Looks like no one added any tags here yet for you.
Producer
Organisms that produce their own source of food (Autotroph)
Consumer
An organism that must eat or consume another organism (Heterotroph)
Food Chain
A linear chain that shows the flow of energy and nutrients through a system
Food Web
All of the food chains of an ecosystem – showing the many different paths
Biotic Selection Pressures
Competition
Predation
Symbiosis
Commensalism
Parasitism
Disease
Competition
When organisms use the same resource in the same way
Competition example
Food sources, habitat, light
Introduced foxes and cats compete with Australian native carnivores like quolls for food (possums, rats etc). As a result quolls have declined in distribution and abundance
Competition as a selection pressure
When two different species compete for the same limited resources, they cannot co-exist in the same place. One species will inevitably harvest resources and reproduce more efficiently than the other, so that the weaker competitor will either become extinct or, over time, evolve enough to use a different set of resources
Predation
One organism eats another organism
Predation example
Wallaby being eaten by a dingo
Ladybirds consuming an aphid
Bird eating a worm
Predation as a selection pressure
Predator and prey numbers will oscillate in a similar pattern. Predator numbers will increase they will eat more prey, causing the number of prey to decrease. There is less food available creating competition for food, decreasing the number of predators. With less predators the number of prey increases
Symbiosis
This is a type of interaction between two species that live together in close association
Mutualism
Commensalism
Parasitism
Mutalism
A relationship in which BOTH organisms benefit and neither could survive without the other
Mutalism example
The clownfish is protected by the sea anemone from predators. The anemone benefits as the prey will go near the anemone thinking it is safe, so the anemone gets its prey
Commensalism
A relationship in which one organism benefits and the other is not harmed
Commensalism example
Barnacles on a whale. The barnacle is exposed to more food sources and the whales are not harmed
Bird nesting in a tree – the bird benefits by gaining shelter and a location to rear its young, however the tree is not harmed
Parasitism
Where an one organism feeds on a host who is harmed
Parasitism example
Head lice and humans
Ticks and dogs
Aphids and plants
Disease
A disorder of structure or function in a human, animal or plant
Disease example
A human with chickenpox
Black spot is a fungal infection that affects plants
Disease vs Parasitism
Infectious diseases are caused by pathogen which results in an infection to the host
A parasite is an organism that lives on or in another organism – it usually takes its nutrients at the expense of the host
Predation vs Parasitism
Predators usually have multiple prey throughout a life stage, whilst a parasite usually only has one
Abundance
The number of organisms in a particular area
Distribution
Where an organism is found
Why is abundance and distribution important?
Ecologists use them to provide a measurement of biodivereisty to gain information about species (extinctions, impact of climate change on species)
Transects
A straight line across a habitat or section of habitat that maps indivduals at different distances across the line (used to measure distribution)
Positives of Transects
Good for vegetation
Negatives of Transects
Only record organisms directly on it
May not correctly represent the sit
Random Quadrats
A _______ is randomly placed in an area and the number and type of each species is recorded. The estimated population is ‘scaled-up’ to the total area (used to measure abundance of slow moving animals and plants)
Positives of Random Quadrats
Beneficial for larger populations (too difficult to count)
Inexpensive and easy
Negatives of Random Quadrats
Try for animals that move
May need lots of samples to get a representative population
Random Quadrats Equation
Estimated Abundance = (total number of individuals counted / area of each quadrat x number of quadrants) x total area
Population Density Equation
Sum of indivduals / area of quadrants
Capture-Recapture
A sample of animals is captured, marked in some way (tagged, coloured dot) and released. A sample is later captured and the ratio of marker (used to measure abundance of moving animals)
Positives of Capture-Recapture
Simple method
Good for moving organisms (neither quadrats or transects work)
Negatives of Capture-Recapture
Destructive/damaging
Time consuming or labour intensive
Capture-Recapture Equation
Total Population = (number marked in the first sample x total number of animals recaptured) / number of recaptured animals that are marked
Extinction
The last existing member of a species dies
Australian Megafauna
In the Pleistocene (2 million to 10,000 years ago) many species of mammals became extinct throughout the world
There is some debate amongst biologists whether this occured due to climate change at the end of the last Ice Age or to human expansion around the globe
In Australia, at least 40 species of mammals disappeared during the Pleistocene, and the species that died out were usually the biggest within a group of related species (collectively known as megafauna)
Examples of Australian megafauna
Procoptodon: 3m tall, blunt-faced kangaroo (largest kangaroo ever known), related to the red and grey kangaroos
Diprotodon: largest marsupial ever lived, 3m long, 2m tall at shoulder, possibly related to the wombat
Thylacoleo: “marsupial lion”, size of a leopard, some parts of the skeleton were similar to modern possums (hindlimb was possum-like, with an opposable first toe)
Dromornis: “giant emu”, 3m tall, weighed over 500kg, rrelated to the modern emu.
What caused the extinction of the megafauna?
Changes in climate – low rainfall, with drought-like conditions – largely affected availability of plants
Indigenous populations
Hunting megafauna directly
Use of fire to change the landscape (seed propagation by First nations people) changed structure of vegetation