6.5 and 6.6

Interspecific Competition

Competition between different species

When does interspecific competition occur?

When 2 or more different species of organism compete for the same resource.

What happens in interspecific competition?

The interaction results in a reduction of the resource available to both populations.

As a result of less food, organisms will have less energy for growth and reproduction, resulting in smaller populations than if only one of the species had been present.

Competition Exclusion Principle

If one species is better adapted, then the less well adapted species will decline in number until it can no longer exist in the habitat alongside the better species.

Examples of Interspecific Competition

Red and Grey Squirrels

Intraspecific Competition

Competition between members of the same species

Intraspecific Competition graph

Stage 1 = Resource is plentiful in a habitat, all organisms can survive and reproduce, so there's an increase in population size

Stage 2 = As a result of increased population, there are many more individuals that share resources, and resources become limited, decreasing the population size

Stage 3 = Less competition exists as the smaller population means less organisms are competing for the same resources. This means more organisms survive and reproduce, increasing population size

Predation

A biotic factor that can influence population size.

Many predators have evolved ways to catch their prey (like speed and stealth) and prey have evolved in ways to avoid capture (like camouflage and stings)

Predator Prey Relationships

- As prey pop increases, there's more food for predator

- So predator pop increase, which decreases the prey pop due to higher death rate than birth rate

- Reduced prey pop then decreases the predator pop. Intraspecific competition for food increases

- Reduced predator pop result in less prey being killing, so the prey pop increases, and the cycle begins again

Phase 1

• A period of slow growth.

• Small individuals that are initially present reproduce, increasing the total population.

• As the birth rate is higher than the death rate, the population increases in size.

Phase 2

A period of rapid growth.

As the number of breeding individuals increases, the total population multiples exponentially. No constraints act to limit the population explosion.

What is Phase 3 in population growth?

A stable state

What prevents further population growth in Phase 3?

External constraints

How do birth rates and death rates compare in Phase 3?

They are approximately equal.

What causes fluctuations in population size during Phase 3?

Limiting factors, such as the presence of predators.

Limiting Factors

Limiting factors prevent further growth of a population and in some cases cause it to decline

Examples of limiting factors

Competition between the organisms for resources

Build up of toxic by products of metabolism

Disease

Carrying capacity

The maximum population size that an environment can support

When does the population size remain stable?

When the number of births and deaths are approximately equal

What is the term for a large decrease in population size that reduces the gene pool?

Genetic bottleneck

Employment of rangers

Controls poachers

Controlled grazing

Allows time for species to recover & reduces the risk of soil erosion

Management of Tourism

Limiting areas tourists can visit & using "ecotourism" prevents the exploitation of the environment

Can also provide revenue for conservation projects

Legal hunting of excess animals

Maintains population numbers. Can bring in money for conservation projects

Establishing wildlife sanctuaries & nature reserves

Allows species to be conserved in their natural habitat

Removal of non-native species

Prevents competition with native species for resources. Allows recovery of native species populations.

Halting succession using coppicing, mowing or grazing

Maintains areas of different ages.

Protects some habitats such as heathland & moorland becoming woodland.

Why is sustainable forest management good?

It provides with sustainable wood fuel resources, secures biodiversity of forests, improves soil and water management.

Sustainable agriculture

Secures economic welfare of residents & biodiversity, improves soil fertility & crop yields.

Rewilding

Rebuilds a natural ecosystem

Footpath signage

Allows walkers to visit area but keeping to designated areas prevents trampling of vegetation or disturbance of ground nesting birds

Limiting recreational activities such as mountain biking

Prevents large tyre treads damaging vegetation and topsoil, prevents soil erosion.

Reintroduction of native species

Restoration of the natural food web

What are the aims of sustainability?

• To preserve environment

• Ensure resources available to future

• Allow all human societies to live comfortably

• Enable less economically developed countries to develop by exploiting their natural resources

• Create a more even balance in the consumption of resources in more economically developed countries and LEDCs.

Timber Production:

- Rotational felling

- Clear felling

- Strip felling

- Selective felling

- Coppicing

- Pollarding

Rotational felling

- Planting a site

- Felling the trees when reached maturity

- Takes 8-20 years

Pros of Clear felling

It is a productive and economical method of timber production

Cons of Clear felling

All trees are removed including their roots which is devastating for the natural environment

Pros of Strip felling

Narrow strips are cut so that forest on either side can regrow and reclaim the land, allowing forests to be logged with minimum effort and damage

- Allows other trees to grow to maturity and also leaves enough for habitats for animals

Cons of Strip felling

Better than clear cutting but leads to habitat fragmentation

Pros of Selective felling

- Only older trees are felled and newer trees remain, ensuring continual regeneration of young seedlings

- This allows other trees to grow to maturity

- Leaves enough trees for habitats for animals

- Works well for forests with fast-growing trees.

Cons of Selective felling

Helicopters are often needed and there is risk of damage to neighbouring trees.

It does not suit forests with slow growing trees.

After felling a tree, what should you do that would make this process sustainable?

Replant the tree

How should you fell sustainably?

- Limit the size of the area being felled to reduce soil erosion

- Replant trees that have been felled

- Have optimum distances between replanted trees

- Rotate areas that are felled to allow trees to mature.

Coppicing

- Trunk cut close to ground level

- Several new shoots will grow from cut surface

- Process repeated after certain time

Pros of Coppicing

- Can be repeated indefinitely

- Lifespan of tree extended

- Provides variety of light levels

- Fewer large trees means more light for smaller plants

- Provides a variety of habitats and maintains biodiversity

- Roots are present, and therefore prevent soil erosion

- Maintains soil quality

- Prevents succession

- Large machinery not needed therefore less disturbance

Cons of Coppicing

Herbivores have access to the newly forming shoots and damage them therefore you need to protect young shoots from grazers.

Pros of Pollarding

The tree trunk is cut high above ground so there is less chance of damage from herbivory (you have to say herbivory cause deers don't eat meat)

Cons of Pollarding

The timber produced is small in size and not suitable for construction.

Sustainable Fishing Organisations:

ICCAT

CFP

NAFO

ICCAT

International Commission for the Conservation of Atlantic Tunas

Organisation responsible for the management and conservation of tuna and tuna-like species in the Atlantic Ocean and adjacent seas

CFP

Common Fisheries Policy

Puts fishing quotas on the numbers of certain fish that are allowed to be caught in a particular area

NAFO

Northwest Atlantic Fisheries Organisation

An intergovernmental organization with a mandate to provide scientific advice and management of fisheries in the north-western part of the Atlantic Ocean

Use of nets with larger mesh sizes

It lets smaller fish out so they can continue to grow and breed until they are larger

Setting up fishing exclusion 'no catch' zones

Provides an area for fish to grow to adulthood and to breed safely. This can restock other, adjacent areas.

Restricting use of small hook sizes

Ensures small fish are not taken and can survive long enough to breed

Issuing fishing quotas or limit mass of fish caught

Limit the mass/number of fish caught

Restocking the sea with young fish

To increase chance of fish reaching adulthood and breeding safely

Allowing commercial and recreational fishing only at certain times of year

Protects the breeding season so that breeding can be maximised.

Limiting the number of boats that can fish in an area

Limit the mass/number of fish caught

Inspection of catches landed at ports

Ensures regulations are being followed

Introduction of fish farming

Reduced pressure on wild populations

Creating marine conservation zones

To protect vulnerable habitats

Allow catching of certain species only

To protect vulnerable/endangered species

Strict enforcement of regulations - issue licenses & penalties/sanctions

To act as a deterrent to poachers

Difficulties in sustainable fishing

- Area too large

- Expense of monitoring

- Monitoring hampered by weather/seasons

- False reporting of catches / trawler size / mesh size

- Fish are killed when caught but not kept due to restrictions

Why does conservation take place?

To manage nature to protect species/habitats

It allows changes to the profile of organisms in an ecosystem

Preservation

- Leaves the environment to not be used by humans (leaves the ecosystems untouched)

- Takes place in areas with little or no human population and allows no human intervention, like the Arctic tundra where mineral mining has been prohibited

Why is conservation important?

Economic, social, and ethical reasons

Economic Reasons

- Ecotourism

- Potential for future medicines

Social Reasons

- Aesthetic

- To stop the impact of deforestation

Ethical Reasons

- Preserves biodiversity / Stops extinction

- Supports the indigenous population

Why does succession occur?

There are changes in the environment (abiotic factors), causing the plant and animal species present to change

Primary succession

Occurs on land that has been newly formed or exposed. There is no soil or organic material present to begin with

Secondary succession

Occurs on land where soil is present, but it contains no plant or animal species. Examples include a forest being burnt down.

What are stages in succession known as?

Sere

What are the main seral stages in primary sucession?

Pioneer community

Intermediate community

Climax community

Pioneer Community

Arrive before the climax community

Subject greater to change

Low biodiversity

Less stable

Low biomass

Example: mosses, lichen

Why is the pioneer community important?

- Fixes nitrogen

- Performs photosynthesis

- Tolerates extreme conditions

- Weathers rocks to create a layer of humus

Intermediate community

When the pioneer species die, they add to the soil, which is now able to support grasses and small flowering plants. These outcompete the pioneer species.

Example: Grasses, small flowering plants

Climax community

When the intermediate species die, they add to the soil, which is now able to support larger shrubs and trees.

These outcompete the grasses and flowering plants for light, space, and nutrients

Examples: Oak tree

Which is the stable community?

Climax community

At the beginning of Primary Succession

Hostile conditions

Low Simpson's index species diversity

Instability

At the end of Primary Succession

Less hostile conditions

High Simpson's index species diversity (unless dominated by 1 species)

More stable

Likely to withstand change

Animal Succession

Primary consumers, such as insects and worms, are first to colonise an area as they consume and shelter in the mosses and lichens present

Secondary consumers will arrive once a suitable food source has been established, and the existing plant cover will provide them with suitable habitats

Deflected Succession

This is where human activity can halt the natural flow of succession and prevent it from reaching its climax community. When succession is artificially stopped, it is called a plagioclimax.

Examples of deflected succession

• Grazing from domesticated animals

• Removing existing vegetation to plant crops (the crops become the final community)

• Burning as a means of forest clearance

Where is carbon stored?

- Atmosphere

- Sedimentary rocks

- Soil

- Vegetation

- Dissolved in the ocean

Photosynthesis

- This process removed carbon from the atmosphere

- CO2 is converted into small carbon containing organic molecules by photosynthesis in plants, and other photosynthetic organisms

- This carbon is then used in the production of macromolecules such as carbs, proteins, and lipids

Respiration

Respiration releases CO₂ into the atmosphere, opposite to photosynthesis

CO₂ is released in the Link Reaction and the Krebs Cycle of aerobic respiration

Anaerobic respiration also releases CO₂ into the atmosphere via fermentation by yeast, mould, and bacteria

Feeding

Carbon is passed from autotroph to heterotroph during feeding

Carbon is also passed from primary consumer to secondary consumer

Biomass transfer always includes the transfer of carbon, the main element in biomass

How does Decay & Decomposition release CO₂ back into the air?

Dead plants and animals are fed upon by detritivores and decayed by saprophytes

• This releases carbon into the surroundings

• Supplies carbon to the detritivores

• Supplies carbon to the saprophytes

• Waste matter such as faeces and urine is used by decaying saprobionts

Such processes can release CO₂ back into the air

What happens if dead organic matter accumulates in areas where decomposers are not present?

The carbon they contain becomes trapped. Over millions of years, these remains form fossil fuels,

They are trapped in the bottom of the ocean or in bogs.

Combustion

- Plants that die are not fully decomposed by saprobionts, and their bodies form layers of sediment that can accumulate over millions of years, locking carbon into the ground

- This sediment is a store of energy and can form fossil fuels

- When fossil fuels are burnt, carbon dioxide is returned to the atmosphere

Fluctuations in atmospheric carbon dioxide

CO₂ levels fluctuate throughout the day

• Photosynthesis only takes place in the light, and so during the day, photosynthesis removes CO₂ from the atmosphere

• However, respirations occurs constantly, so atmospheric CO₂ levels are higher at night than during the day

• CO₂ levels are lower in summer than in winter, where photosynthesis is lower

Why is atmospheric carbon dioxide levels increasing?

- Combustion of fossil fuels

- Deforestation

Why is global warming bad for the oceans?

• Warmer oceans dissolve less gas

• Therefore, global warming is reducing the carbon bank in the oceans, and releases more CO₂ into the atmosphere

Processes in the Nitrogen cycle

1) Nitrogen fixation

2) Nitrification

3) Ammonification

4) Denitrification

What is Nitrogen fixation?

A process of combining nitrogen gas and hydrogen to produce ammonia.

Ammonia is a form of nitrogen that can be absorbed and used by plants.

Nitrogen fixation methods?

- Non living processes - Lightning, and the Haber process

- Living processes - Rhizobium, and azotobacter