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Week 2: Transport across the plasma membrane

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Image result for phagocytosis and pinocytosis

Learning Intention:
“Students will understand the role of different organelles including ribosomes, endoplasmic, reticulum, Golgi apparatus and associated vesicles in the export of a protein product from the cell through exocytosis and cellular engulfment of material by endocytosis.”

Ribosomes translate the messenger RNA into a protein by matching the 3-base pair codon with an anticodon on the transport RNA, allowing the production of a polypeptide. The endoplasmic reticulum allows the transport of polypeptides (protein chains) to the Golgi aparatus, where proteins are collected, packaged and distributed throughout the cell and exported through the cell membrane (exocytosis).

Osmosis is the passive movement of water across a semi-permeable membrane
Diffusion is the natural tendency of particles to move from a higher concentration to a lower concentration. It is a passive process – does not require energy to be expended.
Facilitated diffusion is when a protein channel is required to allow the passive movement of larger molecules through the cell membrane.
Active transport (as opposed to passive transport) means that energy is required for the cell to all transport of substances against the concentration gradient.
Phagocytosis is the movement of solids across a membrane, usually when the cell creates a pocket and engulfs the nutrient.
Pinocytosis is the movement of liquids across a membrane, for example, when a Paramecium expels liquid waste water.
Endocytosis is when substances move into the cell.
Exocytosis is when substances move out of the cell.

Week 1: Fluid mosaic model of the cell membrane

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Which molecules can move through the cell membrane passively (by diffusion)?

Which molecules can move through the cell membrane by active transport (requiring energy)?

Which molecules cannot pass through the cell membrane?

Human Evolution

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evolution_silohettesImage source

One of the earliest defining human traits, bipedalism — the ability to walk on two legs — evolved over 4 million years ago. Other important human characteristics — such as a large and complex brain, the ability to make and use tools, and the capacity for language — developed more recently. Many advanced traits — including complex symbolic expression, art, and elaborate cultural diversity — emerged mainly during the past 100,000 years.

Since Darwin first proposed that humans and apes had a common ancestor, our understanding of human evolution has improved due to fossil finds, analysis of our closest living and extinct relatives, studies of geographic distribution and DNA analysis. Although the image above is often used to represent human evolution, the process is not the simple linear procession that is shown. Your task is to write an essay of at least eight paragraphs that explains why this image is suitable, but also why it is an inaccurate representation of human evolution.

  • Introduction – what will the following paragraphs explain?
  • Outline primate family tree, including lemurs, monkeys, apes, hominins and Homo sapiens.
  • Where do Australopithecus sp., Homo erectus, Homo habilis, Homo neanderthalensis and Homo heidelbergensis fit in?
  • Discuss bipedalism – location of foramen magnum, shape of spine  and ratio of arm to body length.
  • Discuss skull shape, brow ridges, sagittal and nuchal crests, prognathous jaw and facial sloping.
  • Discuss cranial capacity and relationship to body mass and intelligence.
  • What is the evidence that human evolution is not a linear progression, but a many-branched family tree?
  • Conclusion – what are the main characteristics that can be identified in the image and why is the image an inaccurate representation of human evolution.

Introduction to Human Evolution from the Smithsonian 

7 Strange and Surprising ways that humans have evolved recently

Exam Revision continues!

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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

An introduction to ecosystems

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Australia-climate

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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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Equine_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:

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

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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.

Structural, Functional and Behavioural Adaptations

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thorny_devil

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.

 

Unit 1 and Unit 3 Biology Exam Revision

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There are several strategies you can use to revise for mid-year exams – here are just a few:

  • Use the Hawkesdale Biology Quizlet Class to revise terms and definitions for each chapter
  • Copy and revise the Slideshows I have saved in the Year 11 and Year 12 Biology class folders (Student Public Drive)
  • Create a set of study notes with the Chapter headings, diagrams and key concepts. These will be very useful at the end of the year for revision too.
  • Create mind maps that link each of the main concepts – use colour to help you remember.
  • Use the posts in this blog to review YouTube videos and other resources for each chapter.
  • Past exams are a good indication of the standard of questions you will be asked – do as many as you can reasonably cope with! Use questions you find difficult as a guide to what you need to study more of.
  • Create flow charts and posters for the wall at home of concepts that can be represented diagrammatically.