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17 Apr 2012
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ANTA01H3F- Understanding Humans
Adaptation: a feature of an organism that increases the likelihood of its survival and
reproduction in a particular environment
Adaptive radiation: the evolution of multiple divergent species from a single less specialized
ancestral species
Niche: the role of a species in its environment
Evolutionary Processes
Natural selection
Artificial selection
Sexual selection (non-random mating, e.g., inbreeding)
First introduced by Darwin in his book Descent of Man in 1871
Selection on features or behaviours associated with mating
Generally takes two forms: 1) male-male competition, 2) female choice
“A change in DNA… can refer to changes in chromosome number or structure
Genetic Drift
Random changes within smaller populations
Gamete sampling
Changes in the genetic material passed on to the next generation just as a result
of random chance in which variants get passed on.
Changes in the frequency of variants in a population as a result of subdivision
Founder effect
Differences in the frequency of variants in a population as a result of random
chance in which members start a new population
Example: one outcome of founder effect can be an increase in the relative
frequency of a rare type (e.g., a gene for a disease such as porphyria)
Evolutionary bottlenecks
A restriction in genetic variability with a decrease in population size
Gene flow
“Exchange of genes between populations”
Timescale of Evolution
“small changes occurring within species”
Occurs in populations in an observable timeframe
Example: peppered moths in England during the Industrial Revolution
“changes produces only after many generations”
Events at a higher level, such as speciation
Example: evolution of the modern-day horse
Gregor Mendel (1822-1884)
“father of genetics”
Monk who worked in the Czech republic
Blending or particulate inheritance?
What happens if you mate a plant that consistently produces smooth peas with one that
consistently produces wrinkled peas?
Blending inheritance: predict that a mating of
Particulate inheritance: predict that a mating of a smooth pea and a wrinkled pea could
produce either a smooth or wrinkled pea
Gene: a sequence of DNA bases that specifies the order of amino acids in an entire protein…
portion of a protein, or any functional product; Mendel’s factors
Alleles: alternate forms of genes
Homozygous: possessing two of the same allele
Heterozygous: possessing two different alleles
Evolution: A change in allele frequencies with time, i.e., a change in the frequency of the
Dominant allele: the allele that is expressed in a heterozygote
Recessive allele: the allele that is not expressed in a heterozygote
Why do some features appear to blend in offspring?
Monogenic: a characteristic coded for by only one gene (i.e., one set of alleles)
Mendelian traits
Polygenic: a characteristic coded for by more than one gene
The complex interaction of multiple genes can produce the appearance of blending
Some alleles are codominant, which can also produce the appearance of blending
Structure of DNA (deoxyribonucleic acid)
Nitrogenous bases
A= adenine
T= thymine
G= guanine
C= cytosine
A always bonds with T
C always bonds with G
Control centre of the cell
Energy producing part of the cell
Contains mitochondrial DNA (mtDNA)
Much simpler than nuclear DNA
Protein Synthesis
Transcription: sequence of base pairs is copied onto a molecule of messenger RNA (mRNA)