Plant Biology Lecture 20

Exam 3

formation of oil and natural gas

1. organic marine matter accumulates in stagnant water (mostly plankton NO SLVPs)

2. no oxygen

3. covered by inorganic sediments and incomplete decay

4. formation of hydrocarbon-rich muds, broken down by anaerobic bacteria

5. increasing heat and pressure transform hydrocarbons into fatty acids

6. fatty acids are changed into asphaltic material, keragen

7. more pressure and heat cause oil formation

what is the ‘greenhouse effect’?

heat from the sun is either absorbed or reflected, some of the reflected heat is absorbed by CO₂ and other GHGs in the atmosphere, which reflects heat in all directions — leads to warming of Earth’s surface and oceans

consequences of climate change

agricultural production, climatic conditions may lead to increase agriculture production in some regions; in most regions, decrease due to increased stress conditions for crops, most severe for poor countries with no way to cope with climate events

what can be done about climate change?

paris climate agreement, limit global warming to 2°^c , political issue due to immense consequences for all nations (180 countries have ratified the Climate Agreement) U.S. dropped out

positive sign about reducing carbon emissions?

widespread adoption of alternative carbon-neutral electricity generation, technology is available and costs are dropping.

seedless vascular plants

xylem (w/ lignin) and phloem, SP dominant generation, multiple sporangia per sporophyte, dichotomous branching (apical meristems), primary/secondary growth, homosporous

selaginella

SLVP, hetersporous

monilophyta - horsetails

first present in Devonian, almost all species are extinct except Equisetum; fossils show that an identical genus that existed 300 mya in Carboniferous (may be oldest genus on Earth)

horsetail trees

among SLVPs that gave us coal (image: Equisetum pratense)

silica

scouring rush

monilophyta - ferns

abundant during Carboniferous, still abundant; largest group besides flowering plants

fern growth

often in tropics, grow as epiphytes upon trees

tree ferns

up to 25m tall with fronds (leaf) of 5m in length

water ferns

specialized ferns living in water, mostly float on surface of freshwater ponds

Azolla (water fern)

often found on rice paddies because it provides nitrogen fertilizer to rice, in a symbiosis with cyanobacterium (Anabaena azollae)

Anabaena azollae

In root nodules of legumes, can fix atmospheric nitrogen and metabolize it into ammonia, which can be assimilated by Azolla; Azolla provides carbs for Anabaena.

leaves and their stalks (stipes)

fronds (image; fractal organization of some ferns)

emerging fronds are coiled forming a fiddlehead structure

fern life cycle

sporangia are organized in clusters (sori), which are located underneath fronds; homosporous - GP is both male and female gametangia, archegonia and antheridia.

fern reproductive cycle

fern GPs are small but free living, flagellated sperm (need water), SP develops on GP — initially nutritionally dependent on GP (placenta cells); SP becomes independent and GP dies

SP IS DOMINANT GENERATION

life cycle of Polypodium (Filicales)