IGCSE BIOLOGY REVISION [Syallbus 18] - Variation & Selection

[@Cambridgein5minutes]

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keep it up

[@salehkhalid2155]

does evolution lead to natural selection or does natural selection cause evolution?

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I am literally studying at 2am this is my only motivation

[@Cambridgein5minutes]

Keep at it !!

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How did you do

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How’s ur life 2 years later and does this exam matter rn?

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@@laithdababneh6104 I wanna hear his reply 😆

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Finished igcse but still watching your videos! 😂. Between thanks for helping me, i got an A* 😊.

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Awesome Job Mohammad, you deserved it. Congrats!

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Mohammed Awad do i somehow know you?

[@salehkhalid2155]

does evolution lead to natural selection or does natural selection cause evolution?

[@ryze5021]

@@salehkhalid2155 natural selection causes evolution

[@wameymasole8783]

Bro share the trick how did you manage 😭 I'm having exams in 2 months and I'm looking forward for an A*

[@gloriaxx]

Omg you are a God sent ,with this whole corona situation it really hindered everything. Thank you

[@salehkhalid2155]

does evolution lead to natural selection or does natural selection cause evolution?

[@Khushi-qo6qx]

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[@gloriaxx]

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[@wameymasole8783]

@@salehkhalid2155 heyy , evolution is the product of natural selection

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I watched your videos throughout the year. They are the best for revision because most of the time I feel so lazy. These still help me get my revision done efficiently

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Right now I don't have a biology tecaher in school and exams are so near but because of your videos I am able to study properly. Thank you soo much for all the videos they are very helpful💜💜💜

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armyyyyy

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Thank you for making this video! This is currently the most boring chapter for me in Biology, however your video quickly helped me to revise it.

[@Melly3000]

thanks again mate. Cant wait for organisms and their environment

[@Cambridgein5minutes]

I’m glad it helped!

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Your videos are helping me getting through difficult chapters. Thank you so much.

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studying all 18 syllabuses for my final exam, hope this goes well for me!!

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Best channel 👌 i have exams in 2 months

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yessss finally i was waiting for this video for sooo longgggggggg thanks buddy

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Could you make a video on astrophysics please, its in the igcse caie 2023 syllabus and there are very few videos and material online

[@gloriaxx]

Who’s here getting ready for the October exams

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Me :( I m scared

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Really scared

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K-9 me too😖 but we’ll get through this 💗

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Hope fully Which school r u from?

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Thanks for this I got all my notes from the ppt keep up creating such content it will help alot for boards

[@ryze5021]

Under rated channel I love this helps a lot

[@callistomalady6084]

Personal notes - differences in variation within the same specie, it can be both genetic and phenotypic - two forms of variation continuous (spectrum-like) and discontinuous (yes or no) - discontinuous is usually not affected by the environment - Mutation - Sickle cell anemia; caused by a faulty gene. normal allele > faulty allele. people can be normal, carrier (in which case they show traits but not life threating), or have entirely abnormal RBCs (life threatening). - Malaria, RBC is invaded by a parasite that is hosted by certain mosquitos. people with sickle cell anemia is protected (homozygous>heterozygous). people with normal RBC not protected. - By process of natural selection people in tropical areas, where malaria is prevalent, tend to have sickle cell anemia

[@salehkhalid2155]

does evolution lead to natural selection or does natural selection cause evolution?

[@faribashah3415]

Sir is there any video of yours that shows how to answer questions about describing and explaining graphs?

[@heartkiller8405]

What are the adaptive features of mammals that lives in the desert and cold environment

[@ibrahimkhan-lm5bc]

tysm!! this helped me alot in exams

[@wameymasole8783]

What are the symptoms of sickle cell anemia

[@takudzwamunyawarara3692]

hello:) so if we are asked to explain how a change in the base sequence of the gene for haemoglobin results in abnormal haemoglobin and sickle-shaped red blood cells is it correct to say there is a change in the allele hba to hbs which cause the RBC to be stiff and they get stuck in the blood capillaries reducing the flow of blood

[@coolseasheep9401]

Fricking hell

[@alaa7055]

yeah i think that's correct

[@alaa7055]

During mutation one of the genetic code for haemoglobin chain called Beta changes from CTT to CAT. CTT codes for Glutamic acid amino acid while CAT codes For Valine amino acid this change will change the amino acid sequence producing a different protein eventually produces a different haemoglobin leading to a sickle cell

[@salehkhalid2155]

does evolution lead to natural selection or does natural selection cause evolution

[@Cambridgein5minutes]

Good question! Natural selection “selects” individuals with the most favourable genes to survive and reproduce. This is survival of the fittest. When this occurs over a long stretch of time, it leads to evolution. So natural selection leads to evolution, not the other way round :)

[@ShazyKazzy]

Damn, your videos are great!

[@shachibaxi1573]

Hey I have a doubt. You said that the faulty allele is dominated by normal haemoglobin, so it is the recessive one. In heterozygous genotype, how will it then have an effect? (Also your videos are really helpful!!)

[@wadhahinai7419]

its like there co-dominant , so there will be some side effects not major though

[@leenmeshal9558]

Thanks , I swear ur the best. ❤️🥰✨✨

[@adhithi7181]

your videos are amazing by the way thank you so much :)

[@saahilmadhani9510]

can you please explain the mutation again!

[@adhithi7181]

im a little confused because the textbook states that continuous variation is things such as blood type and discontinuous variation is things such as height and weight ??//

[@alaa7055]

noo they have them switched. it's from their names; continuous as in on going as in includes intermediates like heights and weights whereas discontinuous as in limited as in it's either this or that like blood types, tongue rolls etc

[@ramyagururajan]

Sir whats sunken stomata and rolled leaves?

[@Cambridgein5minutes]

Rolled leaves directly means leaves that are rolled up which reduces water evaporating from the plant and therefore conserving water. Sunken stomata means that the stomata is dipped inwards. If you google image 'sunken stomata' you will see what I mean. The purposes of this is to protect escaping water vapor from air currents, reducing water loss from the plant

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❤

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32hr till exam

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"Cambridge in 5 minutes" 9:42 secs long video (btw love your videos❤❤)

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keep doing these videos it is really useful

[@Melly3000]

can you also do some paper 6 questions ?

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I am thinking of going through some past papers in my future videos :) I am not entirely sure when but I will at some point!

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thank you because im writing next month

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he is just reading whats in screen!