Plants Unit Textbook Notes

Protists

Catch-all term for any eukaryotic group not contained within land plants, fungi, or animals → not monophyletic

Are protists monophyletic?

No, “protist” is a catch-all term

Are eukaryotes monophyletic?

Yes

Describe the lineage of eukaryotes.

Eukaryotes are specialized archaea that acquired a nucleus. However, they acquired mitochondria and chloroplasts from bacterial lineages through endosymbiosis.

Name the five important events in the origin of the modern eukaryotic cell.

-The origin of a flexible cell surface

-The origin of a cytoskeleton

-The origin of a nuclear envelope, which enclosed a genome organized into chromosomes

-The appearance of digestive vacuoles

-The acquisition of mitochondria and chloroplasts via endosymbiosis

What possibilities did flexible cell walls create?

-Larger cells (better surface area-to-volume ratio due to infolding)

-Endocytosis

Can prokaryotes have cytoskeleton?

Yes, they have a simple version.

What evolved in eukaryotes to make an advanced cytoskeleton?

Microfilaments and microtubules

What did the development of microfilaments and microtubules allow for?

-Changes in shape

-Distribution of daughter chromosomes

-Movement of materials within cell

-Development of eukaryotic flagellum (in some organisms)

When did the nuclear envelope develop in the eukaryotic lineage?

Early

What was happening at the same time that eukaryotes were developing a flexible membrane, advanced cytoskeleton, and other structural changes?

Cyanobacteria were producing oxygen as a product of photosynthesis.

What was the effect of increasing O2 in oceans on most organisms?

Disastrous. However, some prokaryotes and phagocytic eukaryotes developed ways to use oxygen.

Theory of endosymbiosis

Proposes that certain organelles are the descendants of prokaryotes engulfed, but not digested, by ancient eukaryotic cells

The mitochondria evolved from a…

proteobacterium engulfed by a eukaryote.

What was likely the original function of the mitochondria?

To detoxify O2 by reducing it to water → later coupled with ATP synthesis

Primary endosymbiosis

The engulfment of a cyanobacterium by a larger eukaryotic cell that gave rise to the first photosynthetic eukaryotes with chloroplasts

True or false: All chloroplasts trace their ancestry back to the engulfment of one cyanobacterium by a larger eukaryotic cell.

True! → Primary endosymbiosis

Why are there many different kinds of chloroplasts? Different colors, number of membranes, etc.

Chloroplasts evolved through multiple endosymbiotic events → Secondary endosymbiosis

How many membranes did the original chloroplasts have?

Two membranes → the inner and the outer membranes of the cyanobacterium

Why are there not three membranes around the chloroplast after primary endosymbiosis?

The host membrane was lost in the evolutionary process.

Is peptidoglycan (from cyanobacterial cell walls) present in the chloroplast membranes?

No, only in glaucophytes, the first eukaryotic group to branch off following endosymbiosis

Secondary endosymbiosis

The engulfment of a photosynthetic eukaryote by another eukaryotic cell that gave rise to certain groups of photosynthetic eukaryotes (ex. euglenids)

Why do euglenids have the same photosynthetic pigments as green algae and land plants?

Euglenids gained their chloroplasts via secondary endosymbiosis of a green alga.

How many membranes do euglenid chloroplasts have?

Three

Primary endosymbiosis is a ___ of the group Plantae.

Synapomorphy

Synapomorphy

Shared derived trait

Plantae

The most broadly defined plant group, descending from primary endosymbiosis

Algae

A term of convenience for various distantly related groups of aquatic, photosynthetic eukaryotes

The ancestor of Plantae was ___ and may have been similar to ____.

unicellular; glaucophytes

What is thought to be the sister group to the rest of Plantae?

Glaucophytes

Glaucophytes

Unicellular freshwater algae with chloroplasts containing peptidoglycan; thought to be the sister group to the rest of Plantae

Almost all red algae are ___.

multicellular

Red algae

Mostly multicellular, marine and freshwater algae characterized by the presence of phycoerythrin in their chloroplasts

Phycoerythrin

A red accessory photosynthetic pigment found in red algae

Do red algae contain chlorophyll a?

Yes

Are red algae always red in color? Why or why not?

No, depends on ratio of phycoerythrin and chlorophyll a

What influences the ratio of pigments present in red algae?

The intensity of the light that reaches the organism → red = less light; green = more light

Green plants

Organisms with chlorophyll a and b, cellulose-containing cell walls, starch as a carbohydrate storage product, and chloroplasts surrounded by two membranes

Three important clades of green algae

Chlorophytes, coleochaetophytes, and stoneworts

____ are the sister group of all the other green plants.

Chlorophytes

Chlorophytes

The most abundant and diverse group of green algae; use chlorophylls a and c

Coleochaetophytes

Multicellular green algae characterized by flattened growth form composed of thin-walled cells

Stoneworts

Multicellular green algae with branching, apical growth, and plasmodesmata between adjacent cells

What are the closest living relative to land plants?

Stoneworts

Name a key synapomorphy of land plants

Development from an embryo that is protected by tissues of the parent plant

Land plants are sometimes called ___.

embryophytes

Land plants fall into __ major clades.

10

Vascular plants

Plants with xylem and phloem; aka tracheophytes

Tracheophytes

Vascular plants; named because they possess tracheids

Nonvascular land plants

Land plants that lack specialized vascular tissues

Name the nonvascular land plant clades

Liverworts, mosses, hornworts (BUT not all a clade together!!)

Name the vascular land plant clades

Lycophytes, horsetails + ferns, cycads, ginkgo, gnetophytes, conifers, flowering plants

Adaptations to life on land distinguish land plants from ___.

green algae

When did land plants first appear in the terrestrial environment?

450-500 mya

Adaptations for terrestrial plant life include:

-The cuticle

-Stomata

-Gametangia

-Embryos

-Pigments that protected from UV

-Thick spore walls containing a polymer that resists desiccation and decay (sporopollenin)

-Mutually beneficial association with fungi (mycorrhizae)

The ____ may be the most important (and earliest) of these terrestrial adaptations.

cuticle

A universal feature of land plants is ___.

alternation of generations

Two hallmarks of alternation of generations

1. A multicellular diploid and a multicellular haploid stage

2. Gametes are produced by mitosis. Meiosis produces spores.

Spore

Any asexual reproductive cell capable of developing into an adult organism without gametic fusion

Embryo

Young plant sporophyte while still in its protective structure

Sporophyte

Diploid phase that produces spores

Sporangia

Where spores are formed

Gametophyte

Multicellular haploid phase that produces the gametes

The transitions between generations are accomplished by ___ and ___.

fertilization; meiosis

The sporophyte has ___ cells. The gametophyte has ___ cells.

diploid; haploid

Name the living bryophyte lineages

-Liverworts

-Mosses

-Hornworts

Where do bryophytes grow?

Typically in soil or on vascular plants; however, they can grow on dead plants and buildings because of a mutualistic relationship with fungi

Liverworts

Nonvascular land plants lacking stomata; stalk of sporophytes elongates along its entire length

Mosses

Nonvascular land plants with true stomata and erect “leafy” gametophytes; sporophytes elongate by apical cell division; some have hydroids

Hydroids

Die and leave channels through which water can travel; functionally similar to the tracheid

Hornworts

Nonvascular land plants with sporophytes that often look like horns and grow from the base; cells contain a single large, platelike chloroplast

What distinguishes hornworts from other bryophytes?

1. Hornwort cells contain a single large, platelike chloroplast.

2. Almost limitless sporophyte growth (meristem)

Hornworts developed a symbiotic relationship with ___. Describe it.

Cyanobacteria; converts N gas into usable ammonia

In the nonvascular land plants, the conspicuous green structure visible to the naked eye is the ___.

gametophyte

Gametangia

Any plant or fungal structure within which a gamete is formed; archegonium and antheridium

Archegonium

The multicellular structure that produces eggs in nonvascular land plants, ferns, and gymnosperms

Antheridium

The multicellular structure that produces the sperm in nonvascular land plants and ferns