Ernst Mayr - 1942

• Biological Species Concept - Defines species as a population that can produce fertile and viable offspring in nature

Pre-Zygotic Barriers - Reproductive barriers that occur before syngamy

Temporal Isolation - breeding cycles don’t match

• ex) Three species of orchid live in the same rainforest. Each species has flowers that last only one day and must be pollinated on that day to produce seeds.

Mechanical Isolation - breeding is attempted but unsuccessful

• ex) Two mammals try to mate, but the pH of the female’ uterus kills off the sperm

Gametic Isolation - fusion between gametes doesn’t occur causing the non-organism to terminate

• ex) plants when they produce a lot of pollen in hopes of fertilization

Behavioral Isolation - nonrandom mating

• ex) pigeons won’t want to mate with another pigeon that does the mating dance slightly slower

Post-Zygotic Barriers - Reproductive barriers that occur after syngamy

Reduced Hybrid Viability - no viable and fertile offspring produced

• ex) offspring is produced but dies before reaching reproductive age

Reduced Hybrid Fertility - offspring is produced but is sterile

• ex) Mules are a mix between donkeys and horses, but they can’t interbreed with other mules

Hybrid Breakdown - 1si generation produces fertile and viable offspring, but the next generations are too weak to reproduce

Modes of Speciation

Allopatric Population - some type of barrier that causes the population to split apart and be exposed to different environments

Allopatric Speciation - Because of Allopatric Population, the now 2 populations are reproductively isolated

1. gene pools differ between the population, extreme clines created, differ from 1 pop to another

   • pop small → founder effect

2. Genetic drift occurs until pop1 is large enough. some might be fixed, causing more diversity

3. Evolution by natural selection may differ between populations

Sympatric Population - same environment but 2 different species that can coexist

Sympatric Speciation - one population that splits into 2 based on behavioral isolation

Cladograms - graphs/charts that can show an inference on common ancestry (shows related characteristics)

Gradualism model - very slow change into 2 populations

Punctuated Equilibrium Model - instant point change into 2 populations

Evolutionary Development - interdisciplinary science between evolutionary biology and the study of development

• changes in populations, species, or groups of species. More specifically, evolution occurs because populations vary by the frequency of heritable traits that appear from one generation to the next.

• gene regulation

  • Control Rate

  • timing

  • Spatial pattern of change in form

• Allometric growth

  • growth rates of different parts

Phylogeny and Systematics

Fossil Formations

• Dating - measuring the amount of half-lives that have passed

  • Radioactive Dating - Uranium-238 is used for inorganic and has a half-life of 4.5 billion years

  • Carbon Dating - Carbon-14 is used for organic and has a half-life of 5,730 years

Geological Timescale - 3 eras

• Combines the ideas of George Cuvier (catastrophism), Charles Lyell (Uniformitarianism), and James Hutton (gradualism)

1. Precambrian

   - Not much is known about this era; it is the oldest era

2. Paleozoic (ended 250 mya)

   - Many supercontinents because of plate tectonics

   - Formation of Pangea (at the end) and start of the dinosaurs.

   - Great extinction of most marine life as water levels rose

   - Land organisms now have an increase in competition as isolation was eliminated

3. Mesozoic

   - Pangea breaks; genetic drift occurs (think the sugar gliders and flying squirrels)

   - ends with the asteroid that kills all the dinosaurs and gives rise to mammals

4. Cenozoic

   - Current era where mammals are the predominant species

Plate Tectonics -Theory that explains how major landforms are formed using the Earth’s crust

Allopolyploid vs Autopolyploid

Nondisjunction - the failure of chromosomes to split up during nuclear division

Autopolyploid - difference in chromosome number in offspring of the same species

• Results in a tetraploid instead of a diploid chromosome

• add parent diploid numbers

Allopolyploid - 2 species produce an organism with a different diploid number than both parents

• nondisjunction occurs in 1 parent and doesn’t occur in the other parent

• 2 fertilizations occur

• the offspring is now a different species or a hybrid

• mostly occurs in plants

Mass extinctions

• Habitat destruction or environmental changes

• 2 major extinction periods

  • Permian Period (250 mya) - ended 90% of marine life due to lowered sea levels, and many terrestrial life ended during the start of Pangea

  • Cretaceous period (65 mya) - destroys 50 % of plants and terrestrial animals (dinosaurs); it also was the start of both global warming and global cooling

• Iridium - radioactive and only found on meteorites

  • found in a layer separating dinosaurs and no dinosaurs in fossils

  • the dinosaur one was in the present-day Gulf of Mexico

Phylogenetic Tree - a diagram that shows lines for inferred common ancestry with evolutionary and genetic distance

Law of Parsimony - the easiest-to-explain answer is typically correct

• Always has 2-point branching

• goes from bottom to top

• nodes can pivot if they are the last 2 branches

Monophyletic - explains common ancestry for one clade

Shared primitive - homology feature predating a taxon in all species (monophyletic)

Shared derived - something new and unique to a clade or species

Outgroup comparison - must have some connection

Adaptive Radiation - changes that occur when moving away