The Temple of Flora
Exploring the Biology of Plants
An obvious plant
and another
Characteristics of living things
• Growth• Nutrition• Excretion• Sensitivity• Reproduction• Movement• Respiration
Differences between plants and animals
Plants
• Have cell walls made of complex polysaccharides (eg cellulose)
• Make their own food by the process of photosynthesis, requiring carbon dioxide, water, light energy and the green pigment chlorophyll (in structures known as chloroplasts)
Kingdoms of organisms
• In simpler times:• Plants• Animals• Bacteria• Viruses• Plants and Animals are eukaryotic (ie their cells
contain a nucleus); Bacteria are prokaryotic (don’t have genetic material in a nucleus)
A historical viewpoint
• Thallophyta– Algae– Fungi
• Bryophyta• Pteridophyta• Spermatophyta– Gymnosperms– Angiosperms
More-recent changes
• Since then:Fungi no longer considered to be plantsSingle-celled organisms may be Protista‘Algae’ are several groups of unrelated
simple plants (some people don’t regard them as plants, but we’ll ignore them)
One group of algae (blue-green) now considered to be bacteria
Some modern plant groups
• Rhodophyta• Phaeophyta• Chlorophyta• Bacillariophyta• Bryophyta• Pteridophyta• Spermatophyta• (in other words, algae now seen as being several
different groups, and fungi have been removed)
Other ways of grouping plants
• Non-Flowering Plants (Cryptogams)/Flowering Plants (Phanerogams)
• ‘Algae’, Bryophytes and Pteridophytes are Non-Flowering Plants; Spermatophytes are Flowering Plants.
• Non-Vascular Plants/Vascular Plants• ‘Algae’ and Bryophytes are Non-Vascular Plants;• Pteridophytes and Spermatophytes are Vascular Plants.
Why are fungi not plants?
• Cell wall is not made of polysaccharide• Do not have chloroplasts and do not
photosynthesise
Groups of fungi
• Mushrooms and toadstools• Moulds eg Penicillium, Mucor• Rusts
Fungi
What is missing so far?
• Lichens• These are composed fungi with symbiotic algae
(rather like a fungus-alga-fungus sandwich)• The fungus provides protection; the alga
photosynthesises and produces carbohydrates which can be used by the fungus
• Classified as fungi• Interestingly, the symbiotic alga is not known in
the free-living state
Lichens
Lichen structure
Algae
• Although once regarded as a single taxonomic group, now realised that the different classes of algae are a group of plants in their own right. So, for example, Class Phaeophyceae now Division Phaeophyta
• All simple aquatic plants reproducing by means of spores of one sort or another
• Both marine and freshwater (including soil algae); multicellular and unicellular; macroscopic and microscopic
Algae
• Rhodophyta (red algae)• Phaeophyta (brown algae)• Chlorophyta (green algae)• Bacillariophyta (diatoms)• Various other groups: note, classified according to
colour (ie pigments) although their anatomy is also significantly different
• Blue-green algae (Cyanophyceae), being prokaryotic, now considered to be bacteria (Cyanobacteria) even though they have cell walls and photosynthesise
Rhodophyta: Delesseria sanguinea
Rhodophyta: Phycodrys rubens
Phaeophyta: Fucus vesiculosus
Phaeophyta: Laminaria digitata
Chlorophyta: Pediastrum
Chlorophyta: Volvox
Chlorophyta: Spirogyra
Chlorophyta: Ulva lactuca
Chlorophyta: Codium fragile
Bacillariophyta: Diatoms
Oscillatoria – an example of a Cyanobacteria
Bryophyta
• Mosses (Musci)• Liverworts (Hepaticae)
Cell Division
• Mitosis – the type of cell division which results in identical copies of the original cell – found where organisms are growing or repairing tissues. Also found in simple organisms that reproduce by ‘binary fission’
• Meiosis – cell division which results in halving the chromosome number during the production of gametes (‘sex cells’). As a result, a diploid cell (with two of every chromosome: 2n) produces haploid cells (with one of each chromosome: n). Similarly tetraploid cells (4n) produce diploid ones (2n) and so on.
More terminology
• Gametophyte – the haploid phase in a life cycle. i.e. a stage which produces haploid gametes/spores by mitosis.
• Sporophyte – the diploid phase in a life cycle i.e. a stage which produces haploid gametes/spores by meiosis.
Life cycles
• In both Bryophytes and Pteridophytes there are two stages in the life cycle.
• The moss/liverwort ‘plant’ is haploid (the gametophyte) and lives in damp conditions; the spore capsule is diploid (the sporophyte) and requires dry conditions for the spores to be dispersed.
• The fern ‘plant’ is diploid (the sporophyte) and requires more-or-less dry conditions; there is a second stage (the prothallus: haploid, tiny, and totally different in appearance) and his requires damp conditions.
Mosses
• Yet more terminology if you want it:• Acrocarpous mosses form cushions;
Pleurocarpous mosses creep across the substratum.
Mnium hornum
Mnium hornum
Tortula ruraliformis
Ptilium crista-castrensis
Hypnum cupressiforme
Sphagnum
Marchantia
Pteridophyta
• Psilopsida (Quillworts)• Lycopsida (Club-mosses: no relation to
‘mosses’)• Sphenopsida (Horsetails)• Filicopsida (Ferns)
Psilotum: Quill-wort
Psilotum: Quill-wort
Huperzia selago: Club-moss
Diphasiastrum clavatum: Club-moss
Equisetum: Horsetail
Equisetum: Horsetail
Calamites: Fossil Horsetail
Botrychium lunaria: Moonwort
Dryopteris filix-mas: Male Fern
Dicksonia: Tree Fern
Gleichenia dicarpa
Spermatophyta
• Seed plants• Gymnosperms (Conifers, cycads etc)• Angiosperms (Flowering plants):– Monocotyledons (have one seed leaf eg grasses,
orchids)– Dicotyledons (have two seed leaves – majority of
flowering plants)