Exam 2 biodiversity review

Three domains of life

Bacteria, Archaea, and Eukarya.

What distinguishes Bacteria from Eukarya?

Bacteria are prokaryotes that lack a nucleus and membrane-bound organelles; Eukarya have both.

What distinguishes Archaea from Bacteria?

Archaea lack peptidoglycan and have unique membrane lipids; many live in extreme environments.

What distinguishes Eukarya from prokaryotes?

Eukaryotes have a nucleus and membrane-bound organelles.

Evolutionary relationship of the three domains

Archaea and Eukarya share a more recent common ancestor than either does with Bacteria.

What is a prokaryote?

An organism whose cells lack a nucleus and membrane-bound organelles.

What is a eukaryote?

An organism whose cells contain a nucleus and membrane-bound organelles.

What is a decomposer?

An organism that breaks down dead organic matter and recycles nutrients.

What roles do prokaryotes play in ecosystems?

Decomposers, producers, nitrogen fixers, pathogens, and symbionts.

What is nitrogen fixation?

Conversion of atmospheric N₂ into biologically usable nitrogen compounds.

Why is nitrogen fixation important?

It makes nitrogen available for organisms to build proteins and nucleic acids.

Which prokaryotes evolved oxygen-producing photosynthesis?

Cyanobacteria are the only prokaryotic group known to have evolved oxygen-producing photosynthesis.

What is a pathogen?

An organism that causes disease in a host.

What is mutualism?

A relationship where both species benefit.

What is commensalism?

A relationship where one species benefits and the other is unaffected.

What is parasitism?

A relationship where one species benefits and the other is harmed.

What is horizontal gene transfer?

The movement of genes between organisms outside of parent-to-offspring inheritance.

Why is horizontal gene transfer important?

It spreads useful genes quickly and increases genetic variation.

How can horizontal gene transfer affect evolution?

It can rapidly spread traits such as antibiotic resistance.

What are the three types of horizontal gene transfer?

Transformation, transduction, and conjugation.

What is transformation?

A cell takes up free DNA from its environment.

What is transduction?

A bacteriophage transfers DNA from one bacterial cell to another.

What is conjugation?

DNA transfers between cells through direct contact, often using a pilus.

What is binary fission?

Asexual reproduction where one prokaryotic cell divides into two cells.

Common bacterial shapes

Coccus = sphere; bacillus = rod; spirillum/spirochete = spiral.

What is the bacterial cell wall made of?

Peptidoglycan.

Gram-positive bacteria

Have a thick peptidoglycan layer and no outer membrane.

Gram-negative bacteria

Have a thin peptidoglycan layer and an outer membrane.

Aerobic

Requires or uses oxygen.

Anaerobic

Does not require oxygen; some anaerobes are harmed by oxygen.

Obligate aerobe

An organism that requires oxygen to survive.

Obligate anaerobe

An organism that cannot survive in the presence of oxygen.

Facultative anaerobe

An organism that can use oxygen but can also survive without it.

Photoautotroph

Uses light for energy and CO₂ as its carbon source.

Photoheterotroph

Uses light for energy but gets carbon from organic compounds.

Chemoautotroph

Gets energy from chemicals and carbon from CO₂.

Chemoheterotroph

Gets both energy and carbon from organic compounds.

Halophile

An organism adapted to high-salt environments.

Extremophile

An organism adapted to extreme environmental conditions.

Thermophile

An organism adapted to high temperatures.

Methanogen

An archaeon that produces methane, usually in oxygen-free environments.

What is a symbiosis?

A close, long-term interaction between organisms of different species.

Protists

Diverse eukaryotes that are not classified as animals, plants, or fungi.

Why are protists paraphyletic?

They do not include all descendants of their common ancestor.

What does paraphyletic mean?

A group containing a common ancestor but not all of its descendants.

Why is "protist" not a true clade?

Protists come from several different evolutionary lineages.

How can protists be classified ecologically?

By habitat, ecological role, nutrition, and method of movement.

What are common protist habitats?

Mostly aquatic or moist environments.

What is a protozoan?

A traditionally defined animal-like, heterotrophic protist.

What is an alga?

A photosynthetic organism traditionally grouped outside land plants.

What is a mixotroph?

An organism capable of both autotrophic and heterotrophic nutrition.

What is an amoeba?

A protist that moves and feeds using pseudopodia.

What are pseudopodia?

Temporary cell extensions used for movement and feeding.

What are flagella?

Long, whip-like structures used mainly for movement.

What are cilia?

Short, numerous hair-like structures used for movement or feeding.

What is the SAR clade?

A major eukaryotic group containing Stramenopila, Alveolata, and Rhizaria.

What is Excavata?

A major eukaryotic group containing organisms such as euglenids and diplomonads.

What is Stramenopila?

A group containing diatoms, brown algae, and water molds.

What is Alveolata?

A group containing dinoflagellates, ciliates, and apicomplexans.

What is Rhizaria?

A group containing organisms with thread-like or net-like pseudopodia.

What is Archaeplastida?

A group containing red algae, green algae, and land plants.

What is Amoebozoa?

A group containing many amoebas and slime molds.

What is Opisthokonta?

A group containing animals, fungi, and their close relatives.

What are the main eukaryotic groups?

Excavata, Stramenopila, Alveolata, Rhizaria, Archaeplastida, Amoebozoa, and Opisthokonta.

Primary endosymbiosis

A eukaryotic cell engulfed a cyanobacterium, producing a primary plastid.

Secondary endosymbiosis

A eukaryote engulfed another eukaryote that already contained a primary plastid.

Tertiary endosymbiosis

A eukaryote acquired a plastid from a eukaryote that already obtained one through secondary endosymbiosis.

Importance of endosymbiosis

It explains how photosynthetic organelles originated and spread among eukaryotes.

What is a plastid?

A membrane-bound organelle including chloroplasts that performs photosynthesis or related functions.

What is a mitochondrion?

An organelle that produces ATP through cellular respiration.

What is a haploid cell?

A cell with one set of chromosomes, represented as n.

What is a diploid cell?

A cell with two sets of chromosomes, represented as 2n.

What is a zygote?

A diploid cell formed when two haploid gametes fuse.

What is mitosis?

Cell division that produces genetically similar cells with the same chromosome number.

What is meiosis?

Cell division that reduces chromosome number and produces genetically varied cells.

What is a gametic life cycle?

The diploid organism is multicellular; meiosis produces haploid gametes.

What is a zygotic life cycle?

The organism is haploid; the zygote is the only diploid stage.

What is a sporic life cycle?

Alternation between multicellular haploid and diploid generations.

What is alternation of generations?

A life cycle alternating between multicellular haploid gametophytes and diploid sporophytes.

Chlorophytes

Green algae closely related to land plants.

Rhodophytes

Red algae containing pigments such as phycoerythrin.

Relationship between green algae and land plants

Land plants evolved from a lineage of green algae, especially charophytes.

Brown algae

Large multicellular stramenopiles, including kelp, mostly found in marine environments.

Diatoms

Photosynthetic stramenopiles with silica cell walls.

Dinoflagellates

Alveolates usually with two flagella; some cause harmful algal blooms.

What are land plants?

Embryophytes: plants adapted to life on land with protected embryos and other terrestrial adaptations.

Five major derived land-plant traits

Alternation of generations, multicellular dependent embryos, walled spores, multicellular gametangia, and apical meristems.

What is an apical meristem?

A region of actively dividing cells responsible for plant growth.

What is a cuticle?

A waxy covering that reduces water loss.

What are stomata?

Openings that regulate gas exchange and water loss.

Why are tough-walled spores important?

They protect spores from drying out on land.

Why are multicellular gametangia important?

They protect developing gametes.

What is a sporophyte?

The multicellular diploid generation that produces spores by meiosis.

What is a gametophyte?

The multicellular haploid generation that produces gametes by mitosis.

What is a spore?

A reproductive cell that can develop into a new organism without fusing with another cell.

What is a gamete?

A haploid reproductive cell that fuses during fertilization.

What is a sporangium?

A structure where spores are produced.

What is a gametangium?

A structure where gametes are produced and protected.

What is vascular tissue?

Specialized tissue that transports water, minerals, and sugars.

What is xylem?

Vascular tissue that transports water and minerals.