True mean of SE is ±1.96
In a number of samples each sample will have its own mean
Standard error measures how much the value of a sample mean is
likely to vary
The greater the standard error, the greater the variation of
the mean
Standard deviation (σ)
Measure of the spread of results about the mean of a normal
distribution curve
Thinner bell-shape / smaller standard deviation / less
variation
Same pattern with bigger bell-shape
Causes of variation
Independent assortment of bivalents at the equator during
anaphase I
Chromosomes of bivalents pulled to opposite poles at random
2n different combinations of chromosomes in four haploid cells
produced where n is the haploid number of chromosomes
Crossing over between non-sister chromatids during prophase I
At synapsis, non-sister chromatids of homologous pairs cross
over at chiasmata
Homologous chromatids (corresponding pieces of genetic
material) break and exchange equivalent segments between maternal and paternal
chromatids
Results in new combination of genes from the two parents
Fertilization / random fusion of gametes
Genetic difference amongst the zygote
New combinations of alleles
Gene mutation / increased by environmental factors (eg
radiation)
Addition / at least one base is added during DNA replication
Deletion / at least one base is not copied (frameshift)
Substitution / at least one base is copied wrongly
Interferences with normal base pairing (A-T;C-G)
Degenerate code / different triplets can code for same amino
acids
Discontinuous variation
IMG 5-14-2
Limited number of distinct phenotypes / categories (e.g. blood
group)
Strong genetic factor controlled by alleles on one gene
Frequency histogram has separate bars
Unaffected by the environment
Continuous variation
Continuous range of values / class intervals (e.g. human
height)
Alleles on many genes located on different chromosomes /
polygenic inheritance
Frequency histogram is a smooth (normal distribution) curve
Phenotype is affected by environmental factors
Lower skin temperature activates a gene for pigment production
Diet affects individual's size and health. Malnourishment
results in shorter height
Therefore, genes + environment → phenotype
(continuous variation)
Advantageous of variation to species
Allows different adaptations / some better adapted
Some survive / reproduce / pass on gene/allele
Allows for changing environment / different environment
Ecosystem
Ecosystem
Five Kingdoms
Human Activity
Inheritance
Nutrient Cycle
Photosynthesis
Selection
Variation
Content
Normal distribution about the mean
Causes of variation
Discontinuous variation
Continuous variation
Advantageous of variation to species
No comments:
Post a Comment