Plants & Fungi #18

Eukaryota

• Large group of photosynthetic autotrophs

Green Algae

• The first appearance of Chloroplasts

• an Archaeplastid

• Chlorophytes and Charophytes

  • a paraphyletic group who evolved around 1 billion years ago

• Primarily freshwater adapted

• not considered “true plants”

  • still protists

• most are unicellular, but some have independently evolved multicellularity

Chloroplast

• contain both chlorophyll a & chlorophyll b in membrane proteins called photosystems

Symbiosis

• a close, long-term interaction between two different species, where at least one organism benefits

• mutualism - both benefit

• commensalism - one benefits, other unaffected

• parasitism - one benefits, other harmed

Green algae and symbiosis

• Green algae (w/ their endosymbiotic chloroplasts) are found to be living symbiotically with many other organisms

• ex)

  • Protists - euglenids, ciliates etc.

  • Fungi - lichen

  • Animals

    • corals

    • flatworms

    • salamanders

Embryophyta

• the True Plants / Land plants

• the ancestors of the lineage that green algae came from that allows the green algae to evolve the ability to survive out of the water

Gametophyte

• a unique reproductive cycle involving alternating generations that was evolved by Land plants (Embryophyta)

• Haploid - single set of unpaired chromosomes

Sporophyte

• a unique reproductive cycle involving alternating generations that was evolved by Land plants (Embryophyta)

• Diploid - two complete sets of chromosomes, one from each parent

Bryophytes

• the First Land Plants

• include:

  • Mosses

  • Liverworts

  • Hornworts

• have free swimming sperm produced by gametophytes that get around when under water (are restricted to very moist or wet locations)

Plants evolved specialized tissues and organs

Remember: Plants evolved specialized tissues and organs

Vasculature

• tissues specialized in moving solutions across large distances in an organism

  • like vessels and arteries in animals

Xylem

• dead, hollow cells lined up like pipes to convey water and minerals up from the roots

  • use adhesion & cohesion

  • cell walls are lined with lignin - provides extra strength and stability

  • source of sap

Phloem

• living cells arranged end-to-end into long tubes

• transport sugar, nutrients, hormones and other substances in water, often towards roots

Roots

• Main functions:

  • anchor the plant to the substrate (soil/ground)

  • absorb and transport water and mineral nutrients from soil

• Secondary functions:

  • store excess sugars, starches, and water

  • growth regulations

  • vegetative propagation (they spread and develop new stems)

  • symbiotic partnerships with fungi and/or bacteria

Stem

Leaves

• evolved to maximize surface area for light absorption

  • light absorption is essential for:

    • photosynthesis

    • gas exchange

    • transpiration

Plasmodesmata

• small openings between cell walls and plasma membranes that link the cytoplasm of adjacent cells

• vasculature moves solutions throughout plant cell through this

Vascular plants

• Clubmosses / Lycophytes

• Ferns / Polypodiopsida

Ferns

• the first group of vascular plants to evolve flattened leaves

• primary phase = sporophyte phase

Spermatophytes

• seed plants

• 350 mill yrs ago plants evolved a new reproductive strategy where their fertilized embryos were packaged in protective cases along with a food supply

Seeds

• reproductive strategy where the fertilized embryos were packaged in protective cases along with a food supply

  • the plant equivalent of the amniotic egg

• form of sexual reproduction

• designed to survive drying out

• allow plants to move away from the standing water necessary for spore germination

• plants started to colonize dryer places on land bc of them

• fertilized by pollination

Gymnosperms

• The FIRST seeds

• arose 350 mill yrs ago

• seeds and pollen produced in cones or cone-like structures

  • cone = modified branch with leaves

    • center of cone = branch

    • hard scales of cones = leaves

• significant bc evolution rarely invents something completely new

Pollination

• the pollen of the plant (pollen = plant sperm) is transported physically to the egg cell of the plant (female gamete)

• how seeds are fertilized

Angiosperms

• Flowering plants

• the FIRST flowers

  • evolved 140 mill yrs ago

    • in response to pollination competition

• The majority of plants today

• flower = modified leaves surrounding the reproductive organs

• endosperm = expanded food source for fertilized seeds

• fruit = upon fertilization of the ovules, a special tissue grows around the seeds for protection

Fungi

• Holomycota

• Composition:

  • Cell walls composed of chitin

  • “body” composes of hyphae

• Diverse reproductive strategies:

  • asexual reproduction

  • & sexual reproduction

• form significant symbiotic relationships with most plants

• ecologically important decomposers

• evolved 800 mill yrs ago

• ex) mushrooms, yeast, molds

Chitin

• makes up the cell walls of fungi

• A strong, insoluble, crystalline biopolymer

• Provides armor, structural support, and protection for organisms

• Its structure is comparable to cellulose, and its function is similar to keratin (in hair/nails)

Hyphae

• root-like webs of tissues

• form extensive networks called Mycelia

Mycelia

• extensive networks formed from Hyphae

• have complex dynamics and relationships between them:

  • involved in interspecies communication, parasitism, nutrient absorption etc.

Decomposer

• Fungi / Holomycota

• Organisms that obtain energy by digesting dead organic matter