BIO044 Biodiversity

Evolution of Land Plants

Kingdoms of Life

Prokaryotes small simple unicellular, lack nucleus with chromosomes & sex

→ Bacteria, Archaea

Eukaryotes large complex cells, have nucleus with pairs of chromosomes & sex

Eukarytoes TL Protista → Multicellular Life →  Plants → Fungi → Animals

Algae-Plant TL Protists → Multicellular algae transition → Plant

Land Plants Adaptations

Green Algae

Types

• Multicellular – you have a bunch of different kinds of cells

• Colony – you have a bunch of the same kind of cells 

• Unicellular – you have one single cell

Adapted to Aquatic Life supported by water, absorbs water for nutrients, gametes and spores swim

Characteristics

• Energy stored as starch

• Cellulose cell Walls

• Identical chloroplasts to plants

• Alternation of generations (1n-stage & 2n stage)

• Biflagellated gametes motile reproductive cells propelled by two whip-like flagella

Charophytes green algae that grow along edges of lakes

Resemble Plants fossils, DNA

Adapted to Land supporting tissues keep from drying out, soil= nutrients and water air= gasses, ability to reproduce without swimming

Bryophyta Phylum moss, liverworts, hornworts

Adaptations to Land

• Waxy cuticle → no drying out

• Spongy mats formation → retain water

• Protective jacket → protects embryos while developing

• Dry spores → use air to reproduce

Bryophyte Alternation of Generations Gametophyte Dominant

• Sporophyte (2n) grows from Gameophyte (1n)

Vascular Plants basics/anatomy

Vascular Tissue developed by dominant sporophyte

Anatomy

• Roots → absorb water/nutrients

• Xylem → carry nutrients, dead thick cell walled cell that join into narrow tubes (veins)

• Lignin → forms wood and supports plants

• Stomata → gas exchange and transpiration 

• Phloem → carries sugar throughout plant

• Living cells → active transport and osmosis

Plant growth sporophyte → vascular tissue → apical meristems →  axillary buds

• Controlled by hormones that are influenced by environmental factors (gravity, light, water) 

Seedless Vascular Plants club moss, ferns, horsetails

Anatomy root,stems, leaves with stomata

Coal Forests produced very first forests, which is where the majority of our coal comes from —> lack of decomposers fossilizes into coal

Reproduction similar to moss (dry spore, sperm swims, moist habitat); fern alternation of generations sporophyte dominant

Gametophytes young sporophyte grows from male gametophyte

Sporophytes dry spores

Vascular Seed-Plants gymnosperms; conifers, cycads, ginkgo

→ Dominant sporophyte with gametophytes and spores protected in cones

Female Cones produce spores in ovule

• Spores develop into female gametophyte, female gametophyte makes eggs

Male Cones produce spores that develop into pollen

• Pollination pollen is carried to ovule by wind or animal

• Male gametophyte grows tube to egg

• Fertilization sperm swims to eggs

Ovule becomes seed surrounding zygote

Seed provide food supply for embryo

Mature cone opens to release seeds

Reproduction Model Gymnosperm Alternation of Generations, Sporphyte Dominant

Double Fertilization

Flowers Angiosperms (flowering plants)

Fruit Double Fertilization in flowers produces seeds in fruit

Adaptations per plant division

Flower Anatomy

Stamen Male structure

• Anther produces pollen

Pistil Female structure

• Stigma collects pollen

• Ovary produces eggs

Sepals & Petals modified leaves

Alternation of Generations per plant division

Double Fertilization

1n sperm fertilizers 1n egg cell → 2n Zygote → Embryo

1n Sperm fertilizes 2n Polar Nuclei → 4n Endosperm

Food store in seed for the developing embryo

Flowering Plant Diversity

Monocots one seed leaf, flower in 3s, parallel veins; grasses and palm trees

Dicots two seed leaves, flower in 4s/5s, branching veins, majority of species

Pollination Adaptations

Composites and Orchids have most species, adapted to animal pollination

Trees and Grasses have small inconspicuous flowers, adapted to wind pollination

Transport in Plants

Benefits of H₂O

Cohesion Forces allows water to stay at liquid form for most surface temperatures, easily transported

Adhesion Forces removes majority of impurities (greatest solvent power)

Long Distance Transport

1. Xylem Sap travels upwards from roots to shoot

2. Transpiration of water from leaves creates force that pulls xylem sap up

3. Phloem Sap allows flow between shoots and roots

4. Leaves produce sugar

5. Roots store sugar/ nutrients

Cohesion-Tension Hypothesis explains long distance water movement in the xylem by following the water potential gradient

Short Distance Transport three major routes

• Apoplastic everything external to plasma membranes of living cells

• Symplastic entire cytosol of living cells moves thru plasmodesmata

• Transmembrane across plasma membrane junctions

Membrane Potential the difference in electrical charge between the inside and outside of a cell membrane, causes diffusion, co-transport, osmosis

Water Potential physical property predicting direction of water flow: from areas of high water potential to are of low water potential

Solute Pressure always negative, proportional to molarity, as solute concentration increases, sp becomes more negative, in pure water sp=0, 0.1M sugar = 0.23Mpa

Physical Pressure physical pressure on solution, can be positive or negative and is relative to atmospheric pressure,

Turgor Pressure cell wall exerts pressure on cytoplasm, keeps plant cells from wilting

H₂O Transport to Root Hairs

Cohesion-Tension Hypothesis

Transpiration pull negative pressure at air-water interface in leaf causes transpirational pull, draws water out of xylem

Water Transport

Proton Pumps proton pumps generates membrane potential and H⁺ gradient

Casparian Strips prevents apoplastic flow into central vascular cylinder, thickening of lignin and fatty acids that are impermeable to diffusion forces flow to be through transmembrane and symplastic routes

Plasmodesmata microscopic channels traversing plant cell walls, enabling direct cytoplasm-to-cytoplasm transport known as the symplast pathway critical for water transport, allowing water, nutrients, and molecules to move between cells without crossing the plasma membrane

Stomata Opening and Closing controls rate of transpiration

Opens at dawn: light, CO2 depletion, internal “clock”

Light stimulates guard cells to accumulate K+ and water, guard cells become turgid

Adaptations to reduce evaporative water loss

Xerophytes (cacti) photosynthesis occurs in stem, metabolism where leaf takes in CO2 at night, stomata closed in day (reverse of regular plant)