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VARIATION - Coggle Diagram
VARIATION
Speciation
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Allopatric
- new species rise
- an imposing geographical barrier may be no consequence to another
Exp : Lake subdivides into smaller pools, fish are unable to swim across and become reproductively isolated
Sympatric
- A population forms a new species within same geographical regions
- common in plants
A change in ecology
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Adaptive radiation
Occurs when populations of a single species invade a variety of habitat & evolve (response to environmental changes)
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Definition
The difference between individuals within a species which can be caused by inherited or environmental factors
Continuous Variation
- Shows a smooth gradation from one extreme to the other for a named character
- differences between individuals are slight (do not fall into distinct categories)
- can be shown in a bar chart + normal distribution
Example:-
- Height
- Weight
- Skin Colour
Discontinuous Variation
- Shows a sudden transition between two traits (no intermediate character involved)
- only limited number of possible values
Example :-
- Blood group
- Sex (gender)
- Eye colour
Source
Environmental
- ( Climate, diet, accidents, culture, lifestyle
- exp ( your language, your religion, flower colour in hydrangeas )
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Genetic (Inherited)
- improves ability of species to survive in a changing environment
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Selection
Artificial
- Involve breeding procedure
- to produce desirable phenotype
- man is selection agent
- change the frequencies of alleles & genotypes
Exp :-
- Cultivated numerous popular crops from wild farmers
- Dog breed
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Out breeding
( By selective & controlled crossing among individuals from 2 different population and subspecies )
Natural
- A process by which individuals inherited need & abilities ≥/≤ to resources available
- favourable genes are selected over the unfavorable genes (eliminated)
Types / Class
Directional
- which extreme type is favoured (lower/higher)
- intermediate group will always be suppressed
- weather (factor)
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Stabilizing
- eliminate 2 extreme groups and select then intermediate group
- The middle of the graph will increase in size
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Disruptive
- which 2 extreme groups are selected over intermediate group
- existence of polymorphism
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