General Biology/Classification of Living Things/Eukaryotes/Plants
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General Biology | Getting Started | Cells | Genetics | Classification | Evolution | Tissues & Systems | Additional Material
Multicellular Photosynthetic Autotrophs[edit | edit source]
Plants[edit | edit source]
- Multicellular
- Cellulose cell walls
- Chlorophylls a and b
- Develop from embryophyte
- Alternation of generations
- Major food source for terrestrial life
- Atmospheric O2 and CO2 balance
- Coal deposits
- Intimate association with mycorrhizal fungi
- >250,000 species (~500,000?)
- Taxonomy
- State of flux
- DNA sequencing
- Developmental studies
- Division (old literature) = phylum (new literature)
- ~12 phyla, 9 of which are vascular plants
Plant phyla[edit | edit source]
Phyla are 12 groupings
Plant evolution[edit | edit source]
- Evolved from green algae, likely related to charophytes
- Evidence
- DNA sequences
- homologous chloroplasts: chlorophyll b and beta-carotene; thylakoids in grana;
- Cellulose in both groups; also peroxisomes
- Mitosis and cytokinesis similar
- Sperm ultrastructure
Terrestrial adaptations[edit | edit source]
- Stomata: pores in leaves for exchange of gases; prevent desiccation
- Secondary metabolites:
- cuticle: waxy coating to prevent H2O loss
- lignin: hardens wood
- sporopollenin: resistant polymer; coats pollen
- predator defenses
- Embryonic development
- gametangia in early plants
- spores; seeds
- Mycorrhizae
- Water/food conducting systems
Plant phylogeny[edit | edit source]
Plant life cycles[edit | edit source]
- Alternation of generations
- Sporophyte
- diploid
- produces spores in sporangia
- Gametophyte
- develops from spore
- haploid
- produces gametes in gametangia
- Haplodiplontic life cycle
Moss life cycle[edit | edit source]
Moss has no vascular tissues or flowers. It is a thallus plant (it does not have true roots,stem and leaves). It does not produce seeds like the angiosperm.
Vascular plants[edit | edit source]
- Most have roots
- Aerial shoot systems
- Vascular tissue
- xylem: water, mineral transport
- phloem: food transport
- Lignin
- Branched sporophyte is dominant stage
- amplified production of spores
- evolution of complex plant bodies
- Dominated Carboniferous (360 my)
Vascular plant life cycles[edit | edit source]
- Homosporous (single type of spore)
- Heterosporous (two types of spore)
Pterophyta (ferns)[edit | edit source]
- Non-seed plant
- Sporophyte conspicuous (vascular tissue)
- Rhizome: ground stem, roots
- Fronds: leaves
- Sori: clusters of sporangia
- Motile sperm require external water for fertilization
- Originated in Devonian, 350 my
Tree fern Fern life cycle
Non-seed plants, continued[edit | edit source]
- Lycophyta: club mosses
- E.g., Lycopodium (“ground pine”)
- Many species became extinct 270 my, once dominant (coal formations)
- Gametophyte non-photosynthetic, nourished by fungi
- Arthrophyta: horsetails
- Equisitum
- Some fossil forms (300 my) were tree-size (coal)
- Photosynthetic stems, no leaves
- Silica deposits in epidermal cells
Seed plants[edit | edit source]
- 1st appeared in Devonian, 360 my
- Seed develops from ovule, protects embryo
- withstands drought
- dispersal is enhanced
- no immediate need for water for germination
- Heterosporous
- male gametophyte: arise from microspores
- female gametophyte: arise from megaspores in ovule in ovary
- Two groups
- gymnosperms
- angiosperms
plant
Sporophyte/gametophyte[edit | edit source]
Megasporangium (nucellus)[edit | edit source]
- Key to seed development
- Nucellus: solid, fleshy, surrounded by integuments derived from sporophyte (seed coat)
- Entire structure called ovule
- Flower may have many ovules
Pollen[edit | edit source]
- Develop from microspores, become male gametophyte
- Protected by sporopellenin
- In most plants, sperm lack flagella (loss)
- Many mechanisms to transport pollen
- wind
- insects, birds,
Gymnosperms[edit | edit source]
- “naked seed”
- ovule not fully enclosed by sporophyte at time of pollination
- Conifers, cycads, gnetophytes, Ginkgo
- Small, inconspicuous plants to giants like sequoia
- Conifers: to carry cones fv
- male cones, Female conesvv
- evergreen
Pine life cycle[edit | edit source]
Other Coniferophyta[edit | edit source]
- Cycadophyta: cycads
- tropical, subtropical
- flagellated sperm
- Gnetophyta
- e.g., Ephedra, Mormon Tea
- Ginkgophyta: Ginkgo
- only one surviving species
- diecious (separate % and &trees)
Other gymnosperms[edit | edit source]
Angiosperms[edit | edit source]
- Flowering plants, Anthophyta
- monocots- single seed leaf (grasses, lilies, etc.)
- dicots- two seed leaves (roses, pulses, maples)
- More specialized xylem (water transport)
- vessel elements
- fiber cells
- Fossils date to 130 my
- Animal (e.g., insect) coevolution
Monocots vs dicots[edit | edit source]
Earliest angiosperm[edit | edit source]
- What is earliest angiosperm?
- Recent analysis of nucleotide and amino acid sequences suggests that Amborella, a tropical plant found only on the island of New Caledonia, is closest relative to flowering plants
Angiosperm flower[edit | edit source]
Angiosperm life cycle[edit | edit source]
This text is based on notes very generously donated by Paul Doerder, Ph.D., of the Cleveland State University.