Ecology

Species

groups of individuals that can interbreed to produce fertile offspring

Population

A group of species living and interacting in the same area

Difficulties in distinguishing between a population and species

• species diverge when they do not interbreed

• Two populations can still be the same species if they do not interbreed is because they are seperated

• Over long periods of time, reproductively isolated species tend to evolve differently—gradually becoming a different species

  • it is difficult to decide when exactly they seperate

Binomial system for naming organisms

The first part of the name identifies the genus, with the second part of the name distinguishing the species. Species in the same genus have similar traits. The genus name is given an initial capital letter but the species name is lowercase. When written it is underlined.

Types of biodiversity

• Genetic Diversity – The variety of genes and characteristics that are present within a population of a species

  • Genetic diversity is increased by mutations or sexual reproduction and is decreased by natural selection and genetic drift

• Species Diversity – The range of different species that are found within a particular habitat or ecosystem

  • Species diversity is measured in terms of species richness (number of different species) and species evenness (number of individuals in a species)

• Ecosystem Diversity – The variety of habitat types or ecological niches within a given area of land or water

  • Ecosystems can be categorised according to the specific climate, vegetation and animal life within the region (biome)

example of a loss of terrestrial megafauna

North Island giant moas (Dinornis novaezealandiae)

The giant moa (Dinornis novaezealandiae) was a large flightless bird (terrestrial megafauna) that occupied New Zealand’s North Island

• Before the arrival of humans, the moa’s only predator was the massive Haast’s eagle – meaning the moa was extremely vulnerable to ecosystem perturbances

• Following colonisation by polynesian settlers (1200 – 1300), the giant moa was quickly driven to extinction by overhunting and, to a lesser extent, habitat destruction 

example of a loss of a marine species

Caribbean monk seals (Neomonachus tropicalis)
The Caribbean monk seal (Neomonachus tropicalis) was a marine species that lived in the oceans around the gulf of Mexica and the Caribbean

• Their docile nature made them easy prey to humans, who hunted them for their oil and blubber – additionally, overfishing of their food source led to starvation

• The species was declared officially extinct in 2008, although the last confirmed sighting occurred much earlier (in 1952)

The next mass extinction

Anthropogenic: caused by humans

• overharvesting

• invasive species

• pollution

• climate change

Ecosystem

the biotic and abiotic factors in a given area

The level of biodiversity on Earth is not an immutable constant and instead exists in a state of constant flux

• New species can arise over time as a consequence of evolutionary change leading to eventual speciation

• Species numbers may also be diminished when external factors result in the complete eradication of a species (extinction)

The accuracy of a species diversity estimate is dependent on the mechanisms used to determine species classification

• Taxonomists who are ‘lumpers’ tend to classify species according to shared similarities – resulting in lower estimates

• Taxonomists who are ‘splitters’ tend to focus more on the differences between organisms – resulting in higher estimates

When assessing the biodiversity of a particular region, two key measures are investigated:

• Species richness describes the number of different species present in an area (more species = greater richness)

• Species evenness describes the relative abundance of the different species in an area (similar abundance = more evenness)

Ecosystem stability requires a high level of both species richness and species evenness in order to resist environmental change

• An ecosystem with many species but few individuals within each population would not be stable (low evenness)

• An ecosystem with only a few species consisting of many individuals would similarly lack resilience (low richness)

While more species currently exist than at any time in the remote past…

there has also been an unprecedented reduction in species diversity in recent times.

It is estimated that the world has seen a 73% decline in the average size of monitored wildlife populations over the last 50 years

Assessments of biodiversity are made by collaborative multinational agencies – such as the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES)

• These assessments are based on repeated surveys and may rely on contributions from both expert scientists and members of the public (citizen scientists)

Example: Mixed Dipterocarp Forest

• Dipterocarps are a family of trees that function as a keystone species within the rainforest ecosystems of South East Asia

• Their presence provides an important habitat for native species in addition to providing nutritional support via fruits, pollen and nectar

• These forests are progressively being lost in order to provide timber and clear the land for agriculture (e.g. palm oil plantations)

• In Borneo, excessive deforestation is endangering native species like the orangutan, as well as threatening the water security and food sovereignty of the indigenous populations

Example: Great Barrier Reef

• Coral species form connected reefs that are greatly impacted by changes in oceanic temperature or pH

• Coral polyps receive nutrition from photosynthetic zooxanthellae (algae) that live within the polyp’s endodermis

• Changes in ocean temperature or pH may cause zooxanthellae to leave the coral tissue, leading to coral bleaching

• Anthropogenic greenhouse gas emissions are increasing oceanic temperatures and decreasing pH (ocean acidification)

• This has resulted in mass bleaching of the Great Barrier Reef off the coast of Australia, threatening the indigenous marine ecosystem

Extinction

Extinction is the total cessation of a species or higher taxon level, reducing the overall level of biodiversity

• It can result gradually, as one population of organisms progressively evolve into something else (phyletic extinction)

• Alternatively, a species may not leave any identifiable descendents and simply cease to exist (abrupt extinction)

Mass Extinction

Mass extinction events are categorised by an unusually high number of species dying out in a relatively short period

• There have been five mass extinction events in the history of the Earth – with human activity responsible for a sixth current anthropogenic mass extinction

• Examples of species that have gone extinct as a consequence of human activity include the North Island giant moas, the Caribbean monk seals and the Tasmanian tiger

Blue Macaw - Anodorhynchus hyacinthinus

Primary Cause -illegal trapping for international bird trade, followed by habitat destruction from agricultural expansion 

Establishment of a Recovery Committee, Attempted Reintroduction (1995)

In Situ Conservation

typically involves the designation of protected areas of land as either nature reserves or national parks

• Ecological monitoring of species may be required to ensure viable population levels are maintained

• Legislation may be necessary to ensure adequate funding for policing (no hunting) and education

• Further interventions may be required to prevent habitat degradation or competition from invasive species

  • Rewilding involves the active or passive restoration of damaged ecosystems to the point where they become sustainable

  • Reclamation involves the repurposing of an area that has been utilised for human activity – in order to restore previously existing ecosystems (e.g. quarries)

In situ conservation offers several advantages when protecting endangered species from extinction:

• It allows species to live in the environment to which they are adapted and to occupy their natural position in the food chain

• It maintains the animal's normal behaviour (offspring usually aquire skills from parents and peers around them)

• Retaining the natural habitat prevents its eventual loss and ensures it remains available for other endangered species

• Such areas provide a place to return animals from breeding programs as they provide realistic conditions for reintegration

• Reserves in different areas can share information and provide a place for scientific study and developing public awareness

Ex Situ Conservation

Ex situ conservation may typically be required for critically endangered species when urgent intervention is required

• Captive breeding programs involve animals being raised and bred in containment (e.g. zoos) to ensure survival prospects

• Botanical gardens are areas devoted to the collection, cultivation and display of a wide variety of plant species

• Seed or tissue banks are secure sites that store and catalogue seeds or tissue samples, in order to preserve the genetic diversity of species

There are several advantages associated with ex situ conservation:

• It allows for greater control of essential conditions (e.g. climate control, dietary intake, veterinary care, etc.)

• It can improve the chances of successful breeding by utilising artificial methods (e.g. embryo transfer, IVF, etc.)

Ex situ conservation is also associated with several disadvantages:

• Such conservation methods do not prevent the potential destruction of their natural habitats

• Species raised in captivity are less likely to be successfully reintroduced into the wild (loss of autonomous survival)

• Ex situ conservation increases inbreeding by restricting the gene pool and restricts the evolution of the species

The EDGE of Existence programme

is a global conservation initiative that uses a scientific framework to select species for conservation prioritisation

• A species must be Evolutionary Distinct and Globally Endangered (EDGE) to be selected for prioritisation

  • Evolutionary distinct species have few close relatives and represent unique phylogenetic branches

  • Globally endangered species may be defined as at risk according to the IUCN red list for threatened species

The EDGE of Existence programme is used to inform relevant stakeholders of conservation priorities – it does not make decisions regarding interventions

• Keystone species may not be globally endangered, but they may require greater priority for conservation due to their integral role within an ecosystem

• Certain species may be considered culturally significant and hence be prioritised according to political need