Sciences - Co-ordinated (9-1) - 0973 CIE

Variation

Bayani Gaba-gaba

No two individuals of a species are exactly alike, and that variety is the raw material of evolution. Some differences fall into neat, separate categories; others form a smooth range. Understanding which is which, and where new variation comes from, is the bridge between genetics and natural selection.

In this lesson you will define variation, distinguish continuous from discontinuous variation with examples, link each to its causes, investigate both types, and explain mutation as the source of new alleles, including what raises the mutation rate and (for Extended) the other sources of genetic variation in populations.

Manufura

Describe variation as differences between individuals of the same species
State that continuous variation results in a range of phenotypes between two extremes; examples include body length and body mass
State that discontinuous variation results in a limited number of phenotypes with no intermediates; examples include ABO blood groups, seed shape in peas and seed colour in peas
State that discontinuous variation is usually caused by genes only and continuous variation is caused by both genes and the environment
Investigate and describe examples of continuous and discontinuous variation
Describe mutation as genetic change
State that mutation is the way in which new alleles are formed
State that ionising radiation and some chemicals increase the rate of mutation
[Supplement] Describe gene mutation as a random change in the base sequence of DNA
[Supplement] State that mutation, meiosis, random mating and random fertilisation are sources of genetic variation in populations

Takardar Darasi

Variation is what natural selection acts on, so it underpins evolution, selective breeding and the survival of species facing change. Telling continuous from discontinuous variation, and knowing that mutation makes new alleles, are reliably examined and easy marks once the definitions are secure.

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Nazarin Darasi

Barka da kammala darasi akan Variation. Yanzu da kuka bincika mahimman raayoyi da raayoyi, lokaci yayi da zaku gwada ilimin ku. Wannan sashe yana ba da ayyuka iri-iri Tambayoyin da aka tsara don ƙarfafa fahimtar ku da kuma taimaka muku auna fahimtar ku game da kayan.

Za ka gamu da haɗe-haɗen nau'ikan tambayoyi, ciki har da tambayoyin zaɓi da yawa, tambayoyin gajeren amsa, da tambayoyin rubutu. Kowace tambaya an ƙirƙira ta da kyau don auna fannoni daban-daban na iliminka da ƙwarewar tunani mai zurfi.

Yi wannan ɓangaren na kimantawa a matsayin wata dama don ƙarfafa fahimtarka kan batun kuma don gano duk wani yanki da kake buƙatar ƙarin karatu. Kada ka yanke ƙauna da duk wani ƙalubale da ka fuskanta; maimakon haka, ka kallesu a matsayin damar haɓaka da ingantawa.

Variation is best defined as: A. differences between individuals of different species B. differences between individuals of the same species C. the inheritance of alleles D. a change in the environment Answer: B
Which is an example of continuous variation? A. ABO blood group B. tongue rolling C. human height D. seed shape in peas Answer: C
Discontinuous variation is usually caused by: A. the environment only B. genes only C. genes and the environment D. diet only Answer: B
Mutation is best described as: A. the shuffling of existing alleles B. genetic change that forms new alleles C. a type of meiosis D. an environmental effect Answer: B
Which factor increases the rate of mutation? A. a balanced diet B. ionising radiation C. regular exercise D. drinking water Answer: B