6.3.2 Populations and Sustainability

Draw, label, and annotate with explanations, a generalised growth curve for natural populations.

Lag phase - Slow growth - small number of individuals initially present. Birth rate > Death rate
Log phase - Rapid growth - number of breeding individuals increases, total population multiplies exponentially. No constraints act to limit population explosion. Birth rate >> Death rate
Stationary phase (Carrying capacity) - Stable state - Further population growth prevented by external constraints. Population size fluctuates but remains relatively stable. Birth rate = Death rate

Define the terms "abiotic factor", "biotic factor", "limiting factor" and "carrying capacity".

Abiotic factor - non-living conditions in a habitat
Biotic factor - living components of an ecosystem
Limiting factor - factor which limits the rate of a process
Carrying capacity - the maximum population size that an environment can support

Give 3 examples of limiting factors for population size and explain how each affects population size.

Biotic: Predation, Food supply, Grazing, Parasitism, Disease, Intraspecific and Interspecific competition
Abiotic: Temperature, pH, Light intensity, Water availability, Oxygen concentration, Humidity

Define the terms "density dependent factors" and "density independent factors" and give 3 examples of each.

Density dependent factors - factors whose strength depends on the population size. Competition, Predation, Grazing, Disease
Density independent factors - factors that will affect the same percentage of the population regardless of its size. Natural disasters, Temperature

Define the terms "migration", "immigration" and "emigration"

Migration - the movement of individuals from one place to another
Immigration - the movement of individuals into a particular area
Emigration - the movement of individuals out of a particular area

Define the terms "intraspecific competition" and "interspecific competition"

Intraspecific competition - competition between organisms of the same species
Interspecific competition - competition between organisms of different species

Give 4 examples of what organisms might compete for.

Space, food, light, water

Describe and explain the "competitive exclusion principle"

Where 2 species are competing for limited resources the one that uses the resources more effectively will ultimately eliminate the other

Explain why intraspecific competition is an example of a density dependent biotic factor, and why it may result in fluctuations in population size over time.

When resource is plentiful in a habitat all organisms have enough to survive and reproduce. This results in an increase in pop. size.
As a result of increased population, there are many more individuals that share food or available space. Resources now limited; not enough is available for all organisms to survive - pop. decreases.
Less competition exists as smaller population means fewer organisms are competing for the same resources. This means more organisms survive and reproduce, resulting in population growth.

Define the terms "predator", "prey", and "predation".

Predation - the capturing of prey in order to sustain life
Predator - an animal that naturally preys on others - captures and feeds on other animals

Describe and explain the general pattern shown in predator-prey relationships

An increase in the prey population provides more food for the predators, allowing more to survive and reproduce, resulting in an increase in predator population. The increased predator population eats more prey organisms causing a decline in the prey population as its death rate is greater than the birth rate. Reduced prey population can no longer support the large predator population. Intraspecific competition for food increases resulting in a decrease in the size of the predator population. Reduced predator numbers result in less of the prey population being killed. More prey organisms survive and reproduce, increasing the prey population - cycle begins again.
Rarely this simple in the wild - other factors such as availability of food for prey, presence of other predators and changes in abiotic factors (seasonal) also have an effect.

Define the terms "conservation" and "preservation", and explain the difference between the two

Conservation - the maintenance of biodiversity through human intervention or action
Preservation - protection of an area by restricting or banning human use - so that the ecosystem is kept exactly as it is

Difference - conservation active, preservation passive

Define the term "reclamation" and give 3 examples of conservation and 3 examples of preservation.

Reclamation - Restoration of land/ecosystems that have been degraded by human activity or impaired by natural phenomena

Conservation: Using grazing to keep Fen land from becoming woodland, Removal of invasive species such as Rhododendron, Legal hunting of animals in nature reserves to reduce the population from potentially damaging levels

Preservation: International agreement preventing large scale human activity in Antarctica, Only scientists are allowed on the island of Surtsey - a new island formed by volcanic activity off Iceland, Gating pristine caves to prevent people entering in order to protect the fragile ecosystems and geology

Define the terms "ecological", "economic", and "aesthetic" when referring to reasons for maintaining biodiversity

Ecological - reasons concerning the potential impact on other species and whole ecosystems
Economic - reasons involving people, communities or companies earning a living or making more money from the biodiversity in a sustainable way
Aesthetic - reasons based around the beauty of nature and its ability to enrich lives and inspire people

Define the terms "social" and "ethical" when referring to reasons for conservation of biological resources and give two examples of each.

Social - reasons that are for the benefit of society, providing areas for relaxation,exercise and hobbies
Ethical - reasons based on the rights given to organisms (or the environment) by some people, or on the moral responsibility we have to future generations

Define the term "sustainability" and "sustainable resource"

Sustainability - the ability to continue a particular action indefinitely without using resources in a way that could eventually make them run out and without leading to irreversible damage to the environment
Sustainable resource - a resource that can be exploited economically in a way in which it will not diminish or run out

Describe 5 aims of sustainability.

Preserve the environment
Ensure resources are available for future generations
Allow humans in all societies to live comfortably
Enable less economically developed countries to develop through exploiting their natural resources
Create more balance in the consumption of these resources between LEDCs and MEDCs

Describe 3 things that can be done to reduce the demand for a resource and therefore make it easier to manage sustainably.

Reduce, Reuse, Recycle
Reduce consumption of resource
Reuse resource in original form
Recycle resource after use to create new things

State two methods of small scale timber production.

Coppicing and Pollarding

Define the terms "coppicing", "pollarding" and "rotational coppicing".

Coppicing - cutting a tree trunk back close to ground level to allow new shoots to grow up from this stump, and then harvesting the shoots at regular intervals
Pollarding - cutting a tree trunk back to a few metres above ground level to allow new shoots to grow up from the top of this trunk, and then harvesting these shoots at regular intervals
Rotational coppicing - dividing woodland up into sections, trees are only coppiced in one section each year. There are enough sections so that the first section has fully regrown by the time all other sections have been coppiced.

Describe the process of coppicing and explain the advantage of rotational coppicing

Cutting a tree trunk back close to ground level to allow new shoots to grow up from this stump, and then harvesting the shoots at regular intervals.
Rotational coppicing allows time for growth between cutting so maintains habitats for other organisms in between cutting of areas.

Explain an advantage of pollarding over coppicing.

As new growth is higher up, it is protected from grazers such as deer. The trunks also provide a habitat that is absent in coppiced trees.

Describe the difference between harvesting in large scale timber production and harvesting in small scale timber production.

Trees are replaced by replanting rather than natural regeneration.

Describe 5 practices that can help large scale timber production to be sustainable.

Practise selective cutting
Replace trees through replanting
Plant trees optimal distance apart to reduce competition - maximises yield
Manage pests and pathogens to maximise quality and size of yield
Ensure areas of forest remain for indigenous people

Describe the disadvantages of large scale timber production.

Habitats are destroyed, minerals in the soil are depleted and the bare soil that is left is vulnerable to erosion.

Name and describe an international agreement that aims to ensure fishing is sustainable in the EU.

Common Fisheries Policy (in the EU)
Sets fishing quotas and regulations

Describe 3 methods which can help fishing to be sustainable.

Larger mesh in nets/new net designs - allows younger individuals to escape so they can mature fully and reproduce, reducing by-catch.
Restrictions on time of year for fishing certain species to protect the breeding season allowing the number of individuals to increase.
Fish farming - reduces pressure on wild populations while maintaining protein supply for diets.

Explain why overfishing in one particular area is not likely to make a species extinct.

It will reduce or eliminate the population in the specific area (locally extinct) but the species will survive elsewhere

Define the term "environmentally sensitive ecosystem"

Ecosystems with low resistance to change. Any change disturbs the ecosystem significantly, changing food webs and potentially leading to the extinction of species and massive change in the ecosystem.

State 5 management techniques used in environmentally sensitive ecosystems.

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 plans