AP Biology - Evolution Chapter 22-26

Notes of things I don’t understand….

Chapter 24.3 - Hybrid Zones

• When species with incomplete reproductive barriers come into contact with each other, they could form a hybrid zone.

  • Can lead to hybridization when they breed

1) Reinforcement of Barriers: Hybrids are less fit than their parent species and natural selection will strengthen barriers to reproduction

• Barriers stronger in sympatric populations than allopatric populations

2) Fusion of Species (Weakens Reproductive Barriers): the 2 species mate and form hybrids and the hybridizing species will fuse into a single species

• Some much gene low occurs that the gene pools of both species become increasingly alike

3) Stability: Hybrids continue to be produced because the hybrids survive or reproduce better than the parent species

• Stability can also happen even when Hybrids are selected against

Chapter 25.5 - Molecular

Evo-Devo: slight genetic differences can produce major morphological differences between species

• Genes that alter rate, timing, and Spatial pattern

Heterochrony: evolutionary change in the rate or timing of developmental events

• Relative growth rates of different body parts —> changes can alter the adult form

• Increased growth rates of finger bones led to the wings of bats, slowed growth of bones led to the loss of hind limbs in whales

Paedomorphosis: development of reproductive organs are greater than that of other organs

• Causes the production of animals that look different from their ancestors

Changes in Spatial Pattern

• Master Regulatory Genes (Homeotic Genes) - where basic features will develop

  • Hox genes - provide positional info

• Changing locations of Hox genes/how they are expressed can lead to changes in morphology

Changing in Gene Sequence

• New genes arise after gene duplication events

• Altering the expression of a developmental gene

Changes in Gene Regulation

• May have fewer harmful side effects than a change to the sequence of the gene

• Stickleback fish

Phylogenics vs. Cladistics

• Phylogeny is the evolutionary history and can be represented by a phylogenetic tree

• A clade is a type of phylogenetic tree. It is a group of organisms that includes an ancestor and all of its descendants

  

• Cladistics is a way to compare traits in related species to determine ancestor-descendant relationships

  

Chapter 25.1 - Conditions for the Origin of Life

Produce simple cells through 4 main stages

1) The abiotic synthesis of small organic molecules like amino acids and nitrogenous bases

2) The joining of the small molecules into macromolecules, like proteins and nucleic acids

3) The packaging of these molecules into protocells (droplets with membranes that have a different internal chemistry from the surroundings)

4) the origin of self-replicating RNA that made inheritance possible

The Abiotic Synthesis of small organic molecules

First atmosphere had little oxygen, lots of water vapor and compounds released by volcanic eruptions. The cooling of Earth caused the water vapor to condense into oceans and a lot of the hydrogen escaped into space

Oparin and Haldane: Earth’s early atmosphere was a reducing/electron-adding environment and the energy came from lightning and UV radiation. The ocea was a solution of organic molecules/”Primitive soup”

Millery and Urey: recreated early conditions of life and create amino acids

Organic compounds could have been formed in hydrothermal vents/alkaline vents or brought to earth by meteorites

The Abiotic Synthesis of macromolecules

Synthesis of RNA monomers from precursor molecules.

Dripping solutions of amino acids/RNA nucleotides onto hot sand/clay/rock could produce polymers

Protocells

DNA replication needs a supply of nucleotide building blocks and enzymes. The necessary conditions may have been met in vesicles (fluid-filled compartments enclosed by membrane-like structure)

• Abiotically produced vesicles can have simple reproduction and metabolism, and maintain and internal chemical environment

Vesicles can form when lipids are added to water and adding things like montmorillonite can increase the rate of vesicle self-assembly.

Self-Replicating RNA

RNA was mostly likely the first genetic material

• Can take on a variety of 3D shapes

• Can act as a catalyst - Ribozyme

Learning Module:

In order for speciation to occur, gene flow between populations must be interrupted.

One species with a diploid number of 6 and another with a diploid number of 12 —> come together and form a hybrid with a diploid number of 18 (haploid numer of 9 —> 6/2 + 12/2)

Morphological species concept distinguishes species by body shape and other structural features

Gene flow does not contribute to allopatric speciation because allopatric speciation requires interrupted gene flow

Biological species concept: a species is a group of populations whose members have the potential to interbreed in nature and produce viable, fertile

Mechanical Isolation prevents individuals of closely related species from copopulating successfully

It is clear that speciation has occurred when the gene pool changes establish reproductive barriers between two populations

After the Permian and Cretaceous mass extinctions, the percentage of marine organisms that were predators increased

Geological Eras: Paleozoic ,Mesozoic, Cenozoic

Genetic Drift does not contribute to adaptive radiations

Vesicles are an internal structure that appears in eukaryotic cells and were present in more ancient prokaryotic cells.

The known fossil record is biased in favor of species that existed for a long time

In order for life to evolve on land, there had to be adaptations that facilitated the reproduction and the prevention of dehydration

Neutral Theory: Darwinian selection does not influence a lot of evolutionary change in genes and proteins because many of these changes to not effect fitness

Systematics is a discipline within taxonomy (the scientific naming and classification of organisms)

• Systematics: classifying organisms and determining their evolutionary relationships

Horizontal gene transfer can occur in both prokaryotes and eukaryotes

• Genes are transferred from one genome to another through exchanging transposable elements/plasmids, viral infection, and fusions of organisms

Using molecules as clocks to time evolutionary events

• Nucleotide substitutions in a gene occur at a relatively constant rate

• Orthologous genes: a gene in different species that evolved from a common ancestor by speciation (similar genes in different species)

  • The more differences between genes, the longer ago the species diverges

• Paralogous genes: genes present in a particular organism that are related to each other through a gene duplication event (related genes within the same organism)

mtDNA to explore more evolutionary events

Sister taxa on a phylogenetic tree are defined as groups that share an immediate common ancestor and are each other’s closest relatives

An outgroup is a species or group of species from an evolutionary lineage that is known to have diverged before the lineage that includes all the species under study (the ingroup).

Polytony: A branch point on a phylogeny from which more than 2 descendant groups emerge

Phylogenetic trees are constructed to reflect the evolutionary relationships among organisms

Evolution FRQ Practice