Succession in ecosystems


Learning Intention: Students will understand the process of ecological succession and be able to identify growth stages of a eucalypt forest.

Mountain Ash (Eucalyptus regnans) is an iconic Victorian species, the tallest flowering plant and the second tallest tree in the world, after the Californian redwood. It only germinates after hot and periodic bushfire, greater than 20 years apart. The forest goes through stages of growth:

  • Bushfire
  • Germination (1-8 weeks)
  • Seedlings (0-4 years)
  • Saplings (4-15 years)
  • Pole stage (15-30 years)
  • Spar stage (30-100 years)
  • Mature forest (100-300 years)
  • Old Growth Forest (300-400 years)

Forest Secrets – Stages of succession in Mountain Ash forests

Eucalyptus regnans on Wikipedia – Description, Tallest trees and Ecology.

Exam Revision continues!

Read through the following list of concepts and note any that you couldn’t confidently discuss with a parent or friend:

Unit 3: Area of study 1: Bio-macromolecules, Photosynthesis, Respiration and Enzymes

Unit 3: Area of Study 2: Homeostasis, Nervous and Hormonal Systems, Disease and Immunity

Unit 4: Area of Study 1: Heredity, Genes, Chromosomes and Manipulating DNA

Unit 4: Area of Study 2: Populations, Evolution, Hominins and Human Intervention in Evolution

Exam Revision

Welcome back and thanks for your patience while I have been on study leave. There are only two weeks left before the Unit 3/4 Biology exam on Friday 30th October, so you should have already done the following:

  1. Written out a clear and concise set of study notes, outlining the main concepts in each Area of Study.
  2. Completed practice exams (available at the VCAA website) and identified areas where you need to do further revision.
  3. Joined the Elevate Education #elevatebio Video Series at
  4. You may also like to join the site for a five-day free trial and access their Immunology resources.

Some students have mentioned that they are having most difficulty remembering the cells involved and sequence of events of the cell cycle and immunology. These quick videos and other resources may assist with your revision:

Food webs and energy transfer


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Food chains illustrate the relationship between producers and consumers, showing the different trophic levels in an ecosystem. Because living organisms usually have more than one source of food, these food chains are often linked together, forming food webs. Food webs assist us to identify herbivores, carnivores, omnivores, scavengers, detritivores and decomposers in a community.

Not all relationships within an ecological community are predatory or feeding relationships. Some important relationships are parasitic, mutualistic (both organisms benefit), commensalism (one benefits, the other is not harmed) or parasitism (one benefits and the other is harmed, but usually not killed).

An introduction to ecosystems


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Australian ecosystems are usually described by a combination of living and non-living components – for example, tropical rainforest, temperate or dry sclerophyll woodlands, alpine meadows or mallee scrublands. The types of communities that live in these ecosystems will be dependent upon the range of temperature and rainfall as well as the soil type, which affects the plants that are able to thrive and therefor the animals that live there. Australian soils are mostly very nutrient poor, due to the fact that the landscape has been exposed to rain, wind and erosion for many millions of years, washing nutrients into the rivers and oceans. An exception to this is the areas where volcanic eruptions have brought nutrients to the surface, such as the western volcanic plains.

A biome is a major community of plants and animals classified according to its predominant vegetation and characterized by the adaptations of its organisms to that particular environment.

YouTube videos:

An introduction to evolution


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Good introduction from BBC Earth: How do we know evolution is real?

Evidence for evolution:

Tree of Life Resources:

YouTube Videos:

Reproductive Strategies


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Living organisms have evolved many different reproductive strategies to ensure their survival from generation to generation. Scientists sometimes categorize these strategies as “r-selected” (rapid, related to rate) or “K-selected” (related to carrying capacity). You can read a good comparison of r and K-strategies here: Reproductive strategies

Read the ABC Science article: Antechinus go out with a bang and then do “Part B: A case study in reproductive behaviour” on page 150 of your Jacaranda Activity Manual. If you finish, please do the Chapter 12 Review questions and the Activity manual “In Review” for Chapter 12.

Unit 4 Biology – AoS 1: Heredity


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This Area of Study includes key knowledge about genetics and heredity:

Cell reproduction:

  • binary fission in prokaryotes
  • the phases of the cell cycle in eukaryotes including DNA replication, the division of the nucleus (mitosis), and cytokinesis
  • the key events that result in the production of haploid sex cells from a diploid cell (meiosis), including recombination

Molecular genetics:

  • the nature of genomes, genes and the genetic code
  • gene expression: the genetic code and roles of RNA in transcription, RNA processing in eukaryotes, and translation
  • the concept of gene regulation (the switching on and off of genes by factors expressed by regulator genes and environmental factors)

DNA tools and techniques:

  • gel electrophoresis;
  • DNA amplification;
  • DNA sequencing;
  • making a recombinant plasmid;
  • bacterial transformations;
  • DNA profiling;
  • gene cloning;
  • and using plasmids as gene delivery systems

There are a good series of six, (less than) ten-minute videos on YouTube that cover these concepts:

  1. Gene Technology1 of 6 – Restriction enzymes and ligation
  2. Gene Technology 2 of 6 – DNA probes and amplification
  3. Gene Technology 3 of 6 – PCR and gel-electrophoresis
  4. Gene Technology 4 of 6 – DNA fingerprinting
  5. Gene Technology 5 of 6 – DNA sequencing
  6. Gene Technology 6 of 6 – Gene cloning


  • the nature of chromosomes, alleles, genotype and phenotype
  • the causes of phenotypic variation: mutations; recombination of parental alleles in sexual reproduction; polygenes; and interactions of environmental factors with genes
  • continuous and discontinuous variation
  • patterns of inheritance involving the monohybrid cross: dominance; recessiveness; co-dominance; multiple alleles
  • dihybrid crosses as independent or linked
  • pedigree analysis: autosomal and sex-linked inheritance; use of the test cross.

Some resources to assist your revision of this topic:

DNA tools and techniques

Gel Electrophoresis: This technique is used to separate fragments of DNA according to their size – longer fragments with a large number of base pairs travel more slowly through the substrate (agarose gel), while shorter fragments with a smaller number of base pairs travel a greater distance. A buffer solution is added to the apparatus and DNA fragments are ‘cut’ at specific sites using restriction enzymes and loaded, together with a fluorescent dye, in ‘wells’ at the negative end of the apparatus.  An electric charge is applied and the negatively charged DNA fragments are attracted to the positive end of the gel matrix. Gel Electrophoresis on YouTube. 

DNA amplification: Using a Polymerase Chain Reaction (PCR) researchers can create many copies of DNA in a test tube.

DNA profiling: Also called DNA fingerprinting, this technique compares DNA from victims, suspects and crime scenes to determine which samples have the most in common. How does DNA fingerprinting work from the Naked Science Scrapbook (YouTube). 

DNA recombination: Scientists are able to insert fragments of DNA from one organism into another organism, bringing together genetic material from various sources. Recombinant DNA produces genetically modified organisms, that may add desirable characteristics to food crops, for example.

DNA sequencing: DNA sequencing is the process of determining the precise order of nucleotides within a DNA molecule. DNA Sequencing on YouTube.

Gene cloning: Molecular cloning is a set of experimental methods in molecular biology that are used to assemble recombinant DNA molecules and to direct their replication within host organisms. Gene cloning in plain English on YouTube. 

Gene transformation: “In molecular biology, transformation is the genetic alteration of a cell resulting from the direct uptake, incorporation and expression of exogenous genetic material (exogenous DNA) from its surrounding and taken up through the cell membrane.” Bacterial transformation by zabaaz on YouTube.

Animal Behaviour


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Animal behaviour (ethology) is an interesting field of study that has fascinated biologists for hundreds of years. From Jean-Baptiste Lamarck and Charles Darwin to Konrad Lorenz, Ivan Pavlov and Skinner, scientists have studied animals and wondered how their behaviour relates to humans.

  • Innate Behaviour – Reflexes, Kineses and Taxes (7.15 minute video)
  • Learned Behaviour – Imprinting, Habituation and Conditioning (6.24 minute video)
  • Animal behaviour (23.40 minute YouTube video) – What can we learn by using video cameras attached to animals or in their burrows to see the world from an animal’s perspective? Cameras were attached to reptiles, mammals and even insects to observe animal behaviour in their natural environment. These are animals from North America (wild turkeys, armadillo, moles and chickadees).
  • Produce a slideshow showing the structural, functional and behavioural adaptations of some Australian native animals. For example, koala, kangaroo, emu, echidna, crocodile, tiger snake, thorny devil, platypus or kookaburra.