What do you think is the largest single cell on earth? Remember there are limits to the size of cells due to absorption of nutrients and oxygen and release of wastes. How does a cell bigger than a cricket ball manage these limits? Where do you think you would find such an organism? These strange forms of life belong to the Kingdom Protista and have been discovered in deep ocean trenches, over ten kilometres beneath the surface. Read more about these fascinating xenophyophores at “Strange Forms of Life Discovered in Ocean’s Blackest Depths“.
Author’s photo taken at the Leaning Trees of Greenough, Western Australia
Learning Intention: Students will understand the biotic and abiotic factors that affect the distribution and abundance of organisms on earth.
Success Criteria: Students will successfully complete the Chapter 9 review questions and be able to list biotic and abiotic factors that affect the survival of organisms on earth.
Buffeted by the prevailing southerly winds, these eucalypts have survived despite challenging conditions. The survival of organisms, and therefore their distribuition and abundance, depends on both biotic (living – predators, competitors, pathogens, parasites) and abiotic (physical – temperature, wind speed, pH, atmospheric gases, turbidity, salinity, solar radiation) factors. This chapter of work is about habitats and the factors that affect the survival of organisms in their environments. Learn some definitions for this chapter at Chapter 9: Habitat and Survival Flashcards. You will also learn about niches and resource use graphs. Match some Australian species to their habitats at DECC.
Living organisms survive in their environments due to structual, functional and behavioural adaptations. Evolution is the process by which living organisms have changed over thousands of years to become more suited to their environments. Google ‘evolution’ and you will find an enormous selection of contradictory articles confirming or condemning “The Theory of Evolution”, first proposed by Charles Darwin in 1859.
To summarise Darwin’s Theory of Evolution;
1. Variation: There is variation in every population.
2. Competition: Organisms compete for limited resources.
3. Offspring: Organisms produce more offspring than can survive.
4. Genetics: Organisms pass genetic traits on to their offspring.
5. Natural Selection: Those organisms with the most beneficial traits are more likely to survive and reproduce.
Many humans are watching our weight after the indulgent Christmas and New Year Period. And at the Melbourne Aquarium, we are watching the weight of the Emporer penguins too! The penguin keepers need to monitor the health of their charges and keep a record of the weight of each bird, so they leave the scales in the enclosure to allow the penguins to become used to the equipment. Each bird has a unique pattern of coloured wing tags to identify it, although it is very difficult to identify male and female penguins without a DNA test. Part of the penguin exhibit was a recreation of an Antarctic ice-core, showing how scientists can identify different periods in the earth’s history, using samples from the compacted ice. Measurement of the gas concentrations in small bubbles within the ice has shown the increase in carbon dioxide during the Industrial Revolution, a trend that continues today.
Other interesting animals we found at the aquarium were the huge manta rays, beautiful green turtles, phosphorescent jelly ‘fish’, weedy and leafy sea-dragons, camouflaged and poisonous lionfish, baby hammerhead sharks, a gigantic murray cod and colourful reef fish. The Melbourne Aquarium has an iPhone app which allows you to access heaps of fun facts and cool images of their amazing underwater animals, taking you on a journey through the aquarium’s four exciting worlds; Antarctica, Weird and Wonderful, River to Reef and Sharks Alive.
By Chris and Catherine
The Red Fox (Vulpes vulpes) is a pest which was introduced to Australia from Europe in 1855 for hunting purposes. Populations of foxes in the wild became established in 1870. It took less than 100 years for the foxes to spread across most parts of Australia.
The red fox has had a major, negative impact on Australia since its population increased to uncontrollable proportions. The Red Fox has played a major role in the decline of the population of ground-nesting birds, small mammals and reptiles. It is also thought to be the main cause of population decrease for many threatened species. The Red Fox also poses an economic threat to many farmers by preying on their vulnerable farm stock such as lambs and chooks. It is also a carrier of rabies, a disease which affects mostly dogs but can be passed on to humans, livestock and native mammals.
The government has employed tactics such as bounties in order to reduce the population of the Red Fox. In 2002 the government introduced 24 collection points were people could hand in fox tails in order to receive a $10 reward. In the first year there was 150 822 fox tails handed in. The program was evaluated after the first year and found that the program was ineffective in reducing the fox numbers and so the program was scrapped in mid 2003.
The most effective methods of culling Red Foxes are…
- Lethal baiting
- Den fumigation
- Den destruction
Exclusion fencing is another effective strategy but it is extremely expensive and un-suitable for farmers.
Image Source Wild Display at the Melbourne Museum.
It is important for biologists to classify living organisms so species can identified and organised into groups according to their common features. The National Science Foundation’s “Tree of Life” project estimates that there could be anywhere from 5 million to 100 million species on the planet, but science has only identified about 2 million. Of these two million, the IUCN red list estimates that over 17, 000 species are in one form or another threatened with extinction today. So as fast as taxonomists are identifying new specimens, we are losing known species to habitat loss, introduced pests, pollution, overkill and climate change.
We often hear about threatened extinction of some conspicuous animals or plants, but it is usually not realized that each large species is host to many species of parasites, some of them specific to that host species and therefore doomed to extinction with it. The human species, for example, is host to far more than 100 parasite species, quite a few of these only found in humans. Species have not evolved in isolation – think of the co-evolution of flowering plants and their pollinators, toxic plants and their predators and animal camouflage.
This Chapter of work includes the Linnaean system of naming organisms, binomial nomenclature (Genus species system), heirarchical grouping (Kingdom, Phylum, Class, Order, Family, Genus and Species), dichotomous keys and cladograms. This site has some interesting mnemonics to remember biological terms for your upcoming exams.
You might think that providing water in arid areas would allow native species to flourish, as well as the stock it is intended to supply. However, sinking bores and providing tanks or troughs allows larger predators of native species access to areas that previously they found too dry to survive in. Small, native marsupials have become increasingly rare in the arid zones of Australia due to increased predation from both indigenous predators (wedge-tailed eagles, dingoes, dasyrids) and feral pests (foxes, feral cats, wild dogs). These predators have wide home ranges in desert areas and need to have access to water to survive. Smaller marsupials manage to survive in very dry areas due to a number of structural, functional and behavioural adaptations. These may include low SA:V ratio that reduces evaporation, nocturnal or crepuscular feeding habits, concentrated urine and dry faeces and the ability to obtain their water needs from the food they eat, without drinking.
Martin Westbrook is an environmental scientist working with the University of Ballarat at Nanya station, 140 km north of Mildura. He has been able to perform experiments at the 40,000 hectare former pastoral property, to determine the impact on biodiversity when removing water points. The Age has produced an article about his research here.