Author: Freesciencelessons via YouTube
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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

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