Pre-darwinian time how were categories of living things said to be organized?
There was said to be a “chain of being” or “scala naturae” which was basically a list of increasing complexity, with god being at the top.
Who was the father of taxonomy? How did he oppose the chain of being idea?
Carolus Linneaus didn’t like the linear idea of organisms, but rather he preferred the idea of clusters of different living things. From this he created taxa.
What did Lamarck propose about the idea of living things?
He looked at the fossil record, and marine record, and saw that there seemed to be extinction of animals, proposing the idea that new animals are likely being created, or rather he viewed the progression of animals in the fossil record.
What were Lamarck’s two main ideas? What were the issues with them?
- Pattern: the living world was made of separate lineages with independent origins, each progressing toward greater complexity
- Process/mechanism: “lamarkism” used the idea of “use and disuse of parts”, so that individuals themselves can evolve.
This explains varying complexity in species, but the mechanism is not well supported, and evolution does not mean evolving to greater complexity, rather to their environment.
Explain the PATTERN of evolution said by Darwin.
Darwin believed in descent with modification, meaning species all united in a single tree brach of life that undergo splitting of branches (changes) representing and increase in diversity to a new species as new lineages (off of an old one) are created.
What are the 4 main points of natural selection as said by Darwin?
- First observation leading to natural selection: There is heritable variation within a population
- Observation #2: Within a population there is “excess production” meaning there is more offspring than needed
- These observation leads to inference #1: Differential success/fitness: excess production leads to competition for survival in a population. Because of varying traits, some individuals will have advantage for survival/mating over the others.
- Frequency of Traits: the more favourable traits that allowed individuals in a population to survive over others (with less favourable traits) will continue to increase in frequency. This is the concept of evolution.
What is a critical difference between Lamarck’s and Darwin’s ideas of how variation/evolving traits happens?
Darwin believed that natural selection occurs on existing variation, whereas Lamarck believed variation can be created through “use and disuse”. Ultimately, Darwin’s ideas are more accurate.
It is also important to note that Darwin’s ideas of natural selection are based on adaptive evolution: organisms evolve to be well suited to their environment, different from Lamarck’s idea of increasing complexity/perfection.
Briefly explain how the soapberry bug example demonstrated natural selection (specifically directional selection).
Soapberry bugs have beak lengths that are optimal for the fruit they consume. When a flatter fruit was introduced, with less depth holes, soapberry bugs with shorter beaks began to increase in frequency in the population, while ones with longer beaks decreased in frequency.
Define homology in terms of evolution.
Homology is similarity between species because of common ancestry. It is basically the entire mechanism of descent with modification (divergent evolution).
What are some examples of homologies among species.
- Standard anatomical homologies: similar structures in related species due to common ancestry, but have developed different uses (divergent evolution). (i.e. forelimbs in different mammals).
- Vestigial Structures: strctures in species that have little or no function, but are present as they were dervied from an ancestor that used those strctures. (i.e. appendix in humans, hind limbs in whales).
- Embryological homologies: organs/strctures having very similar form in embryo, but once developed it is much different. (i.e. tail in human embryos).
- Molecular homologies (at biochemical level): molecular vestigial structure, which is a gene that almost resembles a functioning gene used in another species but instead has slight variation and is non-functional (known as a pseudogene).
What are analogous structures and what are type of evolution are they evidence of?
Similar functioning features but different actual structure/mechanism (i.e. wings in birds vs. wings in bees).
This is a type of convergent evolution.
How does biogeography help explain natural selection/provide evidence for evolution?
Biogeography is the distribution of living things, and species that are in an area are usually there because that is where its common ancestor resided. This can show grouping of similar species as they are restricted to that area because of their common ancestor (are endemic).
Example: Galapagos islands, Hawaiian islands.
How does the fossil record provide evidence to evolution?
- It shows transitional forms among species: groups with major adaptations are the distinctiveness of the species/life state (i.e. whales are fully aquatic which is a distinct life state, but there are transitional land to water forms. Birds are the same; there are decent from dinosaurs).
- Order of appearance of fossils can show how on a basic level how an animal evolved (the descent forms found in deeper strata layers).
What is the definition of a population?
A group of interbreeding and interacting individuals. Species can have one or more populations, in which are able to breed upon meeting.
What is the average heterozygosity of individuals?
Most individuals are heterozygous at many loci, averaging about 2-10% heterozygosity.
How are new alleles created and what are the different ways they can affect an environment/individual.
A mutation gives rise to a new allele. Typically is has no affect on fitness: neutral allele.
Some reduce fitness: harmful allele, and few increase fitness: beneficial allele.
How can a gene pool of a population be defined? What are fixed vs polymorphic alleles?
- The sum total of all genetic variables: all alleles at all gene loci in all individuals.
- Fixed alleles are when there is only on version of that gene in a population (1 allele) and so every individual is homozygous at that loci
- Polymorphic is when there are 2 or more alleles present in a population at relatively the same frequency.
What can be defined as microevolution?
The change in frequency of different alleles in a gene pool (can lead to fixed or extinct alleles).
How can you convert from genotype frequencies to allele frequencies?
- Genotype frequency: genotype amount/#of individuals
- To from that to allele frequency: # of homozygous indiviudals for that allele + half of heterozygous individuals for that allele.
What is the hardy Weinberg equilibrium equation? What do the variables represent?
p^2 + 2pq + q^2
- p^2 genotype frequency for homozygous dominant
- q^2 genotype frequency for homozygous recessive
- 2pq genotype frequency for heterozygous
- p and q (not sqaured) are the allele frequencies
Explain how the hardy Weinberg equilibrium can be used to estimate if a population is truly in an equilibrium.
Given genotype frequencies, they can be converted to allele frequencies, and from there the allele frequencies can go reverse and be used to find genotype frequencies by plugging allele frequencies into HW equation. Compare the original genotype frequencies with the calculated ones to see if the population is truly in equilibrium.
What are the assumptions of a population that is in HW equilibrium?
- No net mutations
- Random mating
- No natural selection
- Large (infinite) population size
- No migration (or gene flow)
All of these conditions provide no net evolution in a population.
What are the 3 causes of microevolution?
- Natural selection
- Gene flow/migration
- Genetic drift (occurring more in small populations, random).
What is gene flow?
Dispersal of gametes between populations of the same species. Can introduce new alleles (changing frequency from 0 to 1).
