Evolution Flashcards
Without genetic variation in a population, evolution is not possible. Where does variation occur?
1) Mutations (1 in 5 spermies is mutated, and there are many types of mutations)
2) Chromosomal changes (inversions, translocations, deletions, fusions, and duplications)
3) Sexual reproduction (meiosis recombination/crossing over, meiosis independent assortment, and fertilization)
What are the types of genetic variation that can occur?
1) Discrete/polymorphism (eg. blood type, does not matter how groups are sorted)
2) Quantitative (statistically graphed with a curve using mean/variation)
Allelic diversity
Number of alleles per locus
Do endangered species have lower or higher genetic diversity than similar non-endangered species?
Lower
Hardy-Weinberg Equilibrium
NEUTRAL MODEL states that allelic frequencies will remain constant in the absence of mutations and immigration, and assumes large population size, all genotypes of equal fitness, and random mating
Microevolution
Changing allelic frequencies one generation at a time
Bottleneck
In small populations, random selection leads to genetic drift (loss of genetic diversity and fixation of alleles)
Natural Selection
Favouring some phenotypes over others (Golden vs red gobys)
Adaptive evolution
In theory, reduces genetic diversity (but diploidy and balancing selection prevent this)
Diploid
Organisms that have 2 sets of chromosomes (1 from father, 1 from mother)
Balancing selection
When 2 or more phenotypes are maintained in stable proportion either because heterozygotes are favoured, different alleles are favoured in different environments, or selection is frequency-dependent
Is microevolution by natural selection random?
No, it is a consequence of different survival rates due to relative fitness of the phenotype
3 types of natural selection
1) Directional (extreme phenotypes are favoured)
2) Stabilizing (herds that reproduce over a narrow window in the Serengeti = safety in numbers
3) Disruptive (separation of phenotypes like with Polar and Grizzly bears)
Are there any organism perfectly adapted to its environment?
Nope
What is the story of the Banff Springs Snail?
If this snail was not classified as its own species, it would not have been identified as At Risk, no action plan would have been put in place to save the species, and it would be extinct today
3 types of species
1) Morphological: structurally similar, making this classification practical for fossil records and popular for field guides
2) Ecological: share the same environmental conditions/resources
3) Biological: can reproduce fertile offspring
Problems with biological species concept
1) Androdioecies: hermaphroditic and reproduce via self-fertilization
2) Gynogenetic: internal fertilization requires sperm from a different species to stimulate egg development
3) Hybrid: 2 species interbreed to produce fertile offspring
4) Ring: ring of genetic drift through populations
How does the Mangrove Killfish reproduce?
Hermaphroditically
How does the Amazon Molly reproduce?
Females require sperm donation from another species to internally fertilize diploid eggs
What is special about the Ensantina salamander?
Some subspecies can reproduce while others cannot, due to a ring of genetic drift through the population
Reproductive isolation and its 2 types of mechanisms
Accumulation of genetic differences that ultimately prevent gene pools from 2 species mixing
1) Prezygotic mechanisms: habitat, temporal, behavioural, mechanical, gamete
2) Postzygotic mechanisms: reduced hybrid viability, reduced hybrid fertility, hybrid breakdown (1st generation is fertile, but the hybrid baby of 2 hybrids is infertile)
3 types of speciation:
1) Allopatric/peripatric: 2 populations are geographically separated or a small population becomes separated from the main group
2) Parapatric: a populations spreads over a number of environmental conditions, allowing natural selection to occur
3) Sympatric: habitat differentiation, polyploidy, and sexual selection cause new species to form within a population
Chimera hybridization
2 embryos merge at an early stage to produce a body with 2 sets of DNA, leading to striking patches of colour (Coral chimera)
Reticulate evolution/Syngameon population
Subspecies are created and brought back together again and again (Syngameon: population capable of exchanging genes)
