A Level Biology Revision "Genetic and Environmental Causes of Variation"

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In this video, we look at genetic and environmental causes of variation. First we explore what is meant by interspecific and intraspecific variation. We then look at how variation can have genetic causes such as alleles, independent assortment of chromosomes and crossing-over during meiosis and random fertilisation of gametes. Finally, we look at how variation can be caused by the environment. Image credits Astronotus ocellatus https://commons.wikimedia.org/wiki/File:Astronotus_ocellatus.jpg Jón Helgi Jónsson (Amything), CC BY-SA 3.0 http://creativecommons.org/licenses/by-sa/3.0/, via Wikimedia Commons Fungus https://commons.wikimedia.org/wiki/File:Fungi_at_Springhead,_Shottermill_08.jpg Simon Burchell, CC BY-SA 4.0 https://creativecommons.org/licenses/by-sa/4.0, via Wikimedia Commons Hyena https://commons.wikimedia.org/wiki/File:Spotted_hyena_(Crocuta_crocuta).jpg Charles J. Sharp, CC BY-SA 4.0 https://creativecommons.org/licenses/by-sa/4.0, via Wikimedia Commons Peacock https://commons.wikimedia.org/wiki/File:P%C3%A5f%C3%A5gel_(peacock).jpg Magnus Johansson, CC BY-SA 2.0 https://creativecommons.org/licenses/by-sa/2.0, via Wikimedia Commons Mamba https://commons.wikimedia.org/wiki/File:Mamba_Dendroaspis_angusticeps.jpg Holger Krisp, CC BY 3.0 https://creativecommons.org/licenses/by/3.0, via Wikimedia Commons Snail https://commons.wikimedia.org/wiki/File:Snail_(139998665).jpeg Lauren, CC BY 3.0 https://creativecommons.org/licenses/by/3.0, via Wikimedia Commons Black cat https://commons.wikimedia.org/wiki/File:Tesla_the_cat_2.jpg Sage Ross, CC BY-SA 3.0 http://creativecommons.org/licenses/by-sa/3.0/, via Wikimedia Commons Orange tabby https://commons.wikimedia.org/wiki/File:Orange_tabby_cat_sitting_on_fallen_leaves-Hisashi-01A.jpg Orange_tabby_cat_sitting_on_fallen_leaves-Hisashi-01.jpg: Hisashi from Japanderivative work: Caspian blue, CC BY-SA 2.0 https://creativecommons.org/licenses/by-sa/2.0, via Wikimedia Commons Black and white cat https://commons.wikimedia.org/wiki/File:Black_and_white_cat_sitting_on_a_street-Hisashi-01.jpg Hisashi from Japan, CC BY-SA 2.0 https://creativecommons.org/licenses/by-sa/2.0, via Wikimedia Commons Orange, black and white cat https://commons.wikimedia.org/wiki/File:Kirby.jpg Fquestier, CC BY-SA 3.0 https://creativecommons.org/licenses/by-sa/3.0, via Wikimedia Commons Ob mouse https://commons.wikimedia.org/wiki/File:Fatmouse.jpg The original uploader was Bigplankton at English Wikipedia.Later versions were uploaded by Sunholm at en.wikipedia., Public domain, via Wikimedia Commons Melanoma https://commons.wikimedia.org/wiki/File:Melanoma.jpg See page for author, Public domain, via Wikimedia Commons Havanese litter https://commons.wikimedia.org/wiki/File:Havanese_Litter.png Cartman0052007 at English Wikipedia, CC BY 3.0 https://creativecommons.org/licenses/by/3.0, via Wikimedia Commons Meiosis https://commons.wikimedia.org/wiki/File:Meiosis_(261_35).jpg Doc. RNDr. Josef Reischig, CSc., CC BY-SA 3.0 https://creativecommons.org/licenses/by-sa/3.0, via Wikimedia Commons Fertilisation https://commons.wikimedia.org/wiki/File:Sperm-egg.jpg http://www.pdimages.com/web9.htm, Public domain, via Wikimedia Commons Scar https://commons.wikimedia.org/wiki/File:Scar,_two_months_after_total_thyrodectomy.jpg Starvee44 at English Wikipedia, Public domain, via Wikimedia Commons Blue hydrangea https://commons.wikimedia.org/wiki/File:Hydrangea_macrophylla_02.jpg I, MJJR, CC BY 2.5 https://creativecommons.org/licenses/by/2.5, via Wikimedia Commons Pink hydrangea https://commons.wikimedia.org/wiki/File:Hydrangea_macrophylla_01.jpg I, MJJR, CC BY 2.5 https://creativecommons.org/licenses/by/2.5, via Wikimedia Commons Basketball https://commons.wikimedia.org/wiki/File:Spain_national_basketball_team_2011_01.jpg Christopher Johnson, CC BY-SA 2.0 https://creativecommons.org/licenses/by-sa/2.0, via Wikimedia Commons Blood https://commons.wikimedia.org/wiki/File:Blood_Test_(15575812743).jpg Alden Chadwick from Leeds, UK, CC BY 2.0 https://creativecommons.org/licenses/by/2.0, via Wikimedia Commons