Populations and Sustainability
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Explain the significance of limiting factors in determining the final size of a
population;
Explain the meaning of the term carrying capacity;
Describe predator–prey relationships and their possible effects on the population
sizes of both the predator and the prey;
Explain, with examples, the terms interspecific and intraspecific competition;
Distinguish between the terms conservation and preservation (HSW6a, 6b);
Explain how the management of an ecosystem can provide resources in a
sustainable way, with reference to timber production in a temperate country;
Explain that conservation is a dynamic process involving management and
reclamation;
Discuss the economic, social and ethical reasons for conservation of biological
resources (HSW6b, 7c);
Outline, with examples, the effects of human activities on the animal and plant
populations in the Galapagos Islands (HSW6b).
Limiting Factors
• Population size stays stable, but can also rise
and fall suddenly
• Population size is a balance between death
rate and rate of reproduction
Population Growth
• Lag Phase: a few individuals acclimatising to their
habitat. Growth and reproduction is slow
• Log Phase: resources are plentiful and conditions
are good. Reproduction is greater than mortality.
The population increases
• Carrying Capacity: population has levelled out.
The habitat cannot support a larger population.
Reproduction rates equal mortality rate.
Population stays stable or fluctuates very slightly
Why is there a carrying capacity?
• The habitat has factors which limit the growth
of the population size
• These are called limiting factors
• Examples: food, water, light, oxygen, nesting
sites or shelter, parasites or predators,
intensity of competition within and between
species
Predator Prey Relationships
• Predator = animal that hunts other animals for
food
• Prey = eaten by predator
• Predation can act as a limiting factor
populations and sustainability
• Describe predator prey relationship
Predator Prey Graph
Snowshoe
Hare
Lynx
1. Predator population gets bigger, more prey eaten
2. Prey population decreases- less food for predators
3. Fewer predators survive and they decrease
4. Fewer prey now eaten and numbers increase
5. More prey, so predator numbers increase and the cycle begins again
Predator Prey Graph: Limitations
• Predators may eat more than one type of prey
• Predation shown as the main limiting factor
and disease/ hunting etc. not taken into
account
• This gives the graph a less defined pattern
Populations and Sustainability
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Explain the significance of limiting factors in determining the final size of a
population;
Explain the meaning of the term carrying capacity;
Describe predator–prey relationships and their possible effects on the population
sizes of both the predator and the prey;
Explain, with examples, the terms interspecific and intraspecific competition;
Distinguish between the terms conservation and preservation (HSW6a, 6b);
Explain how the management of an ecosystem can provide resources in a
sustainable way, with reference to timber production in a temperate country;
Explain that conservation is a dynamic process involving management and
reclamation;
Discuss the economic, social and ethical reasons for conservation of biological
resources (HSW6b, 7c);
Outline, with examples, the effects of human activities on the animal and plant
populations in the Galapagos Islands (HSW6b).
Georgyi Frantsevitch Gause
• Outline the study on Interspecific competion
in paramecium carried out by Gause in 1934
Gause
Findings
• 2 species of paramecium grown separately and together
• Together, competition for food arose, paramecium aurelia
more successful than paramecium caudatum which died
out
Conclusions
• The more overlap between two species’ niche, the more
intense the competition
• If two species have the same niche, onw would die out in
that habitat
• This is known as the competitive exclusion principle
• This explains why particular species only grow in particular
places
populations and sustainability
• Explain with examples interspecific and
intraspecific competition
Competition
• Occurs when a resource is in short supply
• As competition increases, reproduction
decreases, death rate increases
• Intraspecific competition: between organisms
of the same species e.g. lions
• Interspecific competition: between organisms
of different species e.g. lions and hyenas
Is extinction always inevitable?
• Sometimes, between two species, one just
gets smaller and both populations then
remain quite constant
• In the lab other variables are not taken into
account e.g. temperature
T. Castaneum
VS.
In the lab, T. Castaneum increased their
population size, but a change in
temperature would mean that T. Confusum
was successful
T. Confusum
• Limiting factors (e.g. space, food, light) create a carrying
capacity – maximum population of a species that an
environment can support. It is often the factor in the
shortest supply
• Predator-prey cycle: increased prey numbers; predator
numbers increase as more food; leads to decrease in prey;
predator numbers fall; increase numbers of prey, etc.
• Intraspecific competition is between individuals of the
same species – competing for a mate, food or nest site.
• Interspecific competition is between individuals of
different species – different plant species competing for
light/soil/water/nutrients, etc.
Populations and Sustainability
•
•
•
•
•
•
•
•
•
Explain the significance of limiting factors in determining the final size of a
population;
Explain the meaning of the term carrying capacity;
Describe predator–prey relationships and their possible effects on the population
sizes of both the predator and the prey;
Explain, with examples, the terms interspecific and intraspecific competition;
Distinguish between the terms conservation and preservation (HSW6a, 6b);
Explain how the management of an ecosystem can provide resources in a
sustainable way, with reference to timber production in a temperate country;
Explain that conservation is a dynamic process involving management and
reclamation;
Discuss the economic, social and ethical reasons for conservation of biological
resources (HSW6b, 7c);
Outline, with examples, the effects of human activities on the animal and plant
populations in the Galapagos Islands (HSW6b).
Conservation VS. Preservation
• Conservation =Management of ecosystems so
that the natural resources in them can be used
without them running out. E.g. timber
management. It can also be reclamation –
restoring ecosystems that have been damaged or
destroyed. It is dynamic and needs to adapt to
constant change
• Preservation = protecting ecosystems so they are
kept exactly as they are. Nothing is removed and
they are only used for activities that don’t
damage them
Sustainable Management and Timber Production
• Using OCR Biology p208-209, explain how the
management of an ecosystem can provide
resources in a sustainable way using timber
production as an example
Sustainable Management and Timber Production
• Population increasing exponentially
• More intensive methods used to exploit environmental
resources destroying ecosystems, reducing biodiversity and
depleting resources
• Especially apparent in timber industry due to a growing need
for wood
• Sustainable management is possible maintaining biodiversity,
sustaining timber companies and also our supply of wood
• Can be small and large scale
Small Scale Timber Production
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Involves coppicing
Harvesting wood keeping tree alive
Trunk cut close to ground
New shoots form from the cut surface and mature
These shoots are eventually cut and again are replaced by more
Shoots are used for fencing etc.
Pollarding is similar but the trunk is cut higher up so deer cannot eat the
new shoots
• Rotational coppicing where woodland is divided into sections and only
cut in the particular section until all have been coppiced, then the cycle
begins again- some trees are not coppiced and are known as standards
• Rotational coppicing is good for biodiversity. The trees never grow
enough to block out the light, so succession cannot happen and more
species can survive
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Timber
Production
management
Involves coppicing
Harvesting wood keeping tree alive
Trunk cut close to ground
New shoots form from the cut surface and mature
These shoots are eventually cut and again are replaced by more
Shoots are used for fencing etc.
Pollarding is similar but the trunk is cut higher up so deer cannot eat the new
shoots
Rotational coppicing where woodland is divided into sections and only cut in the
particular section until all have been coppiced, then the cycle begins again- some
trees are not coppiced and are known as standards
Rotational coppicing is good for biodiversity. The trees never grow enough to
block out the light, so succession cannot happen and more species can survive
Pollarding
coppicing
Large Scale Timber Production
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Mostly clear felling = cutting down large areas of forest
Habitats destroyed, soil minerals reduced and soil left susceptible to erosion. Soil
can also run into water and pollutes them
Trees remove water from soil and maintain nutrient levels through the carbon and
nitrogen cycle
Leaving woodland to mature for up to 100 years allows biodiversity to increase
however this is not a timescale that would be effective nowadays... However
companies nowadays ensure;
1. Trees can be replaced by replanting
2. The biodiversity, mineral and water
cycles are maintained
3. Local people must still benefit from the
forest
Selective cutting involves removing only
the largest trees
More wood is supplied per tree as pests
and pathogens are managed, only well
growing trees are planted and they are
placed an optimal distance apart to reduce
competition
• Selective cutting involves removing only the largest trees
• Trees cleared in patches – woodland grows more quickly
in smaller areas between bits of existing woodland than
in larger open spaces. Less soil erosion will occur.
• Coppicing and pollarding
• Only plant native species as they are adapted to the
climate
• New trees attached to a post for support and covered
with plastic tubes to stop them being eaten.
• Planted with optimum space between to reduce
competition.
• More wood is supplied per tree as pests and pathogens
are managed.
Populations and Sustainability
•
•
•
•
•
•
•
•
•
Explain the significance of limiting factors in determining the final size of a
population;
Explain the meaning of the term carrying capacity;
Describe predator–prey relationships and their possible effects on the population
sizes of both the predator and the prey;
Explain, with examples, the terms interspecific and intraspecific competition;
Distinguish between the terms conservation and preservation (HSW6a, 6b);
Explain how the management of an ecosystem can provide resources in a
sustainable way, with reference to timber production in a temperate country;
Explain that conservation is a dynamic process involving management and
reclamation;
Discuss the economic, social and ethical reasons for conservation of biological
resources (HSW6b, 7c);
Outline, with examples, the effects of human activities on the animal and plant
populations in the Galapagos Islands (HSW6b).
Conservation VS. Preservation
• Conservation = maintenance of biodiversity
including diversity between species, genetic
diversity within species and maintenance of
habitats
• Preservation = protecting areas of land unused
by humans
Importance of conservation
• Economic: provide resources that
humans need e.g. rainforests
species provide drugs, clothes and
food which are traded.
• Social: Many ecosystems are
enjoyed and used for activities e.g.
birdwatching!! They should be
conserved for the enjoyment of
future generations too
• Ethical: organisms have a right to
exist and we have a moral
responsibility to future generations
populations and sustainability
• Outline effects of human activity in the
Galapagos Islands
Human activities have effected the
Galapagos Islands
• A small group of Islands
in the Pacific Ocean.
• Many species of animals
and plants have evolved
here that can’t be found
anywhere else.
• E.g. Galapagos giant
tortoise and the
Galapagos sea lion.
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http://www.youtube.com/watch?v=XpblfFd6a5A
http://www.youtube.com/watch?v=MLX4tkwwieM
http://www.youtube.com/watch?v=NHAz1ak2sqY
Activity
effect
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Eating them
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Explorers in 19th Centuary hunted a
type of Giant Tortoise to extinction on
Floreana Island
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Non-native animals
introduced eat native
species
Non-native plants outcomplete native species
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Non-native dogs, cats and black rats
eat young giant tortoises and
Galapagos land iguanas. Pigs also
destroy the nests of iguansas and eat
their eggs. Goats have eaten much
plant life.
Fishing
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Reduced population of sea cucumbers
and hammerhead sharks. Galapagos
green turtles are accidentally killed in
nets and are now endangered.
Tourism:
– 1991- 41 000 tourists
-2008-160 000 tourists
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Development on islands e.g. airport on
Baltra Island – land cleared, pollution,
pressure on drinking water and energy
supplies
Island population increased
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Increased opportunities from tourism –
more development
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Steps taken
• Restrictions on visiting the uninhabited
islands
• Marine reserves
• Culling alien species e.g. goats and destroying
invasive plants eg. Elephant grass
• Captive breeding and reintroduction e.g. giant
tortoises
• Inspecting visiting boats for alien species.
• Preservation is the protection of an area by restricting
or banning human exploitation or contact – nature
reserves/preserves/parks.
• Conservation is maintaining biodiversity but allowing
sustainable production – replanting mixed tree
species after felling for timber.
• Management (grazing or water level control) and
reclamation (preventing succession by draining) are
part of conservation.
• Conservation is for economic (timber industry), social
(recreation) and ethical (preventing species
extinction) reasons.
Questions
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1. Define and list limiting factors
2.Explain the meaning of the term carrying capacity;
3.Describe predator–prey relationships and their possible effects on the
population sizes of both the predator and the prey;
4. Explain, with examples, the terms interspecific and intraspecific competition
5. Distinguish between the terms conservation and preservation
6. why does conservation need to be dynamic? (gre/rev/96)
7. what is meant by reclamation? (gre/rev/96)
8. Explain how the management of an ecosystem can provide resources in a
sustainable way, with reference to timber production in a temperate country
9.Discuss the economic, social and ethical reasons for conservation of biological
resources
10.Outline, with examples, the effects of human activities on the animal and plant
populations in the Galapagos Islands and the steps taken to aid conservation.
Use words or pictures to show what you think…
500 years before
1 year before
6months after
10 years after
Deforestation is
a necessary evil
•Deforestation
is
a necessary evil