In what ways do green plants provide ecosystem services?
1. Produce oxygen
2. Build & hold soil by providing organic matter & a network of roots
3. Hold water & moderate climate by providing shade, increasing humidity, & blocking wind
4. Dominant primary producers & key to the carbon cycle
What are five main commodities that plants provide to humans?
Food, fuel (wood & coal burning), fiber (cotton for clothing, ropes, paper, etc.), building materials (wood), & pharmaceuticals.
What are 4 morphological traits that are similar between green algae & land plants.
1. Their chloroplasts contain the photosynthetic pigments chlorophyll a & b and β-carotene
2. Similar arrangements of internal membrane-bound sacs (thylakoids)
3. Similar cell walls, sperm, peroxisomes
4. Chloroplasts synthesize starch as storage
What are the 3 major morphological differences among land plants?
1. Non-vascular plants (bryophytes) lack vascular tissue, which conducts water & nutrients throughout the plant (ex: mosses)
2. Seedless vascular plants (ex: ferns)
3. Seed plants have vascular tissue (ex: angiosperms)
The first land plants are hypothesized to have existed at what time?
475 mya (microscopic spores and sheets of cuticle insinuate the existence of green land plants).
During what major event in history did virtually all of the adaptations that allow plants to occupy dry, terrestrial habitats evolve?
During the Silurian-Devonian explosion 416-359 mya.
What did the Carboniferous fossils (359-299 mya) indicate?
Deposits of coal suggest the presence of extensive forested swamps.
According to the fossil record, what is the order in which green algae and plants emerged?
Green algae appeared first, followed by non-vascular plants, seedless vascular plants, then seed plants.
What are the five major intervals in land plant history?
The origin of land plants 475 mya, followed by the Silurian-Devonian explosion, the Carboniferous period, the diversification of gymnosperms, and finally the diversification of flowering plants which is still happening today.
Organisms that appear late in the fossil record are often ______ dependent on moist habitats than are groups that appear earlier. (more/less)
Land plants evolved from...
Of green plants, green algae, land plants, non-vascular plants, vascular plants, and seed plants, which are monophyletic/paraphyletc?
Monophyletic: green plants, land plants, vascular plants, seed plants
Paraphyletic: green algae, non-vascular plants
The story of land plants is the story of adaptations that allowed...
Photosynthetic organisms to move from aquatic to terrestrial environments.
What were two benefits for green plants making the transition to survive out of water?
More light, more carbon dioxide.
Natural selection favored early land plants with adaptations that solved the drying problem. What were these 2 adaptations?
1. Preventing water loss, which kept cells from dying out and drying
2. Moving water from tissues with direct access to water to tissues without direct access
If biologists had to point to one innovation that made the transition to land possible, what would it be?
The random mutations that led to the production of cuticle.
What is the problem that arose with the evolution of the cuticle in land plants, and how was this solved?
Exchange of gases becomes more difficult, and plants need to take in CO2 from the atmosphere in order to perform photosynthesis; this is solved with stomata, openings surrounded by specialized guard cells that open and close to regulate gas exchange.
What are the benefits of upright growth?
Individuals that can grow erect have much better access to sunlight than individuals that are incapable of growing erect.
What two problems have to be overcome for a plant to grow erect?
1. Transporting water from tissues that are in contact with wet soil to tissues that are in contact with dry air, against the force of gravity
2. Becoming rigid enough to avoid falling over in response to gravity and wind
The evolution of which morphological trait allowed early plants to support erect stems and transport water from roots to aboveground tissues?
The evolution of lignin (a strong, complex polymer) in the cell walls of water-conducting cells.
What are two cases in which morphological traits evolved independently (convergence) in different land plant lineages?
1. Water-conducting cells evolved independently in mosses and in vascular plants
2. Vessels evolved independently in gnetophytes and angiosperms
What two things did the evolution of an elaborate gametangium protect gametes from?
Drying & mechanical damage.
What are the five key events that constitute alternation of generations?
1. Sporophyte produces spores by meiosis
2. Spores divide by mitosis -> haploid gametophyte
3. Gametophytes produce gametes by mitosis
4. 2 gametes unite during fertilization -> diploid zygote
5. Zygote divides by mitosis -> diploid sporophyte
What do biologists hypothesize as the reasoning behind the transition from gametophyte-dominated life cycles to sporophyte-dominated life cycles?
Sporophyte-dominated life cycles were advantageous b/c diploid cells can respond to varying environmental conditions more efficiently than haploid cells can, esp. if the individual is heterozygous at many genes.
The evolution of which morphological trait allowed heterosporous plants to lose their dependence on water to accomplish fertilization.
What are the two key reproductive structures in flowers?
Stamens are where microsporangia develop and pollen grains form; carpels contain a protective structure called an ovary where the ovules are found.
What is unique about angiosperm fertilization?
It undergoes double fertilization, with two sperm cells.
The relationship between flowering plants and their pollinators is.....?
What 3 key adaptations are associated with the diversification of angiosperms?
Vessels, flowers, and fruits.
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