Biology 111 - Plants (2023)

What does it mean to be monophyletic?

Having evolved from a common ancestor and including all descendants of that ancestor

Are photosynthesizers monophyletic?

no

What were the eukaryotic branches in the 1969 tree of life?

Plantae (land plants), animalia, protista, fungi

Eukaryotic branches in the 2005 tree of life?

Plantae, excavates, Chromalveolata, Unikonts, Rhizaria etc.

Important branches in the 2019 tree of life?

Both Archaeplastida (plantae) and Opisthokonts are  

Plants

How many eukaryotic kingdoms on the 2019 tree of life?

7-11

What are the photosynthesizers on the 2019 tree of life?

stramenopiles, hapista, rhizarians, archaeplastids, discobids, amaebozoans and alveolates. As well as prokaryotic bacteria 

How do photosynthesizers get carbon?

They ‘fix’ carbon into organic form

Do all plants do photosynthesis?

No

Give an example of why a plant might not photosynthesize and how might you be able to tell

Lost the trait - would not be green.

How would you know if a trait was lost?

An common ancestor of the species had the trait

What is the origin of photosynthesis? (Who and when)

Cyanobacteria (oxygenic photosynthesis) - 2.5-3 bya

Why was cyanobacteria developing oxygenic photosynthesis important for future organisms?

laid the groundwork for other types of metabolism and they changed the atmosphere by releasing a lot of oxygen into the atmosphere. 

Who developed multicellularity and cell specialization? When?

Cyanobacteria 2.2-2.5 bya

What is the great oxygenation event and why was it important?

• Great oxidation event caused the first mass extinction – but then later made complex life possible 

• Great oxidation event wiped out many species because of oxygenic damage – also caused eukaryotic sex to evolve (nuclear membrane, other cell protections etc) 

• Oxygen concentration rapidly rising in the atmosphere

Who are the ancestors of today’s plants?

First photosynthetic eukaryotes (cyanobacteria)

What is the main hypothesis for how photosynthesis transferred to bacteria if bacteria evolved it first?

Eukaryotic chloroplast originated when a eukaryote cell engulfed a cyanobacterium 

What are the steps for how a chloroplast would be engulfed by a eukaryote cell?

Cyanobacterium gets engulfed by a heterotrophic eukaryote -> One of the membranes is lost -> Now the chloroplast has 2 membranes, and the eukaryote is photosynthetic 

What is some evidence in support of the endosymbiotic origin of eukaryotes? (4)

Chloroplasts are similar to cyanobacteria and behave somewhat independently of the cell

Peptidoglycan (forms many bacterial cell walls)

Chloroplasts have at least a double membrane

Extant endosymbiotic cyanobacteria live in cells of some eukaryotes and animals 

In what ways do chloroplasts behave independently of the eukaryotic cell?

Replicate by fission (independently of cell division), manufacture some of their own proteins, have their own (highly reduced) DNA organized into circular molecule very similar to those in some cyanobacteria 

How did chloroplasts spread to other eukaryotic groups?

Secondary endosymbiosis

What is secondary endosymbiosis? (steps for photosynthesis)

A predatory eukaryote engulfs a a photosynthetuc eukaryote , Nucleus from photosynthetic eukaryote is lost, Organelle now has four membranes.  

Whose chloroplasts were transferred to other eukaryotic lineages (like alveolata)?

Red and green algae

Which two groups had primary endosymbiosis and how do we know?

Plantae/ archaeplastids

What are phytoplankton?

single-celled, free living photosynthetic organisms.

Are phytoplankton plants?

no

Why are phytoplankton important?

THey do about 50% of the world’s photosynthesis

Base of (almost) every ocean food web

What are the components of phytoplankton?

Photosynthetic bacteria - including cyanobacteria (blue-green algae) and single celled eukaryotes (diatoms and dinoflagellates)

Which organism is responsible for half of the ocean’s primary productivity?

Cyanobacteria (blue-green algae), Single celled photosynthetic eukaryotes – mostly Dinoflagellates and Diatoms (‘algae in glass houses’)

Are brown algae plants?

nope. multicellular marine organisms

Where does the brown in brown algae come from ?

from carotenoid pigment used in photosynthesis

Whcih pigments do brown algae use in photosynthesis

chlorophyll and carotenoids

How many membranes do brown algae chloroplasts have?

4 (secondary endosymbiosis evidence)

What is a phaeophyte?

brown algae

Give a famous example of a phaeophyte

Kelp

How tall is the largest kelp and how long did it take to grow?

80m, 3-5 years

What is the largest biogenic marine habitat?

Kelp (forests)

How biodiverse is a kelp forest?

> 100 000 invertebrates per m^2 of kelp tissue 

What does biogenic habitat mean?

A habitat formed by an organism

Where does kelp fit in the food chain?

Bottom of the food chain (primary producer), where energy enters the food chain

How did otter decline affect kelp?

Otter decline->No urchin predators -> Urchins overtake kelp -> negative ecosystem effects 

What is the type of seaweed that is the most diverse?

Red algae (>7000 species)

Are all species of red algae multicellular?

No, some are unicellular

Are red algae plants?

Yes! (some plants are red)

What kind of reproduction do red algae undergo?

Sexual and asexual

Why can red algae live a t great depths?

Blue light penetrates more deeply in the ocean and red pigment helps them to photosynthesize deeper because it absorbs more light

Where does the red colour that red algae use for photosynthesis come from?

Carotenoid pigment

How does coralline red algae help build up coral reefs?

• Attracting coral larvae 

• Patching up broken coral like a bandaid 

• Reinforce coral skeletons 

Why is coralline algae so vulnerable to damage and exploitation (like coral harvesting)?

It is very slow growing

What are Viridiplantae?

a monophyletic group which includes non vascular plants and vascular plalnts

How many species of viridiplantae are there?

500 000 species

What are the different types of green plants?

Green algae, mosses, ferns, gymnosperms (trees with no flowers) 

What was the big innovation for green plants? (viridiplantae)

Ability to live on land

What are vascular plants, what was their biggest innovation?

Vascular plants (with vascular tissue being their innovation)

What did key new evolutionary innovations to plants lead to?

enabled the proliferation of new lineages with more complex characteristics and facilitated access to new ecological niches. 

What was seeds plant’s big innovation?

The ability to disperse via seeds and not spores

What are some advantages to seeds?

allow the organism to protect and provide for their embryo

Key innovations for angiosperms?

Flowers

How many species of green algae?

8000

Where do green algae dominate?

freshwater

What are the main primary producers of freshwater? Why is this important?

green algae - super important for ecosystems as they support the base of the ecosystem

How can green algae reproduce?

Sexually and asexually

Can green algae swim?

yes with their flagella

Are green algae present on land?

Yes, but not really a land lineage - single celled green algae with crotonids and non photosynthetic parasites

How long did it take from capture of photosynthetic eukaryotes to first land plants?

around a billion years

Steps in the transition to land?(5)

475 mya – First evidence of land plants: cuticle, spores, sporangia 

416 mya – More morphological innovations: stomata roots leaves 

359 mya – Carboniferious: club mosses and horsetails abundant 

299 mya – Pangea! Gymnosperm become increasingly abundant. Both wet and dry environment blanketed by plants 

145 mya – Angiosperms abundant

Why are land plants, nonvascular plants, vascular plants and angiosperms monophyletic?

the events that lead to their conception only happened once

What are the earliest branching group of land plants?

bryophytes (nonvascular plants)

What are the advantages of moving onto land? (4)

• Photosynthesis is easier (more direct sunlight) 

• Abundant CO2 

• Food chain existed underwater (plants can’t be eaten on land by animals that don’t exist) 

• Open niche (uncolonized) 

What are the challenges of plants moving onto land?(6)

• Gas exchange  

• Sun’s radiation being damaging 

• Gravity – harder to move water up and nutrients 

• Dehydration 

• Dispersal 

• Nutrients 

What are bryophytes?

non-vascular land plants - the ancestors of the first land plants

How many species of bryophytes are there?

more than 14 000 species

What are three types of bryophytes?

• Mosses 

• Liverworts 

• Hornworts  

What are two common “plant” characteristics that bryophytes are missing?

no vascular tissue (no xylem/phloem), no true roots (just little grippy tendrils

How do bryophytes absorb water and nutrients?

Through their (super thin) leaves.

What are some characteristics of bryophyte leaves?

thin, with rudimentary cuticle and no stomata

Where do bryophytes live mostly?

Moist habitats - small short and slow growing. They also live on all 7 continents

What happens when bryophytes go through periods of desiccation tolerance?

• Ability to entirely dehydrate and become physically inactive .  

• When water is available, they rapidly ramp up and begin physiological lives again 

• Can happen super quickly

How do desert moss survive?

Can use long filamentous structures to gather dew or moisture in the air to trickle down their bodies and allows them to survive in arid environments 

• They can stay in “hibernation” state for a very long time 

What led plants to be able to live on land?

better sunscreen, a cuticle, different reproduction

Why was better sunscreen necessary for land plants?

Harmful land UV damages DNA unlike in the water where light is filtered by water 

Algae that survived on land were those that made compounds that absorb UV light 

Most plants today accumulate UV-absorbing compounds like flavonoids and anthocyanins

What is a cuticle?

Watertight sealant covering aboveground plant parts

What is the cuticle made from?

Hydrocarbons + lipids + wax produced by epidermal cells 

What is the main advantage/disadvantage to the cuticle?

prevents water loss, inhibits gas exchange

What were three instrumental innovations for reproduction for land plants (that lead them to be able to live on land).

1. Spores encased in a tough coat ( similar to fungi – the cells protected) 

2. Gametes produced in complex, multicellular structures 

3. Embryos retained and nourished by the parent plant I the developmental stage on plant 

 

How do spores encased in a tough coat help them>

• Resist drying 

• Survive for longish periods of time 

• Be dispersed by wind (resistant and lightweight)

How do protective, complex reproductive organs help plants on land?

protect gamete from drying and physical damage

Are Protective, complex reproductive organs present in all modern land plants?

Yes, except some angiosperm (whose flowers do the same function)

Are male and female reproductive organs always on the same plant?

No, sometimes they are on different plants

Do land plants shed their eggs into the water or soil?

No, they retain them

What do land plants do in contrast with most green algae, to their zygotes?

Begin development on the parent plant and then form multicellular embryos that remain attached to and can be nourished by the parent plant 

Are plants only multicellular in 2n or n generations?

no they’re multicellular in both stages

Alternation of generations: n generation steps?

Spores disperse -> mitosis produces a gametophyte -> gametes -> fusion of spores -> 2n generation 

Alternation of generations: 2n steps?

after fusion of gametes: zygote -> mitosis to sporophyte -> meiosis to produce spores 

Do all plants alter their generations?

No, but all plants that reproduce sexually do that (it’s more apparent in early plants when sporophyte is not as dominant)

For mosses, are they dominated by their gametophyte or sporophyte life stage?

Gametophyte - sporophyte depends on the gametophyte for nutrition

Steps of gametophyte dominant life cycle?(7)

1. Mature 2n sporophyte (diploid) undergoes meiosis 

2. Spores produced by meiosis dispersed by wind - (the spores are haploid) 

3. Spores undergo mitosis 

4. The gametophytes (1n) develop (to male and female gametophytes) - sperm develop in antheridia, eggs develop in archegonia 

5. Sperm from mature male gametophyte go to mature female gametophyte. (fertilization) 

6. Zygote develops in the archegonium (2n) 

7. Mitosis occurs, the plant grows and the cycle restarts 

What is sphagnum moss known as?

Peat

When does peat form?

when plant material does not fully decay in acidic and anaerobic condition

Is sphagnum moss a keystone species?

yes