Populations and Sustainability Explain the significance of limiting factors in determining the final size of a population; Explain the meaning of the term

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).

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

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

Snowshoe Hare

Lynx

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








Georgyi Frantsevitch Gause

• Outline the study on Interspecific competion in paramecium carried out by Gause in 1934

GauseFindings• 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


• 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

VS.

In the lab, T. Castaneum increased their population size, but a change in temperature would mean that T. Confusum was successful

T. Castaneum

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.








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• 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

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• 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 replanting2. The biodiversity, mineral and water

cycles are maintained3. 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.








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


• 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.

• http://www.youtube.com/watch?v=XpblfFd6a5A• http://www.youtube.com/watch?v=MLX4tkwwieM• http://www.youtube.com/watch?v=NHAz1ak2sqY

http://www.youtube.com/watch?v=XpblfFd6a5A

http://www.youtube.com/watch?v=XpblfFd6a5A

http://www.youtube.com/watch?v=MLX4tkwwieM

http://www.youtube.com/watch?v=MLX4tkwwieM

http://www.youtube.com/watch?v=NHAz1ak2sqY

http://www.youtube.com/watch?v=NHAz1ak2sqY

Activity effect• Eating them

• Non-native animals introduced eat native species

• Non-native plants out-complete native species

• Fishing

• Tourism: – 1991- 41 000 tourists -2008-160 000 tourists

Island population increased

• Explorers in 19th Centuary hunted a type of Giant Tortoise to extinction on Floreana Island

• 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.

• Reduced population of sea cucumbers and hammerhead sharks. Galapagos green turtles are accidentally killed in nets and are now endangered.

• Development on islands e.g. airport on Baltra Island – land cleared, pollution, pressure on drinking water and energy supplies

• Increased opportunities from tourism – more development

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• 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 before6months after10 years after

•Deforestation is a necessary

evil

Deforestation is a necessary

evil

Documents

Populations and Sustainability Explain the significance of limiting factors in determining the final size of a population; Explain the meaning of the term