Biology Option C Revision

IB Biology Option C

Limiting Factor

something present in the environment that can restrict the distribution of a species or abundance

Transect

an arbitrary line through a habitat, selected to sample a community. Used to study the distribution of plants and animals along environmental gradients

Law of intolerance

populations have optimal survival conditions for environmental factors, within critical minimal and maximal thresholds

Ecological niche

A species’ use of the biotic and abiotic resources in its environment. It composes of various components:

* Habitat
* Activity patterns
* Resources
* Interactions with other species

Fundamental Niche

describes the full range of conditions and resources which a species could survive and reproduce. Is the potential for theoretical distribution in the absence of competing species

Realized Niche

describes the actual conditions and resources in which a species exists due to biotic interactions. Is smaller than the fundamental niche due to the presence of competing species.

Competitive exclusion

one species has a greater selective advantage and will out-compete the other species, leading to extinction of the population from that environment

Niche portioning

both species alter their use of habitat to divide resources between them

Symbiotic relationship

A long term biological relationship between species. Are obligate (required for survival) or facultative (advantageous but not necessary)

Zooxanthellae algae and reef-building coral

The coral provides the algae with a protective environment and source of inorganic compounds:

* Coral polyps secrete calcium carbonate to build a stony skeleton which encases the polyps (and zooxanthellae)
* Coral polyps recycle the waste products of the algae and supplies the zooxanthellae with carbon dioxide
The zooxanthellae provides the coral polyps with a necessary source of nutrition:
* The algae supplies the coral with oxygen, glucose and other organic molecules (produced via photosynthesis)
* The algae also helps the coral to remove necessary waste products
Up to 90% of organic matter produced in photosynthesis by the algae is transferred to the coral

Keystone species

A species that has a disproportionately large impact on the environment relative to is abundance. It provides stability to the ecosystem.

Predators: exert pressure on lower trophic levels to prevent them from monopolising critical resources (sea otter)

Mutualism: support the life cycle of a variety of species within a community (pollinators)

Engineers: refashion on the environment in a manner that promotes the survival of other species (beavers)

Keystone Species: Sea Otters

keep the sea urchin populations in check, preventing overgrazing of kelp by the sea urchins, and thus allowing enough kelp forests to remain as a habitat for a variety of other species. As a result, the entire ecosystem is kept in balance

Keystone Species: Parrot-fish

help remove dead coral skeletons and keep the coral growth in check, with coral growth rates roughly balancing the amount of coral eaten by the parrotfish. Smaller parrotfish also eat a lot of macroalgae – such as seaweeds - which is important within the reef system. In over-fished or nutrient-enriched reefs, macroalgae can out-compete the corals. Without parrotfish, coral growth and reef structure can change dramatically

Biomass

the total dry mass of organic matter in organisms or ecosystems

Gross production (GP)

the total amount of organic matter produced by a trophic level in an ecosystem

Net production (NP)

the amount of organic matter remaining in that trophic level after respiration

NP = GP – R (loss due to respiration)

Feed Conversion Ratio

A measure of an animal’s efficiency in converting feed mass into the desired output
A low FCR is obtained by minimising the losses of energy by respiration, for example:

* Restricting animal movement
* Slaughtering the animal at a young age (older animals have higher FCRs as they grow more slowly)
* Optimising feed so it is efficiently digested
* Monitoring feeding to ensure that feed levels equal amount consumed

Biome

a geographical area that has a particular climate and sustains a specific community of plants and animals

Tropical rainforest

typically have both high average temperatures and high precipitation (warm and wet)

Taiga

typically have low average temperatures and reasonably low precipitation (cold and icy)

Desert

typically have high average temperatures but low precipitation (hot and dry)

Gersmehl diagram models

Models that predict and explain the natural world. There are 3 nutrient stores:

* Biomass: total mass of living organisms in a given area
* Litter: any organic mater in and on the soil
* Soil: top layer of the earth that is composed of disintegrated rock particles

Gersmehl diagram models: transfer between nutrient stores

* Fallout pathway: as tissues die, waste excreted, unconsumed parts etc
* Decay/decomposition pathway: inorganic nutrients released to soil as litter is composed
* Uptake pathway: nutrient uptake by plants

Ecological succession

a sequence of increasingly complex communities develop over time

Pioneer community

the living organisms which first colonize the region (typically lichen, mass, bacteria)

Climax community

the end result of the succession process

Primary succession

The emergence of a new community from uninhabitable land (i.e. entirely new land without any established soil)

\-          For example: retreating glaciers, sand dunes, exposed rock (formed from lava flow)

Primary succession is a very slow process (hundreds or thousands of years

Primary Succession steps

* Pioneer species arrive and colonize the area (lichen, mass, bacteria)
* As pioneer organisms die, they decompose, creating the first organic oil
* New species of plants colonize the area, these displace pioneer species
* Growth of plans causes changes to the environment
* Leaf litter and decomposing plants result in increased soil depth, nutrient availability and water retention in the soil
* Growth of roots causes weather of rock, soil mineral content, increases and soil pH can be altered
* Growth of roots can also enable soil to be retained, preventing erosion
* As soil depth increases, larger shrubs and plants can colonize the area
* Animal species arrive as species of plants they rely on become established
* A climax community is established

Secondary Succession

Environmental disturbances such as fire, flood, deforestation and abandoned farmland can result in secondary succession,
Secondary succession occurs in an environment where there has already been an established ecosystem. It involves:

* An environmental disturbance, such as a bushfire, destroys the pre-existing climax community
* The disturbance leaves behind empty, but not destroyed, soil
* Grasses and small herbaceous plans grow back first
* Small bushes and trees begin to colonize the area
* Fast growing trees will develop to their fullest
* Shade in-tolerant trees may be replaced, and shade tolerant trees will develop in the understory
* Eventually the fast-growing trees may be overtaken by larger, slower-growing trees
* Stable climax community has established

Alien species

those that are introduced into an area by human activity (deliberately or accidentally). It is one that does not naturally occur in an area.

Invasive species

alien species that have a negative effect on the environment and on endemic species

Endemic species

native to a particular geographic region

Advantages that invasive species have that enable them to reduce numbers of endemic species

\-          Have large fundamental niche (can occupy a wider area than endemic species)



\-          Absence of natural predators that would limit their survival (or invasive species absence of suitable herbivores)



\-          Tend to reproduce rapidly



\-          May have features that are suited to survival in the new environment

Cane toad

Biological control of sugar can beetle.

\-          Competes with native species for resources and is a generalist predator that feeds on a wide range of species

Produces a toxic chemical that poisons native predators

Biological control

can be successful in controlling the invasive species if there is a high degree of host specificity

European rabbits in Australia

Physical:

\-          Destruction of warrens and above-ground harbors

Biological:

\-          Released rabbits infected with myxoma – a rabbit specific virus – into southeastern Asia

Biomagnification

the process by which chemicals become concentrated in the tissues of organisms at higher trophic levels

Bioaccumulation

the build-up of fat soluble chemicals in the tissues of a single organism. Bioaccumulation occurs within one particular trophic level

Pollutants that bioaccumulate

\-          DT (dichlorodiphenyltrichloroethane) is a synthetic pesticide sprayed on crops and used against malarial mosquitos



\-          PCBs (polychlorinated biphenyls) are synthetic chemicals used in flame retardants, paints, insulation of electrical equipment

Case study on biomagnification  

Peregrine falcons and other birds are consuming DDT, causing biomagnification to occur.



Cause: DDT was used to eradicate beetles that carried Dutch elm disease, but instead also led to a slaughter of robins and other birds because they were eating pesticides



Consequences: decrease in thickness of egg shells, decrease in population of birds

Gyres

\-          Most plastics are not biodegradable and may persist in the environment for centuries



\-          Ocean currents transport garbage around the globe, with debris accumulating in 5 convergence zones called “gyres”



\-          It is estimated that approx. 87000 tones of plastic are currently floating in the Great Pacific Garbage Patch, spready over an area 3x the size of France

Penguins

\-          Entanglement, directly eating or indirect ingestion of other organisms



\-          36% found entangled



\-          83% from fishing gear



\-          They think it’s food and it also smells like food



\-          Produced from Asia but floats everywhere

Indicator species

an organism used to assess a specific environmental condition

\-          Species that have limited tolerance and sensitivity – useful indicators

\-          Presence or absence of indicator species may show effects of disturbance

Biotic index assessing environmental conditions

Can be used to provide an overall environmental assessment of an ecosystem



High: unpolluted



Low: polluted

Richness

the number of different species present in one area. Greater number of species – community has greater richness

Evenness

the relative abundance of each species in the community. Similar abundance – community has high evenness (a complex ecosystem with lots of different niches supporting a wide range of species)

In situ

The preservation of species within their natural habitat (on site). Within the boundaries of designated conservation

Ex situ

The preservation of species outside their natural habitats. This is usually implemented for critically endangered species requiring urgent intervention to prevent extinction

EX SITU CONSERVATION APPROACHES

Captive breeding: animals are raised and bred in containment (eg. Zoos), followed by release of captive-bred animals into their natural habitat



Seed banks: secure sites that store plant seeds at low temperatures – seeds can survive under these conditions for long periods of time – this can preserve plant genetic diversity for the future



Botanic gardens: areas set aside to collect and grow of a wide variety of plant species

Disadvantages of ex situ conservation methods

\-          Do not prevent the potential destruction of their natural habitats or the factors threatening the species with extinction



\-          Species raised in captivity are less likely to be successfully reintroduced into the wild



\-          Difficult to maintain genetic diversity and there is a risk of inbreeding



\-          Not all species bred easily in captivity



\-          Aesthetic values can lead to an imbalance in conservation

Nature reserves

Larger habitats/reserves



\-          Have more resources, breeding sites etc that can support a greater range of habitats and species



\-          Can support higher population numbers of each species



\-          Can maintain large species with adequate resources



\-          Allows for migration



\-          Reduces the edge effect and possibility of the invasion of alien species

Impact of edges effects on species diversity

Edge effects exist at the boundary between two distinctly different habitats or ecosystems.



The ecology at the edge of an ecosystem will be different from the central areas (e.g. different abiotic factors like sunlight, temperature, different species, different levels of exposure to human disturbance).



Larger habitat fragments (or native reserves) have a smaller perimeter: area ratio than smaller islands, and have fewer edge effects

As the total area becomes smaller, the edge effect becomes proportionally