Evolution Notes A Flashcards
mutation
- Allelic variation in QTLs for color, morphology, and all other phenotypic traits
- Stochastic and ongoing process
Genetic Drift
- Majority of mutations fixed or lost at random
- More common
- “new alleles occur in populations”
- random
Gene Flow
- Genetic info shared between individuals in the same population or species; maintains a species
Natural Selection
- Individuals with certain alleles (due to mutations) and the corresponding trait (coloration ex) have higher fitness in a given environment
- Less common
Lamarck’s Hypothesis
To account for change over time, Lamarck proposed his Theory of Inheritance of Acquired Characteristics
- In this example, young giraffes need to reach tall leaves so their necks get longer during their lifetime to help them better
deal with the environment
- According to this theory, longer necks are then passed onto the next generation
- This theory is not a correct view of the evolutionary process.
- However, does attempt to tie changes with reproduction, groups, etc.
Darwin’s Theory of Natural Selection
- essentials are variation(genotypic and phenotypic)
- Remember from genetics that variation of a quantitative trait like neck length is due to several QTLs as well as epigenetic influences
- Recognized there will ALWAYS be variation with these traits, passed from parent to offspring; better fit traits more likely to pass on since they have greater fitness
- Variation in genetics leads to variation in phenotype
Apply Darwin’s Natural Selection to the Giraffe example by Lamarck
- The key to Natural Selection is that at any given time, the giraffe species exhibits variation in neck length
- In the environment where there are tall trees, individuals with longer neck can more easily get nutrition and will have increased fitness (survive and reproduce)
- The fit individuals will pass on the allelic variants corresponding to neck length to their offspring
- But despite this, there continues to be variation in neck length since DNA is constantly changing.
How is fitness determined?
- it is determined by number of offspring, NOT by age (so reproductive success, NOT survival)
Name traits of a phylogenetic tree
- generates using DNA, morphology, or combo
- framework to guide asking and answering evolutionary questions
- a fully resolved tree has bifurcations from every node
Name 3 types of phylogenetic trees
cladogram, phylogram, chronogram
Cladogram
o Lineages stop abruptly at the same point
o Can be rectangular, angled, circular… still equivalent!
Phylogram
- branch lengths differ after bifurcation
from the common ancestor - The longer the line, the more changes
on that lineage after the bifurcation
Chronogram
- has specific time scale; allows researchers to date the common ancestors
- Note: triangle off of bifurcation signifies diverse/richness
How to identify type of phylogenetic tree
- keep in mind traits of cladogram, phylogram, and chronogram
- describe the type of tree in detail (such as rectangular, linear, circular)
Types of phylogenetic characters
homology, homoplasy
homology
derived from common ancestors, similarity due to shared common ancestors
used to make phylogenetic tree reconstruction
homoplasy
- Independently derived in two or more taxa in different parts of the tree
- Not useful for phylogenetic tree making
- Results from convergent evolution
Describe the 3 types of homologous characters and how they are measured to create a phylogenetic tree
- Synapomorphy: derived and shared, fully resolved tree (1)
- Symplesiomorphy: ancestral character (0)
- Autapomorphy: unique to single lineage (1)
Why type of homologous character can resolve phylogenetic relationships?
synapomorphies
