Origin & Importance of Plants Flashcards
Define ‘producers’
organisms that can use light energy from the sun to produce food
List some producer taxa
plants, algae and certain bacteria
How long ago was photosynthesis innovated?
3.5Bya
How many plant species are used by humans?
17,000 to 40,000
How many plant species have humans domesticated?
A couple of hundred
Describe some roles of producers
- provision of food to consumers
- regulation of atmospheric gases and temperatures
Define ‘consumers’
organisms that obtain energy from the food they consume
List some consumers
animals, fungi and other bacteria
Greater than … of earth’s land has been cleared for the approximate … plant species in the human food chain (…).
- 40%
- 150
- the equivalent of the area of South America and Africa combined
… species provide ¾ of the world’s food
12
List some megacrops
- maize
- rice
- wheat
Plants are also used in … of prescription medicines, and approximately … people are reliant upon basic plants for medicinal needs
- 25%
- 2Bn
Only … of plants ever in existence are extant, with … having gone extinct
- 1%
- 99%
Only … of plants have been described
10-20%
Only a … of plants have had their genomes sequenced.
small fraction
Define photosynthesis
production of food using radiant light energy from the sun, via carbon dioxide
Photosynthesis can be found across … bacterial phyla
6
Describe the basics of anoxygenic phototrophism
- exhibited by 5 of the 6 photosynthesising bacterial taxa
- anaerobic conditions
Describe the specifics of anoxygenic phototrophism
- uses a variety of reduced inorganic sources (sulphide, ferrous iron and hydrogen) as electron donors
- has a non-cyclic electron transport chain
Describe oxygenic photosynthesis
- polyphyletic phenomenon
- facilitated by the Great Oxidation Event
- exhibited by cyanobacteria and plants
- uses water as its electron donor
- electron transport chain is cyclic
How long ago was the Great Oxidation Event
2.5Bya
Describe Bangia atropurpurea
- extant photosynthetic multicellular eukaryotic red alga with differentiated cells and reproductive structure
- approximately 1.2Bya
When was the origin of oxygenic photosynthesis?
2.5Bya
Describe the origin of oxygenic photosynthesis
facilitated by primary photosynthetic endosymbiosis
Describe primary photosynthetic endosymbiosis
the grazing of a mitochondria-containing heterotrophic eukaryotic cell on cyanobacterium, resulting in engulfment.
Describe the evidence for primary photosynthetic endosymbiosis
- chloroplast DNA shape (circular) and sequence
- 70s ribosomes
- binary fission division
Describe secondary endosymbiosis
- facilitates photosynthesis
- the grazing and consequent engulfment of a unicellular primary plastid-containing, oxygenic photosynthesising eukaryotic alga by another eukaryote
Evolution of the Embryophytes is suggested to be
- around 460-470Mya
- microfossil sporopollenin spores
Describe producer life cycles
designed to regulate ploidy levels.
Describe the life cycle of a Streptophyte algae
- haplontic
- only diploid cell is the zygote
Describe alternation of the generations - the basics
- occurs at the Embryophyte node in the phylogenetic tree
- haplodiplontic life cycle
Describe alternation of the generations - the specifics
- in the haplontic generation, the plant is in its multicellular gametophytic phase, where it produces its gamete
- plant exists, also multicellular, in its diplontic generation: sporophytic phase
Describe the sporophytic phase
produces a spore via meiosis (reduction division)
Meiosis is …
the process which an organism reduces ploidy.
At the Embryophyte node…
– delay interpolates mitosis, which creates a multicellular zygote, the embryo
- causes the rise of the sporophyte and the demise of the gametophyte
Describe the gametophytic generation in angiosperms
- haploid
- occurs in an embryo sac
- extraordinary reduction of the haploid stage as the diploid stage took over
Describe embryophytic innovation
- allows for terrestrialisation (into an dessicating environment)
- evidenced by green algae in desert
Describe crypto spores
- tetrahedral tetrads
- products of meiosis
- produced in 4s
- trilete mark is a physical scar
Describe terrestrial plants
capable of forming complex ecosystems (evidenced by the Rhynie Chert)
Gross primary production (GPP) =
photosynthetic CO2 fixation
Net primary production (NPP) =
GPP – autotrophic respiration
Describe the Rhynie Chert
- oldest ecosystem preserved in situ
- displays the oldest terrestrial arthropods, decomposing fungi and mycorrhizae
- evolved 407 Mya
