Chapter 3 Flashcards
Species diversity
A type of biodiversity which is a product of two variables, the number of species (richness) and their relative proportions (evenness)
Species diversity key points
Both the range (variety) and number of organisms (abundance) not just the total number of organisms, but the number of organisms WITHIN each of the different species
Genetic diversity
The range of genetic material present in a gene pool or population of a species
Habitat diversity
The range of different habitats per unit area in a particular ecosystem
High biodiversity advantages
Resilience and stability due to range of plants present of which some will survive droughts, floods, insect attack, disease
Genetic diversity - resistance to diseases
Plants will have deep roots - can cycle nutrients and bring them to the surface making them available for other plants
High biodiversity disadvantages
Diversity could be the result of fragmentation of a habitat or degradation - species richness is due to pioneer species invading bare areas quickly
Managing grazing can be difficult - plant species have different requirements and tolerance to grazing
Some stable/healthy communities have few plant species - an exception to the rule
Biodiversity hotspot
A region with a high level of biodiversity that is under threat from human activities
Diversity indices
Accurately compare two similar ecosystems/communities
Low diversity - pollution, eutrophication, recent colonization of a site, number of species present
Hotspot key points
Mostly in tropical rainforests, nearer the tropics (fewer limiting factors there)
ALL threatened areas, 70% of habitat has already been lost
Habitat contains more than 1,5000 plant species, cover only 2.3% of the land species
Large densities of human habituations nearby
Useful models to focus our attention on habitat destruction and threats to unique ecosystems/species
How hotspots can be ‘misleading’
Focus on vascular plants, ignore animals
Do not represent total species diversity or richness
Focus on regions where habitats have been lost (or still are)
Do not consider genetic diversity
Speciation
The formation of new species when populations of a species become isolated and evolve differently
Speciation (long definition)
The gradual change of a species over a long time. When populations of the same species become separated, they cannot interbreed and if the environments they inhabit change they may start to diverge and a new species forms. Humans can speed up speciation by artificial selection of animals and plants and by genetic engineering but the natural process of speciation is a slow one. Separation may have geographical or reproductive causes
The theory of evolution
Proposed by Charles Darwin in The Origin of Species - 1859
The theory of evolution key points
Each individual is different (except identical twins) due to their particular set of inherited genes and mutations
Each will be differently adapted to the environment
Resources are limited - there will be competition
Over time these changes show and the whole population changes
Natural selection
The idea where those more adapted to their environment will have an advantage and flourish and reproduce
Survival of the fittest
The fittest survive
Physical barriers
Species can develop into two or more new species if their population is split by some kind of physical barrier, like a mountain rang or ocean
Splits the gene pool
Land bridges
Allow species to invade new areas (eg North and South America were separated for a long time, but now there is a land bridge of Central America)
Species begin to mix
Caused by lowering of seawater levels
Continental drift
Definition: when seven large tectonic plates and many smaller ones drift around, moving at about 50 to 100 mm per year
Continents move to different climate zones - species have to adapt, higher biodiversity
E.g. Antarctica used to have a tropical climate, have a forest -> moved southwards
Plate tectonics
The study of the movement of the plates
Plate tectonics key points
When plates meet, they can slide past each other, diverge, or converge (mountains and ocean trenches)
Similar groups of animals
Llamas and camels - both domesticated animals, distant cousins
Kangaroos and cattle - fulfil a similar ecological role
African and indian elephants
Background extinction rate
The natural extinction rate of all species - around one species per million species per year
Mass extinction
Have been 5, there is an increasing rate of extinction due to climate change, natural disaster (volcanic eruption, meteorite impact)
Cretaceous-Tertiary (K-T extinction) where dinosaurs became extinct - around 65 million years ago
Holocene extinction event
The 6th mass extinction - we are currently undergoing it
Started at the end of the ice age around 9,000 to 13,000 years ago when large mammals such as the wooly mammoth and the sabre-toothed tiger became extinct (hunting)
Mass extinction patterns
Rate has accelerated in the last 100 years - biggest cause: HUMANS
Background rate was 1 per 200 years, but the past 400 years we have seen 89 mammalian extinctions - much more than the background rate
Living dead species
Species which have such small populations that there is little hope they will survive
They have lost a species that they depend upon (e.g. a pollinator insect for a flowering plant)
Causes of mass extinction (specifically K-T extinction)
Volcanic eruption, meteor impact putting huge amounts of dust into the atmosphere, climate change over a long period
The 5 mass extinctions - table
Now - Holocene
65 mya - Cretaceous-Tertiary (17% families and large dinosaurs lost)
199-214 mya End Triassic (23%, some vertebrates)
251 mya Permian-Triassic (95%, 54% of families)
364 mya Devonian (19% families)
440 mya Ordovician-Silurian (25% families)
Weedy species
Organisms that do well in the environments we create, survive and thrive in the current mass extinction (urban rats, domesticated animals)
6th mass extinction causes
Humans - direct cause of ecosystem stress because we:
- Transform the environment (cities, roads, industry, agriculture)
- Overexploit other species (fishing, hunting, harvesting)
- Introduce alien species (may not have natural predators)
- Pollute the environment (kill species directly/indirectly)
Living Planet Report
Periodic report produced by the WWF on the state of the world’s ecosystems
Loss and degradation, decline in living planet index measure of ecosystem health) by 30%
Measures Earth’s biological diversity
changes in biodiversity
Stage 1: modern humans spread over the earth, homo sapiens outcompeted Neanderthal man in Europe
hunting and extinction of wooly mammoths
Stage 2: humans became farmers 10,000 years ago
invention of agriculture meant that humans did not compete with other species in the same way for food
importing goods -> can exceed carrying capacity
Total world biodiversity
7 million species, most are animals and terrestrial, 2/3 are in tropics (tropical rainforests), 50% of tropical rainforests have been cleared by humans
Beetles (coleoptera)
Group with the most identified and named species
Have about 25% of all named species
Current extinction rate
100 species per million species per year
Hotspots
Species are not equally spread over the earth but highly concentrated in some areas
50% of all animals and plants are in 1/30 of the hotspots which make up only 2% of land
Factors that help maintain biodiversity: complexity of the ecosystem
The more complex a food web is, the more resilient it is to the loss of one species or reduction in its population size
If 1 type of prey/predator is lost, the others will fill the gaps left
May not be good for species diversity though, as one species is lost completely but the community continues
Factors that help maintain biodiversity: stage of succession
Plants and animals colonize a bare piece of land, species diversity increases, climax community is reached
Communities in young ecosystems that are undergoing succession may be more vulnerable than those in older ones which are more resilient and stable
Factors that help maintain biodiversity: limiting factors
If the abiotic factors are in abundance, the system is more likely to manage if one is reduced
Factors that help maintain biodiversity: inertia
Inertia is the property of an ecosystem to resist change when subjected to a disruptive force
Helps planners know which site will resist change or recover most quickly
Natural hazards
Naturally occurring events that have a negative impact on the environment (and humans)
Loss of habitat
Major cause of loss of biodiversity, small and large scale due to human activities
Habitat destruction or degradation occur when we develop or build on a piece of land
Fragmentation of habitat
The process whereby a large area is divided up into a patchwork of fragments, separated from each other by roads, towns, factories, fences, power lines, pipelines or fields
Act as islands within an inhospitable sea of modified ecosystems
Invasion of habitat by pest species or humans increases, possibility - disease spreads
Pollution
Caused by human activities - can degrade or destroy habitats and make them unsuitable to support the range of species that a pristine ecosystem can support
Local pollution (pesticides, oil spills); environmental pollution (emissions, transport); run-off of fertilizers into waterways; climate change
Overexploitation
Human populations expand, technology has allowed us to get better at catching, hunting and harvesting
Introducing non-native (exotic/alien) species
Can upset a natural ecosystem - humans have done this by the colonisation of countries, bringing their own crops/livestock
Spread of disease
Decreases biodiversity - diseases of domesticated animals can spread to wild species and vice versa, particularly if population densities are high
Modern agricultural practices
Reduce diversity with monocultures, genetic engineering and pesticides. Fewer are grown commercially and more pest species are removed
Vulnerability of tropical rainforests
Decreasing due to human activity, ranching and logging commercially
Shifting cultivation
A low density of human population is sustainable as they clear a small area of forest, grow crops for two or three years and then move on to the next as the soil is exhausted
Why are rainforests rich in biodiversity
Ecological niches - high levels of heat, light and water - photosynthesis is rapid and not limited by the lack of raw materials, fast rate of respiration and decomposition
What makes a species prone to extinction: narrow geographical range
If a species only lives in one place and the place is damaged or destroyed, the habitat is gone
What makes a species prone to extinction: small population size or declining numbers
Small population has a smaller genetic diversity and is less resilient to change - cannot adapt as well
More inbreeding until populations are the ‘living dead’ or they become extinct
What makes a species prone to extinction: low population densities and large territories
Habitat fragmentation can restrict its territory, and if there is not a large enough area left for each individual, they area less likely to survive as a species
What makes a species prone to extinction: few populations of the species
If there are only 1 or 2 populations left then that is their only chance of survival
What makes a species prone to extinction: a large body
Top predators are rare
What makes a species prone to extinction: low reproductive potential
Reproducing slowly and infrequently means that the population takes a long time to recover
What makes a species prone to extinction: seasonal migrants
Species that migrate have long migration routes, they need the habitats at the end of the migration route - it can’t be destroyed
What makes a species prone to extinction: poor dispersers
Species that cannot move easily to new habitats
What makes a species prone to extinction: specialized feeders or niche requirements
Eating only specific things; eg panda eating bamboo shoots
What makes a species prone to extinction: edible to humans and herding together
Overhunting or over harvesting can eradicate a species, especially if they live in large groups (easier to exploit them at once)
Uses of body parts for medicine - tiger
Island organisms
Vulnerable to extinction. island characteristics: small population; high degree of endemic species; genetic diversity is low; islands are vulnerable to non-native predators
Dodo
Island species that became extinct
IUCN (World Conservation Union)
Founded in 1948, mission is to influence, encourage and assist societies throughout the world to conserve the integrity and diversity of nature and to ensure that any use of natural resources is equitable and ecologically sustainable
IUCN Red List
Monitors the state of the world’s species, determines the conservation status of a species
Conservation biology
The sustainable use and management of natural resources
Preservation biology
Attempts to exclude human activities in areas where humans have not yet encroached
CITES
The Convention on International Trade in Endangered Species of Wild Fauna and Flora
Ecotones
Where two habitats meet and there is a change near the boundary
