Diversity of Life

Biodiversity

Measure of variation (diversity) of living things across different scales (e.g., campus → city → state → continent → globe)

Genetic diversity

Variation in DNA/genes within and among populations or species

Phenotypic diversity

Variation in observable traits/characteristics among organisms

Organismal diversity

Variation in the different kinds of individual living things (organisms) present in a time and place; the most common "unit" of biodiversity

Ecological diversity

Variation in ecosystems, communities, and the interactions among living things

Richness

The number of unique types (e.g., species) present in an area

Evenness

The proportionality (relative abundance) of the different types present in an area

Biomass

The amount of living or recently living matter (biological material), usually measured in mass; plants make up ~80% of organic carbon on Earth, while all animals make up less than 1/2 of 1%

Organism (7 defining traits)

Contains organic molecules; made up of cells (smallest unit of life); uses energy; regulates internal environment (homeostasis); responds to environmental stimuli; reproduces & transfers genetic material; evolves over generations

Homeostasis

The regulation of an organism's internal environment

Why viruses are not considered organisms

They lack cells and cannot independently use energy, regulate homeostasis, or reproduce without a host

Levels of biological organization (low to high)

Molecules → Cells → Groups of Cells (tissues, organs, organ systems) → Organism → Population → Community → Ecosystem → Biosphere

Taxonomic classification

An inclusive, hierarchical system of grouping organisms together

Linnean classification

The widely-used taxonomic system developed by scholar Carl Linnaeus in the 1700s; he did NOT develop the Domain level

Taxonomic hierarchy (broadest to narrowest)

Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species

Taxonomy mnemonic

"Dear King Philip Came Over For Good Spaghetti" = Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species

Binomial nomenclature

An organism's scientific name, combining its genus and species names, written in italics with the genus capitalized and species lowercase (e.g., Puma concolor); genus can be abbreviated

Why scientists use binomial nomenclature

To communicate consistently about the same organism across different languages and common-name conventions (e.g., "mountain lion," "cougar," "puma," and "panther" all refer to Puma concolor)

Domain

The broadest, most inclusive taxonomic rank, placed above Kingdom

Three Domains of life

Archaea, Bacteria, Eukarya

Archaea (Domain)

Domain of prokaryotic organisms (one kingdom: Archaebacteria) lacking a nucleus or other membrane-bound organelles; share some molecular traits with bacteria, others with eukaryotes

Prokaryote

A single-celled organism lacking a nucleus or other organelles enclosed in a membrane

Extremophile

An organism that grows in extreme environmental conditions (e.g., highly saline or very hot environments) that are deadly for most other life; many are found in Archaea

Methanogen

An organism (often Archaea) that thrives in anaerobic (no oxygen) environments and produces methane as a waste product

Ecological role of marine Archaea

Some marine Archaea groups are key contributors to the nitrogen cycle in the oceans

Bacteria (Domain)

Domain of prokaryotic organisms (one kingdom: Eubacteria) whose cell walls are made of peptidoglycan; often evolve quickly due to large population sizes, short generation times, high mutation rates, and multiple mechanisms of gene flow

Peptidoglycan

A combination of sugars and polypeptides that makes up the cell walls of Bacteria

Eukarya (Domain)

Domain of organisms with eukaryotic cells; traditionally includes Kingdoms Fungi, Plantae, and Animalia, plus many other eukaryotic organisms classified outside these kingdoms (historically grouped as "Protista")

Eukaryote

An organism whose cells have well-developed internal structure and key organelles, such as the nucleus

Protist

A diverse group of eukaryotes that are not animals, plants, or fungi; mostly unicellular; includes photosynthetic algae/diatoms and heterotrophic organisms like amoebas and parasites

Phytoplankton

Algae and diatoms (protists) that are key photosynthesizers throughout the planet, especially in the oceans

Plasmodium

A heterotrophic protist parasite that is the cause of malaria

Plantae (Kingdom)

Multicellular eukaryotes that are autotrophic via photosynthesis; classified by the tissue used to transport water and nutrients

Non-vascular plants

Plants (bryophytes, like mosses) that lack a complex tissue system for transporting water and nutrients

Vascular plants

Plants with specialized vascular tissue (xylem and phloem) that extends to roots and leaves

Xylem

Vascular plant tissue that transports water and minerals

Phloem

Vascular plant tissue that transports organic nutrients

Fungi (Kingdom)

Mostly multicellular heterotrophs that secrete enzymes to break down nutrients externally and then absorb them; bodies are made of hyphae with cell walls of chitin; reproduce using spores carried by wind and water

Hyphae

Filaments that make up the bodies of fungi

Chitin

The material making up fungal cell walls; the same material found in insect exoskeletons

Mycelium (mycelia)

Dense structures formed by masses of fungal hyphae

Mycorrhizal fungi

Fungi that use their hyphae to exchange nutrients with plant roots, sometimes living inside the plant's tissue

Fungal decomposers

Many fungi that break down complex organic molecules and help maintain nutrient cycles around the world

Animalia (Kingdom)

Multicellular heterotrophs with specialized cells and tissues, and (typically) symmetrical body plans; sponges are an exception with no symmetry

Bilateral symmetry

A body plan with one line of symmetry, dividing the body into mirror-image left and right halves (e.g., a beetle)

Radial symmetry

A body plan with symmetry around a central axis (e.g., a coral polyp)

Invertebrate

An animal without a backbone; makes up over 95% of all animal species

Vertebrate

An animal with a backbone, included within phylum Chordata

Age of the Earth

Approximately 4.5–4.6 billion years old, based on most recent estimates

Stromatolite

A fossil of sediment bound by a biofilm of cells; provides evidence of the first single-celled prokaryotes, dated to about 3.5 billion years ago

Oxygen revolution

An event about 2.4 billion years ago when photosynthetic prokaryotes (like cyanobacteria) developed and reproduced, causing a huge spike in atmospheric oxygen; led to extinction of many anaerobic organisms but opened opportunities for new strategies like respiration

Cyanobacteria

Photosynthetic prokaryotes responsible for driving the oxygen revolution

Serial Endosymbiosis Hypothesis

Hypothesis that an ancestral prokaryotic host cell engulfed a smaller prokaryote undigested; the engulfed cell was maintained through generations and evolved into mitochondria; a similar process with a photosynthetic prokaryote led to organelles like chloroplasts

Mitochondrion

A eukaryotic organelle believed to have originated from an engulfed aerobic bacterium via endosymbiosis, about 1.8 billion years ago

Chloroplast (plastid)

A eukaryotic organelle believed to have originated from an engulfed photosynthetic bacterium via a similar endosymbiotic process

First eukaryotes

Appeared about 1.8 billion years ago, supported by strong evidence for the Serial Endosymbiosis Hypothesis

First multicellular organisms

Appeared about 1.3 billion years ago; some of the earliest multicellular eukaryotes were likely red algae protists

Cambrian explosion

An event about 535 million years ago marked by a huge diversification of life in the oceans, including hard-bodied animals and predators

Major development of land organisms

Occurred about 500 million years ago; adaptations for preventing dehydration (like vascular tissue in plants) allowed diversification of life outside of water

First tetrapods

Vertebrates with four limbs and digits that evolved from a lobe-finned fish ancestor about 365 million years ago; their limbs supported body weight, allowing diversification of terrestrial vertebrates

"Calendar year" analogy for Earth's history

A method of visualizing Earth's 4.5-billion-year history compressed into a single month/year, showing that complex life, land organisms, and humans occupy only the very last moments