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Biology-II
Assignment # 2
Evolution
Macro and micro evolution
Theory of special creation
Darwin’s process of natural selection
Submitted by Arham Qasmi
Seat no. EB21022009
Submitted to Dr Moin ud Din
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Evolution
Evolution is a process by which the physical characteristics of types of creature
change over time, new type of creature develops and other disappear. It’s a gradual
process
Evolution relies on there being genetic variation in a population which affects
the physical characteristics (phenotype) of an organism.
Some of these characteristics may give the individual an advantage over
other individuals which they can then pass on to their offspring.
There are two types of evolution:
Micro-evolution
You already know that evolution is the change in species over time. Most
evolutionary changes are small and do not lead to the creation of a new species.
When populations change in small ways over time, the process is
called microevolution. Microevolution results in changes within a species.
The five "forces" that can cause shifts in gene frequency (microevolution) are:
Natural Selection: when some genes are more beneficial than others to
survival and/or reproduction, those genes tend to increase in frequency in
the population over generations.
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Gene Flow (Migration): when there is mixing of genes from previously
isolated populations that have diverged, this can rapidly change gene
frequencies in the newly merged population.
Mutation: when an advantageous mutation spontaneously arises in an
organism, this mutated gene can increase in frequency over generations if it
conveys an advantage over those who do not have it. If a neutral mutation
(one that is neither beneficial nor harmful) arises in a population, it can
increase in a population by genetic drift. If a deleterious mutation arises in
an organism, it is likely to be selected against and will generally not increase
in frequency. While recombination during meiosis can shuffle genes into new
combinations, mutation is the only source of new genes.
Genetic Drift (Bottlenecks, Founder Effects): In a small population, gene
frequencies can change rapidly due to random events. For example, in a
population of only 10 individuals, each one carries 10% of the genes. In a
population of 100 individuals, each one carries only 1% of the genes. In a
population of 1000 individuals, each one carries only 0.1% of the genes. If an
accident happens to one individual in each of these populations, it is more
likely to significantly change gene frequencies in the small population.
are the pesticide-resistant mosquitoes. When these mosquitoes reproduce the
next year, they produce more mosquitoes with the pesticide-resistant trait. Soon,
most of the mosquitoes in your state are resistant to the pesticide.
This is an example of microevolution because the number of mosquitoes with this
trait changed. However, this evolutionary change did not create a new species of
mosquito because the pesticide-resistant mosquitoes can still reproduce with other
non-pesticide-resistant mosquitoes.
Macro-evolution
Macroevolution refers to much bigger evolutionary changes that result in new
species. Macroevolution may happen:
1. When microevolution occurs repeatedly over a long period of time and
leads to the creation of a new species.
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