ESS topic 3
3.1
Biodiversity: total diversity of living systems, which includes the diversity of a species, habitat, diversity, and genetic diversity.
High biodiversity areas:
Close to the equator (high rainfall, and insulation) so high primary productivity.
Active plate tectonics create barriers to populations
Altitude variation on mountains creates zonation and a diversity of habitats.
Protected area or national park.
Habitat diversity: the range of different habitats in an ecosystem.
Genetic diversity: the range of genetic material present in a population of a species.
Species with high genetic diversity have a wide genetic variation (large number of genes with different versions of those genes)
Will be more stable and show greater resilience to environmental change as within the pop. There will be a greater likelihood of some individuals surviving a move away from equilibrium.
Species diversity: a function of the number of species and their relative abundance.
Diversity index: a quantitative measure of species richness, calculates using a combined measure of species richness and evenness.
Evenness: a measure of the relative abundance of different species making up the species richness of an area.
Changes to biodiversity:
Humans affect biodiversity
Disturbance of habitats can lead to a reduction in the realized niches of organisms to increase the overlap of niches and increase competition
Simplification of habitats leads to a reduction of biodiversity, with decreased evenness between species adapted to the changed environment.
Ex. Logging can reduce canopy cover. This opens up the forest, increases temperatures, and reduces humidity. Species adapted to closed, undisturbed forest ecosystems can be expected to reduce in number whilst species adapted to these new conditions increase, leading to an overall reduction.
Species diversity indices: to understand the nature of biological communities and the conservation of biodiversity
3.2
Evolution: gradual change in the genetic character of populations over many generations.
Evolution by natural selection
First developed by Charles Darwin
Because species show variation (difference), those individuals that have adapted best to their surroundings (those that fit the environment) survive. The individuals that are fitter and survive can then go on to reproduce.
The genetic characteristics of an individual help to determine whether or not it will survive. The characteristics that are successful are passed on to the next generation when an individual reproduces. Over time there is a gradual change in the genetic characteristics of a species and this leads, eventually, to the formation of a new species. (e.g. birds with longer, thinner beaks might have it easier to catch food hiding in the trees than shorter-beaked ones, so they are more likely to survive and produce offspring).
Natural selection: the process where organisms that are better adapted to their surroundings are more likely to survive and produce more offspring.
The theory can be summarized like this:
The population of a species shows variation.
All species over-produce.
Despite over-production, population levels remain the same.
Over-production leads to competition for resources.
The fittest, or best-adapted organisms, survive.
The survivors reproduce and pass on their adaptive genes to the next generation.
Over time, the population's gene pool changes, and new species emerge.
Speciation: the process through which new species form.
With natural selection, the genetic makeup (or “gene pool”) of the species changes over time.
This combines with isolation can lead to speciation. If gene flow between the two subpopulations is prevented, subpopulations become genetically different to the point that they can no longer interbreed.
Isolation: the process by which one population becomes divided to form subpopulations separated by geographical, behavioural, genetic, or reproductive factors. If gene flow between the two subpopulations is prevented, the subpopulations become genetically different to the point that they can no longer interbreed and so are different species.
Isolation is essential to the process of speciation
Without isolation, populations undergoing separate processes of natural selection, due to environmental differences, in the areas they inhabit, would continue to interbreed and genetically distinct species and would be unable to develop.
Isolating mechanisms separate the populations, leading to speciation.
There are different types of isolation:
Geographical isolation: as a result of island formation, loss of land bridges, mountains
Behavioural differences: different reproductive display, songs, daily activity
Anatomical differences: reproductive organs, size.
Isolation can lead to behavioral differences that cause reproductive isolation i.e the isolated populations develop behavioral differences and so are no longer capable of interbreeding. For example, male birds of paradise, found in Papa New Guinea attract females using elaborate dances which vary according to species. Over time, populations become so genetically different they form distinct species.
Plate tectonics: the movement of the eight major and several minor internally rigid plates of the Earth in relation to each other.
Plate activity has led to the generation of new and diverse habitats, thus promoting biodiversity.
Island populations are separated by mountain uplift: the uplift creates new habitats, promoting biodiversity through adaptation to new surroundings.
Collision of plates allows convergence of land masses and produces a mixing of gene pools, promoting new ecological links and possibly hybridization.
Land masses are shifted to new climatic conditions, creating new environments with different selection pressures.
Tectonic plates: massive areas of solid rock that make up the Earth’s surface, both on land and under the sea. Plate size can vary from a few hundred kilometres to thousands of kilometres across.
Outer crust and upper mantle (lithosphere) of the Earth are divided into many plates that move over the molten part of the mantle.
Magma can be released through plate movement, causing landmass to form.
Extinction: the loss of species from Earth.
Levels of extinction are low as they have been balanced rates of speciation. However, there have been several major peaks of extinction.
The fossil record shows that there have been five periods of mass extinction in the past.
Mass extinctions occur when species disappear in a geologically short time period, usually between a few hundred thousand to a few million years.
Animals and plants die due to both the initial event and the events that followed. Causes of mass extinction have been associated with relatively sudden changes in natural global cycles — volcanic activity due to plate tectonic activity or asteroid impact. These changes either led to climate change or planetary cooling.
Mass extinctions of the past took place over geological time, which allowed time for new species to evolve to fill the gaps left by the extinct species.
Fossil record: the remains of organisms preserved, for example, in rock, with simpler organisms found in older rock and more complex ones in newer rock.
Evidence of plate movement comes from rock formation and fossil records on different continents, which show a shared history.
The shapes of Earth’s main land masses also show how they were once connected.
Geological time: the arrangement of events that have shaped the Earth over long periods, such as mountain-building. It is usually presented as a chart, with the earliest event at the bottom and the latest at the top.
3.3
Factors that lead to the loss of diversity include:
Habitat degradation, fragmentation and loss.
Agriculture practices (production of monocultures, the use of pesticides).
Introduction of non-native species.
Pollution.
Hunting, collecting and harvesting.
Human population growth has led to increased demand on natural resources.
One of the main threatens to ecosystem biodiversity is the introduction of non-native (invasive species).
Human population growth has led to conflict with wildlife.
Exponential growth has led to greater demand for resources, which has led to clearance of land and reduction of species habitat.
Pollution such as chemicals, litter, nets, plastic bags and oil spills damage habitats and lead to loss of life and reduction in species’ population numbers.
Habitat degradation: decrease in quality and complexity of area where organisms live
This leads to a reduction in biodiversity
Habitat fragmentation: when habitat is divided into smaller areas that are separate from each other.
This leads to a reduction in biodiversity
International Union for the Conservation of Nature (IUCN) — the world’s oldest and largest global environmental organization. Its aim is to show how biodiversity is essential to solve the problems of climate change, sustainable development and food security.
Red List: information that assesses the conservation status of species on a worldwide basis.
Factors used to determine conservation status:
Population size: species with small populations are more likely to have low genetic diversity and their inability to adapt to changing conditions can be fatal. For example Cheetahs and tigers. Reduction in population size may indicate that a species is under threat, for example the European eel.
Degree of specialization: Specialized species have a narrow niche so, if their surroundings change, they may not be able to adapt and change. For example, a species’ food resources may be very specialized, such as the panda, which mainly eats bamboo. Some animals can only survive on certain tree species.
Distribution: species with small population sizes and limited distribution are more likely to become extinct than common and widespread species.
Reproductive potential and behaviour: species that produce few offspring are vulnerable to extinction. If there is a change in habitat or a predator is introduced, the population drops and there are not enough reproductive adults to support and maintain the population.
Geographic range and degree of fragmentation: species with a limited geographic range may be under greater threat from extinction, for example, the peacock parachute tarantula. Species that live in a smaller area are under greater threat from extinction than more widespread species. May not be able to maintain large population sizes.
Quality of habitat: even if a species is not directly under threat, if its habitat is being reduced or degraded, this will indirectly affect the species. Species that live in habitats that are poorer in quality are less likely to survive than species in habitats with better quality.
Trophic level: top predators are sensitive to any disturbance in the food chain. Any reduction in the number of species at lower trophic levels can have dramatic consequences. It is also possible that in high trophic levels, such as the American bald eagle, may accumulate toxins.
Probability of extinction.
Impact of human beings on the biodiversity of tropical biomes:
Tropical rainforests are vulnerable because they are under constant threat from logging or the removal of forests for other land use, such as agriculture. Deforestation and forest degradation occur as a result of external demands for timber, beef, soya, and biofuels.
Rainforests have thin nutrient soils. It is difficult for them to regrow once a rainforest is destroyed.
If too much timbre is removed the forest will likely not grow back.
An are is good if it has a high number of endemic or unique species, contains multiple ecosystems, has high species richness and high biodiversity, etc.
Conservation status: a measure of how endangered a species is; a sliding scale operates from being of least concern to extinct.
3.4
IGO (UNEP): an organization that is established through international agreements to protect the Earth’s natural resources
NGO (WWF, Greenpeace): an organization that is not run by the government of any country; they are not funded or influenced by governments in any way
CBD: International legally binding agreement created at the Rio Earth Summit. It has three main goals: the conservation of biodiversity, the sustainable use of its components, and the fair and equitable sharing of the benefits arising from genetic resources.
Compare and contrast GOs and NGOs:
Intergovernmental work with the law, and NGOs can be more confrontational.
NGOs use the media more to get specific messages about conservation across.
NGOs carry out publicity stunts and run campaigns.
NGOs tend to have local groups encourage community involvement
GOs works more slowly and is concerned about government-level changes to protect the environment.
Rio Declaration: a document produced at the Earth Summit in 1992 that outlined future sustainable development around the world.
First ever UN conference to focus on sustainable development.
Led to agreement on legally binding conventions.
Arguments on species and habitat preservation:
Ethical:
Intrinsic value
Biorights — humans have no right to destroy a species
Owe it to future generations to pass on the same environmental heritage we received
Economic:
Species contribute to overall natural capital – sustainable goods ecosystem provides.
Ecotourism provides a significant source of income
Aesthetic:
Beauty, cute
Ecological reasons:
Balancing the ecosystem
Keystone or flagship species
All species add diversity — more stable and resistant to change
Island biogeography: a theory that predicts that smaller islands of habitat will contain fewer species than larger ones
Habitat conservation:
Edge effect: changed environmental conditions at the edge of habitats
May change in abiotic components: wind, warmth.
Will attract species that are not found deeper in the reserve but survive successfully in the edge conditions.
May attract exotic species.
Fewer edge effects = less of an area is disturbed.
Corridor: a piece of land containing habitats that joins two other areas:
Is better for conserving the genetic diversity of species as it allows organisms to migrate between reserves, leading to a greater number of opportunities for a wider population. — more indivudsals can mix.
Species-based approach to conservation: a method that focuses on the specific individual species that are vulnerable, with the aim of attracting interest in their conservation.
CITES: the Convention on International Trade in Endangered Species of Wild Fauna and Flora. This is an international agreement between governments that aims to ensure that international trade in wild animals and plants does not threaten their survival.
Captive breeding: the process of raising animals outside their natural surroundings in controlled environments such as zoos, with the aim of increasing population numbers for reintroduction to the wild.
May be important for promoting conservation during visits by members of the public and education.
Maintains population numbers and genetic diversity, with a view to returning animals to the wild once their natural habitats have been protected.
Provide opportunity for research
Breeding pairs – increase numbers of endangered animals
Can be ethically wrong
Difficult to recreate suitable habitats
Species can become stressed in captivity
The Montreal Protocol on Substances that Deplete the Ozone Layer (the Montreal Protocol) is an international agreement made in 1987. It was designed to stop the production and import of ozone-depleting substances and reduce their concentration in the atmosphere to help protect the earth's ozone layer.
Flagship species: charismatic species that help protect others in the area. Wide appeal to the public. Will result in habitat protection and will also protect other species.
Keystone species: central role in the way an ecosystem functions. Loss of keystone species can lead to different ecosystems or the collapse of an ecosystem.
Success of protected are:
Funding from local government
Involvement of government agencies
Presence of flagship species
Scientific research programme to assess
Ecotourism to raise money for conservation
Support of local people
Use value is the price we can put on something for using it directly, whereas non-use value is the price we can imagine for something existing