Lecture 1

Why are plants important? 

- Conversion of sun's energy
- Agriculture 
- Drugs, fossil fuels, clothing, etc. 
- BiodiversityWhy are plants important for agriculture? 

Why are plants important for agriculture? 

- Allowed human groups to settle down. 
- Created a more diverse economy 

What is botany?

The study of plants

What is a plastid? 
What is an example? 

A plastid is an organelle in cells that used to be a free living organisms that was engulfed by a cell. 
eg. Chloroplasts & Mitochondria

What clade are "plants" in? 

Viridiplantae 

What are some of the consequences of agriculture? 

(don't need to like memorize but have a good idea) 
- Permanent villages, towns, & cities 
- Larger family +> larger population 
- Less cooperation 
- Socieconomic classes 
- Seperation of humans from rest of nature 
- Large-scale war

Tags

What are embryophtes? 

Land plants

What are chlorophytes?

- They are originally marine plants (most live in freshwater, but there are also many marine and some land(terrestrial) species)
- Green Algae 

What are charophytes?

- Green algae
- Includes the algae most closely related to land plants.

What are "Plant Secondary compounds" and give an example

Plant secondary compounds means that its apart of the plant but it's not necessary for metabolism, growth, or development. 
EXAMPLE: MANY DRUGS

Quinine
What plant is it from? 
Where is their natural range? 
What does it treat?

1. From the bark of a cinchona tree
2. South America, now widely introduced worldwide 
3. Malaria from 1650s in Europe, anemia, muscle spasms, & cancer 

What is primary endosymbiosis?

(Plants (incl.green algae) and red algae)

Primary endosymbiosis: prokaryote + eukaryote = eukaryote.

Non-photosynthetic eukaryote engulfed a photosynthetic cyanobacterium (now a plastid)

What is secondary endosymbiosis?

(Other eukaryotes)

eukaryote + eukaryote = eukaryote.

Non-photosynthetic eukaryote engulfed a photosynthetic eukaryote (green or red algae).

When do plants appear in the history of life?

1. Plants split from red algae around 1500 mya

• Both single-cell and multicellular forms

• marine

• moist environments near ocean shores.

What were the adaptions plants had to do when coming into drier environments?

1. Cuticle

2. Vascular tissue: roots & shoots

3. Relationship with fungi

4. Seeds and pollen

When was the oxygen revolution?

2400 mya

When was the earth formed?

4550 mya

When did photosynthesis appear?

3500 (cyanobacteria)

When did the plants and red algae diverge?

1500

When was the colonization by plants, fungi, the animals.

500?

What are the features of all plants?

1. Starch as the main energy story molecule

2. Chlorophyll b

3. Cellulose is a major component of cell wall

4. Thylakoids in stacks “grana”

What is chlorophyll b?

Chlorophyll b is an accessory pigment

What is an accessory pigment?

A pigment that absorbs different wavelengths than chlorophyl a.

What are the closest relatives of land plants?

What is the evidence?

Charophytes.

1. Both nuclear and chloroplast DNA

2. Anatomical structure

What are features of charophytes & land plants?

• Cell plate & phragmoplast (short microtubules)

• Plasmodesmata (extensions of cell membrane throug pores in cell wall)

• Sperm structure

• Peroxisome enzymes

• Rose-shaped cellulose-synthesizing complexes

• Sporopollenin: durable polymer

What is sporopollenin?

Durable Polymer (impermeable to the environment, protected from the world)

Found in walls of:

• Plant spores

• Pollen

Chemically inert:

• Stable

• Persists in environment

Protects from decay, etc.

What are the potential advantages moving to land?

1. Air filters less sunlight than water. There’s more light for photosynthesis.

2. Air has more CO2 than water. There’s more fuel for photosynthesis.

3. Early land habitats lacked pathogens or predators/herbivores.

4. Land soil is richer in nutrients than aquatic soil.

IN WATER:

Is it supportive?

Does it retain water?

How is reproduction?

1. Supportive

2. Retains water

3. Reproduction is easier:

   1. Sperm swim in water

   2. Dispersal easy (float)

   3. Eggs do not dry out

ON LAND:

Is it supportive? Adaption?

Does it retain water? Adaption?

How is reproduction? Adaption?

1. Not supportive

• Turgor (positive pressure); cell walls with lignin; xylem; stems

1. Loses water

• Cuticle; vascular tissue; roots; stomata

1. Reproduction is harder:

   1. Sperm cannot fly

   2. Young not dispersed

   3. Egg & embryos need protection from drying out + predators.

      • Egg & embryo retained on parent; sporopollenin; protected embryo; seed coat; pollen; flower; fruit

Features of just LAND plants

1. Cuticle-waxy covering

2. Multicellular, jacketed sex organs = gametangia

3. Embryophyte condition

   1. Zygote retained on maternal tissue

4. Alternation of generations

What is gametangia?

sex organ

What is an antheridium?

Male sex organ

Haploid

Produces sperm

What is an archegonium?

Female sex organ

Haploid

Produces egg

(each archegonium produces 1 egg)

What is the alternation of generations?

The process by which plants alternate between 2 life stages (arose independently in evolution several times):

1. A haploid gametophyte (makes gametes by mitosis)

2. Diploid sporophyte (makes spores by meiosis)

DOES NOT OCCUR IN CHAROPHYTES ONLY IN EMBRYOPHYTES

What is an exception to the alternation of generations?

A green alga “Chlamydomonas”

Most of its life it’s single cell & haploid.

How did alternation of generations originate?

Zygote delays meiosis and divides and grows.

Result: multicellular diploid