plant diversity i: how plants colonized land

Plant Diversity I: How Plants Colonized Land

Kingdom - Plantae

nonvascular vascular(xylem/phloem)

(food)(water)

Nonvascular

Division - Bryophyta

mossesliverworts

vascular

Seedless Seed

horsetailsclub mossesferns

seed

gymnosperm angiosperm(Naked) (Covered)

GinkgoGnetophytaCycadsConifers

Angiosperm

Anthophyta

DicotsMonocots

anth - male

arch - female

epi - upon

phyte - plant

Plant Characteristics:

1. Structure:

specialized – cells and tissuesphotosynthetic – (autotrophic)multicellular – (many celled)

2. Pigments:

carotenoidschlorophyll bchlorophyll a

3. Storage polysaccharide (carbohydrate) – amylose starch

Structural polysaccharide (carbohydrate) – is cellulose

Strengthening agents: pectin lignin

4. Sporic life cycle:

Alternation between diploid sporophyte and haploid gametophyte

5. Reproduction: embryo is multicellular (many-celled) housed in multicellular gametophyte tissue

•meiosis in diploid (2n) sporophyte yields single celled, haploid (n) spores

• then, cells in the gametophyte form gametes (sperms/eggs)

• sperm and egg meet - fertilize to form new diploid (2n) sporophyte (In animals there is no equivalent to gametophyte in plants)

Nonvascular plants – bryophytes

includes mosses, liverworts, and hornworts

• gametophyte is dominant

• sporophyte is reduced

• all other plants – sporophyte is dominant (plant)gametophyte is reduced

Spores: homospory - one form of spore

Small spores - microspores give rise to microgametophytes (male)

(in seed plants – the pollen)

heterospory - 2 distinct types of spores

megaspores – give rise to megagametophytes (female)

(in the ovule, located in the ovary of the flower)

• require water to reproduce (sperm swims)

Bryophytes - mosses, liverworts, and hornworts

• conducting/supporting tissue? no, therefore size is limited

• cannot tolerate pollutiontherefore they may be an indicator species

• anchorage – threadlike rhizoids

Rhizoids are not used for absorption of water

liverworts: name from the fact they were once used to treat liver disease

• wort - herb• leafy, gametophyte body - thallus

thallus

• pore-like stomata (exchange of gases)

• example of liverwort - Marchantia

Asexual: 2 ways

• fragmentation - parts grow into complete gametophyte

• gemmae - form cups

Sexual: 2 kinds of gametangia

1. egg-forming - archegonia produces stalked archegoniophores

2. sperm-forming - antheridia produces stalked antheridiophores

• may be monoecious (one house) or dioecious (two houses)

• sperm are splashed against archegonia

•upon fertilization – new diploid sporophyte produces sporangia meiosis (reduction division) produces haploid spores which develop into new gametophytes

Mosses: most numerous and most common of the bryophytes

• withstand drying conditions by “drying out”

• ground cover in tundra (arctic)

• importance - pioneer (colonizing) plants

• peat - Sphagnum for mulching(flavor in scotch whiskey)

Moss gametophyte - protonema (similar to filamentous green algae)

gametophyte

sporophyte – capsule (which is spore-filled)

•may produce 50 million spores

operculum (cap) falls away releasing haploid spores

sporophyte

Class Musci - mosses

gametophyte

sporophyte

capsule

Vascular Plants - tracheophytes (tube plants)

• contain vascular tissue: xylem (conducts water) and phloem (conducts food)

• horizontal stems - rhizomes

• water conducting elements (tube-like) - tracheids

Early: club mosses / horsetails (ground pine) (scouring rushes)

cone - strobilus at end of branches

Pterophyta - ferns

• leaves which emerge above ground from the rhizomes - fiddleheads

• spores produced in sporangiaclustered into sori (sorus)

• fern gametophyte - prothallus - heart-shaped (short lived)

• the embryo develops into sporophyte (plant)

• sperm escape from antheridia and swim to archegonia where fertilization occurs

Seed Plants:

• came about due to climate changes – geological changes(upheavals) - drying, cooling trends

• female gametophyte fully enclosed in sporophytic tissues for protection

Reproductive adaptations:

1. different spores – heterosporous

2. pollen - minute, resistant – carried from one plant to another by air and water currents or animals

• the pollen grain contains a generative cell which gives rise to 2 sperm cells and a tube cell which directs the growth of the pollen tube after pollination has occurred

• pollen tubes literally digest their way to the female gametophyte, no water is necessary

Seeds: consist of embryo region of stored food

hardened seed coat

gymnosperm means “naked seed”

Division - Ginkgophyta

•one species left - Ginkgo biloba

• thought to be extinct – therefore a “living fossil”

• common name – maidenhair tree

• living Ginkgo found on grounds of oriental temple(year 1946)

• now commonly cultivated as decorative plants

• trees have separate sexes - dioecious

• sheds leaves in autumn

• primitive trait – swimming sperm

Division – Cycadophyta - cycads (palm-like)

• common in time of dinosaurs• today live in tropics

• sperms produced in strobili (cone-like)

• swimming sperm

Division - Gnetophyta

• have water-conducting xylem vessels within stem(other gymnosperms have water-conducting tracheids)

•Welwitschia – description - twisted

Where do they grow? African desert

• examples: pine, firs, spruce, hemlock

Division - Coniferophyta

• male pollen conesfemale ovulate cones

• biome - taiga

• remain green - evergreen

• sperm enter through micropyle

• zygote gives rise to the embryomade up of root - hypocotyl2 apical meristems8 cotyledons (seed leaves)

3. major catastrophe - giant asteroid hit earth (Alvarez theory) blocked sun

Geological changes at the end of the Mesozoic:

1. mountain building

2. plate tectonics

• pollination more efficient and selective

co-evolution with insects

Division Anthophyta (flowering plants)

Class – Dicotyledonae (dicots)

• larger class

Class – Monocotyledonae (monocots)

Monocot

Veins - parallel

Cotyledon - one

Flowers – 3’s

Vascular bundles - scattered

Dicots

Veins – branching (net)

Cotyledon - two

Flowers – 4’s or 5’s

Vascular bundles – in a ring

carpels are above receptacle

Flower:

primitive – floral parts are numerous and unfused

symmetry - radialexample: buttercup

bilateral symmetry

advanced - fused parts

Plant body has four organs:

1. Root – anchors plant, absorbs water and minerals, stores food

2. Stem – conducts water and minerals to leaves, displays leaves to light, conducts food to roots, stores food

3. Leaf – photosynthesizes food

4. Flower - reproduction

• flowers are modified leaves

Flower Parts

Sepal – outer, green, leaf-like part which covered the bud

Calyx – ring of sepals

Corolla – ring of petals

Stamen – male structure of filament and anther which produce pollen

Pistil – female structure consisting of the following:

Stigma – sticky tip

Style – slender neck leading to the ovary

Ovary – base containing ovules