6.6 Populations and sustainability Flashcards
What is lag phase?
shown by shallow gradient on graph
few individuals, slow rate of reproduction (but higher than death rate). SLOW POPULATION GROWTH (species still acclimatising
What is log phase?
steep gradient on graph
plentiful resources, rate of reproduction much greater than that of mortality. FAST POPULATION GROWTH
What is stationary phase?
plateau/ curve levels off
reached limit/ carrying capacity -> habitat cannot support a larger population. rate of reproduction = mortality
population stays stable with slight fluctuations
Define carrying capacity
maximum population size that can be maintained over a period in a particular habitat
Limiting factors limit population size growth. What 2 types are there and what are some examples?
DENSITY INDEPENDENT: temperature, earthquakes. These act just as strongly and affect the same proportion of the population, no matter the size of the population.
DENSITY-DEPENDENT:
factor influences more strongly as population size increases. e.g. competition, availability of resources, parasitism, predation
State the characteristics of k-strategists
mammals, birds, larger plants
population size levels out gradually and is determined by carrying capacity
low reproductive rate, slow development, late reproductive age, long lifespan, large body mass, few offspring
State the characteristics of r-strategists
insects, spiders, bacteria
population size increases rapidly - exceeds carrying capacity before limiting factor starts to have an effect.
boom and bust/death phase
high reproductive rate, quick development, short life span, small body mass, young reproductive age, many offspring
What does quick population growth mean for pioneer r-strategist species?
They colonise a disturbed habitat before k-strategists
Describe the predator-prey relationship
- When the predator population gets bigger, more prey are eaten
- Prey population then decreases = less food for predators, so predator population size reduces
- With fewer predators, fewer prey are eaten, and their population can increase again
- With more prey, the predator population gets bigger and the cycle starts again. However there is a delay for this due to reproduction time.
Why do studies of predators and prey in the wild yield graphs of a similar shape but not as well defined?
In the wild, predators often eat more than one type of prey and there are a number of not-controlled, other limiting factors
Define intraspecific competition. What are the characteristics?
Competition between individuals of the same species
There are slight fluctuations during stationary phase, but the population does remain relatively stable
If population size drops, competition reduces and population size increases
If population size increases, competition increases and population size drops
Define inter specific competition
Competition between individuals of different species
What leads to more intense inter specific competition? What are the results of this competition? What is important to be cautious of?
More overlap between two species’ niches -> two organisms cannot occupy exactly the same niche since one will be out competed by the other = competitive exclusion
So if two species are grown together, most likely one will dominate the other (one species population will grow, slower than when alone but still faster than that of the other species - the other species’ population will decrease)
OR, sometimes it results in one population being smaller than the other, with both population sizes remaining relatively constant
However, there are many limiting factors in the wild, so these outcomes could be changed
Define preservation
Keeping species and habitats as they are now - eliminating human effects
Define conservation
Active management to restore biodiversity (range of habitats, diversity between species and genetic diversity within species), involving human intervention.
What are some examples of conservation methods? (7)
- protected areas like National Parks, SSSIs, zoos or botanical gardens
- dispersal corridors to encourage natural dispersal between fragmented habitats
- restrict dispersal by fencing
- control predators and poachers
- vaccinate individuals against disease
- restricting succession such as coppicing, mowing or grazing
- preventing pollution, littering etc
Why should we conserve?
Social:
- recreation
- ecotourism
- educational benefit
- improve well being
Aesthetic
- landscape more attractive to people
Ethical
- duty to care for environment
Economic:
- valuable food source
- drugs discovered from valuable plant species
- natural predators of pests can act as biological control agents, to try and increase yields
- ecotourism also
- maintaining water quality and soil protection also increases yield for farmers
How is small scale timber production managed? What are the advantages?
COPPICING:
- trunk of deciduous tree/ broadleaved species is cut close to ground
- several new shoots grow from cut surface and mature into narrow stems - these grow rapidly
- after certain time, the shoots can be cut off, and the process repeated
- rotational (divide wood into sections and cut one section each year).
- Diff areas of woodland provide diff habitats and more light can reach the ground as fewer large trees dominate (prevent succession), increasing diversity of tree species
- in each section, some trees are left to grow larger without being coppiced (standards)
- can be repeated indefinitely
- roots prevent soil erosion, maintains soil quality
What is pollarding?
-cutting stem higher up
- brings same benefits as coppicing but means herbivores are less likely to be able to consume the new shoots as they grow
How is large-scale timber production managed? How WAS it managed in the past?
- past often involved clear felling, but this could destroy habitats on a large scale, reduce soil mineral levels and leave soil susceptible to erosion
However now the following principles are applied:
- any tree which is harvested is replaced by another tree
- forest as a whole must maintain its ecological function
- local people should benefit
SELECTIVE cutting: involves removing only the largest, most valuable trees, leaving the habitat broadly unaffected. Try to ensure each tree supplies more wood by controlling pests and pathogens, only planting tree species where they will grow well, and positioning trees and optimal distance apart
The Marine Stewardship Council has proposed which three principles for sustainable management of fisheries?
- fishing must take place at a level which allows it to continue indefinitely. Overfishing must be avoided. If it does happen, reducing fishing to let stocks recover can increase productivity.
- fishing must be managed to maintain structure, function and diversity (should not be permanent damage to local habitat)
- a fishery must adapt to changes in circumstances and comply with regulations on a local and national level.
What is the benefit of Aquaculture?
Raising stocks of fish in aquaculture restricts impact of oceanic fish stocks.
What other enforcements can be made for fishing?
Fishing quotas
Agreeing areas where fishing is banned
Regulating mesh size
Banning certain practices and promoting sustainable ones such as trolling
Restrictions on species of fish that can be caught (i.e. not endangered species)
Seasonal limitations
Fish farms are one potential solution to declining fish stocks. List three other strategies that governments could use to increase the sustainability of commerical fishing (3)
- quotas
- nets with larger mesh
- limit to certain times of year
- areas where it is banned
- allow certain species only
- issuing licenses/ strict enforcement
Suggest why international agreements are particularly important in the case of sustainable fishing (1)
fish swim between countries
much of ocean doesn’t belong to any one country
people catch fish in countries other than their own
The Madidi National Park is also home to approximately 260000 humans who support
themselves by means of cattle-farming, and the production of timber and brazil nuts (a large
nut harvested from a local native tree).
Conservationists have been working with:
* local people to promote sustainable use of these resources; and
* government agencies to maintain the quality of the national park.
Explain why the Madidi National Park is an example of conservation rather than preservation
there are (local) people there
sustainable use
(area used for) logging / farming / nut production
active measures / work , to maintain , biodiversity / habitat/ park
