Population Genetics + Inbreeding

• Mutation-selection balance maintains genetic diversity.
• Inbreeding is mating between closely related individuals.
• Inbreeding depression is the reduced fitness in a population due to inbreeding.
• Genetic purging is the process where inbreeding exposes deleterious recessive alleles, allowing selection to remove them.
• Inbreeding increases the frequency of expression of recessive alleles by increasing homozygosity.
• Deleterious alleles are harmful variants of genes.
• Inbreeding and bottlenecking are related because both can reduce genetic diversity and increase the expression of deleterious alleles.
• Genetic purging can reduce the impact of deleterious alleles in inbred populations.
• Hybrid is offspring resulting from the mating of individuals from two different species or distinct populations.

Isolating Mechanisms

• Isolating mechanisms are reproductive barriers that prevent gene flow between populations.
• Prezygotic isolating mechanisms occur before the formation of a zygote.
• Postzygotic isolating mechanisms occur after the formation of a zygote.
• Geographic isolation is when populations are separated by physical barriers.
• Habitat isolation is when species live in the same area but have different habitat requirements.
• Behavior isolation is when species have different mating rituals or signals.
• Temporal isolation is when species breed during different times.
• Mechanical isolation is when species have incompatible reproductive structures.
• Gametic isolation is when species have incompatible eggs and sperm.
• Reduced hybrid viability results in hybrids that do not survive.
• Reduced hybrid fertility results in hybrids that are infertile.
• Hybrid breakdown results in reduced fitness in later-generation hybrids.

Speciation

• Speciation is the process by which new species arise.
• Allopatry (allopatric) is speciation that occurs when populations are geographically separated.
• Sympatry (sympatric) is speciation that occurs in the same geographic area.
• Allopatric speciation can occur through vicariance (geographic barrier arises) or dispersal (migration to a new area).
• Vicariance is the separation of a continuously distributed ancestral population or species into separate populations, due to the development of a physical barrier
• Dispersal is the movement of organisms from a parent population to a new geographic location
• Sympatric speciation can occur through adaptive radiation, hybrid speciation, or polyploidy.
• Adaptive radiation is the rapid diversification of a lineage into many different forms.
• Reinforcement is the process where natural selection strengthens reproductive isolation between diverging populations.
• Biological Species Concept defines species as groups of interbreeding populations that are reproductively isolated from other such groups.
• Phylogenetic Species Concept defines species as the smallest diagnosable cluster of individual organisms within which there is a parental pattern of ancestry and descent.
• Lineage Species Concept views species as distinct evolutionary lineages.
• Anagenesis is evolutionary change within a single lineage.
• Pluralism acknowledges that different species concepts may be useful in different situations.

Classification & Taxonomy

• Classification arranges organisms into groups based on similarities.
• Systematics studies the evolutionary relationships among organisms.
• Taxonomy is the science of naming and classifying organisms.
• Taxon is a group of organisms in a classification system.
• Dichotomous key is a tool used to identify organisms based on a series of paired choices.
• Carolus Linnaeus is the founder of modern taxonomy.
• Systema Naturae, 10th Edition (1758) is a foundational work in taxonomy, establishing binomial nomenclature.
• Binomial nomenclature is the system of naming species with two names.
• Ranks are the levels in the taxonomic hierarchy.
• Species names are the unique two-part names given to each species.
• Codes of Nomenclature govern the naming of organisms.
• Stability is the principle that scientific names should be stable over time.
• Universality is the principle that scientific names should be used worldwide.
• Uniqueness is the principle that each species should have a unique name.
• Taxonomic freedom allows taxonomists to make independent judgments about classification.
• Type specimen is a reference specimen used to define a species.
• Synonym is a different name for the same species.
• Homonym is the same name for two different species.

Origin of Life

• Abiogenesis is the origin of life from non-living matter.
• Protobionts are aggregates of abiotically produced organic molecules surrounded by a membrane or membrane-like structure.
• Homeostasis is the ability to maintain a stable internal environment.
• Metabolism first suggests life began with metabolic processes.
• Replication first suggests life began with self-replicating molecules.
• RNA World Hypothesis suggests that RNA was the primary genetic material in early life.
• Iron-Sulfur World Hypothesis suggests that life originated in hydrothermal vents with iron-sulfur catalysts.
• Colonial Theory suggests that multicellularity arose from colonies of unicellular organisms.
• Symbiotic Theory is that organelles like mitochondria and chloroplasts originated as separate prokaryotic organisms that formed a symbiotic relationship within a host cell.
• Cellularisation Theory proposes that multicellular organisms evolved by partitioning a single multinucleate cell into many cells.
• Stromatolites are layered sedimentary structures formed by microbial communities.
• Oxygen catastrophe refers to a period in Earth's history when atmospheric oxygen levels rapidly increased, leading to a mass extinction of anaerobic organisms.

Geological Time Scale & Events

• Eons, Eras, Periods, and Epochs are divisions of the geological time scale.
• Ediacaran Period is a period in the Precambrian characterized by the first evidence of multicellular life.
• Gondwana was a supercontinent that existed in the Southern Hemisphere.
• Laurasia was a supercontinent that existed in the Northern Hemisphere.
• Pangaea was a supercontinent that existed in the late Paleozoic and early Mesozoic eras.
• Cambrian Explosion was a period of rapid diversification of animal life.
• Burgess Shale is a fossil site in British Columbia that contains well-preserved fossils from the Cambrian period.
• Trilobites are extinct marine arthropods that were abundant during the Paleozoic era.
• Sea scorpions (Eurypterids) are extinct aquatic arthropods, some of which were very large.

Fossils

• Impression fossils are fossils formed when an organism leaves an imprint in sediment.
• Index fossils are fossils used to define and identify geologic periods.
• Trace fossils are fossils of footprints, burrows, or other traces of an organism's activity.
• Amber fossils are fossils preserved in amber (fossilized tree resin).
• Bark-bearing trees and lignin were significant developments in plant evolution.

Extinction

• Mass extinction is a widespread and rapid decrease in the biodiversity on Earth.
• Background extinction is the normal rate of extinction in the absence of major disturbances.

Macroevolution vs. Microevolution

• Macroevolution is evolution above the species level, while microevolution is evolution within a population or species.

Speciation Factors

• Mutations, natural selection, and geography all play a role in speciation.

Species Concepts

• Three main species concepts include the Biological Species Concept, Phylogenetic Species Concept, and Lineage Species Concept.
• Ranks of nomenclature, from most general to most specific: Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species.
• Species names are structured with the genus name followed by the specific epithet.
• Biological nomenclature principles include priority, first reviser, and the use of type specimens.
• Type specimens serve as reference points for defining species.
• Synonyms in taxonomic names are different names for the same species.
• Homonyms in taxonomic names are the same name for different species.

Precambrian Characteristics & Events

• Five general characteristics of the Precambrian that made it seemingly hostile to life: reducing atmosphere, intense UV radiation, lack of ozone layer, frequent volcanic activity, and a slushball earth.
• Five major events in the evolution of life during the Precambrian: origin of life, origin of photosynthesis, origin of eukaryotes, origin of sexual reproduction, and origin of multicellularity.

Early Life

• Major components and steps to form the earliest life: formation of organic molecules, self-replication, and membranes.
• Huronian Glaciation was a prolonged period of glaciation during the Precambrian.

Evolution of Eukaryotes

• The origin of complex cells (eukaryotes) is explained by the theory of endosymbiogenesis.
• Four pieces of evidence for concluding that mitochondria are derived from bacteria: mitochondria have their own DNA, mitochondria have double membranes, mitochondria are similar in size to bacteria, and mitochondria divide independently.

Sexual Reproduction

• The double cost of sex: sexually reproducing organisms contribute only half of their genes to the next generation unlike asexually reproducing organisms
• Sexual reproduction could be an adaptation for: genetic variation and adaptation to changing environments.

Asexual Reproduction Benefits

• Archeae and Bacteria are asexual; their lineages have survived through mutation, genetic drift, natural selection and rapid reproduction.

Multicellular Life

• Three possible explanations for the origin of multicellular life: colonial theory, cellularization theory, and symbiotic theory.
• The Ediacaran Period is important because it represents the first evidence of multicellular life.
• The Burgess Shale is significant for preserving fossils from the Cambrian explosion.

Extinction Causes

• Several causes often put forth for extinction events: asteroid impacts, volcanic activity, climate change, and changes in sea level.

Plant & Animal Evolution

• "Bark-bearing" trees with lignin were significant because they allowed plants to grow taller and colonize new environments.
• The evolution of the amniotic egg was significant because it allowed reptiles to reproduce on land.
• Formation and breakup of Pangaea affected the evolution of living things by: altering environments and creating new opportunities for dispersal.
• Global changes in oxygen levels affect the size of living things by: allowing for larger and more active organisms.
• Independent evolutions of powered flight occurred in: insects, pterosaurs, birds, and bats.

Origin of Groups

• Animals originated during the: Ediacaran Period/ late Precambrian
• Fungi originated during the: Proterozoic Eon
• Vertebrates originated during the: Cambrian Period
• Plants originated during the: Ordovician Period
• Land plants originated during the: Silurian Period
• Land animals originated during the: Silurian Period
• Land fungi originated during the: Silurian Period
• Tetrapods originated during the: Devonian Period
• Synapsids originated during the: Pennsylvanian Period
• Archosaurs originated during the: Late Permian
• Seed plants originated during the: Late Devonian
• Insects originated during the: Devonian Period
• Amniotic animals originated during the: Carboniferous Period
• Pterosaurs originated during the: Late Triassic
• Dinosaurs originated during the: Late Triassic
• Birds originated during the: Late Jurassic
• Mammals originated during the: Late Triassic
• Flowering plants originated during the: Early Cretaceous
• Bats originated during the: Early Eocene
• Whales originated during the: Early Eocene