BSC2011 Exam 1 Plant Biology

What is the term used to describe properties or characteristics that are shared by an evolutionary group?

Synapomorphies

What are synapomorphies that all plants share?

The ability to preform photosynthesis

Selective response to respond to stimuli

High surface area to volume ratio

Anchored

Why is it important that plants have a high surface area to volume ratio?

Fast exchange of resources like gas and water.

Overcomes growth/size limitations

Why is it important that all plants are anchored?

Root systems: Structural support, ability to absorb water and nutrients

Lytico-Bodig (ALS-PDC) backstory

Chamorro people of Guam use the sea + land as their resources

Researchers noticed high frequency of disease that resembles ALS, Parkinson’s and Alzhiemer’s

Common in adults (30-45), 1/3 of all deaths were caused by this disease

ALS-PDC conclusion

Concluded that flying fox (bats) were ingesting high amounts of neurotoxins through eating cycad seeds

Flying foxes were considered a Chamorro delicacy, where consumption caused neurotoxin level to increase in the consumer.

Why were there a delayed onset of symptoms after consumption of the flying foxes?

BMAA (neurotoxin) is key in protein synthesis

Bats have high levels of free BMAA and low amounts associated with proteins

Causes long-term high exposure to toxin which is released during protein degredation

How does BMAA relate to cyanobacteria?

BMAA is important in plants

Fixes nitrogen for sugars and amino acids in return

Cyanobacteria passed this trait through endosymbiosis

What are symptoms of ALS-PDC?

Stooped

Blank expression

Move slowly

Resting tremors

Muscle atrophy

Death

What is the photosynthesis equation?

6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂

carbon dioxide + water → glucose + oxygen

What is the main catalyst for the photosynthesis reaction to occur?

Sunlight

3 domains of life

Bacteria, Eukarya, Archaea

Bacteria

Prokaryotes

W/out nuclei

Peptidoglycan in cell walls

1 RNA polymerase

Circular DNA

Locomotion w/ Flagella

Cilia

Archaea

Prokaryotes

W/out nuclei and peptidoglycan in cell walls

3 RNA polymerase

Eukarya

Eukaryotes

Cells w/ nuclei

3 RNA polymerase

Where are archaea commonly found?

Extremophiles

Found in extreme environments such as thermal vents

Cyanobacteria

Photosynthetic prokaryotes

NO nucleus, have circular chromosomes

True or False: Cyanobacteria were NOT the first organisms to do oxygenic photosynthesis

False

They were first

What are two adaptations that were key for cyanobacteria to become the first photosynthetic organisms?

Membrane that invaginates

Heterocysts

Explain how invagination of the cyanobacteria’s membrane is related to its ability to preform photosynthesis?

Cyanobacteria do NOT have chloroplasts

Membrane invagination creates folds called thylakoid membranes

Thylakoid membranes establish the proton gradient that is essential for ATP production that enables photosynthesis

Explain how heterocysts enabled cyanobacteria to become the first photosynthetic organisms?

Heterocysts are a type of differentiated cyanobacteria cell

Since nitrogenase (the enzyme preforming nitrogen fixation) is sensitive to oxygen, once oxygen was present in Earth’s atmosphere these organisms had to adapt.

Heterocysts preform nitrogen fixation

Features of heterocysts

Thickened cell walls that limit oxygen gas exchange

Houses nitrogenase

Maintains low-oxygen environemnt

Fix N₂ into usable nitrogen (essential for amino acids in proteins and nucleic acids in DNA and RNA)

When did O₂ begin to be produced on Earth?

3.5 billion years ago

When did the first photosynthetic organism arise?

1.5 billion years ago

True or False: All photosynthetic chloroplasts originate from 1 cyanobacteria

True

Primary Endosymbiosis

Ancestral eukaryote engulfs cyanobacteria that was capable of photosynthesis.

Cyanobacteria stayed alive within the cell and over many generations became an organelle → Chloroplasts

What is the importance of primary endosymbiosis?

Eukaryotes gained the ability to preform oxygenic photosynthesis

Cyanobacteria gained space within a protected environment in the host cell

Chloroplasts derived from cyanobacterium

What species did the “domestication” of cyanobacteria occur in?

Ancestral red algae, green algae, and land plants

How many membranes does a cyanobacterium have? What are they?

3: Cyanobacterium outer membrane, cyanobacterium inner membrane, host cell membrane

What species were derived from primary endosymbiosis?

Red algae, Green algae, Land plants, and Glaucophytes

Why are glaucophytes different than the other species derived from primary endosymbiosis?

Glaucophytes are the only type of organism that retains peptidoglycan in its cell walL

Peptidoglycan

Provides structural support by creating osmotic pressure within cyanobacteria

Maintains bacterial shape

True or False: Mitochondria did not originate from primary endosymbiosis?

False

Secondary endosymbiosis

Eukaryote engulfs other eukaryote that contains chloroplast from primary endosymbiosis

True or False: Chloroplasts from secondary endosymbiosis usually have 3-4 membranes

True

Invagination membrane, cell membrane, chloroplast membrane

What are diatoms, brown algae, cryptomonads, haptophytes, and dinoflagellates derived from in secondary endosymbiosis?

Red algal cells

What are euglenids and chlorachinophytes derived from in secondary endosymbiosis?

Green algal cells

Types of brown algae

Fucus (rockweed)

Giant kelp

Characteristics of brown algae

Chloroplasts at cell plates

Pigments absorb blue light

Deep water

Important characteristics of dinoflagellates

2 flagella: axial and longitudinal

Red tide: when population concentration of Karenia brevis is very high, produces toxin (brevetoxin) that harms marine life + humans → red tide event

Bioluminescence: some species are bioluminescent, luciferin being the light-producing molecule, used as defense mechanism against predators

Synapomorphy of plants related to primary endosymbiosis

Photosynthetic eukaryotes with double-membraned chloroplast that resulted from primary endosymbiosis

Important characteristics of diatoms

Silica shell: “Sparkle reflects light”

Split into 2 halves that during mitosis split apart, one going to each daughter cell

Plantae

Clade of eukaryotic life with chloroplasts that were derived from primary endosymbiosis

True or False: Most of the early species of plants that resulted from primary endosymbiosis were land lineages

False: Most were aquatic lineages (Algae) in either fresh or marine water

What is the order of the phylogenetic tree from most ancient to most recent in terms of plant species?

rhodophytes → glaucophytes → chlorophytes → streptophytes → bryophytes → vascular plants

True or False: the emrbyophytes (bryophytes and vascular plants) are “land plants”

True

What are the first synapomorphies that are shared between lineages of streptophytes up to land plants?

Multicellularity

Uniaxial growth

What are the second group of synapomorphies that are shared between lineages of streptophytes up to land plants?

Phragmoplasts

Oogamy

Cell-Cell communication with plasmodesmata

Cell and filament polarity with apical cells

What are the third group of synapomorphies that are shared with lineages of streptophytes up to land plants?

Structural simplification

Loss of flagella

Extracellular polysaccharides

What are synapomorphies specific to embryophytes and land plants?

Tolerance of dryer habitats

Symbiosis with AM fungi

Sporophytes

Key characteristics of red algae

Cell wall made of cellulose

Photosynthetic pigment: chlorophyll a (same as cyanobacteria)

Red color from phycoerythin pigments that absorb red and green light

What is the main type of red algae and its key features?

Coralline

Cell walls have calcium carbonate

Extremely important as reef-builders, food for reef organisms, also inhabit deeper waters

What characteristics constitute a green plant?

Photosynthetic pigments: Chlorphyll a and b

Carbohydrates are stored as starch whcih have two main types of polysaccharide

With reference to the phylogenetic tree, what are considered green plants?

Chlorophytes → streptophytes → embryophytes/land plants

What is the earliest branching of green plants?

Green algae

Where do green algae species mainly occur?

Fresh water or marine environments

What is spirogyra and its role?

Long filamentous chain of green algae cells

Spiral shaped chloroplasts

Type of streptophytes that does not exhibit oogamy, plasmodesmata or apical growth

Phragmoblasts

The machinery that helps a plant cell build a new cell wall between two daughter cells during cytokinesis

Assemble perpendicular to the plane of the future cell plate so that the cell can grow outwards

What type of plants have phragmoplasts?

Most streptophytes

What type of plants have phycoplasts?

Clorophytes

Clorophytes

Fibers that assist in the formation of the cell plate during cytokinesis are parallel to the location that the new cell plate will form.

Tranverse fibers

True or False: Most streptophytes do not have plasmodesmata

False: Most do have plasmodesmata

Plasmodesmata

Channels that penetrate the cells walls of adjacent cells

Facilitates cell-cell communication

Parenchyma

Basic tissue type in the streptophytes with cells that are linked by plasmodesmata

Explain the relationship between parenchyma and plasmodesmata

Parenchyma are the ground tissue cells that are common in plant cell walls

Plasmodesmata are the connections between cells, connecting adjacent cell cytoplasm

Plasmodesmata allow the parenchyma to communicate and exchange substances such as sugars, ions, signaling molecules and proteins

Symplast

The interconnected cytoplasm of plant cells that are connected through plasmodesmata

Isogamy

Iso = same

Both gametes contribute the same amounts of cytoplasm, are similar size and structures

Oogamy

Gametes vary in size, shape, and function

Typically classified as “egg” and “sperm”

Allows thick walled spores to stay inert over time

Egg vs Sperm

Eggs are larger, generally nonmotile, contain lots of cytoplast and stored resources

Sperms are smaller, generally motile, specialized for delivering genetic material

Apical growth

Plants grow from their tips

Cells at the apex continuously divide/elongate

Allows for the organism to grow longer, reach toward light, extend through its environment, produce branching structures

What syanpomorphies are specific to the third generation of streptophytes/characteristics specific to zygnematophycae?

Loss of apical growth

Loss of plasmodesmata

Loss of oogamy

What is an example of a plant type that has lost oogamy, plasmodesmata and apical growth capabilites?

Spirogyra and Zygematophyceae (other green algae)

Alternation of generations

Plants alternate between a multicellular haploid and a multicellular diploid stage

Gametophytes = haploid (n)

Sporophytes = diploid (2n)

What is the life cycle of an example of alternation of generations?

Gametophyte (n) → mitosis → gametes (n) → fertilization sperm (n) + egg (n) → zygote (2n) → sporophyte (2n) → meiosis → spores (n) → growth → gametophyte (n)

Types of plants that exhibit alternation of generations

Chara (Stonewort)

typical of many algae and other eukaryotes

What is another name for zygnematophyceae?

Other green algae

What are challenges that land plants had to adapt to in order to colonize land?

High heat, dryness, and light

Need for transport systems of water and nutrients

Need for structural support (weather, erosion, predation)

Need to find ways for dispersal of reproductive cells

What were the key adaptations that permitted plants to colonize land?

Cuticle, Spores, Stomata, Pigments, mutually beneficial association with fungi (mycorrhizae)

Cuticle

Waxy coating that slows water loss on leaves

Structures of the cuticle

Cuticle, Upper epidermis, Pallisade layer, Spongy mesophyll, Lower epidermis, Cuticle

Upper cuticle

Thin, waxy waterproof layer

Reduces water loss and protects the leaf

Upper and lower epidermis

Usually one layer of tightly packed transparent cells

Protects the leaf

Lets light pass into photosynthetic tissues (upper only)

Reduces water loss

Palisade mesophyll

Tall, tightly packed cells containing many chloroplasts

Main site of photosynthesis

Spongy mesophyll

Loosely arranged cells with many air spaces

Allows CO₂, O₂, and water vapor to diffuse through the leaf

Preforms some photosynthesis

Lower epidermis

Protective layer containing many stomata

Protects the leaf and regulates gas exchange and water loss

What is the role of the mutualistic relationship that plants form with mycorrhizae?

Promotes nutrient and water uptake from soil / Mining of minerals through enzymatic reaction

Assists with preventing phosphate deficiency in plants

Associated with plant roots

Ectomyocorrhizal (EM) fungi

Forms dense network between roots or around roots (connection to roots)

Increases surface area for water and mineral absorption

Vesicular-arbuscular myocorrhizal (VA) fungi

Grow into and invades root cells

Arbuscles that grow inside the plant cells, increasing surface area for nutrient exchange

Key features of EM fungi

Hartig network, Myecelium, Mantle

Myecelium vs Hyphae

Hyphae: one individual thread like fungal filament

Myecelium: entire network of hyphae

Mantle

Thick layer of fungal hyphae that forms a sheath around the outside of the root

Hartig network

When the fungal network grows between the plant root cells it is referred to as the Hartig network

Key features of VA fungi

Arbuscles, spores

Arbuscles

A highly branched hyphae structure that grows into the root cells

Bryophytes

Non-vascular land plants

How was Gametangia a key adaptation of land plants that allowed them to colonize land?

Organs that enclose gametes and prevent them from drying out

Embryos

Young plants that are contained within a protective structure

Stomata

Stomata are pores in the epidermis of the leaf that allow water vapor to exit in transpiration and gas exchange

Each stoma is surrounded by guard cells

Guard cells

Control whether the pore is open or closed