Stability and change

What are the requirements for stable environments

• Supply of energy

• Recycling of nutrients

• genetic diversity

• Climactic variables within tolerance levels.

Define tipping point

Critical threshold that when crossed leads to large and irreversible changes in the climate system

What is a mesocosm

Indoor experimental system that examines the natural environment under controlled conditions. Allows scientists to manipulate variables while investigating ecosystem.

What is a keystone species

Species that have disproportionate affect on the structure of their community. 

Define maximum sustainable yield

Largest amount of fish caught or plants harvested that can be sustainable over time (population doesn’t decrease over time)

Without causing market stock to decrease

Ways to monitor fish stocks

• Capture-mark-release-recapture

• Echo sounders

• analysis of fish catch

What affects sustainable agriculture (4)

• Soil erosion: Many agriculture practices erode soil, which reduces fertility of soil for future generations. 

• Leaching of nutrients: Over use of fertiliser can cause nutrients from fertilisers draining into nearby ecosystems. (eutrophication of rivers and lakes)

• Supply of fertilisers and other inputs: Manufacture of fertiliser and other chemicals has impact on enviro. eg mining and phosphate for fertiliser

• Pollution due to agrochemicals: Health of soil

• Carbon footprint: Many farm practices are carbon sources. 

State the steps of eutrophication

• Phosphate and nitrate enters aquatic ecosystem

• Increase in nutrients provides nutrients for algal population, increases exponentially

• Algae bloom forms on the surface of the lake, preventing sunlight reaching the plants on the bottom of the lake

• Plants die

• Overabundance of algae absorbs nutrients, causing nutrient levels to decrease → algae die

• Dead plant and algae accumulate at the bottom of aquatic ecosystem

• Aerobic bacteria decomposes dead plants and algae

• Aerobic bacteria population increase → Biological oxygen demand increase

• Aquatic ecosystem may become anoxic

• Fish and other organisms die due to low oxygen levels.

• Algae release toxins, water is no longer fit for drinking.

Define biomagnification

Increase in concentrations of a substance (eg pesticides) in tissues of organisms at successively higher levels in a food chain

Steps of biomagnification of DDT

DDT: Pesticides used to kill insect pests.

Some insects survive, but DDT stored in their fat tissue, doesn’t readily break down.

Insects eaten by fish → Fish eaten by ospreys.

High concentration of DDT accumulated in tissues of ospreys.

Causes osprey eggs to be very think and breaks easily during incubation → Death of osprey offsprings. Causes osprey population to decrease.

What is Minamata disease

Neurological disease caused by biomagnification of methylmercury in ecosystem. 

Mercury dumped by mines and factories. Mercury converted to methylmercury by bacteria → absorbed by plankton → Fish consume plankton → People consume fish. 

Define plastic

Range of organic synthetic materials that do not biodegrade

What is the difference between macro and microplastics

Macroplastics: More than 1 mm across, visible

Microplastics: Less than 1 mm across, produced by physical breakdown of macroplastics

What is rewilding

Restoration of degraded ecosystems back to their natural state

• Reintroduction of keystone species eg apex predators like wolves in yellowstone

• Re-establishing connectivity of habitats over large areas through wildlike corridors

• Management of ecosystems to reduce human impact

What are wildlife corridors

Areas of habitats that connects wildlife populations separated by human activities. Allows:

• Migration: Many animals need to migrate between seasonal habitats

• Expanding habitat range: Allows animals and plants to recolonise areas that were once part of their natural habitats. 

• Increase biodiversity: Movement of animals

• Genetic variety: Increase size of gene pool

Ecological succession

Process of change in a particular area over time. Caused by complex interactions between organisms and environment.

Define primary succession

Begins on area of ground or bare rock, no existing soil is colonised for the first time. Happens after volcanic eruptions or retreats of glaciers.

Starts off with a pioneer species

Define secondary succession

Process started by a disturbance (forest fires, harvesting, hurricane) that reduces already established ecosystem to a smaller community of species.

Define climax community

Ecological community which population of organisms remain stable and exists in balance with each other.

Define cyclic succession

Community is changed by recurring events or changing interactions.

Define arrest succession

Process where natural progression of plant species is halted due to human intervention etc.