chapter 25 & 26 (2): seedless and seeded plants - BIOL 2130

vascular plants

tracheophytes that can grow far away from water due to their tissues (xylem and phloem)

• 90% of earth’s vegetation

• diploid sporophyte phase dominant 

  • plant produces spores by meiosis which is what is visibly seen 

• can grow into large plants

• roots for water and nutrient uptake

• leaves increase photosynthesis

• ex: seeded general sherman tree — sequoia 275 ft tall, 36 ft in diameter

• ex: unseeded ferns, club mosses, horsetails, whisk ferns

vascular tissues

responsible for the transport of water and nutrients thru the plant body

• xylem

• phloem

• roots

• leaves

xylem

vascular tissue that stores and long-distance transports water and nutrients, from the roots upward to the leaves

• transfers water growth factors from site of synthesis to target

• rigid cells maintain plant structure

• up-take of these nutrients

phloem

vascular tissue that transports sugars, proteins, and other solutes throughout the plant

• transports materials in both directions

roots

vascular tissue that anchors plants to terrestrial environment, and absorbs water and nutrients from soil

• not well preserved in fossil record

• appear to evolve after vascular tissue

leaves

vascular tissue with chloroplasts to increase surface area for photosynthesis

• fossil record: leaves evolved more than once

• microphylls: small with single vein (ex: club moss)

• megaphylls: larger with branched venis (ex: ferns)

• sporophylls: leaves modified for sporangia (ex: pinecones, ferns)

modern seedless plants

all vascular and reproduce via spores

ferns: large, megaphyll

club moss: microphylls

horsetails: joined stems, reduced leaves

whisk ferns: no true leaves/roots, simple branching

seedless importance

• recolonization after a disaster

• food and shelter for organisms

• info on presence of pollution

• fix nitrogen in aquatic systems

• used by humans for food, medicine, and fuel

  • ex: dried peat moss burned for heat/fuel

  • fossil fuels

nonvascular plants

have to get water and nutrients by direct contact

• no specialized conductive tissue, cannot transport long distances

• limited growth: small and close to moist env

• need water for reproduction

• alternation of generations: gametophyte (haploid) dominant 

• seedless plants

• ex: bryophytes (mosses, liverworts, hornworts)

seeded plants

the most successful group of plants, earliest distinct 350 mya

• heterosporous: produce male and female spores (dependent on sporophyte for water and nutrients)

• dominant sporophyte generation: reduced gametophyte size to hide inside sporophyte

• do not need water for fertilization to occur

• seeds and pollen

• gymnosperms (319 mya) and angiosperms (most diverse and 100 mya)

pollen

male gametophytes of seeded plants containing sperm (haploid gamete)

• surrounded by grain: prevents dessication and mechanical damage

• can disperse sperm far from sporophyte (wind, insects, animals)

seeds

combination of haploid sperm and egg (diploid zygote, fertilized egg) that provides and protects in seeded plants

• protected by itself

• contains embryo

• provides nutrients for developing embryo

• physical protection

• dormancy until favorable conditions for germination

• survival advantages

gymnosperm

any vascular plant that reproduces by means of an exposed seed

• transitioned from wet period (fern trees) to a dry period for flourishing

• diversified and spread to various habitats

• resistant to dessication

• not reliant on water to reproduce

• ex: pines, firs, ginkgoes (first!)

gymnosperm characteristics

• naked seeds

• separate male and female gametophytes

  • pollen cones (male) and ovulate cones (female)

• pollination by wind and insects

• tracheids: in vascular tissue to transport water/nutrients

gymnosperm reproduction

seeds exposed on cones, pollination by wind, single fertilization

• diploid sporophyte dominant in alternation of generations

• ex: christmas tree

• heterosporous

  • male cones produce microspores

  • female cones produce megaspores

  • monoecious plant: both male and female

  • dioecious plant: separate male and female

• pollen carried (wind/insects) sperm to ovule

• seeds developed on exposed female cones → can be eaten by predators

• polyploid: many copies of chromosomes

gymnosperm adaptation

• can live where water is scarce certain times a year

• can live in nitrogen poor environments (bogs)

• maintain low levels of photosynthesis

• most are susceptible to leaf infestations since do not shed 

• ex: conifers, gingkos, cycads, gnetophytes

angiosperm

plants that produce flowers and bear seeds in fruits

• flowers contain both male/female parts

• evolved in conjunction with primitive insect species

  • ex: amborella trichopoda — related to all flowering plants

• mutualistic relationship from pollen as food source, insects transfer pollen, plants evolve diverse structures for pollinators and seed dispersal, rapid speciation 

• likely evolved from sister clade to gymnosperms

• ex: basal, monocots, dicots

flowers and fruit

protects the embryo, increases genetic variability, and increases range of genetic material

• improved reproductive strategy, dominates most terrestrial env with 300,000 species

• gametes produced in separate organs, in flower

• fertilization and embryo within a protective structure (ovary → seed → fruit)!!!!

• can vary in size, shape, taste, smell

  • designed for mutualistic relationships with pollinators for reproduction and disperse their seeds (wind, digestive tract, cling to fur)

• dry fruit: nut (acorn), legumes (peas)

• fleshy fruit: drupe (peach), berry (strawberry), pome (apple)

flowers

angiosperms that ensure pollination and protect developing embryo

• modified leaves around central receptacle

• sepals, petals, carpals, stamen

• colorful petals attract specific pollinators

• before fertilization: produce gametes

  • monoecious or dioecious

  • resulting fruit = protect seeds and aid in their dispersal

• few self-fertilize

• most rely on cross-pollination

angiosperm reproduction

seeds enclosed in ovary → fruit, pollinate by insects/animals/wind in flowers, double fertilization

• diploid sporophyte is dominant in alternations of generations

• heterosporous: male microspores (sperm/pollen) and female megaspores (egg)

• double fertilization:

  • one diploid zygote formed → embryo

  • triploid cell = endosperm (food for embryo) supports early growth until photosynthesis

• embryo: radicle (first root) and cotyledons (first seed leaves in embryo)

  • monocots: 1 cotyl (ex: grasses, lilies, palms)

  • dicots: 2 cotyl (ex: beans, sunflowers, flowering plants)

fruit

angiosperms that is anything that contains seeds and developed from thickened ovary tissue walls

• protects seeds and aids in dispersal

• after fertilization

• fleshy or dry

• derived from single flower or clusters

• come from flowering plants (veggies are edible parts of plants)

monocots

angiosperm with one cotyledon

• parallel veins in leaves

• vascular tissue scattered in stems

• fibrous root

• flower parts of 3 or multiples of 3

• ex: corn, rice, lilies, tulips, onions, coconut, banans

dicots

angiosperms with two cotyledons

• branched leaf veins

• vascular tissue arranged in a ring in stem

• 1 tap root and many smaller lateral roots

• flower parts in 4 or 5

• ex: oak tree, maple tree, beans, peas, tomatoes, roses, sunflowers

seeded importance

life on earth could not persist!

• maintains terrestrial ecosystems (stabilize soil, carbon cycle, climate moderation)

• release O2 and uptakes CO2

• shelter and food

• can provide medicines

humans:

• foundation of diets for humans

• construction

• energy production

animals and seeded plants

coevolution: bloom in diversity in both groups at the same time

herbivory: animals obtain nutrients, plants seeds are dispersed

pollination: animals get nutrients, plants facilitated in pollen spread