Changes in ecosystems

Dynamic ecosystems Ecosystems change over time in a variety of ways. They are not STATIC. Migration Habitat change (eg. Destruction, pollution) Introduced species Fluctuations of climate Natural seasonal change

Primary and secondary changes Primary change = original change in ecosystem Secondary changes = the effects of the primary change Deforestation Decreased primary production (photosynthesis) Loss of habitat Decrease in insect species Decreased herbivores Other species affected

Reversing negative change Humans are often involved in reversing negative change Culling pest species (eg. Kangaroos, foxes, rabbits) Restoring habitat Removing/changing chemical concentrations Creating false habitats Assisting reproduction in affected species

Causes of change Natural Human Flood Fire Plate tectonics Seasonal change Migration Pollution Introduction of species Deforestation Clearing of land

Exotic species introduction – Cane Toads Cane toads were introduced in 1935 to attempt to control the sugarcane beetles affecting our crops. Since, they have flourished in the Australian environment . They can kill native animals with their toxin, and also create competition and habitat destruction. Now, Cane Toads are often killed by people trying to control the population growth.

Exotic species introduction - Rabbits Rabbits were brought to a single property in Victoria in 1859, for hunting purposes. Many escaped, and their descendents now are pest species across the entire continent. They reproduce quickly, so spread was rapid. The myxoma virus has been introduced to wipe out populations. It was initially 99% effective, but rabbits now are immune, with about 20% mortality rate. Calici virus was released in 1995, and has reduced the rabbit population by causing haemorrhaging.

Fascinating: how we control pest species Infecting rabbits with a virus that includes a modified gene that stops conception in females A gene is switched off in the females, so that they can only have male offspring.

Overuse of resources Humans often deplete ecosystems of resources Water Land Trees/plants Fishing

Wasting water Parts of Australia have been in drought for 20-30 years Water levels in Melbourne critical in about 2008-2009. Since, reservoirs have been replenished to about 50% Use of household water decreased significantly between 1990 and 2005 due to better education (among other things) BUT water use in the mining industry has increased

Sustainability Sustainability = use of resources within a renewable rate ie. Resources that renew quickly can be used more quickly than those which take many years to form (eg. Fossil fuels)

Salinity Salinity is the salting of the earth Not many plants can live in salty soil Causes: Removal of trees Excessive irrigation Improved by: Removing excess water in the ground Maintaining plantlife Regulating irrigation

Waste disposal Waste must be disposed somewhere, usually in landfill Effluent and factory chemicals may end up in waterways, which causes problems such as: Chemicals evaporate and rain back down Overgrowth of algae etc, which depletes the system of other nutrients

Litter Litter is often only semi-biodegradable: it takes many years to break down eg. Plastic bags Made of fossil fuel products (sustainability) Partially biodegradable Can choke wildlife, particularly in aquatic habitats

Dredging the bay Port Phillip Bay is being “dredged” (making parts deeper so ships can go through) Impacts: Disturbance of marine life Disturbance of sediment on bottom of Bay may release non-biodegradable chemicals stored there (eg. Iron, pesticides, factory chemicals, arsenic, zinc etc). As these are not biodegradable, they will undergo bioaccumulation through the food chain

Natural change: bushfire The Australian bush is very prone to fire. Destroys some habitat New life grows from ash: many Australian plant species REQUIRE fire to germinate their seeds

The Global Ecosystem (biosphere) Global Warming!!! We’re all going to die!! (right?) The main greenhouse gas is Carbon Dioxide, which is formed and sent into the atmosphere via normal cellular respiration, as well as activities such as burning fossil fuels, deforestation and increased energy consumption. Planting more trees can help, as they use atmospheric CO2 to photosynthesise.

SAC preparation Using your results table, summarise the changes we’ve seen, why they’ve occurred, and the impact on the rest of the terrarium ecosystem. You may bring in to the SAC: your results table, up to one page of hand written summary notes.

WE ARE DONE!! Complete all quick check, biochallenge, chapter review. THEN REVISE, REVISE, REVISE!!