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UNIT 6
Chapter 29: Plant Diversity IChapter 30: Plant Diversity II
Chapter 31: FungiChapter 35: Plant Structure & Growth
Types of Land PlantsTypes of Land Plants
Plants are: multicellular, eukaryotic, Plants are: multicellular, eukaryotic, photosynthetic autotrophsphotosynthetic autotrophs
Four MAIN groups of land plants exist:Four MAIN groups of land plants exist:– BryophytesBryophytes: seedless, non-vascular: seedless, non-vascular– PteridophytesPteridophytes: seedless, vascular: seedless, vascular– GymnospermsGymnosperms: seeded, non-flowering: seeded, non-flowering– AngiospermsAngiosperms: seeded, flowering: seeded, flowering
VascularVascular plants possess vessels plants possess vessels (tubes) for transport of water and (tubes) for transport of water and nutrientsnutrients
Features of Land PlantsFeatures of Land Plants
Main characteristics of the four Main characteristics of the four groups of land plants:groups of land plants:– MeristemsMeristems
Regions located at specific places from Regions located at specific places from which new growth occurswhich new growth occurs
– Apical, lateralApical, lateral
– Multicellular embryos dependent on Multicellular embryos dependent on the parent plantthe parent plant
Embryo is retained by parent; provides Embryo is retained by parent; provides nutrientsnutrients
– Alternation of Alternation of generationsgenerations
Two multicellular Two multicellular body forms body forms alternatealternate
– SporophyteSporophyte: : 2n2n, , produces produces nn spores by spores by meiosismeiosis
– GametophyteGametophyte: : nn, come , come together to together to form form 2n2n zygote zygote
– Sporangia that produce sporesSporangia that produce spores Organs on the sporophyte that produce Organs on the sporophyte that produce
sporesspores– MegasporangiaMegasporangia: produce : produce
megaspores, becomes female megaspores, becomes female gametophyte = produces egggametophyte = produces egg
– MicrosporangiaMicrosporangia: produces : produces microspores, becomes male microspores, becomes male gametophyte = produces spermgametophyte = produces sperm
Spores will be released into airSpores will be released into air– Gametangia that produce gametesGametangia that produce gametes
Organs on gametophyte that produce Organs on gametophyte that produce gametesgametes
– ArchegoniumArchegonium: female gametangium : female gametangium produces a single haploid eggproduces a single haploid egg
– AntheridiaAntheridia: male gametangia that produce : male gametangia that produce many haploid spermmany haploid sperm
Other Features of Land Other Features of Land PlantsPlants
Many land plants possess a Many land plants possess a cuticlecuticle, , a waxy layer on leaves to prevent a waxy layer on leaves to prevent water loss and infectionwater loss and infection
StomataStomata, present mostly on the , present mostly on the leaves allow for gas exchange and leaves allow for gas exchange and evaporation of waterevaporation of water
Vascular tissue transports water and Vascular tissue transports water and nutrients (except bryophytes)nutrients (except bryophytes)– XylemXylem: transport of water and : transport of water and
nutrients from rootsnutrients from roots
Xylem is “dead” at maturity – only cell wall Xylem is “dead” at maturity – only cell wall remainsremains
– PhloemPhloem: distribution of sugars, amino : distribution of sugars, amino acids and other organic moleculesacids and other organic molecules
Phloem is living tissuePhloem is living tissue
END
SeedsSeeds
A A seedseed is a sporophyte embryo with is a sporophyte embryo with its own food supply in a protective its own food supply in a protective coatcoat– Seed plants (gymnosperms and Seed plants (gymnosperms and
angiosperms) retain their sporesangiosperms) retain their spores Microspores develop into Microspores develop into pollenpollen
– Carried off by wind or animalsCarried off by wind or animals – Pollen carry sperm (1 or 2) to Pollen carry sperm (1 or 2) to ultimately ultimately pollinatepollinate an egg an egg
Sperm are unflagellatedSperm are unflagellated
GymnospermsGymnosperms
Modern gymnosperms appeared Modern gymnosperms appeared ~350mya~350mya
Gymnosperms reflect 3 Gymnosperms reflect 3 major changes in the major changes in the evolution of plantsevolution of plants– Increasing dominance of Increasing dominance of
the sporophytethe sporophyte– Seeds resistant enough for Seeds resistant enough for
dispersaldispersal– PollenPollen
Conifers are the most common Conifers are the most common group of gymnospermsgroup of gymnosperms– Most have male and female Most have male and female conescones on on
the same plantthe same plant Smaller pollen cones produce microspores Smaller pollen cones produce microspores
which develop into male gametophytes = which develop into male gametophytes = pollenpollen
Larger ovulate cones make megaspores Larger ovulate cones make megaspores that develop into female gametophytesthat develop into female gametophytes
– Seeds typically dispersed by windSeeds typically dispersed by wind
Most conifers are evergreen (vs. Most conifers are evergreen (vs. deciduous) and photosynthesize all deciduous) and photosynthesize all yearyear
Needles are modified leaves Needles are modified leaves adapted to dry conditionsadapted to dry conditions– Most have thick cuticlesMost have thick cuticles
Most lumber and paper comes from Most lumber and paper comes from conifers (xylem tissue)conifers (xylem tissue)
Conifers are among the oldest and Conifers are among the oldest and largest organisms on earthlargest organisms on earth
AngiospermsAngiosperms
Angiosperms have existed for Angiosperms have existed for ~130my~130my– Categorized into two groups: Categorized into two groups: monocotsmonocots
and and dicotsdicots– ~250,000 known species~250,000 known species
TheThe flower flower is the most significant is the most significant evolutionary adaptation found in evolutionary adaptation found in angiospermsangiosperms– Reproductive structureReproductive structure
Animals (esp. insects) often used to Animals (esp. insects) often used to transfer pollen transfer pollen
Angiosperms – The Angiosperms – The FlowerFlower
Flowers are Flowers are modified shoots modified shoots with four types with four types of modified of modified leaves called leaves called whorlswhorls– SepalsSepals, , petalspetals, ,
stamensstamens, , carpelscarpels
Female – carpelFemale – carpel Male – stamenMale – stamen
Angiosperms – The FruitAngiosperms – The Fruit
A A fruitfruit is a mature ovary is a mature ovary– After fertilization, ovary wall thickens After fertilization, ovary wall thickens
to form fruitto form fruit– Protect dormant seeds and aid in Protect dormant seeds and aid in
dispersaldispersal
Various modifications exist to aid in Various modifications exist to aid in dispersaldispersal– Ex. Dandelions and maples use windEx. Dandelions and maples use wind– Many angiosperms use animals for Many angiosperms use animals for
dispersaldispersal Edible fruits eaten and passed unharmed Edible fruits eaten and passed unharmed
(along with fertilizer)(along with fertilizer)
Three Three main fruit main fruit types types existexist
Plants & HumansPlants & Humans
All animals ultimately depend on All animals ultimately depend on plants, either for oxygen or for foodplants, either for oxygen or for food
Angiosperms provide virtually all of Angiosperms provide virtually all of our food (~12 species)our food (~12 species)– Fruits, vegetables, grasses (corn, Fruits, vegetables, grasses (corn,
wheat, rice)wheat, rice) Diversity in plants is a non-Diversity in plants is a non-
renewable resourcerenewable resource– Human growth vs. plantsHuman growth vs. plants
Many plant (and animal) species go Many plant (and animal) species go extinct as forests are cut down for extinct as forests are cut down for agricultureagriculture
Ethical concerns are not the only Ethical concerns are not the only issueissue– Food, building materials, medicinesFood, building materials, medicines
Only about Only about 2% of the 2% of the 250,000 250,000 known plant known plant species have species have been studiedbeen studied– More than More than
25% of 25% of prescription prescription drugs are drugs are isolated from isolated from plantsplants END
Fungi
Fungi are (usually) multicellular, eukaryotic, non-vascular, heterotrophic and possess a cell wall made of chitin Acquire nutrients by secreting exoenzymes
and absorbing nutrients Act as decomposers, mutualistic symbionts
and parasites Mycorrhizae are mutualistic associations
between plant roots and fungi
Fungus increases surface area for absorption by plant roots Fungus provides
minerals from soil to plant; plant provides organic nutrients
Almost all vascular plants have a mycorrhizae Plant growth is
often stunted without mycorrhizae
END
Plant Anatomy
Plants have three basic organs: roots, shoots and leaves
Angiosperms have most features in common, but a few major features distinguish the monocots from the dicots
A basic plant
Plant Tissue Systems
There are three main types of tissues found in plants: ground, dermal and vascular All types are found
throughout the plant Dermal
Covers outer surface of plant
Extends to create root hairs
Secretes cuticle
Vascular (xylem) Tracheids are
individual units of xylem
Vascular (phloem) Organic material
moves through chains of cells called sieve-tube members
Ground Neither dermal nor vascular Photosynthesis, storage and support
The three tissue types are made up of three major cell types Parenchyma: (living) sieve-tube members,
photosynthesis, storage Collenchyma: (living) support young parts
of plant Sclerenchyma: (dead) thick cell walls,
tracheids, support & transport
Growth & Development
Most plants grow and develop throughout their lifetime – indeterminate growth Growth: increase in mass due to cell division Development: changes that elaborate an
organism’s body Plant life cycles vary based on when they are
capable of reproduction Germination flowering seed production
death Annual, biennial, perennial
Meristems are regions of embryonic cells Apical: increase in
plant’s length/height – primary growth
Lateral: increase in plant’s width – secondary growth
Leaf Anatomy
Leaf epidermis comprised of tightly packed cells Stomata: tiny pores found
in the epidermis flanked by guard cells
Water pressure in guard cells control stomata opening/closing
Mesophyll is ground tissue sandwiched in between two epidermal layers
O2 and CO2 circulate in the spaces in the parenchyma
Vascular tissue is continuous with that of the stem
END
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