Phylogeny: the evolutionary history of a species or a group of species

Convergent evolution: the process where species from different evolutionary branches may come to resemble one another if they live in similar environments and natural selection has favored similar adaptations

Analogy: similarity due to convergent evolution

Systematics: the discipline of biology that focuses on classifying organisms and determining their evolutionary relationships

Taxonomy: the system of naming and classifying species started by Carolus Linnaeus to avoid confusion in the scientific world

Binomial: the two-part names that biologists assign to each species

Genus: the first part of the binomial that is a group of species (ex. Sciurus, which is a species of tree squirrels)

Specific epithet (added): this is the second part of the binomial that distinguishes the species within the genus (ex. carolinensis, which is part of the binomial naming the Eastern gray squirrel, Sciurus carolinensis)

Family: what the Linnaean System places related genera into

Orders: what the Linnaean System places related family into

Classes: what the Linnaean System places related orders into

Phyla: what the Linnaean System places related classes into

Kingdoms: what the Linnaean System places related phyla into

Domains: what the Linnaean System places related kingdoms into

Taxon: what each taxonomic unit at any level is called

Phylogenetic trees: this is what scientists use to depict hypotheses about the evolutionary history of species

Cladistics: this is the most widely used method in systematics

Clades: these are branches, or groups of organisms that are usually grouped according to common ancestry

Monophyletic: this is when a genus, family, or a broader group is grouped into an inclusive group of ancestors and descendants

Shared ancestral character: this is something that all organisms of one group and their ancestors have (ex. All vertebrates, including mammals, have backbones)

Shared derived character: this is something that differentiates a group of organisms from their ancestors (ex. All mammals have hair, but their ancestors do not)

Ingroup: this is the group that scientists focus on and usually study

Outgroup: this is usually one of the first groups to diverge from the lineage of the ingroup

Parsimony: the adoption of the simplest explanation for an observed phenomenon

Molecular systematics: this is a method that uses DNA or other molecules to infer relatedness, and is a valuable approach for tracing phylogeny

Ecology: the scientific study of the interactions of organisms with their environment

Biotic factors: these are the living components of the environment, and includes all organisms in the area

Abiotic factors: these are the nonliving component of the environment, and include the physical and chemical factors such as temperature, forms of energy available, water, and nutrients

Habitat: this is the specific environment it live in, and includes the biotic and abiotic factors present in its surroundings

Organism: this level is where researchers may examine how one kind of organism meets the challenges and opportunities of its environment through its physiology or behavior

Population: a group of individuals of the same species living in particular geographic area

Community: this is the third level that includes the assemblage of all the populations of organisms living close enough together for potential interaction, including the biotic factors in the environment

Ecosystem: this is the fourth level of ecological study that includes both the biotic and the abiotic components of the environment

Landscapes: scientists take a wider perspective by studying these, which are arrays of ecosystems

Biosphere: this extends from the atmosphere several kilometers above Earth to the depths of the oceans, and is all of Earth that is inhabited by life

Benthic realm: the substrate, or seafloor of the ocean

Pelagic realm: this includes all open water and the substrate, which is also known as the benthic realm

Photic zone: this zone is marked by the depth of light penetration (200 m)

Continental shelves: the photic zone includes both the pelagic and benthic realms, In shallow areas such as the submerged parts of continents

Phytoplankton: (microscopic algae and cyanobacteria) and multicellular algae that provides energy and organic carbon for a diverse community of animals by photosynthesis in sunlit regions.

Zooplankton: (small, drifting animals), fish, mammals, and many other types of animals are abundant in the pelagic photic zone.

Aphotic zone: The zone Below the photic zone of the ocean

Intertidal: the zone where the ocean meets land, the shore is pounded by waves during high tide and exposed to the sun and drying winds during low tide.

Estuary: a biome that occurs where a freshwater stream or river merges with the ocean.

Wetlands: a biome that is transitional between an aquatic ecosystem- either marine or freshwater- and a terrestrial one.

Tropical Forests: A terrestrial biome characterized by high levels of precipitation and warm temperatures year round.

Savanna: A biome dominated by grasses and scattered trees.

Desert: A biome characterized by organisms adapted to sparse rainfall (less than 30 cm per year) and rapid evaporation.

Desertification: The conversion of semi-arid regions to desert.

Chaparral: A biome dominated by spiny evergreen shrubs adapted to periodic droughts and fires; found where cold ocean currents circulate offshore, creating mild, rainy winters and long, hot, dry summers.

Temperate Grassland: A grassland region maintained by seasonal drought, occasional fires, and grazing by large animals.

Temperate Broadleaf Forest: A biome located throughout mid latitude regions, where there is sufficient moisture to support the growth of large, broadleaf deciduous trees.

Coniferous Forest: A biome characterized by conifer, cone-bearing evergreen trees.

Taiga: The northern coniferous forests, characterized by long, snowy winters and short, wet summers, extending across North America and Eurasia to the southern border of the arctic tundra; also found just below alpine tundra on mountainsides in temperate zones.

Temperate Rain Forest: Coniferous forests of coastal North America (from Alaska to Oregon) supported by warm, moist air from the Pacific Ocean.

Tundra: A biome at the northernmost limits of plant growth and at high altitudes, characterized by dwarf, woody shrubs, grasses, mosses, and lichens.

Permafrost: Continuously frozen ground found in the arctic tundra.

Polar Ice: A terrestrial biome that includes regions of extremely low temperature and low precipitation located at high latitudes north of the arctic tundra and in Antarctica.

Community: An assemblage of all populations of organisms living close enough together for potential interaction.

Interspecific interactions: Relationships with individuals of other species in the community- that greatly affect populations structure and dynamics.

Mutualism: When both populations benefit.

Herbivory: Consumption of plant parts or algae by an animal.

Ecological niche: The sum of its use of the biotic and biotic resources in its environment.

Trophic structure: A pattern of feeding relationships consisting of several different levels.

Food chain: The sequence of food transfer up the trophic levels

Producers: The trophic level that supports all others consists of autotrophs, starting at the bottom

Primary consumers: Herbivores which eat plants, algae, or phytoplankton

Secondary consumers: Small mammals, such as the mouse shown here eating an herbivorous insect, and a great variety of birds, frogs, and spiders, as well as lions and other large carnivores that eat grazers.

Tertiary consumers: Higher trophic levels, such as the snakes that eat mice and other secondary consumers.

Detritus: The dead material produced at all the trophic levels.

Scavengers: Which are large animals, such as crows and vultures , feast in carcasses left behind by predators or speeding cars.

Detritivores: Their diet is made up primarily of decaying organic material.

Decomposers: Mainly prokaryotes and fungi secrete enzymes that digest molecules in organic material and convert them to inorganic forms.

Decomposition: The breakdown of organic materials to inorganic ones

Food web: A network of interconnecting food chains.

Species diversity: Defined by two components, species richness, or the number of different species in a community, and relative abundance, the proportional representation of each species in a community.

Disturbances: Events such as storms, fires, floods, droughts, as human activities that damage Biological communities and alter the availability of resources.

Ecological succession: Process of biological community change resulting from disturbance

Primary succession: When ecological succession begins in a virtually lifeless area with no soil

Secondary succession: Occurs when a disturbance has cleared away an existing community but left the soil intact.

Invasive species: Species that spread far beyond the original point of introduction and causing environmental or economic damage by colonizing and dominating wherever they find a suitable habitat.

Biological control: The intentional release of a natural enemy to attack a pest population.

Ecosystem: All the organisms in a given area, along with the nonliving (abiotic) factors with which they interact; a biological community and its physical environment.

Energy Flow: The passage of energy through the components of an ecosystem.

Chemical Cycling: The use and reuse of a chemical element, such as carbon, within an ecosystem.

Primary Production: The amount of solar energy converted to chemical energy (in organic compounds) by autotrophs in an ecosystem during a given time period.

Biomass: The amount, or mass, of organic material in an ecosystem.

Nitrogen Fixation: The conversion of atmospheric nitrogen (N2) to nitrogen compounds (NH4+, NO3-) that plants can absorb and use.