BIO182 Exam 3

What is a microorganism?

A microscopic organism, which may exist in its single-celled form or as a colony of cells, including bacteria, archaea, and some protists.

What is horizontal gene transfer?

The movement of genetic material between unicellular and/or multicellular organisms other than by the transmission of DNA from parent to offspring.

What is the two-stage hypothesis for the origin of eukaryotic cells?

The theory that eukaryotic cells originated through the infolding of the plasma membrane to form the endomembrane system, followed by endosymbiosis to acquire mitochondria and chloroplasts.

Define endosymbiosis.

A symbiotic relationship where one organism lives inside the body or cells of another organism; it is the process by which mitochondria and chloroplasts were acquired by early eukaryotes.

What are the three main groups of protists?

Algae (photosynthetic), protozoa (ingestive), and fungus-like protists (absorptive).

What is the evolutionary significance of green algae to plants?

Green algae are the most recent common ancestor of land plants; both are classified as streptophytes.

What are the primary adaptations of land plants for terrestrial life?

Development of a waxy cuticle to prevent desiccation, stomata for gas exchange, and specialized tissues for structural support and water transport.

Compare vascular and nonvascular plants.

Vascular plants possess specialized tissues (xylem and phloem) for transporting water and nutrients, allowing for larger size, while nonvascular plants lack these tissues and rely on diffusion.

What is alternation of generations?

A life cycle in plants where a multicellular diploid sporophyte stage alternates with a multicellular haploid gametophyte stage.

What is the difference between xylem and phloem?

Xylem transports water and minerals upward from roots to shoots, while phloem transports sugars and organic nutrients from leaves to other parts of the plant.

What is the evolutionary advantage of a seed?

Seeds protect the embryo, provide a food supply, and allow for dormancy and dispersal, increasing the chances of survival in varied environments.

What are the four whorls of a flower?

The sepals (calyx), petals (corolla), stamens, and carpels.

What is the result of double fertilization in angiosperms?

One sperm fertilizes the egg to form a diploid zygote, and the other sperm fertilizes two polar nuclei to form a triploid endosperm.

Compare monocots and dicots.

Monocots typically have one cotyledon, parallel leaf veins, and flower parts in multiples of three; dicots have two cotyledons, branched leaf veins, and flower parts in multiples of four or five.

What is a fruit?

A mature ovary of a flowering plant that protects enclosed seeds and aids in their dispersal.

What are the three main organ systems in angiosperms?

The root system, the shoot system (stems), and the leaves.

Define primary and secondary growth in plants.

Primary growth increases plant length via apical meristems; secondary growth increases plant girth via lateral meristems (vascular and cork cambium).

What are the three primary meristems?

Protoderm (gives rise to dermal tissue), procambium (gives rise to vascular tissue), and ground meristem (gives rise to ground tissue).

What is the modular structure of the shoot system?

The shoot system is composed of repeating units called phytomers, each consisting of a node, an internode, a leaf, and an axillary bud.

What is the purpose of roots?

To anchor the plant in the soil, absorb water and dissolved minerals, and store carbohydrates.

What are the three methods of protist reproduction?

Asexual reproduction (binary fission), sexual reproduction (via gametes), and conjugation.