A Level Biology Notes: Unit 16 - Selection and Evolution
Delve into the fascinating processes of selection and evolution with these comprehensive Level Biology notes for Unit 16! Perfect for students aiming to understand the mechanisms that drive the diversity of life on Earth.
Natural Select...
17 1 variation differences that exist between individuals
of a species intraspecific variation
Phenotypic Variation difference in phenotypes between
organisms of the same species
can be caused by due to qualitative or
quantitative differences
genetic factors
environmental factors
for a combination of both
phenotype genotype environment
Genetic Variation
1
small differences in DNA base sequences between individual
organisms within a species population
genetic variation is transferred from one generation to
the next generates phenotypic variation
can be caused by results in a new combination of
alleles in a gamete or individual
independent assortment of bivalents during metaphase I
crossing over of non sister chromatids during prophase I
, random fusion of gametes during fertilisation
nntionnutingenerationofnewa.lu
may beadvantageous disadvantageous or have no
apparent effect on phenotype
genetic code is degenerate
not always seen in the individual they first occur in
can remain hiddennot expressed within a population for
several generations before they contribute to phenotypic
variation
Genes effects on an
organisms phenotype
may be affected by a single gene or several
the impact the gene has on the phenotype varies
, Environmental factors impacts phenotype
e
g
length of sunlight seasonal
food nutrients
availability of water
temperature
oxygen levels
changes in these factors can affect how organisms grow develo
phenotypic variation caused solely by environmental pressures
or factors cannot be inherited by offspring
only alterations to genetic component of gametes
is inherited
by offspring
directly affects
DNA of gametes
enviro doesn't
Discontinuous and Continuous Variation
Discontinuous variation
differences in the phenotypes of individuals within a
qualitative
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