Species Concepts, Taxonomy, Prokaryotes & Protists Lecture

A comprehensive set of question-and-answer flashcards covering species concepts, reproductive isolation, speciation patterns, taxonomy, phylogenetics, prokaryotic biology, and protist diversity from the lecture notes.

What is the biological definition of a species?

A group of organisms whose members interbreed naturally to produce fertile offspring and do not interbreed with other groups.

Which two scientists championed the Biological Species Concept?

Theodosius Dobzhansky and Ernst Mayr.

According to the Morphological Species Concept, when are two organisms considered different species?

When they possess sufficiently different physical traits.

Who championed the Morphological Species Concept?

Carolus Linnaeus.

What is a major problem with the Morphological Species Concept?

Difficulty deciding which traits to measure and how to quantify them.

Which species concept defines a species as the smallest group with a unique combination of characteristics?

Phylogenetic Species Concept.

Who is most closely associated with the Phylogenetic Species Concept?

E.O. Wilson.

What does the Ecological Species Concept emphasize?

The ecological niche (role) an organism occupies.

Who proposed the Ecological Species Concept?

Leigh Van Valen.

Which hypothesis states that species must constantly evolve to survive against competitors and predators?

The Red Queen Hypothesis.

What is reproductive isolation?

Mechanisms that prevent gene flow between different species, maintaining their genetic distinctiveness.

Give an example of habitat isolation.

Two populations separated by a geographic barrier such as a mountain range or river.

What type of isolation occurs when two species breed at different times of the year?

Temporal isolation.

Differences in courtship songs of eastern and western meadowlarks represent which prezygotic barrier?

Behavioral isolation.

Why can mechanical isolation prevent mating?

Anatomical incompatibilities prevent successful copulation (e.g., mismatched genitalia).

What is gametic isolation?

Gametes of different species fail to fuse and form a zygote.

Hybrid inviability, hybrid sterility, and hybrid breakdown are examples of which type of barrier?

Postzygotic isolating mechanisms.

Define hybrid sterility.

Hybrid offspring develop but are sterile (e.g., mule).

What is anagenesis?

Evolutionary change within a single lineage where one species gradually becomes another.

What is cladogenesis?

Branching evolution where one species splits into two or more species.

What is allopatric speciation?

Speciation that occurs when populations are geographically separated.

How can the founder effect promote speciation?

A small isolated population experiences different selective pressures, leading to divergence from the parent population.

What is adaptive radiation?

Rapid diversification of a single ancestral species into many species, often after colonizing new habitats.

Define sympatric speciation.

Speciation that occurs without geographic separation, often via ecological shifts or polyploidy.

Differentiate autopolyploidy and allopolyploidy.

Autopolyploidy: chromosome doubling within one species; Allopolyploidy: chromosome sets combined from two species, followed by doubling.

Which model of speciation suggests slow, steady change over long time periods?

Gradualism.

Which model proposes long periods of stasis punctuated by rapid evolutionary change?

Punctuated equilibrium.

What is pedomorphosis (neoteny)?

Retention of juvenile traits in the adult form.

Give an example of an animal showing neoteny.

Axolotl salamander or domesticated dogs retaining puppy behaviors like tail wagging.

What is taxonomy?

The science of naming, describing, and classifying organisms.

Who wrote Species Plantarum and established binomial nomenclature?

Carolus Linnaeus.

List the basic taxonomic ranks from broadest to most specific.

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

How many kingdoms are in Carl Woese's six-kingdom system?

Six: Bacteria, Archaea, Protista, Plantae, Fungi, Animalia.

Which three domains make up the modern classification?

Bacteria, Archaea, and Eukarya.

What code governs the naming of animals?

International Code of Zoological Nomenclature (ICZN, 1758).

Define monophyletic group (clade).

A group containing a common ancestor and all its descendants.

What is a paraphyletic taxon?

A group containing a common ancestor but not all descendants.

What is a polyphyletic taxon?

A group composed of species with different, unrelated ancestors.

What principle states that the simplest evolutionary pathway is preferred?

Principle of parsimony.

What is homoplasy?

Similar traits that evolved independently in different lineages (convergent evolution).

Define synapomorphy.

A derived character shared by all members of a clade.

Which domain includes methanogens, halophiles, and thermophiles?

Domain Archaea.

What molecule do methanogens produce as a metabolic by-product?

Methane (CH₄).

Proteobacteria are gram-negative and gave rise to which eukaryotic organelle?

Mitochondria.

Which bacterial group performs oxygenic photosynthesis and possesses heterocysts for nitrogen fixation?

Cyanobacteria.

Name the three basic bacterial shapes.

Coccus (spherical), Bacillus (rod), Spirillum (spiral).

What is quorum sensing?

Communication among microbes using signaling molecules that coordinate group behaviors once a threshold concentration is reached.

What polymer composes bacterial cell walls?

Peptidoglycan.

Why are gram-positive bacteria more vulnerable to many antibiotics?

They have thick exposed peptidoglycan layers targeted by antibiotics.

Describe binary fission.

Asexual reproduction where the cell duplicates its DNA, elongates, and splits into two identical cells.

What is an endospore?

A highly resistant, dormant structure formed inside some gram-positive bacteria to survive harsh conditions.

How does bacterial conjugation occur?

DNA is transferred between cells via a sex pilus; F⁺ donors mate with F⁻ recipients.

Define chemoautotroph.

An organism that uses inorganic chemicals for energy and CO₂ as a carbon source.

What is an obligate anaerobe?

An organism that is poisoned by oxygen and must live in anoxic environments.

What critical ecological role do Rhizobium bacteria perform in legumes?

Nitrogen fixation in root nodules, converting N₂ into ammonia.

Approximately what fraction of Earth’s biomass is bacterial?

About 50%.

Which kingdom’s members produce roughly half of Earth’s oxygen?

Kingdom Protista (algal protists).

Name the six eukaryotic supergroups.

Excavata, Amoebozoa, Opisthokonta, Rhizaria, Archaeplastida, Chromalveolata (also called SAR + Haptista).

Which supergroup includes all animals and fungi?

Opisthokonta.

Give two distinguishing features of Euglenids (Excavata).

Proteinaceous pellicle under plasma membrane and an eyespot (stigma) for phototaxis.

What disease does Trypanosoma brucei cause?

African sleeping sickness.

Which phylum of Archaeplastida contains red algae with phycoerythrin pigment?

Phylum Rhodophyta.

What commercially valuable polysaccharide is extracted from red algae?

Carrageenan (and agar).

Name a colonial green alga often described as a “disco ball.”

Volvox.

Which alveolate group includes dinoflagellates?

Subphylum Dinozoa (Phylum Myzozoa).

What parasite from Phylum Apicomplexa causes malaria?

Plasmodium falciparum.

Which protists caused the Irish potato famine?

Phytophthora infestans (an oomycete).

Diatoms belong to which class and are primarily composed of what material?

Class Bacillariophyta; their frustules are made of silica dioxide (glass).

Foraminifera shells are rich in which mineral?

Calcium carbonate (CaCO₃).

Which supergroup contains amoeboid slime molds like Physarum?

Amoebozoa.

What are choanoflagellates and why are they important evolutionarily?

Collar-cell protists considered the closest living relatives of animals.

Define mixotroph.

An organism capable of both autotrophic (photosynthetic) and heterotrophic nutrition.

Which photosynthetic pigment absorbs blue-green light and gives brown algae their color?

Fucoxanthin.

How do dinoflagellates defend themselves physically?

Cellulose plates forming a protective armor.

What structure do ciliates use for defense that can discharge like a harpoon?

Trichocyst.

Which asexual process is common in Paramecium?

Binary fission (asexual fission).

What is the 9 + 2 arrangement?

Typical eukaryotic flagellum/cilium structure of nine doublet microtubules surrounding two central microtubules.