Chapter 3: An introduction to biodiversity Flashcards
Species diversity
measures both the variety and abundance of species.
Genetic diversity
the range of genetic material present in a gene pool or population of a species - more genetic diversity, more resilient to disease.
Habitat diversity
habitat diversity is the range of different habitats per unit area in a particular ecosystem or biome - such as tropical rainforests, as there are many ecological niches.
Biodiversity
concerns the richness and evenness of species, and is made up of three types of diversity (see above)
It typically indicates the wellbeing of an ecosystem’s health: they are more resilient: resistant to disease when higher genetic variation.
However, high diversity can also lead to fragmentation or degradation of habitats when species richness is too high. This can also lead to grazing (different species also have different requirements.
Endemic species
species whose range is extremely limited (found only one place on Earth)
Biodiversity hotspots
Biodiversity is not equally distributed on Earth, and some regions have more biodiversity than others. Some places need focal protection.
The definition of hotspot: at least 1500 endemic species; unique area; more than 75% loss of original habitat.
Simpson’s biodiversity index
Calcualte with D= N(N-1) / (ZIGMA)n(n-1)
D= Simpsons diversity index
N = the total number of organisms found in the sample
n = the number of individuals of a particular species (so n1 = the number of yellow-star-thingies, n2= the number of red circles, n3= the number of green hearts etc etc)
is a summation sign
Darwin
The theory of evolution (1859): The Origin of Species: Each individual is different due to genes and mutations: each will be slightly differently adapted to its environment: resources are limited for any population and there will be competition (survival of the fittest, natural selection): over time these changes show and the whole population gradually changes.
As species develop in different directions (speciation), they may stop interbreeding, which can lead to the discontinuation of a species.
Speciation
the gradual change of a species over a long time. When the population of the same species becomes separated (due to e.g. isolation on an island or physical barriers such as mountains), they cannot interbreed, and if the environments they inhabit change they may start to diverge and a new species forms.
Land bridges and continental drifts
Land bridges allow species to invade new areas (when land appears due to e.g. lower water levels).
Continental drifts concern continents drifting over the globe, creating new climate zones, whereby the conditions and therefore food supplied forces species to adapt.
Continental drifts may create new mountain ranges when colliding or diverging, which can cause physical separation of populations.
Mass extinction causes
- Vulcanic eruptions (over millions of years; if they continually erupt) leading to dust clouds and disrupts flight routes.
- Meteor impact causing dust in the air
- The results of climate change over a long period - the dust caused by the other two would have blocked solar radiation (no photosynthesis - collapse of food webs).
Holocene extinction
The 6th mass extinction which many argue is anthropogenically caused - we are currently living it.
Threats to biodiversity with examples
Habitat fragmentation (islandization)
- edge effect: disturbance from surrounding areas (noise, pollution, light, etc.)
- Some species cannot cross open spaces between habitat zones (created by humans to preserve species)
- Small population in each “island”: may be isolated, leading to small genetic variation (incest, prone to disease); if a population dies out it cannot be restored elsewhere; extinction.
Habitat loss:
Agriculture, city expansion.
Pollution:
CO2 - climate change
biome shift: some can’t move, some too slowly (trees)
Overexploitation:
- Hunting: humans are very effective hunters, killing prey faster than they can reproduce - extinction. Humans are switching predators, meaning they are not affected by lack of a certain prey.
- Deforestation: quick to cut down, slow to regrow.
- Fishing: very efficient methods, overfishing.
Invasive species:
- Hedgehogs on Scottish islands - no predators. It is itself a switching predator, ate bird eggs.
- Rabbits in Australia: population boom, overgrazing, sudden mass rabbit death.
- Snails on Hawaii
Vulnerability of a habitat (example)
Tropical rainforest:
-leeching (non-fertile soil). The nutrients are not stored in the soil, but in the plants. Once the plants are cleared, fertility reduces rapidly because the heavy rainfall washes the nutrients and soil away and vegetation is not there to lock up the nutrients.
-holds 50% of world species, but only covers 6% of the world.
-Produces 40% of the oxygen that animals use.
-Can’t return to original state once destroyed (estimates 1000 years to regain same level of biodiversity).
-Rapid photosynthesis because of high levels of heat, light, and water: many ecological niches as a result.
-high species diversity in small area.
-Lost species at massive rates in last 50 years due to human activity (timber). The forest cannot regrow before more is destroyed.
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Vulnerability of a species (example)
- Bigger mammals (island animals): top predators are rare as only 10% of energy is passed on through trophic levels.
- Specialized food source: more likely to die out if one food source - e.g. giant panda: if food disappears, then it dies off.
- Seasonal migrants: if one habitat is destroyed they find no food or place to live. Barriers on their journey can also be hazardous.
- Animals that can’t migrate easily are more prone to extinction.
- Animals that are edible to humans.
- Animals that have low populations over large territories, as well as low reproductive potential.
- Low genetic diversity.
- Island organisms: low genetic diversity and population. Island can be prone to the arrival of non-native species. An example is the Dodo, which is extinct.