Week 13: Questions Flashcards
There are three main components of biodiversity:
Species richness
Important because it allows for varied interactions among species
Genetic diversity
Important because the more genetically diverse a species is, it is less vulnerable to extinction, which helps to conserve biodiversity
Individuals will vary in their traits, making them more resistant to diseases, more tolerant of changing temperature/environments
Species with large populations and wide geographic distribution are the most genetically diverse (can thrive even when conditions change)
Habitat diversity
Important because a larger and more diverse habitat can support more species
Different species are adapted to different habitats, therefore the more a habitat is diverse, the more species it can have
There are several hypotheses to explain why biodiversity tends to be highest in the tropics. Which one suggests that the lack of effects of the ice ages has simply allowed new species in the tropics more time to evolve?
The stability hypothesis
What are the hypotheses as to why the gradient exists?
Climate hypothesis
Areas away from the equator are more cold and the climate becomes more cold, harsh, variable and less predictable
Productivity hypothesis
In areas where climates are colder there is less variety of food, which means animals have to be able to eat whatever is available to them
This causes more competition for food and leads to elimination of species
Tropical areas have more of an abundance of food so species can specialize on a specific food source, therefore there is less competition and elimination of species
Stability hypothesis
In colder climates there is a lot of dramatic change which affects species survival
In tropical areas the climate is more stable, making it easier for species to survive
According to the theory of island biogeography, would you expect a large island to have more, fewer, or about the same number of species as a very large island nearby?
The same
According to the species area relationship, small islands have more species than very small islands, but a large island and very large island have the same number
What is the theory of island biogeography?
The idea that the number if species found on an island is determined by the rates of immigration by new species and extinction of established species
Immigration will increase the number of species on an island and extinction will reduce it
Large islands have a higher immigration rate (bigger target) and lower extinction rates (more resources and habitats, leading to less competition)
Smaller islands have a lower immigration rate (lower target) and higher extinction rates (less resources and habitats, leading to more competition)
How does the theory of island biogeography show the consequences of human activity?
When we cut into a forested area for human activity, the forest becomes split into “islands”
This theory shows that small areas cannot hold all the species from the original forest, therefore extinction will occur
Realms
Biological realms (continents) are homes to a large set of species that are are different from others and that can only be found in that realm
Wallace’s line shows this because species from two areas were separated by the ocean and species were unable to migrate, therefore these areas had extremely different species
Before the Cambrian Explosion, most species had what sort of body design?
Unicellular and lived on the ocean floor
Why does biodiversity increase productivity?
A diverse collection of species can make more complete use of an ecosystem’s resources
If a plant species is diverse, it can grow well in different conditions and make better use of the resources available to it, increasing productivity
Why does biodiversity increase stability?
In a biologically diverse ecosystem, several species can take on a given role
This way, at least some species will do well, regardless of what happens
Rivet hypothesis
If an important species or too many species are lost, the ecosystem will crash quickly
Loss of biodiversity will have the same effect on an ecosystem
How does biodiversity keep the food web intact?
Biodiversity stabilizes the food web
In a diverse food web, if one species becomes too common, its predators will reduce its number and if a species becomes too rare, its predators can switch to another prey
What regulating services do intact old-growth forests provide?
Provisioning services
They provide lumber
Their genetic diversity has given us products like tamoxifen
Regulating services
They retain soil and purify water
Cultural services
They support a strong ecotourism industry
They can provide a spiritual connection with nature
Supporting services
They have tremendous productivity
They create soil
They remove carbon dioxide from the atmosphere
Why might we be facing the sixth mass extinction?
Blitzkrieg hypothesis
Humans have hunted most of the large mammals on the North American continent to the point of extinction
Some evidence for this hypothesis is that the extinction of large mammals and birds has occurred on every continent soon after humans arrived
How has human activity caused a decline in biodiversity?
Habitat destruction
Species habitats have been destructed when humans used them by clearing forests for things like lumbering, building villages and agricultural purposes
This affects all three components of biodiversity
Overharvesting
When individuals are taken from a population faster than they can grow back
This can destabilize an ecosystem and reduce the services it delivers (especially of it is a keystone species)
Displacement by invasive species
Chemical pollutants
