Extinction Flashcards
(24 cards)
Define biodiversity.
Biodiversity is the total variety of life on Earth.
It includes all living organisms, the ecosystems they inhabit, and the genetic differences within and between populations.
Outline how biodiversity is quantified at different levels of biological organization.
There are three forms of biodiversity that work together to create the complexity of life that is seen on Earth:
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)
State the imporatnce of genetic diversity.
Genetic diversity refers to the variation of genes within and between populations of a species. It includes:
* Differences between populations (e.g., wolves in different regions).
* Variations within a single population (e.g., coat color in a herd of deer).
Genetic diversity is essential for species’ survival and adaptability:
Disease resistance: Populations with high genetic diversity are more likely to survive disease outbreaks.
Adaptability: Genetic variation helps species adapt to changing environments, such as rising temperatures or habitat loss.
Reduced inbreeding: Low genetic diversity increases the risk of inbreeding, leading to genetic disorders and reduced fertility.
State the imporatnce of ecosystem diversity.
Ecosystems provide critical services that support life, such as:
Climate regulation: Forests absorb CO2 and moderate global temperatures.
Water purification: Wetlands filter pollutants from water and reduce flood risks.
Soil fertility: Grasslands prevent soil erosion and enrich it with nutrients.
State the imporatnce of species diversity.
Species diversity refers to the number and variety of species in a given ecosystem or the entire planet. It has two key components:
Species richness: The total number of species in an area.
Species evenness: The relative abundance of individuals among different species.
Every species has a specific ecological role that contributes to the stability and functioning of ecosystems:
* Predators: Prevent overpopulation of prey species (e.g., wolves controlling deer populations).
* Pollinators: Bees and butterflies are essential for plant reproduction and food production.
* Decomposers: Fungi and bacteria recycle nutrients, maintaining soil health.
The loss of a single species can have cascading effects, destabilizing entire ecosystems.
Compare the number of species on earth today with past levels of biodiversity.
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)
Millions of species have been discovered, named and described but there are many more species to be discovered. Evidence from fossils suggests that there are currently more species alive on Earth today than at any time in the past.
Define 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)
State the number of mass extinction events that have occurred on Earth.
Earth has experienced five major mass extinction events, each drastically reducing biodiversity.
Permian-Triassic Extinction (~252 mya): The largest extinction, eliminating ~90% of marine species.
Cretaceous-Paleogene Extinction (~66 mya): Ended the reign of dinosaurs, paving the way for mammalian diversification.
Define anthropogenic extinction.
Anthropogenic extinction, also known as the sixth mass extinction or Holocene extinction, refers to the ongoing extinction event driven by human activities.
Outline anthropogenic causes of species extinction.
Overexploitation: Unsustainable hunting, fishing, and harvesting of species.
Habitat destruction: The conversion of natural habitats into agricultural land, urban areas, and industrial zones.
Invasive species: Non-native species introduced by humans that outcompete or prey on native species.
Pollution: The contamination of ecosystems with harmful chemicals, plastics, and waste.
Climate change: Rapid shifts in environmental conditions caused by human-induced global warming.
Outline the extinction of the Moas.
The giant moa (Dinornis novaezealandiae) was a large flightless bird (terrestrial megafauna) that occupied New Zealand’s North Island.
Human Settlement:
With no natural predators, moa populations were highly vulnerable to hunting.
Overhunting: Moa were hunted to extinction in less than 200 years.
The loss of moa disrupted forest regeneration, as seeds previously dispersed by these birds could no longer travel far from parent plants.
Outline the extinction of the Caribbean monk seal.
The Caribbean monk seal (Neomonachus tropicalis) was a marine species that lived in the oceans around the gulf of Mexico and the Caribbean.
Overhunting: European colonists hunted the seals for blubber, which was rendered into oil.
Habitat Destruction: Coastal tourism and urbanization degraded the seals’ breeding habitats.
Extinction: The species was declared extinct in 2008 after decades of unsuccessful conservation attempts.
The loss of the monk seal altered predator-prey dynamics,
This potentially contributed to overpopulation of certain fish species and disrupting coral reef health.
Outline the extinction of the Passenger Pigeon.
Once numbering in the billions, passenger pigeons were among the most abundant birds in North America.
Their massive flocks played critical roles in seed dispersal and forest dynamics.
Mass Hunting: 19th-century hunters used advanced firearms and transportation networks to decimate pigeon populations.
Deforestation: Widespread logging destroyed nesting and feeding habitats.
Extinction: The last known passenger pigeon, Martha, died in captivity in 1914.
List direct and indirect anthropogenic causes of ecosystem loss.
1. Land-Use Change
Agricultural Expansion: Forests, grasslands, and wetlands are cleared to grow crops or raise livestock.
Urbanization: The rapid growth of cities and infrastructure development has led to widespread destruction of natural habitats.
2. Overexploitation of Resources
Overharvesting of timber, fuelwood, and animal populations destabilizes ecosystems.
3. Climate Change
Rapid changes in temperature, precipitation, and sea levels disrupt ecosystems.
Coral reefs, for instance, are highly sensitive to ocean warming and acidification.
4. Introduction of Invasive Species
Non-native species introduced intentionally or accidentally can outcompete, prey upon, or hybridize with native species, destabilizing ecosystems.
Define ecosystem loss.
Ecosystem loss refers to the degradation or destruction of natural systems.
It is primarily driven by human activities, including deforestation, pollution, and climate change.
It can manifest as:
* Degradation: Reduced ecosystem health (e.g., polluted rivers).
* Destruction: Total conversion to another land use (e.g., a forest replaced by agriculture).
Outline the cause of the loss of mixed dipterocarp forest ecosystem in Southeast Asia.
Mixed dipterocarp forests are rich, biodiverse rainforests dominated by trees from the Dipterocarpaceae family.
Causes of Loss
* Logging: Dipterocarp trees produce valuable timber, making them a target for both legal and illegal logging operations.
* Agricultural Expansion: Nutrient-rich peat soils are cleared for oil palm plantations, replacing diverse forests with monocultures.
* Infrastructure Development: Roads and settlements fragment habitats, leaving them vulnerable to further degradation.
Consequences
* Biodiversity Loss: Endangered species, such as orangutans, lose critical habitats.
* Carbon Emissions: Peatland drainage releases stored carbon, contributing significantly to climate change.
* Flooding and Erosion: Forest loss destabilizes soil and alters water cycles, increasing flood risks.
Outline the cause of the loss the Aral Sea Ecosystem.
Causes of Loss
* Water Diversion: Rivers feeding the Aral Sea were diverted in the 1960s to irrigate cotton fields, drastically reducing water inflow.
* Salinization: As the water volume decreased, the salinity of the remaining lake increased, killing fish and aquatic plants.
Consequences
* Ecosystem Collapse: All 24 endemic fish species went extinct, along with most other aquatic life.
* Dust Storms: Exposed lakebeds became a source of salt-laden dust, contributing to respiratory diseases in nearby populations.
* Economic Decline: The fishing industry vanished, and agriculture in the region suffered due to increased soil salinity.
List the types of evidence that can be monitored to assess the status of a biodiversity crisis.
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)
Compare in situ to ex situ approaches to conservation.
Conservation involves the protection and maintenance of natural resources (such as trees, water and wildlife) in order to preserve biodiversity:
In situ conservation is the preservation of plant and animal species within their natural habitat (on-site)
Ex situ conservation is the preservation of plant and animal species outside their natural habitats (off-site)
Outline the advantages of an in situ approach to conservation.
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
Explain the in situ approach to conservation.
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)
Explain the ex situ approach to 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
It can improve the chances of successful breeding by utilising artificial methods (e.g. embryo transfer, IVF, etc.).
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).
Outline the rationale used for conservation by the EDGE of Existence programme.
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.
What makes a species “evolutionarily distinct”?
Unique Traits: EDGE species often have characteristics found nowhere else in the animal kingdom.
For example, the axolotl can regenerate entire body parts, a trait with significant scientific value.
Rare Lineages: Some species represent the sole surviving members of ancient evolutionary branches.
For instance, the Yangtze giant softshell turtle or the kakapo.
Vulnerability: Once lost, these lineages cannot be recovered, erasing a unique piece of evolutionary history forever.
