IB Biology Option C (SL) — Ecology & Conservation

Limiting factor

Factor that is the most scarce in relation to an organism's needs.

• Plants — temperature, water availability, light intensity, soil pH, soil salinity, minerals.

• Animals — temperature, water, breeding sites, food supply, territory.

Transect

A straight line between two points, along which samples are taken. It prevents any bias in the selection of samples.

(very useful where it is suspected that there is a change in abiotic factors and populations)

Keystone species

A species that has a disproportionate effect on the structure of an ecological community.

It is often, but not always, a predator in the food web.

If keystone species are removed, there may be a dramatic shift in the balance of species remaining in the community.

The Niche Concept

Each species plays a role within a community because of the unique combination of its spatial habitat and interaction with other species.

• Fundamental — this is the niche that an organism could potentially occupy.

• Realised — this is the proportion of the fundamental niche that is actually occupied by the organism (usually due to competition).

The Competitive Exclusion Principle

Two species cannot survive indefinitely in the same habitat if their niches are identical.

Parasitism

A relationship between two different species where only one species benefits and the other one is usually harmed.

Mutualism

A relationship between two different species where both species have some degree of physiological dependency on one another and benefit from the relationship.

Commensalism

A relationship between two different species where one species benefits in some way but the other is not affected.

Predation

A predator killing its prey.

Herbivory

A primary consumer feeding on a plant or its products.

Competition

When two or more species compete for a particular resource.

Zooxanthellae & reef-building corals

• Zooxanthellae are tiny green algae. They require sunlight for photosynthesis (reef-building corals grow near the surface).
• The algae live in the coral polyps (it gives them protection from being eaten).
• Sugars, glycerol, amino acids and other molecules produced by the algae are used by the coral.

Trophic levels

An organism's trophic level is its feeding position in a food chain.

A consumer can be assigned to a trophic level depending on what it is eating at the time, or depending on its main food source.

Pyramids of energy

They model the energy flow through ecosystems (bar chart).

• Units are KJ ⁻² year ⁻¹

The lowest bar represents gross primary production by the producers.

• Width — has to be drawn to scale.

• Height — not significant, but they should be uniform.

Biomass

The total dry mass of organic matter in organisms or ecosystems.

By measuring the biomass of an ecosystem, we can see how productive it is — and compare this to other ecosystems or past data.

Can be used to measure the 'health' of an ecosystem.

Net production

The amount of organic matter remaining after respiration.

Gross production

The total amount of organic matter produced in an ecosystem.

Ingested energy

The % of ingested energy converted to biomass is dependent on the respiration rate.

Net production = Gross production - Respiration (energy lost as heat)

The Food Conversion Ratio

It is a measure of an animal's efficiency in converting feed mass into the desired output.

FCR = mass of food eaten (g) / (increase in) desired out (g)

(per specified time period)

• The lower the FCR the more efficient the method of food production.

Closed ecosystems

Isolated from other ecosystems.

Matter is cycled within the ecosystem and is neither lost nor gained.

Ex. The Eden Project (Cornwall, UK)

Climate & Ecosystems

An ecosystem develops as a result of its climate (the final ecosystem is called a biome).

Biosphere

Those regions of the Earth that are able to support life.

Biome

A large area of land with similar conditions, and characteristic types of plants adapted to those conditions.

The main factors affecting the distribution of biomes is temperature + rainfall.

6 major biomes

• Tropical evergreen forest
• Savannah
• Temperate deciduous forest
• Grassland
• Cold desert
• Tundra

Climograph

A diagram which shows the relative combination of temperature and precipitation in an area.

Ecological succession

After an ecosystem has been disturbed it passes through a series of phases to return to the stable ecosystem.

This is a process in which communities of plant and animal species are replaced in a particular area, over time, by a series of different and usually more complex communities.

There are 2 types.

Primary succession

Only starts where there is no existing community.

Ex. volcanic lava flow

Secondary succession

When an existing ecosystem has been damaged.

Ex. by fire or grazing

Eutrophication

Excessive richness of nutrients in a lake or other body of water, frequently due to runoff from the land, which causes a dense growth of plant life and death of animal life from lack of oxygen.

Gersmehl diagrams

The diagram is a model of nutrient storage and flow for terrestrial ecosystems.

Alien species

One species that is non-native and has been introduced either deliberately or accidentally.

They can establish themselves in native ecosystems and become invasive (predator, diseases, additional competition).

• May not survive to their new environment.

Ex. Cane toad in Australia

Biological control

Using a predator or parasite to control a pest species.

Biomagnification

The process by which chemical substances become more concentrated at each trophic level (higher in final consumers).

• Chemicals which do not break down in the environment or in an organism's body will accumulate.

Macroplastic debris

Large pieces of plastic such as bottles, bags, toys, fishing lines, cigarette lighters, six-pack rings or pieces of fishing nets.

• Transported by currents
• Extremely harmful to marine life.

Microplastic debris

Broken down macroplastic debris.

• Transported by currents
• Extremely harmful to marine life + harder to remove.

Gyres

The five major areas ocean currents concentrate garbage into.

• Circular currents isolate the waste there.

Indicator species

An organism used to assess a specific environmental condition.

• Sensitive to specific environmental conditions
• They have a limited range of tolerance
• Their presence or absence can be used as an indicator of environmental conditions.

Ex. Lichens show how much the air is polluted with sulphur dioxide (they are very vulnerable to it)

BI

Σ (nᵢ x aᵢ) / N

Σ = the sum of
nᵢ = the number of individuals of a species
aᵢ = the tolerance rating of the species
N = the total number of individuals collected

• The higher the BI, the healthier the ecosystem.

Simpson's Reciprocal Index of Diversity

Measure of species richness.

D = N(N - 1) / Σn(n - 1)

N = total of organisms of all species
Σ = the sum of (species)
n = number of organisms of a single species

Extinction

The end of a species.

• Has always been a part of evolution. Those species that are best adapted to their environment will survive to reproduce.

Anthropogenic factors that lead to extinction

• Habitat destruction
• Pollution
• Overfishing or hunting
• Climate change
• Invasive species

In situ Conservation

Animal conserved in its natural habitat.

• Natural habitat is conserved
• Maintain's the animal's normal behavior
• Food web / chain structure of the ecosystem maintained

Ex situ Conservation

Animal conserved away from its natural habitat.

• Will work if habitat is lost
• Easy to isolate the animal from threats
• Species maybe too rare to breed / maintain population in the wild
• Captive breedings can quickly increase numbers (for some species)

Nature reserves

Areas of aquatic or terrestrial ecosystems that have been protected in order to conserve biodiversity, heritage or are home to unique species.

• Large size is better
• Those with less "edge" are better than those with more
• Clustered ones are better than fragmented and isolated ones
• Habitat corridors are good (encourage greater diversity

Benefits:
- control of invasive species
- control of human exploitation
- legal protection of endangered species
- opportunities for research
- restoration of degraded areas