Biology: Chapter 5,6,7 Flashcards
Human Impact of biodiversity and ecosystem ( ningaloo reef)
can impact on the magnitude, duration and speed of ecosystem change
eg. Ningaloo reef
What is an ecosystem?
an ecosystem consists of a community and it environment ( the biotic and abiotic factors in a given area ) and the interactions between them
What is a stable ecosystem? Def
Can be sustained over long periods of time
Signs of an healthy ecosystem:
stress in the form of extreme conditions:
- flood
- droughts
- invasive species
- disease
- overexploitation
> overall shows resilience
Human Population Increase ->
human impact on biodiversity and ecosystem increase
Biodiversity Hotspots must include: (2)
- it has a minimum of 1500 vascular plants that are not found in any other region on earth
- it has suffered at least a 70% reduction in its original natural vegetation
Habitat def
habitat are environments in which species normally live
Why are habitats being destroyed?
- urbanisation
- manufacturing
- agriculture
- forestry
- mining
- fishing
what is habitat destruction ?
is a human activity that greatly impacts ecosystems
what is habitat loss ?
is a human activity and is the greatest threat to biodiversity
what is urbanisation?
Urbanisation is the extreme modification of an ecosystem by humans to support a human population of gradually increasing density; often, this happens as more people migrate to towns and cities from rural areas.
What do urban ecosystem have ?
Urban ecosystems have reduced biodiversity and are dominated by people
Communication between communities in urban ecosystems:
There is little recycling of matter between the community (the living things present) and the non-living surroundings.
Additional inputs of energy and matter are needed from other ecosystems to maintain modern standards of living
what is agriculture?
Agriculture is the practice of farming; cultivating soil, growing crops, raising animals, preparation of plant and animal products for market
what has happened due to agriculture ?
Many animals and plants have lost their habitat due to land clearing
what is habitat fragmentation?
Habitat fragmentation – some parts of the habitat of an ecosystem are separated into isolated sections
Human Activities: Urbanisation and Agriculture
Create: Habitat Fragmentation
- isolation of animal groups
- habitat in fragments
No interbreeding between sub-populations:
- no sharing of genetic diversity
- loss of resilience
the gondwana link
The Gondwana Link program has been working to reconnect fragmented habitats across the south-west of Australia. If the Gondwana team reach their goal, 1000 km of continuous habitat will reconnect habitats from the dry woodlands of the inner region to the tall wet forests of the far south-west corner. Traditional land managers, organisations, farmers and conservation scientists have worked together to strategically revegetate gaps of cleared land to restore the fragmented habitat.
Land and Soil Degradation examples
Overgrazing and the hard hooves of farm animals are factors that lead to land and soil degradation.
Shallow rooted plants have more of an opportunity to grow on degraded land.
With significantly reduced tree cover and an increase in shallow-rooted grasses, the topsoil becomes more exposed to the effects of abiotic factors such as wind and rain.
Past land clearance practices, the move to shallow-rooted pastoral grasses and the overuse of fertilisers that have affected soil organisms have placed enormous pressures on the structure of the soil and the ability of the land to hold its topsoil.
Dry Salinity
Salinity’ refers
to the concentration of salt in the soil. If the
concentration of salt in soil becomes too high,
plants such as crops will no longer grow and the
soil is infertile.
why is a significant problem?
Salinity is a significant problem that can happen when natural vegetation is replaced with crops that require irrigation
In many agricultural areas of WA, the
underlying reason behind the rising water table
is the removal of deep-rooted, perennial (long lived),
usually native, vegetation.
The Steps leading to dryland salinity:
Step 1:
human population increases, leading to increased food consumption and need
Step 2:
farming increases, with further clearing of deep-rooted trees
Step 3:
removal of deep-rooted native perennial species and planting shallow-rooted annual crops. Deep-rooted native plants remove water from underground aquifers and use in transpiration: this balances the input and output of aquifers. The root of shallow-rooted crops do not grow down far enough to reach the watertable to access water for transpiration or evaporation
Step 4:
watertable rises.As it rises , salt from surrounding soil dissolves into the water
Step 5:
water evaporates at the soil surface, leaving behind soil that is too salty for most plants to survive.
Introduced species def
Introduced species are species that humans have intentionally or unintentionally moved from their native location to a new ecological region.
Why are invasive species a problem?
In their new location, they are without their natural predators, parasites and pathogens, which would usually limit their growth.
The rate at which they have been introduced has increased with the increase in human travel by ship and air.
Many introduced animals and plants become invasive species if they manage to establish populations in new areas; out-competing natives.
Examples of WA’s invasive species declared pest:
- Fox
- Feral Camels
- Cane Toad
- ## Rabbit
Environmental Management: Chemical Control
The use of chemical pesticides (chemical control) is a quick and effective method of getting rid of pests, but there is a downside: pesticides can be ecologically damaging as well as costly.
A chemical control is a chemical such as a pesticide or poison, such as a bait, used to control the population of a pest/invasive species.
Environmental Management: Biological Control
Biological control is another method of management, in which a species is used to control the population of a pest species.
Biological control agents exploit relationships between organisms.
Sometimes an integrated approach (using two or more measures) when rapid response is needed in the early stages of a pest reaching a new area.
It combines the use of biological measures with the use of chemicals limited to narrow-spectrum agents that target specific species.
Four Kinds of biological control agents
- general predators
- specialised predators
- parasites
- microbial diseases eg caused by a virus
Precautions to the release of biological control agents
Field trials must be conducted in an isolated area to discover any unexpected effects before wide release, especially to check the risk of the biological control species becoming a pest itself.
To be released more widely, the biological control species must:
only target the pest species and not impact on other populations
decrease in number as the pest species decreases in number
not compete with native species for a resource (e.g. food or habitat).
Biological control agents: Lady birds
Ladybirds have been introduced to Australia to battle aphids on citrus trees. This reduces the use of expensive chemical pesticides and limits the impact of these chemicals on other species.
Environmental management: culling
Under strict regulations, invasive organisms are culled (killed) eg Australian red and grey kangaroos out-compete other species for resources in some ecosystems. Each year, more than 2 million kangaroos are culled. A small proportion of the meat is processed for human consumption, most of it for export
Environmental management: reintroducing populations
Some species are released from breeding programs back into their original or a disease/pest free environment for the purpose of building up their population. For example, Galaxias is a genus of native freshwater fish whose numbers have suffered since the introduction of the mosquitofish. Introducing Galaxias back into the wild is through finding uninfested waterways or artificially created ponds that have no linkswith infested water bodies.
What is unsustainable use of natural resources ? def
Unsustainable use of natural resources – using resources more quickly than they can naturally be restored – has a huge effect on biodiversity.
what is overharvesting ?
Overharvesting means harvesting a species at a rate that exceeds the replenishing rate of the population
why is overharvesting a problem ?
Organisms that have low reproductive rates, such as the African elephants (often poached for their ivory tusks), are especially vulnerable to overharvesting.
This is because the sum of new individuals from births and immigration does not exceed the total individuals lost to death plus emigration.
Sustainability and Fishing
There is competition for their use: for food, recreation, transport, commercial livelihood and as a repository for our wastes.
Particularly by over-harvesting, commercial fishing has reduced the populations of many species, some almost to extinction.
Shark numbers, for example, are at an all-time low.
The reduction in populations of these and other fish affects other species through disruptions to food chains. Penguins and seals, for example, now compete with the fishing industry for food.
Sustainability and fishing: by-catch and bottom trawling
PROBLEM: by-catch
The by-catch (undersized and over-sized fish caught and discarded) poses problems for species that are fished commercially.
As populations of fish (such as the valuable snapper) decrease, there are fewer fish reaching reproductive age to sustain population growth
PROBLEM: bottom trawling
Destructive to ocean ecosystems; involves dragging a large net across the seafloor.
Deep-sea fish species are targeted globally, but bottom trawling is known to also remove vast amounts of non-target species, including habitat forming deep-sea corals and sponges.
Management strategies: creating and monitoring protected areas
In WA, recreational fishing licences and fishing seasons are compulsory and are used to control fishing levels
what is eutrophication?
Eutrophication is a process that occurs when excess nutrients, particularly nitrogen and phosphorus, enter a body of water and become highly concentrated, leading to excess growth of organisms such as algae.
Farmer dealing with nutrient-deficient soil use fertilsers
- The fertilisers are usually enriched in nitrogen and phosphorous
- Excess nitrogen and phosphorous not absorbed by roots are often leached from the soil by run-off (rain water or irrigation).
- The run-off can reach local water bodies such as lakes and cause algal blooms
- An algal bloom is a rapid increase in the population of algae or other microorganisms at the surface of a water body that blocks sunlight from entering. When this happens, autotrophs that live under the surface die.
- Algae die and are decomposed by bacteria.
- As bacteria consume the dead algae, they use large amounts of oxygen from the water, which depletes oxygen levels. The water can become hypoxic (low in oxygen) and possibly anoxic (completely devoid of oxygen).
- The low oxygen levels do not meet the respiration needs of aquatic organisms, so fish and other populations die.
what is Biomagnification ?
Biomagnification is the sequence of processes in an ecosystem by which higher concentrations of a particular non-biodegradable chemical are reached in the tissues of organisms higher up the trophic levels
what does biomagnification do ?
Biomagnification occurs because the biomass at any given trophic level is produced from a much larger biomass ingested from the trophic level below.
The concentration of the chemical increases in the tissue at each trophic level.
A classic example of biomagnification is DDT, a pesticide
The impact of pollution: plastic
Large amounts of the world’s plastic rubbish enter waterways. Many aquatic animals mistake plastic for food. Turtles frequently ingest plastic bags, confusing them with their prey, jellyfish.
Plastic can be consumed by wildlife, causing disease and death
What is climate ?
the average long-term, predictable atmospheric weather conditions at a site over a period ranging from months to many thousands of years). Climate is made up of such variables such as rainfall (precipitation), temperature, intensity of sunlight and wind.
