Exam 3 BOO Flashcards
List the evolution of plants from least to most complex
Algal mats, multicellular marine/freshwater green algae, terrestrial bryophytes, lycopods and ferns, gymnosperms, angiosperms
What did early embryophyte land plants evolve from?
Green algae
Charophytes
Closest common ancestor of land plants
What traits do plants share only with charophytes?
*cellulose-synthesizing membrane proteins arranged in rings rather than linear sets
*structure of flagellated sperm
*similarities in all types of DNA
*Sporopollenin
What is sporopollenin and where is it found?
It is a polymer that prevents zygotes from drying out. It’s found in plant spore walls, as well as charophyte cell coating
List the benefits of moving to land.
Unfiltered sunlight, more plentiful CO2, and nutrient rich soil
List the challenges of moving to land.
Scarcity of water, and lack of structural support against gravity
What are derived traits?
Traits that arose in the most recent common ancestor and passed on the lineage
Derived traits in plants
*Alternation of Generations
*Multicellular, dependent embryos
*Apical meristems
*Cuticle
*Stomata
What are the characteristics of early land plants?
*no true roots, stems, or leaves
*formed associations with soil fungi (mycorrhizae)
*require water for fertilization
What is vascular tissue?
Cells joined into tubes for the transport of water and nutrients
What is the difference between vascular and nonvascular plants?
Vascular plants have a complex vascular tissue system while nonvascular plants lack an extensive transport system
List the types of nonvascular plants
Bryophytes, mosses, liverworts, and hornworts
Seedless Vascular Plants
*have an extensive vascular transport system but don’t produce seeds
*Lycophytes (club mosses and their relatives)
*Monilophytes (ferns and their relatives)
Seed Plants
*produce seeds
*have vascular tissues
*Cycad/cardboard palms/Sego palms
*Ginkgo
*Mormon tea
*pines
Phylum Cycadophyta
Cycad/cardboard palms/Sego palms
Phylum Ginkgophya
Ginkgo only living species
Phylum Gnetophyta
Mormon Tea
Phylum Coniferophyta
Pines
Phylum Lycophyta
Club mosses and their relatives
Phylum Monilophyta
Monilophytes are ferns and their relatives
Phylum Bryophyta
Mosses
Phylum Marchantiophyta
Liverworts
Phylum Anthoceratophyta
Hornworts
For mosses, which generation is dominant?
Gametophyte (1N)
How does reproduction work in Bryophytes (mosses, liverworts, and hornworts)?
*Male and female reproductive structures are separated
**female gametophyte produces archegonia which produces 1N eggs
**male gametophyte produces antheridia that produces 1N sperm
*Egg and sperm fuse during fertilization producing 2N sporophyte
*Sporophyte 2N depends on gametophyte for nutrition
**Meiosis occurs in sporangium of sporophyte to produce 1N spores
**1N spores germinate into new 1N gametophyte generation
**Water still needed for fertilization to occur
What were the benefits of adaptations leading to seedless vascular plants?
*Vascular tissue allowed plants to grow much taller
*taller plants were better able to compete for sunlight and could disperse spores further than shorter plants
Characteristics of vascular plants
*life cycles with dominant sporophytes
*transport in vascular tissues called xylem and phloem
*Well-developed roots and leaves
*sporophylls
*gametophyte is microscopic, sporophyte is dominant
Sporophyll
Modified leaves with sporangia that bear spores
Xylem
Vascular tissue in charge of water transport
Phloem
Vascular tissue in charge of food transport
What are the two types of true leaves?
Microphylls and Megaphylls
What three “upgrades” did plants gain after adapting into seedless vascular plants?
True stems, true roots, and true leaves
Microphylls
Small, often spine-shaped leaves with a single vein, found only in lycophytes
Megaphylls
Larger leaves with a highly branched vascular system, found in all plant groups except lycophytes
Strobili
Clumps of sporophylls in cone-like structures
Are seedless vascular plants homosporous or heterosporous?
Most are homosporous, but some are heterosporous
Describe homosporous plants
*They have one type of sporophyll and sporangium that produces one type of spore
*Microsporophyll–>Microsporangium–>Microspores
*Spores usually produce bisexual gametophytes
Describe heterosporous plants
*All seed plants and some seedless vascular plants
*Two types of sporophylls bearing different sporangia that produce different spore types
*Mega/microsporophylls produce mega/microsporangia produce mega/microspores which give rise to female/male gametophytes
Which groups in Phylum Lycophyta are heterosporous vs homosporous?
Spikemosses and quillworts are heterosporous, while clubmosses are homosporous
What is the fern sporophyte like?
Large megasporophylls (fronds), coiled at the tip (fiddlehead) that unfurls as leaf grows. Most are homosporous
Sori/Sorus
Fern sporophytes have spores born in clusters, covered by a piece of tissue called an indusium. Found on underside of fern fronds
Division Pteridophyta
Whisk Ferns and Fern Allies
*Sporophytes have branching stems but no roots
*3 fused sporangia form a yellow knob on each stem
*homosporous with bisexual gametophytes
*sporophyte dominance
Division Polypodiophyta
Horsetails
*sporophytes have jointed stems with rings of small leaves or branches
*stems contain silica
*bisexual gametophytes
*sporophyte dominance
Division Lycopodiophyta
Club Mosses, Spike Mosses, and Quillworts
*Not true mosses
*Vascular plants
What adaptations allowed seed plants to make up the majority of plant biodiversity?
*Seeds
*Reduced gametophytes
*Heterospory
*Water not being required for fertilization
*Seeds and pollen grains
*sporophyte dominance
Describe the reduced gametophytes of gymnosperms
Ovules (female)
Pollen (male)
What is a seed?
*Consists of an embryo and nutrients surrounded by a protective coat
*can disperse over long distances by wind or other means
What are gymnosperm gametophytes like?
*Microscopic and dependent
*Develop from spores within sporangia of sporophyte
*Protected from environmental stress, receiving nutrients from parent sporophyte
What is the gymnosperm female gametophyte like?
Ovule consists of megaspore within megasporangium surrounded by one or more integument (gymnosperms usually have one integument while angiosperms usually have 2)
What is the gymnosperm male gametophyte like?
Each microspore develops into a microgametophyte within the pollen wall, a pollen grain.
Pollen grains germinate when they reach the female reproductive structure, and once germinated they produce a pollen tube. Pollen tube grows into the ovule and discharges sperm into the female gametophyte. If a sperm fertilizes the egg of a seed plant, zygote grows into a sporophyte embryo.
What are the evolutionary advantages of seeds?
*multicellular while spores are single cells
*can remain dormant for years until conditions are favorable for germination (spores are shorter-lived)
*stored food to nourish seedlings (spores don’t produce nourishment to gametophytes)
*can be transported longer distances
What are the 3 key reproductive adaptations of seeds?
*Miniaturization of gametophytes
*Production of the seed as a resistant, dispersible stage in the life cycle
*Pollen, an airborne agent bringing gametes together
What are gymnosperm seeds like?
They have “naked seeds” exposed on sporophylls that usually form cones
Life cycle of a Pine
*Sporophyte is dominant
*Pollen cones/staminate are small, consisting of microsporophylls that bear microsporangia
*Microsporocytes undergo meiosis, producing haploid microspores within microsporangia
*Each microspore develops into a pollen gran containing a male gametophyte (pollen)
*Cones release large amounts of wind-carried pollen
*Ovulate cones are larger, consisting of modified stem tissue and megasporophylls bearing megasporangia
**within each megasporangium, megasporocytes undergo meiosis to produce haploid megaspores which develop into female gametophytes (megagametophytes in megasporangia)
**Scales of each ovulate cone separate at maturity and seeds are dispersed by wind
*At germination, sporophyte embryo emerges as a seedling
What is a cone?
Modified strobilus
Describe conifers
Largest phylum of the gymnosperms; most have woody cones while some have fleshy cones.
Leaves are needlelike in some and scalelike in others
Most are evergreens
Some deciduous species drop their leaves in autumn
What phylum do angiosperms belong to?
Anthophyta
What two key adaptations do angiosperms have?
Flowers and fruit
Floral Organs
-Modified Leaves
-Most flowers have 4
-sepals, petals, stamens, and carpels
Sepals
Usually green and enclose and protect developing flower bud
Petals
Often brightly colored to attract pollinators (wind-pollinated flowers aren’t usually)
Stamens
*microsporophyll (male reproductive organ)
*consists of a stalk (filament) with a terminal sac (anther)
*Microspores produced within anthers and develop into pollen grains containing male gametophytes
Carpels
Megasporophyll (female reproductive organs)
*Carpel consists of ovary at base of a style, leads up to sticky stigma that receives pollen
*ovary contains female gametophyte within ovule (fertilized ovules develop into seeds)
Radial symmetry
Any imaginary line through central axis divides flower into two equal parts
Bilateral symmetry
Flower can only be divided into two equal parts by a single imaginary line
What are fruits?
Mature ovaries; they protect seeds and aid in their dispersal
What types of fruits are there?
Fleshy or dry; fleshy are things like tomatoes, plums, and grapes, while dry include beans, nuts, and grains
Where are angiosperm male and female gametophytes found?
Male: within pollen grains produced by microsporangia of anthers
Female: Within the ovule in the ovary, it’s also called an embryo sac (egg within embryo sac)
Describe the double fertilization process
*Pollen is released from anther and carried to sticky stigma at tip of carpel
*Pollen grains germinate on stigma, producing pollen tube that grows down to the ovary
*Pollen tube penetrates micropyle, discharging two sperm cells
*One sperm fertilizes egg and forms diploid zygote
*Other sperm fuses with 2 nuclei in embryo cell, forms triploid cell called endosperm
Micropyle
A pore in the integuments
Endosperm
A triploid cell in the embryo sac that provides nutrients for the developing sporophyte
What are angiosperms divided into?
Monocots and dicots/eudicots
Monocots
One cotyledon
Eudicots
Includes most once categorized as dicots (two cotyledons)
What are the 2 major threats to plant diversity?
Habitat destruction
Loss of forests (reduces absorption of CO2, leading to global warming)
