Updated Exam 2

What is taxonomy?

Naming and classifying organisms into groups.

What is binomial nomenclature?

Giving each species a two-word scientific name

How do you write a scientific name?

Capitalize the genus, lowercase the specific epithet, and italicize both words. Example

What is a phylogenetic tree?

A branching diagram showing a hypothesis about how organisms are evolutionarily related.

What does a node, or branching point, represent?

A common ancestor of the groups branching from it.

How do you find the closest relatives on a phylogenetic tree?

Find the groups that share the most recent common ancestor. Look at the branching connections, not which names are closest together.

What are sister groups?

Two groups that share their most recent common ancestor with each other.

Does rotating branches around a node change the relationships?

No. The connections stay the same even if the tips change positions.

What is a clade or monophyletic group?

A common ancestor and ALL its descendants. Think “the whole family.”

What is a paraphyletic group?

A common ancestor and only SOME of its descendants. Think “part of the family is missing.”

What is a polyphyletic group?

Organisms grouped from different lineages without including their most recent common ancestor, often because they have similar traits.

What is homology?

Similarity because of shared ancestry. Example

What is analogy?

Similarity that evolved independently. Example

What is convergent evolution?

Unrelated or distantly related groups independently evolving similar traits because they face similar challenges.

How are analogy and convergent evolution connected?

Convergent evolution produces analogous traits.

What is a synapomorphy?

A shared derived trait that helps identify a clade. Example - flowers identify angiosperms

What is the endosymbiotic hypothesis?

Mitochondria and chloroplasts began as bacteria living inside another cell and eventually became permanent cell parts.

What is the difference between primary and secondary endosymbiosis?

Primary: a cell engulfs a bacterium.

Secondary: a cell engulfs a photosynthetic eukaryotic cell.

What is a heterotroph?

An organism that gets organic food from other organisms instead of making it from carbon dioxide.

What are the seven eukaryotic supergroups on the vocabulary list?

Opisthokonts, Amoebozoans, Archaeplastids, Stramenopiles, Alveolates, Rhizarians, and Excavates.

Which organisms belong to Opisthokonts?

Animals, fungi, and choanoflagellates. Their ancestral identifying trait is a single rear flagellum.

What are choanoflagellates, and why do they matter?

Small filter-feeding organisms that are the closest living relatives of animals.

Which organisms belong to Amoebozoans?

Amoebas and slime molds. They commonly use broad cell extensions called pseudopods.

What are pseudopods?

Temporary extensions of a cell used to move and capture food.

Are slime molds fungi?

No. Despite their name, they belong to Amoebozoans.

Which organisms belong to Archaeplastids?

Red algae, green algae, and land plants. Their chloroplasts originated through primary endosymbiosis.

Which algae gave rise to land plants?

A lineage of green algae.

Which organisms belong to Stramenopiles?

Brown algae, including kelp, and diatoms. Their ancestral identifying trait is two unequal flagella.

Which organisms belong to Alveolates?

Dinoflagellates, Paramecium, and Plasmodium. They have small membrane sacs beneath the cell surface.

Which organisms are associated with red tides?

Dinoflagellates, which are alveolates.

What is Paramecium?

A ciliated alveolate that uses tiny beating hairs called cilia to move.

What organism causes malaria, and which supergroup contains it?

Plasmodium, an alveolate.

What should you know about Rhizarians?

They are one of the seven supergroups, and many have thin pseudopods. Your instructor explicitly excludes detailed questions about foraminiferans and radiolarians.

Which organisms belong to Excavates?

Euglena, trypanosomes, and Giardia. The group is associated with a feeding groove.

Which excavate can photosynthesize?

Euglena.

Which excavate causes Chagas disease?

Trypanosoma cruzi, a trypanosome.

Which excavate causes hiker’s diarrhea?

Giardia.

What does SAR stand for?

Stramenopiles, Alveolates, and Rhizarians.

What advantages can multicellularity provide?

A larger body can improve feeding, discourage predators, and allow cells to specialize.

What three features characterize complex multicellularity?

Cells stick together, communicate, and form an integrated three-dimensional body.

What is division of labor?

Different cells perform different jobs for the same organism.

What is a major problem multicellular organisms must control?

Cells acting selfishly and reproducing at the organism’s expense, as happens in cancer.

Did complex multicellularity evolve only once?

No. The earlier class slides show six independent origins.

What is diffusion?

Particles spreading from higher concentration to lower concentration. It works well over short distances.

What is bulk flow?

Fluid carrying many substances together over a distance, such as blood circulation or transport through plant vascular tissue.

Why do large organisms need bulk flow?

Diffusion alone is too slow to supply cells deep inside a large body.

What happens to surface-area-to-volume ratio as an organism grows larger?

It decreases. There is less exchange surface available for each unit of body volume.

What are embryophytes?

Land plants. The name refers to their protected, retained developing embryos.

What main challenges did plants face when moving onto land?

Drying out, obtaining water, supporting their bodies, and reproducing without being surrounded by water.

What is a cuticle?

A protective coating that helps prevent a plant from drying out.

What are stomata?

Adjustable pores that let gases enter and leave the plant, but also allow water loss.

What major plant innovations should you place in order?

Alternation of generations → vascular tissue → seeds and pollen → flowers and fruits.

What is alternation of generations?

A plant life cycle with two multicellular stages

What does haploid, or n, mean?

Having one set of chromosomes.

What does diploid, or 2n, mean?

Having two sets of chromosomes.

What is a gametophyte?

The haploid plant stage that makes gametes. Remember “GAMETOphyte makes GAMETES.”

What are gametes?

Sperm and egg cells. They must fuse during fertilization to begin a new sporophyte.

What is a sporophyte?

The diploid plant stage that makes spores. Remember “SPOROphyte makes SPORES.”

What is a spore?

A reproductive cell that can grow into a gametophyte without joining another cell.

What is the key difference between a spore and a gamete?

A spore grows on its own; a gamete joins another gamete.

How does a gametophyte make gametes?

By mitosis, because the gametophyte is already haploid.

How does a sporophyte make spores?

By meiosis, which reduces the chromosome number from 2n to n.

What is a sporangium?

A spore-producing structure. Meiosis happens inside it.

What are gametangia?

Gamete-producing structures, including antheridia and archegonia.

What are antheridia?

Structures that produce sperm.

What are archegonia?

Structures that produce and contain eggs.

What happens during fertilization?

A haploid sperm and haploid egg fuse to form a diploid zygote

What does a zygote grow into?

An embryo, which develops into a sporophyte.

What does a spore grow into?

A gametophyte.

What is the basic plant life cycle?

Sporophyte makes spores → spores grow into gametophytes → gametophytes make gametes → fertilization forms a zygote → the zygote grows into a sporophyte.

What does “dominant generation” mean?

The stage that is larger, more noticeable, and generally longer-lived.

What are bryophytes?

Nonvascular plants

Which generation is dominant in bryophytes?

The gametophyte. The familiar green moss is the gametophyte.

What is the moss sporophyte?

The stalk and spore-producing capsule growing from the gametophyte.

Is the moss sporophyte independent?

No. It stays attached to and receives nourishment from the gametophyte.

Why do mosses need water for fertilization?

Their sperm must swim to the egg.

What are rhizoids?

Structures that anchor mosses. They are not true roots.

Do bryophytes have true roots, stems, leaves, xylem, or phloem?

No. Their similar-looking structures lack true vascular organization.

What is the moss life cycle in simple terms?

A spore grows into green moss → moss produces sperm or eggs → sperm swims to an egg → a sporophyte grows on the moss → its capsule releases new spores.

What are vascular tissues?

Xylem and phloem, the plant’s long-distance transport tissues.

What does xylem carry?

Water and minerals, mainly from roots upward.

What does phloem carry?

Sugars and other organic nutrients to parts of the plant that need or store them.

What is lignin?

A material that strengthens plant cell walls and helps support taller growth.

Why was vascular tissue an important innovation?

It allowed efficient transport and stronger support, helping plants grow taller and develop true roots, stems, and leaves.

Which groups are seedless vascular plants?

Lycophytes and ferns.

Are clubmosses actual mosses?

No. Clubmosses are lycophytes and have vascular tissue.

Which generation is dominant in ferns and lycophytes?

The sporophyte. The familiar leafy fern is a sporophyte.

Are fern gametophytes and mature sporophytes independent?

Yes. Both can live independently, although the sporophyte is much larger.

What is a prothallus?

The small, usually heart-shaped fern gametophyte.

Why do ferns still need water for fertilization?

Their sperm must swim to eggs on the gametophyte.

What is a fern frond?

A fern leaf.

What is a fern rhizome?

A stem, often growing horizontally underground.

What is a sorus?

A cluster of sporangia, often visible as dots on the underside of a fern leaf.

What is the fern life cycle in simple terms?

The leafy fern releases spores → a spore grows into a small gametophyte → it produces gametes → sperm swims to an egg → a new leafy fern develops.

What is homospory?

Producing one type of spore.

What is heterospory?

Producing two types of spores

What do microspores become?

Male gametophytes. In seed plants, these are pollen grains.

What do megaspores become?

Female gametophytes, which produce eggs.

Which plants are heterosporous?

All seed plants and some seedless vascular plants, including some lycophytes.

What is a strobilus?

A cone-like reproductive structure containing sporangia.