The Evolution of Plants Flashcards
What was needed for photosynthetic plants to move into land?
The evolution of chloroplasts
What is the Primary endosymbiosis derived from?
Plantae
First Clades to branch off after primary endosymbiosis?
Aquatic (algae)
Three key characteristics of the evolution of land plants:
Protected embryos, vascular tissues, and seeds
Ancestor of Plantae
Unicellular, similar to modern glaucophytes
Chloroplasts retain:
Peptidoglycan between membranes (as cyanobacteria)
Key synapomorphy of land plants:
Embryo that is protected by tissue.
Land plants are also called:
Embryophytes
Ten major clades:
Liverworts
Mosses
Hornworts
Lycophytes
Vascular plants
Tracheophytes, called tracheids (7 clades)
Nonvascular plants:
Some have conduction cells, but no tracheids
Classifications of Land Plants:
- Nonvascular Land Plants
- Vascular Plants
- Seed Plants
Land Plants develop
- Transport systems
- Structural support
- New ways to disperse gametes and progeny.
Adaptations of Land Plants
-Cuticle
-Stomata
-Gametangia
-Embryos
Pigments and Spores
Cuticle
Waxy coating that slows water loss
Stomata
Closable opening that regulate gas exchange and water loss
Gametagia
Organs that enclose gametes and prevent them from drying out
Embryos
Young plants contained within a protective structure
Pigments
Protect against UV radiation
Spores
With thick walls containing a polymer that prevents drying and resists decay
Land plants have alternation of generations:
- Multicellular diploid stage and multicellular haploid stage
- Gametes produce by mitosis
- Spores produced by meiosis
- Spores develop haploid organisms.
Diploid zygote:
Develops by mitosis and cytokinesis
Multicelluar diploid plant is called :
sporophyte
Spores develop into
Gametophyte, multicellular haploid plant
Gametophyte produces
Haploid gametes
Fusion of gametes produces:
Diploid Zygote, which then develops into sporophyte
Nonvascular Plants
Liverworts, mosses, hornworts
Charateristics of nonvascular plants:
- Live in moist habitats
- Small
- No vascular system to transport water
Liverworts
- Green
- Sporophyte attached to gametophyte
- Can reproduce asexually or sexually
Mosses
- Stomata-important for gas exchange and water retention
- Cells called hydroids which die and leave a channel through water can move.
Hornworts:
- Sporophytes look like small horns.
- Cells have one chloroplast
- Sporophyte
- Symbiotic relationships with cyanobacteria and fix nitrogen.
Nonvasular plants, gametophyte is:
Photosynthetic
What does the sporophyte depend on:
Gametophyte
Where are Gametes produced:
Gametangia (antheridia and archegonia)
Sperm must:
Swim or be splashed by water to reach the egg
What must be present for reproduction
Water
Vascular system consists:
Tissues for transport of water and materials
How did evolution help Vascular tissue:
Allowed plants to spread to new environments and diversify
Xylem conducts:
Water and minerals
Phloem conducts:
Products of photosynthesis
Tracheid:
Evolved in sporophytes and critical for invasion of land.
Tracheid includes;
Transport, the lignin provides support and allowing taller growth, which means more sunlight and disperse spores.
Vascular plants also developed:
Branching
What does branching do:
Spore production
Sporophyte of a vascular plant
Independent of the gametophyte
Invasion of land by vascular plants:
Made environment more hospitable to animals
What moved to land after vascular plants
Arthropods, vertebrates, and animals
When did trees appeared:
Devonian
When did trees dominate:
Carboniferous, when huge club mosses, horsetails, and tree ferns
What transformed into coal
Buried plant material
What happend in the Permian:
Gymnosperms replaced loycophyte - fern forests
Rhyniophytes
Earliest vascular plants
Rhyniophytes include:
No roots, anchored in soil by rhizomes with rhizoids ( ferns today) and dichotomous
Lycophytes
Club mosses, spike mosses and quilworts
Lycophytes include:
Microphylls and Strobili
Monilophytes
Horsetails and ferns. All have different main stem and side branches
Horsetails
Independent sporophyte and gametophyte
When did ferns appeared:
Devonian period, terrestrial
How long can sporophyte live:
Hundreds of years
Why is water so important:
Needed to transport of male gametes to female gametes so ferns are inhabit shaded, moist woodlands and swamps.
Sporangia
Borne on a stalk in clusters called sori
Microphylls evolved from:
Sterile sporangia
How did
Megaphylls of monilophytes arise:
Photosynthetic tissue developed between branch pairs that were left behind as dominant branches overtopped them.
Euphyllophytes
Clade consisting of monilophytes
A synapomorphy of euphyllophytes
Overtopping growth
Euphyllophytes lead to
Megaphylls
Seed plants
Provide lasting dormant stage for the embryo. Can also be dormant for many years.
Trend in plant evolution:
Sporophyte became less dependent and gametophyte became smaller.
Seed plants evolved:
Independence from water for getting the sperm to the egg.
Male gametophyte
Pollen grain
Sporopollenin
Prevents drying and chemical damage
Megaspores develop:
Into female gametophytes
What are megagametophytes are dependent:
On sporophyte for food and water
Megagametophytes develop in:
Ovule, which later became the seed
Pollination
Arrival of a pollen grain near a female gametophyte
Pollen tube
Grows the grain and digests its way toward megagametophyte.
Diploid Zygote:
Divides to form an embryonic sporophyte, enters a dormant stage
Seed contains tissues from three generation:
A seed coat, Haploid tissue from the female gametophyte provides nutrients, and embryo is the new diploid Sporophyte.
Many seeds remain:
Viable for long periods
Seed coat:
Protects from drying, potential predators and other damage.
What do the adaptiations of seeds to help:
Aid in dispersal
Where does the embryo get nutirients:
Stored in the seed
Secondary growth:
Increasing diameter of roots and stems by growth of xylem
Older wood:
Becomes clogged with resins but provide support and allows plants to grow.
Gymnosperms
Seed plants that do not form flowers or fruits
What is not protected in gymnosperms:
Ovules and seeds.
Gymnosperms have:
Tracheids as water conducting and support.
Four groups of gymnosperms:
Cycads, Gingkos, Gnetophytes, Conifers
Cycads
Tropical, earliest diverging clade
Gingkos
Common in Mesozoic, today only species: Gingko biloba
Gnetophytes
Some characteristics similar to angiosperms; Welwitschia
Conifers
Cone-bearing plants
Conifers include:
Dominate forests at high latitudes and high elevations
Cones contain:
Megastrobilus and Microstrobilus
Megastrobilus
Female cone
Microstrobilus
Male pollen
What transports pollen grains
Wind
What are the most exposed:
Conifer Ovules
Angiosperms
Reproductive organs in flowers; seeds are enclosed in fruits
Carpel
Ovules and seeds enclosed in modified leaf
What is very reduced:
Female gametophyte
Xylem of amgiosperms
Vessel elements- water transporting cells
Fibers
Structural support
Pholem
Companion cells
Synapomorphies of the angiosperms
Germination of pollen on a stigma, Double fertilization, Endosperm
Infloresence
Group of flowers
Stamens bear
Male microsporangia
Stamen is composed
Filament and anther
Carpels bear
Megasporangia
Carpels contain:
Ovary, style and stigma
Imperfect flowers
two flowers types male and female
Monoecious
Male and female flowers occur on the same plant
Dioecious
Male and female flowers are produced on different plants
Evolution of flowers
Earliest diverging clades have many tepals, carpels and stamens
Most angiosperms are pollinated by:
Animals
Double fetilization:
Each pollen contains two male gametes: one combines with egg. The other combines with two other haploid nuclei to form a triploid cell, triploid cells give rise to endosperm
Zygote develops:
Into an embryo with embryonic axis and cotyledons (seed leaves)
Fruits:
Develop from ovaries after fertilization, protect seeds and aid in dispersal
Single fruit
Develops from a single carpel or fused by carpels ( plum or peach)
Aggregate fruit
Develops from several separate carpels of a single flower (raspberry)
Multiple fruit
Forms from a flower cluster, inflorescence (pineapples and figs)
Accessory fruit
Develop from other parts in addition to the carpel (apples, pears, strawberries)
Amborella (magnoliids)
Sister group of all other flowering plants
- Angiosperm clades:
Monocots (1 cotyledon) grasses, cattails, ilies, orchids and palms.
- Angiosperm clades:
Eudicots (2 cotyledons) majority of familiar seed plants
