways polluting them
What principles must you abide by to sustainable remove wood from a forest at a large scale
-Limit the size of the area felled
-Minimum distance between replanted trees
-Allow time for trees to fully grow
Selective cutting
Removing only the largest most valuable trees leaving the habitat broadly unaffected
How do foresters make sure each tree supplies more wood
-Control pests and pathogens
-Only plant particular tree species where they know they will grow well
-Position trees optimal distance apart - of trees are too close there is too much competition for light and they grow tall and thin = not good quality timber
Marine stewardship council three principles for sustainable management of fisheries
-Fishing must take place at a level where it can continue indefinitely - overfishing avoided
-Fishing managed to maintain the structure and diversity of the ecosystem
-Fishery must adapt to changes in circumstances and comply with local/national/international regulations
Aquaculture
Sustainable way of providing fish - farming in water
How to fish sustainably
-Maintain fish population at carrying capacity
-Fishing quota - hard to police
-Minimum catch sizes - net sizes
Conflicts of the Terai region
-Densely populated and home to endangered species i.e. Bengal tiger
-Pressure from the expansion of agriculture into forested areas
-Grazing from farm animals
-Over-exploitation of forest resources
-Replacement of traditional agriculture crop varieties
-Rural livelihoods are heavily dependant on forests resources, fuel, food, building
Solutions to the Terai region
-Many national parks
-WWF and the Nepalese government introduced community forestry initiatives where local people had the right to exploit the forest
-Forest corridors between national parks
-Counteracting poachers and illegal felling
-Developed and diversified on and off-farm activity
-Stimulated small credit and marketing schemes
-Constructing waterholes
-Monitoring endangered species
-Eradicating invasive species
the Maasai Mara
In Kenya and famous for large populations of antelope and other mammals
Conflicts of the Maasai Mara
-Land designated as ‘group ranches’ triggered the land-use change
-Intensification of agriculture
-Limited wildlife to small islands and constrained the mobility of live stock
-Density of native species reduced
Solutions of the Maasai Mara
-National parks
-Payment for wildlife conservation schemes (pwc)
-Schemes to reward local people financially whilst also conserving - Ecotourism
Conflict of the PWC scheme
Landowners must move livestock during the tourist season which leads to increased stock densities outside the reserve
-landowners often forced to settle elsewhere and constraints on how they use their land
What is a peat bog
Where a lack of oxygen prevents the complete decomposition of organic matter usually where the area is waterlogged
-Peat bogs retain moisture and form wetland habitats
-Support a high biodiversity and provide an important feeding and stopping off point for migrating birds
Exploitation of peat bogs
The ability to retain moisture has led to widespread use as compost for improving soils in gardens
-Agriculture expansion
-Forestry
-Landfill
-Peat extraction
Solutions to peat bogs
UKBAP aims to conserve and increase biodiversity through low-level schemes - identifies peat bogs for restoration
Conflicts in Galapagos islands
-Habitat disturbance, building and agricultural use of land
-Over-exploitation of resources - whaling and fur traders
-Effects of introduced species
Solutions in Galapagos islands
Charles Darwin Research station
-Prevent introduction of species and treat problems
-Search arriving boats for foreign species
-Controlled release of natural predators to reduce damage of predator which has a harmful affect on ecosystem
-Culling i.e. against feral goats
-Education
The Antarctic conflicts
-Increased no. of tourists and scientists
-Fishing boats congregate in areas with large amounts of Krill, a vital food source
-Whaling
-Albatrosses and Petrels affected by human activities i.e. pollution, poaching, longline fishing
The Antarctic solutions
-Trigger level catch limits
-Fish evenly across all areas
-Within sanctuary illegal to hunt whales - International Whaling Commission
-use bird scaring lines and streamers
lake district biodiversity
-Invasive species produce toxic chemicals - removed
-Limestone pavement where rare ferns grow - legally protected
-Hay meadows rich biodiversity - Framers paid to maintain
-Heathland, heather - Burning strips of vegetation new shoot growth is promoted
-Cliff rock habitats - restrictions on walkers
Impacts and solutions Snowdonia national park
-Farmers dig open drainage ditches, poor water quality rivers and rain flows quickly through habitat ditches- blocked by hay bales
-Conifers planted as cash crops, dries out moorland as trees absorb water - when trees cut branches block drainage ditches to slow water flow
-Moorland burnt for grouse but with sheep stopped, old heather burns easy and accidental fires are high risk - burning controlled fires before heather gets to dry
