Food webs and energy transfer

Food_web

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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

Inheritance:

  • 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.

 

Welcome Back – Term 3!

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Year 12 students will be counting down the next 14 weeks until their VCE Biology exam on the morning of Friday 30th October. We will start this term with a review of the structure of DNA, using the GTAC resources, “Exploring the structure of DNA“.

On Wednesday 22nd July we will be heading to the University of Melbourne Genetics Department to complete three practical activities that will contribute to your school-based assessment:

  1. An investigation using a DNA tool and a manipulation technique
  2. An investigation of inheritance in Drosophila melanogaster including a review of meiosis in gamete formation
  3. Meiosis in Drosophila

On Friday 4th September you will have the opportunity to travel to Brauer College and participate in GTAC outreach program, “From Hominoids to Hominins”.

On Tuesday 13th October you will be able to attend a “Get into Genes” program as revision prior to your exam.

Structural, Functional and Behavioural Adaptations

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Image Source – 20 Amazing Animal Adaptations for Living in the Desert

Living organisms are spread across the planet in a wide variety of different habitats and environments. Various adaptations assist organisms to survive in the hottest and driest deserts, coldest arctic tundra and wettest rainforests. Structural adaptations are how an organism is built, such as the wings, feathers and hollow bones of birds that assist them to escape from predators and find their food. Functional or physiological adaptations are how an organism works, which you may not necessarily be able to see from the outside, such as the ability of desert dwellers to survive without drinking water by re-absorbing much of the water from their faeces and producing small amounts of very concentrated urine. Behavioural adaptations are the actions that an animal takes – what it does – to survive, such as migration, resting in the heat of the day or huddling with other individuals to conserve body heat and moisture.

 

Semester 2 Biology – Adaptations (Y11) and Heredity (Y12)

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This semester we will be starting Unit 2 (Organisms in their Environment) Area of Study 1: Adaptations of Organisms and Unit 4 (Continuity and Change) Area of Study 1: Heredity. We have created Quizlet Sets for each of these topics: