C.3 Impacts of humans on ecosystems Flashcards
What are the two ways to describe species within any ecosystem?
Endemic or alien species
What is an endemic species?
Those which are native to a defined geographic region
What are alien species?
Those that have been transferred from their natural habitat to a new environment
When is a species classed as invasive?
If an introduced alien species should have a detrimental effect on pre existing food chains
What does the competitive exclusion principle state?
That two species cannot occupy identical niches within a community
What is the argument to support the competitive exclusion principle?
One species will have a competitive advantage and survive at the expense of the other
What happens to minimise direct competition between species in nature?
Evolution via natural selection causing adaptations
What are four advantages that invasive species possess?
- They have a larger fundamental niche
- Faster reproductive rates
- Lack a predator capable of limiting their survival
- Have certain features suited to the new environment
Why were cane toads introduced?
To control the spread of the sugar cane beetle that was damaging crops
Why did the cane toad fail at limiting the beetle population?
It couldn’t reach the top of the sugar cane where the beetles live
What is the cane toad classified as?
An invasive species
What three reasons are the cane toads invasive?
- has a wide diet and depleted the prey population for native insectivores
- secretes a toxic chemical from its skin which has poisoned native predators
- carried diseases which has transmitted to native species
Why have cane toads reproduced so successfully?
They have no natural predators
What three strategies have been implemented to control rabbit populations?
- rabbit proof fences
- hunting and poisoning and rabbit borne diseases
-Destroying rabbit warrens
What effect have the rabbits had on native australian ecology?
- killed native plant species by ringbarking
- loss of said plants have left topsoil exposed and vulnerable to extensive erosion
Why were wild rabbits reproducing so quickly?
As australian conditions promoted a population explosion
When and where were European rabbits introduced?
To australia with the arrival of the first fleet
What are the three main methods of population control?
Physical
Chemical
Biological
What is physical control?
The removal or restriction of invasive species by manual or mechanical measures
What are examples of physical control?
Barriers, fences or removing habitats by trimming
How else can population numbers be reduced physically?
Hunting, trapping and culling
What is the problem with physical control methods?
Not species specific and can impede endemic wildlife
What is chemical control?
The use of chemical agents to limit population numbers and spread
What are examples of chemical control?
Herbicides, pesticides or other compounds
What is the disadvantages of chemical control?
Can be detrimental to local wildlife, expensive and have moderate specificity
When will the effect of chemical agents become more pronounced and why?
In higher trophic levels due to biomagnification
What is biological control?
Using a living organism to control an invasive species
What might the biological control do?
Eat the invasive species or cause it become diseased
Why must biological agents be assessed before release?
To ensure they do not become invasive themselves
What are examples of biological control?
Vedalia beetle and myxoma virus
Why must biological control agents be monitored?
For unintended side effects
What is the cottony cushion scale?
A pest form australia that was released in california
What did the cottony cushion scale do?
Damaged the californian citrus industry
What is the vedalia beetle?
A predator from australia that was used in california as a biological control
What did the vedalia beetle succeed in doing?
Limiting the numbers of the cottony cushion scale and minimise impact to the citrus industry
What is biomagnification?
The process where chemical substances become more concentrated at each trophic level
What is bioaccumulation?
The build of a chemical substance in the tissues of a single organism
Why does biomagnification occur?
Because organisms at higher trophic levels must eat more biomass to meet their needs
Why will higher order consumers experience increased contamination from a chemical substance?
As there energy transformations are only 10% efficient so they have to eat more to meet energy demands
What is an example of a chemical substance which is biomagnifies?
DDT
What is DDT?
A chemical pesticide that is sprayed on crops and subsequently washed into waterways at low concentrations
What is the chemical description of DDT?
It is fat soluble and selectively retained in the tissues of an organism rather than being excreted
What happens when DDT is sprayed on water to eliminate mosquito larvae?
It is taken up by the algae and passed on to primary consumers
What happens at each subsequent trophic level to the concentration of DDT stored?
It increases due to increased food intake
How did DDT affect fish?
It interfered with eggshell formation
How did DDT affect birds?
Decreased survival rates of babies due to thinner shells
When and why was DDT used as a chemical pesticide?
In the 1940s/50s to control insect borne diseases
What did the use of DDT as an agricultural insecticide lead to?
The complete eradication of malaria in rich countries
Why was using DDT in poor countries not as successful?
Eradication programs could not be sustained
Why were eradication programs using DDT stopped?
Over safety and environment concerns
What do they use for current interventions for malaria now?
Non spraying strategies like bed nets
What are the four arguments supporting DDT spraying?
- It is affordable and effective
- Once it stopped malaria rates and deaths increased
-When sprayed health costs associated with malaria decreased - alternative strategies are not as cost effective or successful
What are the three arguments against DDT spraying?
- associated with adverse health effects in humans
- Persists in the environment for a long time
- Is biomagnified in higher order consumers which is bad for ecosystems
What are plastics?
A type of synthetic polymer found in clothes, bottles, bags and containers
Why do plastics persist in the environment for centuries?
As most plastics are not biodegradable
What is a macroplastic?
Large visible plastic debris (> 1mm)
What is a microplastic?
Small plastic debris (<1mm)
How can macroplastics be degraded into microplastics?
UV radiation and the action of waves
Where will ocean currents concentrate plastic debris?
In gyres
What are gyres?
Large oceanic convergence zones
What does plastic debris do to the water?
Leach chemicals into it
What does plastic debris absorb?
Toxic contaminants called persistent organic pollutants
What absorbs more persistent organic pollutants and why?
Microplastics due to their smaller size and larger surface area
How does plastics damage marine animals when they eat them?
- causes bioaccumulation and biomagnification of persistent organic pollutants
- damages their stomach and cause them to stop eating
Where are the laysan albatross nests found?
In the north pacific gyre where large amounts of plastic debris is found
How does the albatross ingest large quantities of plastic?
As they feed by skimming the ocean surface with their beak
Why is the mortality rate of albatross chicks high?
As adults can regurgitate the plastics swallowed but the plants can’t
Why do turtles eat a lot of plastic bags?
They mistake them for jellyfish
How can plastic damage a turtle if ingested?
Plastic can be lodged in the oesophagus and cause future feeding problems
How can plastic damage a turtle if it wraps around it?
Restricts movement and developmental growth
