Species and Speciation

• A species is currently defined as a group whose members can potentially interbreed and produce fertile offspring.

Limitations of the Biological Species Concept

• The concept relies on the ability to interbreed, making it unusable for species with asexual reproduction.
• Determining if extinct organisms could interbreed is impossible.
• Different species may mate in the wild and produce healthy, fertile offspring.
• Some organisms can breed in captivity but not in nature.

Reproductive Pre-Mating Isolation Mechanisms

• Geographical isolation occurs when populations live in different places.
• Ecological isolation occurs when species occupy different habitats.
• Temporal isolation occurs when species breed at different times.
• Behavioral isolation occurs when species have different mating rituals.
• Mechanical incompatibility occurs when species reproductive structures are incompatible.

Reproductive Post-Mating Isolation Mechanisms

• Gametic incompatibility happens when sperm from one species cannot fertilize eggs of another.
• Hybrid inviability occurs when hybrid offspring die early.
• Hybrid infertility occurs when hybrid offspring are sterile or have reduced fertility.

Speciation (Birth of a Species)

• Reproductive isolation of populations prevents gene flow.
• Genetic divergence of population must occur.

Pathways

• Allopatric speciation occurs when two populations become separated by a geographical barrier.
• Sympatric speciation occurs when an area contains two distinctly different habitats (ecological isolation).
• Adaptive radiation is the rise of many new species over a relatively short period, often when a species invades a variety of new habitats with few competitors.

Characteristics of Early Earth

• There was no atmosphere (no oxygen/ozone).
• There were extremely high UV rays.
• There were high amounts of methane/ammonia/water/hydrogen.
• There were many meteorite strikes and volcanic eruptions.
• Prebiotic simulation was used in the 1950s to mimic early Earth.
• Panspermia states that life originated elsewhere in the universe.

Modern Scientist Findings

• Scientists can produce amino acids, the building blocks of proteins, and potentially even protocells and ribozymes, when mimicking early Earth.

General Order of Organisms & Advantages of Each New Evolutionary Change

• Prokaryotes appeared first and then photosynthesis, oxygen, eukaryotes, multicellular organisms, plants on land, and animals on land (lobefin fish), amphibians, reptiles, and birds & mammals.

Primate Characteristics

• Grasping hands and feet, relatively large brains, and enhanced vision, including binocular vision are all features of primates.
• Lemurs, monkeys, apes, and humans are primates.

Hominin Characteristics

• Bipedalism, larger brains relative to body size, and the ability to make and use tools characterize hominins.
• Hominins also display behavioral and communication adaptations like specialized tool use and potential language.

Australopithecines Characteristics

• Early characteristics include a mix of ape-like and human-like traits, including bipedal locomotion.

• Retaining features like long arms and smaller brains suggests a transition from ape-like ancestors to humans.

• Later characteristics include a mix of ape-like and human-like traits, including bipedalism and adaptations for both tree climbing and ground walking.

• Homo erectus and Neanderthals migrated out of Africa, are extinct, and are not direct ancestors.

• Homo sapiens are approximately 150,000 years old, based on genetic diversity across the globe.

Taxonomy

• Taxonomy is the branch of biology concerned with naming and classifying organisms.
• Naming is a two-part scientific name based on genus and species.
• A genus includes a number of very closely related species.
• A species contains organisms that can potentially interbreed.

Taxonomic Classifications

• Domain, Kingdom, Phylum, Class, Order, Family, Genus, and Species.
• The three domains of Eukarya include Eukaryota (chromists, plants, animals, fungi, alveolates, rhodophytes, flagellates, basal protists), Bacteria (cyanobacteria, heterotrophic bacteria), and Archaea (halophiles, thermophiles).
• The four groups of Eukarya include animals, plants, fungi, and protists.
• Phylogenetics studies the evolutionary relationships among species.
• Reading evolutionary trees is done irrespective of which side one puts a group on, since branches can be spun at the nodes, which represent speciation.
• Clades group all organisms that share a common ancestor.

Prokaryotes

• Prokaryotes are the smallest living thing and are single-celled.
• They have three common shapes: spherical, rod, and spiral.
• They reproduce by binary fission and undergo asexual cell division.
• Conjugation involves exchanging genetic material without reproducing with a sex pilus connecting donor to recipient
• Prokaryotes exchange plasmids, which are circular DNA.
• Rapid revolution occurs, explaining why antibiotic resistance occurs.

Bacteria & Archaea

• Archaea can produce methane, but bacteria can't.
• Bacteria can undergo photosynthesis, but archaea can't.
• Some bacteria are pathogenic, but archaea aren't.
• Bacteria contain peptidoglycan, but archaea don't.
  • Gram + stains are purple.
  • Gram - stains are red/pink and have a fatty layer.
• Some bacteria produce endospores or biofilms, but archaea don't.
• Biofilms are slime-secreting bacteria.
• Endospores are resistant to extremely harsh conditions.

Anthrax

• Plasmids make strains of Anthrax virulent via toxins/capsule.
• Modes of infection include inhalation, cutaneous, and gastrointestinal.
• Virulent factors are plasmids that code for Anthrax toxins and create a capsule.

Key Terms

• Heterotrophs absorb nutrients that surround them.
• Autotrophs self-feed through photosynthesis.
• Pathogens cause harm, disease, illness, and even death.

Prokaryotes & Other Organisms/Environment

• They have 4 positives: nutrition, recycling, nitrogen fixation, and bioremediation.
• They also have 1 negative: pathogenic qualities.

Viruses

• Viruses contain DNA or RNA and a protein coat.
• Viruses are not cells and are smaller than bacteria.
• Viruses cannot reproduce without a host, and they can attack all living organisms.
• Examples include SARS-COVI-2, Influenza, and Measles.

Viroids

• Characteristics include short, only RNA that affect crops only.

Prions

• Characteristics include that they are only protein, have no genetic material, and are resistant to heat.

• Bacteria are single-celled, microscopic, prokaryotic organisms with a cell wall containing peptidoglycan.

• Viruses are acellular, obligate intracellular parasites, lacking cells and only replicate inside a host cell, consisting of a nucleic acid core (DNA or RNA) encased in a protein coat (capsid), and some have an outer envelope.

• Prions are unique infectious agents composed solely of protein, lacking genetic material, and cause transmissible spongiform encephalopathies (TSEs), which are fatal and neurodegenerative diseases in both humans and animals.