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• Land plants are monophyletic and colonized land once.
• Plants have a good fossil record, which shows adaptations that evolved a single time.
• Four major adaptive radiations will be traced.

History of Green Plants

• There were four successive adaptive radiations.
• Over these radiations, trends include increased independence from water, increased body size, and increased parental contribution to the zygote.

Reproduction and Alternation of Generations

• Meiosis goes from 2N -> 1N.
• Mitosis goes from 2N -> 2N or 1N -> 1N.
• Alternation of generations is universal in land plants.
• The multicellular haploid phase (gametophyte) alternates with a multicellular diploid stage (sporophyte).
• There is no multicellular haploid phase in humans/animals.
• The gametophyte produces gametes by mitosis.
• The zygote develops into the sporophyte through mitosis.
• A single spore develops into a gametophyte.
• Spores develop into gametophytes and not sporophytes.

Non-Vascular Plants

• Non-vascular plants successfully protect spores/zygotes with sporopollenin and have cuticle pores.
• Rhizoids anchor the plant but do not absorb water/minerals.
• Non-vascular plants lack true roots, or structural support to defy gravity.
• Non-vascular plants lack roots and mostly obtain water via diffusion
• Non-vascular plants tend to be small, and are often resistant to desiccation.
• They require water for reproduction.

Mosses - Bryophyta (12,000 spp)

• Mosses exist in a wide range of habitats and experience dormancy.
• Mosses have a gametophyte-dominant phase.
• The zygote is retained on the plant and becomes a sporophyte.The gametophyte is large and long lived, while the sporophyte depends on the gametophyte for nutrition.
• Reproduction requires standing water.

Sphagnum

• Sphagnum is a component of peat bogs.
• Sphagnum covers 1% of the Earth's land in high-latitude areas.
• Peat is semi-decayed organic material with many human uses, including heat source, insulation, soil additive, and clean up oil spills.
• Peat bogs act as carbon sinks because decomposition is slow.
• Climate change increases peat decomposition.
• Carnivory evolved in 10 different plant lineages through convergent evolution.
• What plants compete for in a terrestrial world covered in moss-like plants is not clear.
• 400 mya +: Vascular plants evolved to compete for resources like sunlight.

Evolution of Vascular Tissue

• The evolution of vascular tissue (roots and leaves) enabled more efficient and taller growth.
• Seedless vascular plants led to extensive coal-forming swamps.
• Vascular tissue allowed plants to defy gravity and improved water conduction.
• A plant with lignin is more advanced than one without it.
• Seedless vascular plants are typified by homospory, and sporophyte dominance.

Seed Plants (360 + mya)

• Seed = embryo + nutrition + seed coat.
• Advantages include protection and the ability for the embryo to disperse far away from the parent.
• The radiation of gymnosperms started 300 mya as Pangaea formed, establishing a dry, warm interior climate.
• Heterospory involves two spore types and associated structures (microspore=male; megaspore=female).
• Pollen is the male gametophyte.
• Pollen enabled fertilization by use of wind.

Gymnosperms

• Gymnosperms, or "naked seeds", have five extant phyla and are monophyletic.
• Conifers = redwoods & pines
• They are highly abundant in cold & dry places and contain resins.
• There is low species diversity and tough leaves (needles): thick cuticle, small surface area
• The dominant land form during the Mesozoic Era.
• Gymnosperms continued to dominate land during the Cenozoic Era

Angiosperms

• Angiosperms account for 80% of extant land plants and have vessels for efficient transport leading to development of flowers and eventually fruits.
• Angiosperms arose in the Mesozoic Era & radiated in Cenozoic.
• Angiosperms exhibit reproductive adaptation (i.e. Flower, with its ovary containing female gametophyte.) and coevolution with animals.
• Angiosperms have the ability to extend heterospory, while further reducing gametophyte stage.
• They have Floral displays increased pollination success & efficiency.
• Endosperm extends seed dormancy.
• Two fruit functions are seed dispersal and seed protection.

Plant-Animal Coevolution

• Review: Species are agents of selection when they interact.
• Coevolution is when two interacting species influence each other's adaptations on a sustained basis..

Mutualistic Coevolution

• Angiosperms and their pollinators exhibit mutualistic coevolution.
• Pollination syndrome exhibits itself as a close correlation between structure of flower and size, shape, & behavior of its pollinator.
• Water lilies have reproductive adaptations such as giant spines on large leaves that float and flowers that changed color and scent and trapped insects

Antagonistic Coevolution

• Two interacting species influence each other's adaptations on a sustained basis. This influence can can categorized on a mutualistic vs antagonistic basis
• Antagonistic coevolution is when an Evolution of adaptations and counter-adaptations occurs between competing species or between predators and their prey.
• Plants exhibit mechanical and chemical defenses against herbivory.
• Milkweeds (Asclepias) produce a distinct cardenolide with adaptations to avoid herbivores.
• There can be genetic correlations between host and parasite.
• Longhorn beetles live on milkweed, which provide these beetles with immunity to species eat.
• Aposematism, such as warning coloration can also evolved .
• Each beetle specialises on one host plant species.
• 10-13 co-speciation events can happen over 40 my.
• Coevolution increases number of species.
• There are potential costs to plants, for example: production competes for resources, have to be sequestered and reduces photosynthesis.
• Organisms have finite resources that need to be allocated strategically to maximize fitness.
• Trade-offs are inevitable.
• Inducible and constitutive defenses play a role in plant development.
• Inducible defense - physical, chemical, behavioral trait that is induced in the "prey" by the presence of the predator/consumer.
• Constitutive defense - a defense present in a prey species even in the absence of a predator/consumer.

Plant Uses

• Plants provide ecosystem services through soil composition, water retention, primary production, O2 production, and carbon cycle.
• Humans use plants for various purposes.
• The loss of forests attributes to 25% of atmospheric carbon increase.

Summary

• Colonization of land had adaptations to increase size, independence rising to standing water and increasing nutrition to offspring. Most adaptations evolved once.
• Key general knowledge includes knowing traits of each level of organization (non-vascular plants, seedless ,vascular plants, seed plants, differences between angiosperms vs gymnosperms)
• Specific knowledge involves knowing traits of mosses, ferns, pinophytes/cupressophytes Also, it is required to know patterns of coevolution between angiosperms and other groups
• Two types of coevolution: mutualistic and antagonistic.
• Mesozoic was the advent of Angiosperm/insect coevolution beginning. In the Cenozoic, coevolutionary radiation escalated