Unit 6 - Population and Sustainability Flashcards
Stages on population graph
Slow growth
Rapid growth - resources plentiful, reproductive rate > mortality rate
Stable state (no growth) - mortality = reproduction
Cannot support a larger pop. due to carrying capacity, small fluctuations
Populations can
Remain stable
Rise or fall suddenly
Oscillate up and down w. the reg. pattern
Types of limiting factors
Density dependent
Density independent
Density dependent
Factors that affect pop. the more they increase in size e.g resources, predators, intra and inter spp comp.
These limiting factors place the carrying capacity on population size
Density independent
Factors that affect the the same proportion of the population regardless of size
Types of strategists
k and r
K selection
Offspring have a high prob of survival Heavy parental care and nurturing Larger organisms Much lower reproductive rate Young are altricial, longer lifespans and have overlapping generations
Altricial
Born in an undeveloped state and requiring care and feeding by the parents
R selection
Produce many low effort organisms
Species grow rapidly
Found in less competitive and low quality environments
Young are precocial
High of mortality so start reproducing earlier
Non overlapping generations, shorter lifespans
Boom and bust (cyclical)
Precocial
Born in an advanced state and able to feed itself almost immediately
Predator prey interactions
When predator pop increases, more prey eaten
Prey pop decreases, less food available for predator s
W/ less food, fewer predators survive so their pop. decreases
W/ fewer predators, fewer prey are eaten so their pop. increases
More prey = more food, predator pop. increases
Two populations are in eqm and stable due to -ve feedback
When does competition occur
When there are not enough resources to satisfy all of the organisms that depend on them
How does intraspp comp affect population
Population drops –> comp. reduces –> pop. increases –> pop. drops (oscillates)
Examples of interspp comp. affecting population
Red and grey squirrels - Invasive species
May leads to extinction of one species
Greater specialisation to avoid competition
Change in distribution of the species
Where does invasive species have a largest effect
Islands
Competitive exclusion principle
2 competitive species cannot coexist at the same population level esp if ones staring population is higher than the other
Preservation
Keeping habitats/species as they are now (assuming they are currently undisturbed)
Focuses on eliminating any human effects on ecosystems
Conservation
Active management of ecosystems by humans to maintain biodiversity
Involves management of ecosystem so that natural resources can be used sustainably and reclamation
Reclamation
Restoring ecosystems that have been damaged/destroyed
Threats to biodiversity
Over-exploitation of ecosystems by humans
Habitat disruption and fragmentation
Intro of invasive species by humans that outcompete native species to extinction
Potential management strategies
Raise carrying capacity by increasing nutrients Move individuals to enlarge pop Encourage natural dispersion using dispersion corridors between fragmented habitats Fencing Controlling predators and poachers Vaccinate individuals Prevent pollution/disruption Intervene to restrict succession
Ethical reasons to conserve
Moral responsibility
All organisms have a right to live
Every species has value in and of itself
Why does interspp competition have diff effects in the wild
Species may migrate
Other biotic and abiotic effects on the organism
Availability of resources vary
Organisms may not have exactly overlapping niches
Small scale timber production
Coppicing
Pollarding
Sustainable management
Carrying out processes indefinitely w/out damaging the ecosystem
Coppicing
Stem of deciduous tree is cut close to ground
New shoots grow from the cut surface
Mature into narrower stems
Happens cyclically
What is coppicing used for
Fencing
Firewood
Furniture
Pollarding
Sim technique to coppicing
Only done higher up so that the animals cant eat the new shoots
Negative of small scale timber production
Labour intensive
Rotational coppcing
Divide wood into sections
Cut one each year
Why is rotational copppicing good for diversity
Light is still able to reach forest floor as tress never grow tall enough –> increasing diversity of species
Can control succession (deflection - plagioclimax)
Large scale timber production
Clear felling
Selective cutting
Clear felling
Felling all the trees in one area destroying habitats on a large scale
Drawbacks of clear felling
Decreases soil mineral level
Leaves soil susceptible to erosion
Takes 50-100 years of succession
Trees bind soil
Trees remove water from soil and stops it from being washed away
Trees maintain nutrient levels through their roles in the carbon and nitrogen cycle (decomposition)
Selective cutting
Only cutting down the largest, most valuable trees
How is tree growth encouraged for selective cutting
Controlling pests and pathogens
Only planting species where they will grow well
Position tress at optimum distance to decrease comp
Aims of sustainability
Preserve the environment
Ensure resources are available for future generations
Allow all humans to live comfortably
Enable LEDCs to develop
Modern sustainable forestry
Any tree harvested is replaced by another (naturally or planted)
Forest must maintain its ecological function
Local people must benefit from the forest
Main principles of fisheries
Take place at a level that allows it to continue indefinitely (ideally carrying capacity and excess are harvested)
Must maintain structure, productivity, function and diversity of the ecosystem
Must adapt to changes in circumstances and comply w. local, national and international regulation
Strategies put in place for fisheries
Large mesh sizes so only mature fish are caught
Limiting recreational/ commercial fishing to certain times of the year
EU common fisheries policy - Fishing quotas limiting no. of certain fish and where they can be caught
Aquaculture
Farming fish
Restricts impacts on oceanic fish value
Allows susceptible fish species numbers to recover
But decreases genetic biodiversity
Why do fish numbers fall
Too few adult fish left to breed and maintain fish numbers
Scramble competition
Relies on all individuals finding food and nest sites by chance this allows natural selection as some may be better adapted than others
Dominance hierarchy
Strongest, most dominant individuals breed and pass on their alleles - if there’s only 1 dominant individual there is likely to be less variation in the next gen.
Why is preservation not enough to maintain biodiversity
Preservation only keeps the environment as it is
If the ecosystem has already decreased preservation doesn’t prevent further loss
Takes active intervention
Masai Mara region
National reserve in Kenya
Combined needs for locals to run farms w/ larger land owner who use land to encourage conservation and generate income (ecotourism)
Terai region
Home to Bengal Tiger (endangered)
Forest is under pressure due to increased agriculture and grazing
Comm forestry initiatives allow locals to exploit but also adopt responsibility
Marketing products made for forests also generates income
Peat bogs
Peat takes 1000’s of years to accumulate
Ideal for Sphagum moss - feeding and stopping off points for migrating birds
Local level schemes aim to restore certain peat bogs and end commercial use
Human activities affecting the Galapagos
Fishing and whaling have upset the marine ecosystem
Intro of new species e.g. goats (eat vegetation), rodents (damage eggs of natives), dogs and cats (chase and eat native)
Tourism
Scientific research
Increasing pop.
Strategies to maintain the Galapagos
Searching boats for foreign species Using natural predators Culling feral goats Educating Captive breeding for tortoises Galapagos Marine Reserve
Antartica
Overfishing of krill (keystone species)
Moinitor catch size
Whales protected by marine reseves
Sea birds protected by night fishing and during the non-breeding seasons
Measuring distribution
Line or belt transects (systematic sampling)
Measuring plant abundance
Randomly placed quadrats
No. of individuals in sample / Area of sample
Measuring animal abundance
Capture, mark, release, recapture (all occurs in orig. sample area)
(no. in first sample * no in 2nd sample) / no. of recaptured marked individuals
