BIOL 1020U Lecture Notes - Lecture 21: Headstander, Species Complex, Population Genetics
Evolution Lecture
How Genotypes and Phenotypes Change Over Time (Part 1)
Textbook Reference: Chapter 21 in Biology How Life Works (2nd ed.)
Sections 21.1 – 21.3; pp.425 to 432
Adaptation, Unity and Diversity
•Three key observations about life:
1. organisms suited to their environments
2. shared characteristics (unity within our species)
3. rich diversity
Examples:
Grasshopper:
Grasshopper in camouflage – often a dramatic example of adaptation, one form of
evolution – adaptation makes it very well suited for its environment – unity is when they
have similar structure and diversity would be the color
Headstander beetle:
Found in dry parts of the dessert – must need something to collect water – adaptations
with needles that flow towards their mouth (oriented in a certain way) – head is in the
ground in order to collect water droplets from the fog – directs droplets into the mouth
via the little hairs (specific adaptation that allows beetle to get water) – unity being the
similarities and diversity being the differences. Adaptation being the way a species
adjusts in certain environments
Genetic Variation
•Since Darwin, we have appreciated that species do not conform to a type and
instead consist of a range of variants.
•What does natural selection depend on?
•Depends on the differential success, in terms of surviving and reproducing, of
variants (some similar characteristics, but many variations) – different abilities to
succeed and survive based on what gets passed on through generations
•Variation can be phenotypic or genotypic
Comparison of genetic variation:
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Phenotypic variation Overall genetic variation
Humans High degree Rank low compared to
other species
Fruitflies Can vary
About 10 times more
variable than humans in
terms of number of DNA
pairs
Adelie penguins Low degree of variation 2-3 times more variation
than humans
Population genetics is the study of patterns of genetic variation in natural populations
•Important terminology:
–Species – group of individuals that can exchange genetic material through
interbreeding, or share alleles through reproduction
–Gene pool – all alleles present in all individuals in a species
–Populations – an interbreeding group of organisms of the same species
living in the same geographical area
Individuals represent different combinations of alleles from the species’ gene pool
What can cause genetic variation?
•Mutation - generates new variation
–Somatic (end up being more
localized)
–Germ-line (more important – can
get passed on)
–Deleterious (produce alleles that
do not provide an advantage –
usually gives disadvantage –
results in disease)
–Neutral (happen in noncoding
regions – no advantage or
disadvantage)
–Advantageous adaptations (important in natural selections) – can
become adaptations in they are advantageous enough
•Recombination
shuffles mutations to create new combinations of mutations – both of which result
in new alleles being formed – does not typically have huge effect – where you get
a bunch of new combinations
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Document Summary
How genotypes and phenotypes change over time (part 1) Textbook reference: chapter 21 in biology how life works (2nd ed. ) Sections 21. 1 21. 3; pp. 425 to 432. Adaptation, unity and diversity: three key observations about life, organisms suited to their environments, shared characteristics (unity within our species, rich diversity. Grasshopper in camouflage often a dramatic example of adaptation, one form of evolution adaptation makes it very well suited for its environment unity is when they have similar structure and diversity would be the color. Adaptation being the way a species adjusts in certain environments. About 10 times more variable than humans in terms of number of dna pairs. Population genetics is the study of patterns of genetic variation in natural populations. Species group of individuals that can exchange genetic material through interbreeding, or share alleles through reproduction. Gene pool all alleles present in all individuals in a species.
