Natural heritage and biological diversity Natural heritage and biological diversity.
Chapter 29 & 30 - Biological Diversity of Plants
Transcript of Chapter 29 & 30 - Biological Diversity of Plants
PLANT DIVERSITYChapters 29 & 30
Definition of Plants
• Multicellular• Eukaryotic• Photosynthetic• Autotrophic• Cell walls made of cellulose• Chlorophylls a and b
Plant Evolution
4 Main Groups of Land Plants• Bryophytes – non vascular plants
• Mosses, liverworts, hornworts
• Pteridophytes - seedless vascular plants• Lycophytes, ferns, horsetails, whisk ferns
• Gymnosperms – naked seed plants• Ginko, cycads, gnete, conifers
• Angiosperms – flowering plants
Land Plant Evolution
• Ancestral green algae
• Aquatic plants: Charophyceans
• Land plants:• Development of vascular tissue• Development of seeds• Development of flowering plants
Charophyceans
• Closest relative of land plants
• Algal group
• Similarities with land plants• Rosette cellulose-synthesizing
complexes• Located in plasma membranes
• Peroxisomes• Flagellated sperm (some land
plants)
Evidence of common ancestor with charophycean algae
• Homologous chloroplast• Homologous cellulose walls• Homologous peroxisomes• Homologous sperm• Molecular systematics
• Chloroplast DNA• Ribosomal RNA
Adaptations of Land Plants• Apical meristems
• Roots and shoots – growth• Multicellular, dependent embryos
• “embryophytes”• Transfer of nutrients from parent
• Alternation of generations• Sporophyte (diploid) and gametophyte (haploid)
• Gametangia – gametes are produced within multicellular organ• Female – archegonia• Male - Antheridia
• Walled spores – resist drying out• Cuticle – waxy covering, water conservation• Stomata – pores, water conservation• Vascular tissue – transport water and minerals
Apical meristems of plant shoots and roots
Embryos of Land Plants
Alternation of generations
Walled Spore
Gametangia: Gametes produced within multicellular gametangia
Archegonium - female Antheridium - male
egg sperm
Cuticle of a stem: Prevents drying out
Vascular Tissue: Xylem and Phloem
Xylem(water)
Phloem(food)
Development of Alternation of Generations
• Delay in meiosis until one or more mitotic divisions of the zygote occurred
• Result: multicellular, diploid sporophyte• Increases number of spores produced per zygote
What is the Plant Kingdom?
Bryophytes
• Three phyla• Hepatophyta: liverworts• Anthocerophyta: hornworts• Bryophyta: mosses
• Non-vascular• Earliest land plants• Gametophyte (haploid) is dominant form• Anchored by rhizoids• No true roots or leaves
Bryophytes
Life cycle of a moss
Moss life cycle
gametophyte gametangia sporophyte
sporophyte sporesProtonemata
(pre-gametophyte)
Sphagnum, or peat moss
gametophyte sporophyte
Vascular Plants• Vascular plants have
• Xylem – transports water• Phloem – transports food• Dominant sporophyte generation
• First vascular plants were seedless
• Three Groups• Seedless plants• Gymnosperms• Angiosperms
Seedless Vascular Plants
• Two phyla• Lycophyta – lycophytes• Pterophyta – ferns, whisk ferns, horsetails
• Most have true roots and leaves
• Still require water for fertilization
Pteridophytes
Club “moss” Whisk fern
Horsetail Fern
Hypothesis for the development of leaves
• Probably evolved from a flap of stem tissue• Stem had vascular tissue• Microphylls
• Macrophylls – larger leaves with branched veins
Ferns
Life cycle of a fern
Fern sporophyll, a leaf specialized for spore production & sori
Sorus (sori): Clusters of sporangia – found on underside of leaves
Mature fern sporangium – releasing spores
Fern gametophyte
Archegonia of fern
zygote
Flagellated sperm from antheridium fertilize eggs in archegonium
Fern sporophytes
Evolution of Seed Plants
• Reduction of gametophyte continued
• Seeds – important means of dispersal
• Pollen – eliminated water requirement for fertilization• Pollination
• Two clades• Gymnosperms• Angiosperms
Gametophyte/ Sporophyte Relationships• Seed plants: further reduced gametophyte• Female gametophyte and embryo protected by
parental sporophyte
Seed Development
• Fertilization initiates the transformation from ovule to seed• Sporophyte embryo• Food supply• Protective coat
Seed Dispersal
• Seeds have adaptations for dispersal
• Wind• Water• Animal
Gymnosperms
• Four phyla• Ginko• Cycads• Gnetophytes• Conifers
• Naked seed – no fruit (ovary)• Seeds develop on surface of sporophylls• Evolved before angiosperms
Phylum Coniferophyta
Douglas fir Sequoia
Phylum Coniferophyta: Frasier Fir
Characteristics of Conifers• Cone: reproductive structure
• Cluster of sporophylls• Female cones: produce ovules - “pine cones”• Male cones: produce pollen
• Seed develops from fertilized ovule – scale of cone
• Dominate in areas with short growing season• High latitude or altitude
• Most are evergreens
• Some have needle-shaped leaves• Adapted for dry conditions• Thick cuticle
Life cycle of a pine
Pollen cone (male) – produces pollen
Pine pollen
Pine embryo
Embryo(new sporophyte)
Angiosperms: Flowering PlantsMajor Clades:
Phylum Anthophyta: Angiosperms
• Vascular seed plants• Reproductive structures: flowers, fruits• Most diverse group of plants today• 2 groups
Monocots Dicots
# Petals Multiples of 3 Multiples of 4 or 5
# Cotyledons 1 2
Vascular bundles Scattered Circle
Root Fibrous Tap root
Xylem cells in Angiosperms
• Trachids• Support• Water transport
• Fiber **• Support
• Vessel element **• More efficient
** Evolutionary adaptations of angiosperms
Flower Structure: Reproductive Adaptation of Angiosperms
Life cycle of an angiosperm
Fruit and Seed Dispersal
Flower-pollinator relationships