Species Diversity And Ecological Stability Flashcards
Where is species diversity often low?
In extreme environments dominated by abiotic factors and where populations fluctuate dramatically
What creates a cycle of population rise and fall?
In an area with few food species a change in availability of one food species will have a big impact on the number of predators
What areas will have a higher biodiversity?
Less abiotically extreme environments
Where populations are dominated by biotic factors
What are some areas that are dominated by biotic factors?
Tropical rainforests
Coral reefs
What is a common way diversity can be quantified?
The Simpsons diversity index
What is the formula for the simpsons diversity index?
D= N(N-1)
———-
Sum of n (n-1)
What is N on the simpsons diversity index?
Total number of all organisms (all species)
What is ‘n’ on the the simpsons diversity index?
Total number of organisms of an individual species
How is diversity calculated from the Simpson diversity index?
The higher the value of D the higher the biodiversity
What can be used to predict how many species are in a habitat?
Past rate of discovery can be used as the basis for estimating the number
The gradual reduction of finding new species can be sued to estimate how many individuals have not been found
How many new species are found every year?
20,000 a year
What are the estimates for the total number of species?
5 to 100 million
How many species have been named so far?
2 million
What areas of habitats are currently inaccessible?
Tree canopy of tropical rainforest
Deep sea-floor
So not fully researched
What are population dynamics?
The processes that can cause populations to change in size and structure
What controls the number of species that live in an area?
The balance of factors that either increase or reduce the population
What will cause a population to increase?
Reproduction rate is high and death rate is low
What will cause a population to decline?
Reproduction rate is low and death rate is high
What is the maximum birth rate determined by?
The natural ability of the species to reproduce
How has evolution affected birth rates? I
Evolution has procured birth rates that are appropriate for the death rate
What will the birth rate be for a species with a lower chance of survival?
Higher birth rate
What is death rate controlled by?
Environmental factors such as disease, drought, predation and shortage of food
What are r-selected species?
Theses are species that can respond rapidly to low survival rates
They reach sexual maturity quickly and produce many young and can disperse widely
What are some examples of r-selected species?
Locust
Spiders
Rowan (plant)
Rabbit
What are k-selected species?
Theses are species that recover slowly from population decline
Reach sexual maturity at an older age
Produce few young
Often live for a long time
What would happen if the death rate of k-selected species increased due to habitat change or human exploitation?
May cause a population crash as the slow reproduction rate means the losses couldn’t be replaced
What are some examples of k-selected species/
Whales
Elephants
Rhinos
What is the maximum sustainable yield?
An estimate of the greatest population that is possible without causing unsustainable long-term population decline
What variables are needed to forecast a change in population size?
Current population
Number of births and deaths
Number of individuals immigrating or emigrating
How do you work out population?
Population= starting population+ births+ immigrants- deaths- emigrants
What are density independent factors?
Factors where the population density has no effect on the chances of survival of an individual
What are some examples of density independent factors?
Drought
Flood
volcanic eruption
What are density dependant factors?
Factors where the chances of an individual surviving depend on the population density of the species
when is population density a bad thing?
if individuals are closely related and are all vulnerable to disease then rapid spread due to close proximity could cause extinction
How does food supply affect mortality rates? (population density)
Intra-species competition for food is greatest when the population density is high
How does disease affect mortality rates?
Diseases spread more easily between individuals when they are close together
What happens to the dependant factors as density increases? (Animal survival)
The dependant factors become more important until the combined mortality rate caused by density dependant factors plus density independent factor cause population to reduce
What is carrying capacity?
The greatest that an area can support indefinitely without damaging or over exploiting the environment
How are mortality rate and carrying capacity linked?
The mortality rate changes if population size is above or below the carrying the capacity so the population size. Changes back to the carrying capacity
What happens when prey population rises?
There is a lot of food for the predators so their population increases
What happens when the predators population rises?
Causes prey population to decline creating a food shortage so the predator population declines allowing the prey population to rise again
Why might artificial population control be needed?
To enable species or habitats to survive where the natural control mechanism no longer controls population
What is a method of artificial population control?
Culling
How might the artificial population control help an endangered species with a low breeding rate?
A captive breeding and release programme to maintain or increase the population
How can a non-indigenous species can act as artificial population control?
A non-indigenous species may reduce populations of indigenous species because it is a predator, competitor or pathogen
How can removing an indigenous predator lead to artificial population control?
As its prey species becomes overpopulated and needs to be culled to avoid ecological damage it may cause to other species
What is an example of how removing the indigenous predator lead to artificial population control?
Wolves were exterminated in Scotland now their prey the red deer has to be culled to prevent over-grazing
